Powered by Deep Web Technologies
Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


1

Turbulent flow in graphene  

E-Print Network (OSTI)

We demonstrate the possibility of a turbulent flow of electrons in graphene in the hydrodynamic region, by calculating the corresponding turbulent probability density function. This is used to calculate the contribution of the turbulent flow to the conductivity within a quantum Boltzmann approach. The dependence of the conductivity on the system parameters arising from the turbulent flow is very different from that due to scattering.

Kumar S. Gupta; Siddhartha Sen

2009-11-03T23:59:59.000Z

2

Coshcous turbulence and its thermalization  

SciTech Connect

Dissipation rate {mu}[cosh(k/k{sub c}) - 1] in Fourier space, which reduces to the Newtonian viscosity dissipation rate {nu}k{sup 2} for small k/k{sub c}, can be scaled to make a hydrodynamic system either actually or potentially converge to its Galerkin truncation. The former case acquires convergence to the truncation at a finite wavenumber k{sub G}; the latter realizes as the wavenumber grows to infinity. Intermittency reduction and vitiation of extended self-similarity (ESS) in the partially thermalized regime of turbulence are confirmed and clarified. Onsager's pictures of intermittent versus nonintermittent flows are visualized from thermalized numerical fields, showing cleanly spotty versus mistily uniform properties, the latter of which destroys self-organization and so the ESS property.

Zhu, Jian-zhou [Los Alamos National Laboratory; Taylor, Mark [SNL

2008-01-01T23:59:59.000Z

3

Modeling Turbulent Flow  

National Nuclear Security Administration (NNSA)

Turbulent Turbulent Flow with Implicit LES L.G. Margolin 1 Proceedings of the Joint Russian-American Five Laboratory Conference on Computational Mathematics/Physics 19-23 June, 2005 Vienna, Austria 1 Applied Physics Division, Los Alamos National Laboratory, Los Alamos, NM 87545, len@lanl.gov 1 Abstract Implicit large eddy simulation (ILES) is a methodology for modeling high Reynolds' num- ber flows that combines computational efficiency and ease of implementation with predictive calculations and flexible application. Although ILES has been used for more than fifteen years, it is only recently that significant effort has gone into providing a physical rationale that speaks to its capabilities and its limitations. In this talk, we will present new theoret- ical results aimed toward building a justification and discuss some remaining gaps in our understanding and our practical

4

Tidal Flow Turbulence Measurements  

NLE Websites -- All DOE Office Websites (Extended Search)

max quire specification of a turbulence intensity, and it is a metric in the wind energy industry. For acoustic Dop surements, a noise-corrected expression of...

5

Stochastic models for turbulent reacting flows  

SciTech Connect

The goal of this program is to develop and apply stochastic models of various processes occurring within turbulent reacting flows in order to identify the fundamental mechanisms governing these flows, to support experimental studies of these flows, and to further the development of comprehensive turbulent reacting flow models.

Kerstein, A. [Sandia National Laboratories, Livermore, CA (United States)

1993-12-01T23:59:59.000Z

6

Influences of peripherally-cut twisted tape insert on heat transfer and thermal performance characteristics in laminar and turbulent tube flows  

SciTech Connect

Effects of peripherally-cut twisted tape insert on heat transfer, friction loss and thermal performance factor characteristics in a round tube were investigated. Nine different peripherally-cut twisted tapes with constant twist ratio (y/W = 3.0) and different three tape depth ratios (DR = d/W = 0.11, 0.22 and 0.33), each with three different tape width ratios (WR = w/W = 0.11, 0.22 and 0.33) were tested. Besides, one typical twisted tape was also tested for comparison. The measurement of heat transfer rate was conducted under uniform heat flux condition while that of friction factor was performed under isothermal condition. Tests were performed with Reynolds number in a range from 1000 to 20,000, using water as a working fluid. The experimental results revealed that both heat transfer rate and friction factor in the tube equipped with the peripherally-cut twisted tapes were significantly higher than those in the tube fitted with the typical twisted tape and plain tube, especially in the laminar flow regime. The higher turbulence intensity of fluid in the vicinity of the tube wall generated by the peripherally-cut twisted tape compared to that induced by the typical twisted tape is referred as the main reason for achieved results. The obtained results also demonstrated that as the depth ratio increased and width ratio decreased, the heat transfer enhancement increased. Over the range investigated, the peripherally-cut twisted tape enhanced heat transfer rates in term of Nusselt numbers up to 2.6 times (turbulent regime) and 12.8 times (laminar regime) of that in the plain tube. These corresponded to the maximum performance factors of 1.29 (turbulent regime) and 4.88 (laminar regime). (author)

Eiamsa-ard, Smith [Department of Mechanical Engineering, Faculty of Engineering, Mahanakorn University of Technology, Bangkok 10530 (Thailand); Seemawute, Panida [Department of Civil Engineering, Faculty of Engineering, Mahanakorn University of Technology, Bangkok 10530 (Thailand); Wongcharee, Khwanchit [Department of Chemical Engineering, Faculty of Engineering, Mahanakorn University of Technology, Bangkok 10530 (Thailand)

2010-09-15T23:59:59.000Z

7

FLIHY EXPERIMENTAL FACILITIES FOR STUDYING OPEN CHANNEL TURBULENT FLOWS AND HEAT TRANSFER  

E-Print Network (OSTI)

1 FLIHY EXPERIMENTAL FACILITIES FOR STUDYING OPEN CHANNEL TURBULENT FLOWS AND HEAT TRANSFER B was constructed at UCLA to study open channel turbulent flow and heat transfer of low-thermal and low supercritical flow regimes (Fr>1), in which the surface waves are amplified and heat transfer is enhanced due

California at Los Angeles, University of

8

FLOW CONDITIONING DESIGN IN TURBULENT  

E-Print Network (OSTI)

for HYLIFE-II · Measure loss coefficient across the flow conditioner / nozzle assembly for different flow conditioner configurations #12;5 Flow Loop A Pump H 400 gal tank B Bypass line I Butterfly valve C Flow meter

9

Colloidal particle deposition in turbulent flow  

SciTech Connect

A theoretical analysis is presented which describes the initial deposition of monodispersed spherical colloidal particles from a steady fully developed turbulent flow onto conduit walls. When the net particle-conduit electrical interaction potential is attractive, particle deposition is shown to be often governed by turbulent hydrodynamics. When the net particle-conduit electrical interaction potential possess a repulsive maximum, particle deposition to first order is uniform and depends solely on electrical interaction effects. The developed theoretical model specialized to orifice deposition with the use of Harwell Flow3D turbulence modelling software qualitatively described the deposition of 0.5 {mu}m silica particles onto glass orifices from an aqueous suspension. The effect of the electrical double layer on the rate of colloidal particle deposition in laminar flow has been described by Spielman and Friedlander (1), Dahneke (2), Bowen et al. (3) and Bowen and Epstein (4). This article describes the extension of their work to colloidal particle deposition under steady fully developed turbulent flow conditions. This article also reports the results of orifice particle deposition experiments which were conducted to qualitatively investigate the developed theoretical model.

Morton, D.S.

1994-05-01T23:59:59.000Z

10

Particle Heating by Alfvenic Turbulence in Hot Accretion Flows  

E-Print Network (OSTI)

Recent work on Alfvenic turbulence by Goldreich & Sridhar (1995; GS) suggests that the energy cascades almost entirely perpendicular to the local magnetic field. As a result, the cyclotron resonance is unimportant in dissipating the turbulent energy. Motivated by the GS cascade, we calculate the linear collisionless dissipation of Alfven waves with frequencies much less than the proton cyclotron frequency, but with perpendicular wavelengths of order the Larmor radius of thermal protons. In plasmas appropriate to hot accretion flows (proton temperature much greater than electron temperature) the dissipated Alfven wave energy primarily heats the protons. For a plasma with $\\beta \\lsim 5$, however, where $\\beta$ is the ratio of the gas pressure to the magnetic pressure, the MHD assumptions utilized in the GS analysis break down before most of the energy in Alfven waves is dissipated; how the cascade then proceeds is unclear. Hot accretion flows, such as advection dominated accretion flows (ADAFs), are expected to contain significant levels of MHD turbulence. This work suggests that, for $\\beta \\gsim 5$, the Alfvenic component of such turbulence primarily heats the protons. Significant proton heating is required for the viability of ADAF models. We contrast our results on particle heating in ADAFs with recent work by Bisnovatyi-Kogan & Lovelace (1997).

Eliot Quataert

1997-10-13T23:59:59.000Z

11

Direct numerical simulation of turbulent reacting flows  

SciTech Connect

The development of turbulent combustion models that reflect some of the most important characteristics of turbulent reacting flows requires knowledge about the behavior of key quantities in well defined combustion regimes. In turbulent flames, the coupling between the turbulence and the chemistry is so strong in certain regimes that is is very difficult to isolate the role played by one individual phenomenon. Direct numerical simulation (DNS) is an extremely useful tool to study in detail the turbulence-chemistry interactions in certain well defined regimes. Globally, non-premixed flames are controlled by two limiting cases: the fast chemistry limit, where the turbulent fluctuations. In between these two limits, finite-rate chemical effects are important and the turbulence interacts strongly with the chemical processes. This regime is important because industrial burners operate in regimes in which, locally the flame undergoes extinction, or is at least in some nonequilibrium condition. Furthermore, these nonequilibrium conditions strongly influence the production of pollutants. To quantify the finite-rate chemistry effect, direct numerical simulations are performed to study the interaction between an initially laminar non-premixed flame and a three-dimensional field of homogeneous isotropic decaying turbulence. Emphasis is placed on the dynamics of extinction and on transient effects on the fine scale mixing process. Differential molecular diffusion among species is also examined with this approach, both for nonreacting and reacting situations. To address the problem of large-scale mixing and to examine the effects of mean shear, efforts are underway to perform large eddy simulations of round three-dimensional jets.

Chen, J.H. [Sandia National Laboratories, Livermore, CA (United States)

1993-12-01T23:59:59.000Z

12

Electron Thermal Transport in Tokamak: ETG or TEM Turbulences?  

E-Print Network (OSTI)

Electron Thermal Transport in Tokamak: ETG or TEM Turbulences? Z. Lin, L. Chen, Y. Nishimura, H. Qu studies of electron transport in tokamak including: (1) electron temperature gradient turbulence; (2) trapped electron mode turbulence; and (3) a new finite element solver for global electromagnetic

Zonca, Fulvio

13

Regulation of thermal conductivity in hot galaxy clusters by MHD turbulence  

E-Print Network (OSTI)

The role of thermal conduction in regulating the thermal behavior of cooling flows in galaxy clusters is reexamined. Recent investigations have shown that the anisotropic Coulomb heat flux caused by a magnetic field in a dilute plasma drives a dynamical instability. A long standing problem of cooling flow theory has been to understand how thermal conduction can offset radiative core losses without completely preventing them. In this Letter we propose that magnetohydrodynamic turbulence driven by the heat flux instability regulates field-line insulation and drives a reverse convective thermal flux, both of which may mediate the stabilization of the cooling cores of hot clusters. This model suggests that turbulent mixing should accompany strong thermal gradients in cooling flows. This prediction seems to be supported by the spatial distribution of metals in the central galaxies of clusters, which shows a much stronger correlation with the ambient hot gas temperature gradient than with the parent stellar population.

Steven A. Balbus; Christopher S. Reynolds

2008-06-05T23:59:59.000Z

14

Regulation of thermal conductivity in hot galaxy clusters by MHD turbulence  

E-Print Network (OSTI)

The role of thermal conduction in regulating the thermal behavior of cooling flows in galaxy clusters is reexamined. Recent investigations have shown that the anisotropic Coulomb heat flux caused by a magnetic field in a dilute plasma drives a dynamical instability. A long standing problem of cooling flow theory has been to understand how thermal conduction can offset radiative core losses without completely preventing them. In this Letter we propose that magnetohydrodynamic turbulence driven by the heat flux instability regulates field-line insulation and drives a reverse convective thermal flux, both of which may mediate the stabilization of the cooling cores of hot clusters. This model suggests that turbulent mixing should accompany strong thermal gradients in cooling flows. This prediction seems to be supported by the spatial distribution of metals in the central galaxies of clusters, which shows a much stronger correlation with the ambient hot gas temperature gradient than with the parent stellar populat...

Balbus, Steven A

2008-01-01T23:59:59.000Z

15

Petascale Direct Numerical Simulations of Turbulent Channel Flow  

NLE Websites -- All DOE Office Websites (Extended Search)

Petascale Petascale Direct Numerical Simulations of Turbulent Channel Flow MyoungKyu Lee mk@ices.utexas.edu Department of Mechanical Engineering University of Texas at Austin ESP Meeting May, 2013 M.K. Lee (Univ of Texas, Austin) Petascale DNS of Turbulent Channel Flow ESP Meeting May, 2013 1 / 30 Contents Project Overview Performance Optimization Early Result Conclusion M.K. Lee (Univ of Texas, Austin) Petascale DNS of Turbulent Channel Flow ESP Meeting May, 2013 2 / 30 Project Overview Project Title ◮ Petascale Direct Numerical Simulations of Turbulent Channel Flow Goal ◮ Expanding our understand of wall-bounded turbulence Personnel ◮ P.I. : Robert Moser ◮ Primary Developer : M.K.Lee ◮ Software Engineering Support : Nicholas Malaya ◮ Catalyst : Ramesh Balakrishnan M.K. Lee (Univ of Texas, Austin) Petascale DNS of Turbulent Channel Flow ESP Meeting May, 2013 3 / 30 Turbulent

16

A turbulence model for buoyant flows based on vorticity generation.  

SciTech Connect

A turbulence model for buoyant flows has been developed in the context of a k-{var_epsilon} turbulence modeling approach. A production term is added to the turbulent kinetic energy equation based on dimensional reasoning using an appropriate time scale for buoyancy-induced turbulence taken from the vorticity conservation equation. The resulting turbulence model is calibrated against far field helium-air spread rate data, and validated with near source, strongly buoyant helium plume data sets. This model is more numerically stable and gives better predictions over a much broader range of mesh densities than the standard k-{var_epsilon} model for these strongly buoyant flows.

Domino, Stefan Paul; Nicolette, Vernon F.; O'Hern, Timothy John; Tieszen, Sheldon R.; Black, Amalia Rebecca

2005-10-01T23:59:59.000Z

17

Filtering Turbulent Sparsely Observed Geophysical Flows  

Science Journals Connector (OSTI)

Filtering sparsely turbulent signals from nature is a central problem of contemporary data assimilation. Here, sparsely observed turbulent signals from nature are generated by solutions of two-layer quasigeostrophic models with turbulent cascades ...

John Harlim; Andrew J. Majda

2010-04-01T23:59:59.000Z

18

Particle transport in turbulent curved pipe flow  

E-Print Network (OSTI)

Direct numerical simulations (DNS) of particle-laden turbulent flow in straight, mildly curved and strongly bent pipes are performed in which the solid phase is modelled as small heavy spherical particles. The objective is to examine the effect of the curvature on particle transport and accumulation, in particular how the turbophoretic drift of the particles is affected by weak and strong secondary motions of the carrier phase and geometry-induced centrifugal forces. A total of seven populations of dilute particles with different Stokes numbers, one-way coupled with their carrier phase, are simulated. Even a slight non-zero curvature in the flow configuration shows a strong impact on the particle dynamics. Near-wall helicoidal particle streaks are observed in the curved configurations with their inclination varying with the strength of the secondary motion of the carrier phase. A reflection layer, as previously observed in particle laden turbulent S-shaped channels, is also apparent in the strongly curved pip...

Noorani, Azad; Brandt, Luca; Schlatter, Philipp

2015-01-01T23:59:59.000Z

19

Turbulent Transport Reduction by Zonal Flows: Massively Parallel Simulations  

Science Journals Connector (OSTI)

...University, Post Office Box 451,-Princeton, NJ 08543,-USA. * To whom correspondence should be addressed. Email: zlin@pppl.gov Turbulence shear suppression by E -B flows (plasma flows induced by an electric field perpendicular to a magnetic field...

Z. Lin; T. S. Hahm; W. W. Lee; W. M. Tang; R. B. White

1998-09-18T23:59:59.000Z

20

Turbulent heat transfer in a channel flow at transitional Reynolds numbers  

E-Print Network (OSTI)

Direct numerical simulation of a turbulent channel flow with heat transfer was performed at very low Reynolds numbers. Two different thermal boundary conditions were studied, and temperature was considered as a passive scalar. The computations were carried out with huge computational boxes (up to 327.7 x 2 x 128 in the streamwise, wall-normal, and spanwise directions, respectively). The emphases of this paper are to investigate the large-scale structure (puff) in the intermittent-turbulent flow including the scalar fields and to provide the values of the transitional and critical Reynolds numbers, below which the turbulent flow becomes intermittent and laminar, respectively. The statistics, such as the skin friction and the Stanton number, were also examined: they suggest that the puff should be effective in sustaining turbulence and in heat transfer enhancement.

Tsukahara, Takahiro

2014-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


21

Compound cooling flow turbulator for turbine component  

DOE Patents (OSTI)

Multi-scale turbulation features, including first turbulators (46, 48) on a cooling surface (44), and smaller turbulators (52, 54, 58, 62) on the first turbulators. The first turbulators may be formed between larger turbulators (50). The first turbulators may be alternating ridges (46) and valleys (48). The smaller turbulators may be concave surface features such as dimples (62) and grooves (54), and/or convex surface features such as bumps (58) and smaller ridges (52). An embodiment with convex turbulators (52, 58) in the valleys (48) and concave turbulators (54, 62) on the ridges (46) increases the cooling surface area, reduces boundary layer separation, avoids coolant shadowing and stagnation, and reduces component mass.

Lee, Ching-Pang; Jiang, Nan; Marra, John J; Rudolph, Ronald J

2014-11-25T23:59:59.000Z

22

Quantitative imaging of turbulent and reacting flows  

SciTech Connect

Quantitative digital imaging, using planar laser light scattering techniques is being developed for the analysis of turbulent and reacting flows. Quantitative image data, implying both a direct relation to flowfield variables as well as sufficient signal and spatial dynamic range, can be readily processed to yield two-dimensional distributions of flowfield scalars and in turn two-dimensional images of gradients and turbulence scales. Much of the development of imaging techniques to date has concentrated on understanding the requisite molecular spectroscopy and collision dynamics to be able to determine how flowfield variable information is encoded into the measured signal. From this standpoint the image is seen as a collection of single point measurements. The present effort aims at realizing necessary improvements in signal and spatial dynamic range, signal-to-noise ratio and spatial resolution in the imaging system as well as developing excitation/detection strategies which provide for a quantitative measure of particular flowfield scalars. The standard camera used for the study is an intensified CCD array operated in a conventional video format. The design of the system was based on detailed modeling of signal and image transfer properties of fast UV imaging lenses, image intensifiers and CCD detector arrays. While this system is suitable for direct scalar imaging, derived quantities (e.g. temperature or velocity images) require an exceptionally wide dynamic range imaging detector. To apply these diagnostics to reacting flows also requires a very fast shuttered camera. The authors have developed and successfully tested a new type of gated low-light level detector. This system relies on fast switching of proximity focused image-diode which is direct fiber-optic coupled to a cooled CCD array. Tests on this new detector show significant improvements in detection limit, dynamic range and spatial resolution as compared to microchannel plate intensified arrays.

Paul, P.H. [Sandia National Laboratories, Livermore, CA (United States)

1993-12-01T23:59:59.000Z

23

Generalized Flows, Intrinsic Stochasticity, and Turbulent Transport  

E-Print Network (OSTI)

The study of passive scalar transport in a turbulent velocity field leads naturally to the notion of generalized flows which are families of probability distributions on the space of solutions to the associated ODEs, which no longer satisfy the uniqueness theorem for ODEs. Two most natural regularizations of this problem, namely the regularization via adding small molecular diffusion and the regularization via smoothing out the velocity field are considered. White-in-time random velocity fields are used as an example to examine the variety of phenomena that take place when the velocity field is not spatially regular. Three different regimes characterized by their degrees of compressibility are isolated in the parameter space. In the regime of intermediate compressibility, the two different regularizations give rise to two different scaling behavior for the structure functions of the passive scalar. Physically this means that the scaling depends on Prandtl number. In the other two regimes the two different regularizations give rise to the same generalized flows even though the sense of convergence can be very different. The ``one force, one solution'' principle and the existence and uniqueness of an invariant measure are established for the scalar field in the weakly compressible regime, and for the difference of the scalar in the strongly compressible regime.

Weinan E; Eric Vanden Eijnden

2000-03-10T23:59:59.000Z

24

Turbulence-chemistry interactions in reacting flows  

SciTech Connect

Interactions between turbulence and chemistry in nonpremixed flames are investigated through multiscalar measurements. Simultaneous point measurements of major species, NO, OH, temperature, and mixture fraction are obtained by combining spontaneous Raman scattering, Rayleigh scattering, and laser-induced fluorescence (LIF). NO and OH fluorescence signals are converted to quantitative concentrations by applying shot-to-shot corrections for local variations of the Boltzmann fraction and collisional quenching rate. These measurements of instantaneous thermochemical states in turbulent flames provide insights into the fundamental nature of turbulence-chemistry interactions. The measurements also constitute a unique data base for evaluation and refinement of turbulent combustion models. Experimental work during the past year has focused on three areas: (1) investigation of the effects of differential molecular diffusion in turbulent combustion: (2) experiments on the effects of Halon CF{sub 3}Br, a fire retardant, on the structure of turbulent flames of CH{sub 4} and CO/H{sub 2}/N{sub 2}; and (3) experiments on NO formation in turbulent hydrogen jet flames.

Barlow, R.S.; Carter, C.D. [Sandia National Laboratories, Livermore, CA (United States)

1993-12-01T23:59:59.000Z

25

Isolation of metals from liquid wastes: Reactive scavenging in turbulent thermal reactors. 1998 annual progress report  

SciTech Connect

'The objective of this project is to develop the fundamental science base necessary to assess the utility of high-temperature processes to volatilize metals in DOE metal-bearing liquid wastes, so that they can be reactively scavenged by sorbents. The problem is addressed through a collaborative research program involving a team of five senior scientists and their respective laboratories, at four institutions. Specific goals are to: (1) Understand high-temperature reaction kinetics between sorbent substrates and certain volatile and semi-volatile metals in the DOE liquid waste inventory (e.g., Cs and Sr), using a laminar-flow reactor for which extraction of kinetic data is not complicated by turbulence; (2) Develop models to predict both trajectories of individual droplets in turbulent high-temperature reactors, and rates of metal evolution from droplets, and compare model predictions with experimental data from a pilot-scale turbulent thermal reactor; (3) Connect the reaction kinetic models with the droplet trajectory/mass evolution models, in order to predict and optimize metal scavenging processes in turbulent-flow reactors, and to test these combined models against data taken from a turbulent high temperature reactor. This report summarizes work at a point midway through the first year of a 3-year project. At the University of Arizona (UA), two tasks are underway. The first task is concerned with attempting to understand high-temperature reaction kinetics between sorbent substrates and certain volatile and semi-volatile metals. The second task is concerned with applying Kerstein''s One Dimensional Turbulence model to prediction of droplet trajectories in turbulent flow.'

Wendt, J.O.L. [Univ. of Arizona, Tucson, AZ (US); Linak, W.P. [Environmental Protection Agency, Research Triangle Park, NC (US); Kerstein, A.R. [Sandia National Labs., Livermore, CA (US); Pearlstein, A.J.; Scheeline, A. [Univ. of Illinois, Urbana, IL (US)

1998-06-01T23:59:59.000Z

26

Interaction of turbulent plasma flow with a hypersonic shock wave  

SciTech Connect

A transient increase is observed in both the spectral energy decay rate and the degree of chaotic complexity at the interface of a shock wave and a turbulent ionized gas. Even though the gas is apparently brought to rest by the shock wave, no evidence is found either of prompt relaminarization or of any systematic influence of end-wall material thermal conductivities on the turbulence parameters. {copyright} {ital 1997 American Institute of Physics.}

Belay, K.; Valentine, J.M.; Williams, R.L.; Johnson, J.A. III [CeNNAs, Florida AM University, Tallahassee, Florida (United States)] [CeNNAs, Florida AM University, Tallahassee, Florida (United States)

1997-02-01T23:59:59.000Z

27

Flow characteristics of finite aspect ratio fences in turbulent shear flows  

E-Print Network (OSTI)

FLOW CHARACTERISTICS OF FINITE ASPECT RATIO FENCES IN TURBULENT SHEAR FLOWS A THESIS by JOSEPH RODNEY MATTE Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement for the degree of MASTER... OF SCIENCE December 1977 Major. Subject: Aerospace Engineering FLOW CHARACTERISTICS OF FINITE ASPECT RATIO FENCES IN TURBULENT SHEAR FLOWS A Thesis by JOSEPH RODNEY MATTE Approved as to style and content by: (Chairman of Committee) (Head...

Matte, Joseph Rodney

2012-06-07T23:59:59.000Z

28

Entropy Generation In The Viscous Layer Of A Turbulent Channel Flow  

SciTech Connect

The local (pointwise) entropy generation rate per unit volume S''' is a key to improving many energy processes and applications. Entropy generation due to friction occurs from viscous dissipation of mean-flow kinetic energy (called "direct dissipation") and dissipation of turbulent kinetic energy into thermal energy ("indirect" or turbulent dissipation). The objective of the present study is to compare two approaches for the prediction of S''' for the viscous layer in near asymptotic (high Reynolds number) turbulent flows. By employing available direct numerical simulations (DNS) it was found that about two-thirds of the entropy generation occurs in this layer. A popular approximate approach does not agree with the result from the more exact evaluation of S''' but its integral falls within about four per cent at the edge of the viscous layer.

D. M. McEligot; E. J. Walsh; E. Laurien; James R. Wolf

2006-09-01T23:59:59.000Z

29

TURBULENT SHEAR STRESS IN HETEROGENEOUS SEDIMENT-LADEN FLOWS  

E-Print Network (OSTI)

TURBULENT SHEAR STRESS IN HETEROGENEOUS SEDIMENT-LADEN FLOWS By Hyoseop Woo,1 Associate Member are the beginning of motion of sediment particles and sediment transport in alluvial channels. If shear stress can be well defined in clear-water flows, compar- atively little is known about shear stresses in sediment

Julien, Pierre Y.

30

Self-assembly of magnetically interacting cubes by a turbulent fluid flow  

Science Journals Connector (OSTI)

Previous work has demonstrated that combining mechanical vibration with magnetic interactions can result in the self-assembly of complex structures, albeit at low yield. Here we introduce a system where the yield of self-assembled structures is quantitatively predicted by a theoretical analysis. Millimeter-sized magnetic blocks, designed to form chains as their minimal energy state, are placed in a turbulent fluid flow. The distribution of chain lengths that form is quantitatively consistent with predictions, showing that the chain length distribution coincides with that of monomers or polymers in a thermal bath, with the turbulence strength parametrizing the effective temperature.

Filip Ilievski; Madhav Mani; George M. Whitesides; Michael P. Brenner

2011-01-05T23:59:59.000Z

31

Asymptotic scaling in turbulent pipe flow  

Science Journals Connector (OSTI)

...obtained in industrial piping such as a transcontinental natural gas pipelines. D is the pipe diameter and is the volume-averaged...Marati, N , C.M Casciola, and R Piva2004Energy cascade and spatial fluxes in wall turbulence. J. Fluid Mech...

2007-01-01T23:59:59.000Z

32

Linear Stability and Subcritical Turbulence in Rotating Shear Flows  

E-Print Network (OSTI)

The relation between rotating plane Couette and Taylor-Couette flows is clarified. The identity of their linear stability limits is explained by considering the effect of the Coriolis force in the rotating frame. Experimental data are used to quantify the behavior of the minimum Reynolds number for subcritical turbulence as a function of rotation and curvature. This last dependence is understood through a phenomenological analysis, which also implies that the Coriolis force reduces the efficiency of subcritical turbulent transport with respect to nonrotating flows, as observed numerically.

P. -Y. Longaretti

2003-05-28T23:59:59.000Z

33

Wave turbulence revisited: Where does the energy flow?  

E-Print Network (OSTI)

Turbulence in a system of nonlinearly interacting waves is referred to as wave turbulence. It has been known since seminal work by Kolmogorov, that turbulent dynamics is controlled by a directional energy flux through the wavelength scales. We demonstrate that an energy cascade in wave turbulence can be bi-directional, that is, can simultaneously flow towards large and small wavelength scales from the pumping scales at which it is injected. This observation is in sharp contrast to existing experiments and wave turbulence theory where the energy flux only flows in one direction. We demonstrate that the bi-directional energy cascade changes the energy budget in the system and leads to formation of large-scale, large-amplitude waves similar to oceanic rogue waves. To study surface wave turbulence, we took advantage of capillary waves on a free, weakly charged surface of superfluid helium He-II at temperature 1.7K. Although He-II demonstrates non-classical thermomechanical effects and quantized vorticity, waves on its surface are identical to those on a classical Newtonian fluid with extremely low viscosity. The possibility of directly driving a charged surface by an oscillating electric field and the low viscosity of He-II have allowed us to isolate the surface dynamics and study nonlinear surface waves in a range of frequencies much wider than in experiments with classical fluids.

L. V. Abdurakhimov; I. A. Remizov; A. A. Levchenko; G. V. Kolmakov; Y. V. Lvov

2014-04-03T23:59:59.000Z

34

Flow, Turbulence and Combustion 70: 153181, 2003. 2003 Kluwer Academic Publishers. Printed in the Netherlands.  

E-Print Network (OSTI)

in the Netherlands. 153 On Fokker­Planck Equations for Turbulent Reacting Flows. Part 2. Filter Density Function

Heinz, Stefan

35

Flow, Turbulence and Combustion 70: 115152, 2003. 2003 Kluwer Academic Publishers. Printed in the Netherlands.  

E-Print Network (OSTI)

in the Netherlands. 115 On Fokker-Planck Equations for Turbulent Reacting Flows. Part 1. Probability Density Function

Heinz, Stefan

36

Chemical preconcentrator with integral thermal flow sensor  

DOE Patents (OSTI)

A chemical preconcentrator with integral thermal flow sensor can be used to accurately measure fluid flow rate in a microanalytical system. The thermal flow sensor can be operated in either constant temperature or constant power mode and variants thereof. The chemical preconcentrator with integral thermal flow sensor can be fabricated with the same MEMS technology as the rest of the microanlaytical system. Because of its low heat capacity, low-loss, and small size, the chemical preconcentrator with integral thermal flow sensor is fast and efficient enough to be used in battery-powered, portable microanalytical systems.

Manginell, Ronald P. (Albuquerque, NM); Frye-Mason, Gregory C. (Cedar Crest, NM)

2003-01-01T23:59:59.000Z

37

Subgrid-scale model for the temperature fluctuations in reacting hypersonic turbulent flows  

E-Print Network (OSTI)

Subgrid-scale model for the temperature fluctuations in reacting hypersonic turbulent flows M. Pino fluctuations for use in large-eddy simulations of turbulent, reacting hypersonic flows. The proposed model uses, a greater understand- ing of turbulent hypersonic flows is needed. Direct numerical simulations DNS

Martín, Pino

38

Turbulent flow between counter-rotating concentric cylinders: a ...  

E-Print Network (OSTI)

We report three-dimensional direct numerical simulations of the turbulent flow ... Comparisons between the standard TaylorCouette system (rotating inner cylinder, .... 2004) and implemented using the message passing interface (MPI). ..... (negative peak), ZC0, provides a measure for the characteristic size of the near-wall.

S. DONG

2008-10-13T23:59:59.000Z

39

Turbulent flow of gas in fractures  

E-Print Network (OSTI)

. Permeability for Shale core, 20 - 40 mesh sandals . . ~ . . . ~ . ~ . ~ 39 Concentration of proppants vs. Turbulence factor for Shale core, 10 - 20 mesh sands. ~ ~ . , 40 Concentration of proppants vs. Permeability for Shale cox e, 10 - 20 mesh sands... in Figures g and 4. 10 H J K L M A ~e Steel tubings PlaBtlt! tubitlgi mnnumm Alloy A. Core Sample B. Pressure cell C ~ Flowmeter D. High pressure water reservoir E. Heise guage, 10, 000 psi F. Husks pump G. Hydraulic pump, 40, 000 psi H...

Koh, Wong In

2012-06-07T23:59:59.000Z

40

Cyprinid swimming behaviour in response to turbulent flow  

Science Journals Connector (OSTI)

Turbulence is a complex phenomenon which commonly occurs in river and fishway flows. It is a difficult subject to study, especially biologically, yet turbulence may affect fish movements and fish passage efficiency. Studies on quantifying fish responses to turbulence, particularly within fishways, are lacking. This study investigated the swimming behaviour of 140 adult Iberian barbel (Luciobarbus bocagei) of two size-classes (small fish: 15?TLpool-type fishway: (i) offset orifices, (ii) straight orifices and (iii) straight orifices with a deflector bar of 0.5bo located at 0.2L from the inlet orifices, where bo is the width of the square orifices ranging from 0.18 to 0.23m and L is the pool length (1.90m). Water velocity and turbulence (turbulent kinetic energy, Reynolds shear stress, turbulence intensity and eddy size) were characterized using a 3D Acoustic Doppler Velocimeter (ADV) and were related with fish swimming behaviour. The influence of turbulent flow on the swimming behaviour of barbel was assessed through the number of successful fish passage attempts and associated passage times. The amount of time fish spent in a certain cell of the pool (transit time) was measured and related to hydraulic conditions. The highest rates of passage and the corresponding lowest times were found in experiments conducted with offset orifices. Although size-related behavioural responses to turbulence were observed, Reynolds shear stress appeared as one of the most important turbulence descriptors explaining fish transit time for both size-classes in experiments conducted with offset and straight orifices; furthermore, swimming behaviour of larger fish was found to be strongly affected by the eddies created, in particular by those of similar size to fish total length, which were mainly found in straight orifices with a deflector bar arrangement. The results provide valuable insights on barbel swimming behavioural responses to turbulence, which may help engineers and biologists to develop effective systems for the passage of this species and others with similar biomechanical capacities.

Ana T. Silva; Christos Katopodis; Jos M. Santos; Maria T. Ferreira; Antnio N. Pinheiro

2012-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


41

Scaling bounds on dissipation in turbulent flows  

E-Print Network (OSTI)

We present a new rigorous method for estimating statistical quantities in fluid dynamics such as the (average) energy dissipation rate directly from the equations of motion. The method is tested on shear flow, channel flow, Rayleigh--B\\'enard convection and porous medium convection.

Seis, Christian

2015-01-01T23:59:59.000Z

42

Numerical simulation of buoyant turbulent flow. Final report  

SciTech Connect

Two models have been developed for predicting low Reynolds number turbulent flows in the free and mixed convection regimes. One, the KEM model, is based on the notion of eddy diffusivities for momentum and heat. The other, the ASM model, is based on algebraic relations derived for the anisotropic turbulent fluxes by suitable truncation of the parent transport equations. Both formulations apply to variable property flows with high overheat ratios. A comparison between measurements and predictions for the case of the vertical plate shows that both models yield fairly accurate results for the mean flow and heat transfer. As a result, only the simpler of the two models, the KEM, was used to predict the cavity flows. Predictions for the case of the vertical flat plate show excellent agreement with measurements of mean velocity, temperature and Nusselt number. Nearwall results predicted by both models reveal the existence of a 1/3 power-law dependence. Regions of negative buoyant and shear production of turbulence kinetic energy are clearly revealed by the calculations. Calculations of the cavity configuration were performed for the free and mixed flow conditions. Fairly good agreement is obtained between measurements and predictions of the velocity and temperature fields. Many of the complex characteristics of heated cavity flows, revealed experimentally, are resolved numerically. Although differing in absolute value, calculations of the cavity Nusselt number show trends which are in accord with the measurements. Thus, in the free convection regime it is shown that when the cavity is tilted forwards stable stratification of fluid dampens the turbulence fluctuations which works to reduce heat transfer.

Humphrey, J.A.C.; Sherman, F.S.; To, W.M.

1985-08-01T23:59:59.000Z

43

Simulations of Turbulent Flows with Strong Shocks and Density Variations  

SciTech Connect

In this report, we present the research efforts made by our group at UCLA in the SciDAC project ???¢????????Simulations of turbulent flows with strong shocks and density variations???¢???????. We use shock-fitting methodologies as an alternative to shock-capturing schemes for the problems where a well defined shock is present. In past five years, we have focused on development of high-order shock-fitting Navier-Stokes solvers for perfect gas flow and thermochemical non-equilibrium flow and simulation of shock-turbulence interaction physics for very strong shocks. Such simulation has not been possible before because the limitation of conventional shock capturing methods. The limitation of shock Mach number is removed by using our high-order shock-fitting scheme. With the help of DOE and TeraGrid/XSEDE super computing resources, we have obtained new results which show new trends of turbulence statistics behind the shock which were not known before. Moreover, we are also developing tools to consider multi-species non-equilibrium flows. The main results are in three areas: (1) development of high-order shock-fitting scheme for perfect gas flow, (2) Direct Numerical Simulation (DNS) of interaction of realistic turbulence with moderate to very strong shocks using super computing resources, and (3) development and implementation of models for computation of mutli-species non-quilibrium flows with shock-fitting codes.

Zhong, Xiaolin

2012-12-13T23:59:59.000Z

44

Neoclassical generation of toroidal zonal flow by drift wave turbulence  

SciTech Connect

Zonal-flow instabilities due to drift-wave turbulence in the presence of toroidicity-induced parallel (neoclassical) viscosity and allowing for the toroidal flow are studied. It is shown that, as a result of the neoclassical viscosity a new type of zonal-flow instability is possible, leading to the generation of the considerable toroidal zonal flow. The toroidal instability is complementary to the previously studied instability resulting in the poloidal flow generation and occurs as a second branch of the general dispersion relation describing the evolution of the poloidal and toroidal flow. Nonlinear saturation of the new instability is studied. It is shown that saturated zonal toroidal velocity, generated in this instability, is large compared to the mean cross-field drift velocity as the ratio q/{epsilon}, where q is the safety factor and {epsilon} is the inverse aspect ratio. In addition to the broad turbulent spectrum of drift waves, a monochromatic wave packet is considered. It is revealed that for the case of sufficiently strong neoclassical viscosity such a wave packet is subjected to generation of the toroidal zonal flow due to instability of hydrodynamic type.

Mikhailovskii, A.B.; Smolyakov, A.I.; Tsypin, V.S.; Kovalishen, E.A.; Shirokov, M.S.; Galvao, R.M.O. [Institute of Nuclear Fusion, Russian Research Centre Kurchatov Institute, Kurchatov Sq., 1, Moscow 123182 (Russian Federation) and Nonlinear Physics Laboratory, Moscow Institute of Physics and Technology, Institutskii per. 9, Dolgoprudnyi 141700, Moscow Region (Russian Federation); University of Saskatchewan, 116 Science place, Saskatoon S7N 5E2 (Canada) and Institute of Nuclear Fusion, Russian Research Centre Kurchatov Institute, Kurchatov Sq., 1, Moscow 123182 (Russian Federation); Physics Institute, University of Sao Paulo, Cidade Universitaria, 05508-900, Sao Paulo (Brazil); Nonlinear Physics Laboratory, Moscow Institute of Physics and Technology, Institutskii per. 9, Dolgoprudnyi 141700, Moscow Region (Russian Federation) and Institute of Nuclear Fusion, Russian Research Centre Kurchatov Institute, Kurchatov Sq., 1, Moscow 123182 (Russian Federation); Institute of Nuclear Fusion, Russian Research Centre Kurchatov Institute, Kurchatov Sq., 1, Moscow 123182 (Russian Federation) and Moscow Engineering Physics Institute, Kashirskoe Shosse 31, Moscow 115409 (Russian Federation); Physics Institute, University of Sao Paulo, Cidade Universitaria, 05508-900, Sao Paulo (Brazil) and Brazilian Center for Research in Physics, Rua Xavier Sigaud, 150, 22290-180, Rio de Janeiro (Brazil)

2006-03-15T23:59:59.000Z

45

MEASUREMENTS AND COMPUTATIONS OF FUEL DROPLET TRANSPORT IN TURBULENT FLOWS  

SciTech Connect

The objective of this project is to study the dynamics of fuel droplets in turbulent water flows. The results are essential for development of models capable of predicting the dispersion of slightly light/heavy droplets in isotropic turbulence. Since we presently do not have any experimental data on turbulent diffusion of droplets, existing mixing models have no physical foundations. Such fundamental knowledge is essential for understanding/modeling the environmental problems associated with water-fuel mixing, and/or industrial processes involving mixing of immiscible fluids. The project has had experimental and numerical components: 1. The experimental part of the project has had two components. The first involves measurements of the lift and drag forces acting on a droplet being entrained by a vortex. The experiments and data analysis associated with this phase are still in progress, and the facility, constructed specifically for this project is described in Section 3. In the second and main part, measurements of fuel droplet dispersion rates have been performed in a special facility with controlled isotropic turbulence. As discussed in detail in Section 2, quantifying and modeling the of droplet dispersion rate requires measurements of their three dimensional trajectories in turbulent flows. To obtain the required data, we have introduced a new technique - high-speed, digital Holographic Particle Image Velocimetry (HPIV). The technique, experimental setup and results are presented in Section 2. Further information is available in Gopalan et al. (2005, 2006). 2. The objectives of the numerical part are: (1) to develop a computational code that combines DNS of isotropic turbulence with Lagrangian tracking of particles based on integration of a dynamical equation of motion that accounts for pressure, added mass, lift and drag forces, (2) to perform extensive computations of both buoyant (bubbles) and slightly buoyant (droplets) particles in turbulence conditions relevant to the experiments, and (3) to explore whether the corresponding predictions can explain the experimentally-observed behavior of the rise and dispersion of oil droplets in isotropic turbulence. A brief summary of results is presented in Section 4.

Joseph Katz and Omar Knio

2007-01-10T23:59:59.000Z

46

Subcritical turbulent transition in rotating and curved shear flows  

E-Print Network (OSTI)

The effects of global flow rotation and curvature on the subcritical transition to turbulence in shear flows are examined. The relevant time-scales of the problem are identified by a decomposition of the flow into a laminar and a deviation from laminar parts, which is performed for rotating plane Couette and Taylor-Couette flows. The usefulness and relevance of this procedure are discussed at the same time. By comparing the self-sustaining process time-scale to the time-scales previously identified, an interpretation is brought to light for the behavior of the transition Reynolds number with the rotation number and relative gap width in the whole neighborhood (in parameter space) of the non-rotating plane Couette flow covered by the available data.

P-Y. Longaretti; O. Dauchot

2005-09-19T23:59:59.000Z

47

Inertial particle resuspension in a turbulent, square duct flow  

Science Journals Connector (OSTI)

Particle resuspension in a turbulent square duct flow is studied using large eddy simulation combined with Lagrangian particle tracking under conditions of one-way coupling with the particle equation of motion solved with the Stokes drag lift buoyancy and gravitational force terms. Here resuspension is taken to mean the movement of particles in close proximity to the duct walls back in to the mainstream of the flow. The flow considered has a bulk Re = 250 ? k with four particle sizes ranging from 5 to 500 ? ? m examined. The results demonstrate that turbulence-driven secondary flows within the duct play an important role in the resuspension process. In the vertical direction resuspension is promoted by the drag force arising from the secondary flows which is balanced by the gravitational force with this effect increasing with decreasing particle size. In the horizontal direction particle resuspension is promoted by the particles inertial force with this effect increasing with increasing particle size. For resuspension in both directions the drag force dominates small particle resuspension while for large particles the lift force is also a contributing factor. In the horizontal direction the effect of the lift force varies with the direction of the secondary flow and becomes more significant when a particle is large or close to the duct wall. The influence of the lift force is also larger in the vertical than in the horizontal direction due to the effects of gravity.

J. Yao; M. Fairweather

2010-01-01T23:59:59.000Z

48

Decay of swirl in turbulent two phase flow  

E-Print Network (OSTI)

decrease in Reynolds number. Also, it was found that within experimental accuracy the decay was independent of initial swirl intensity. Their theoretical analysis of swirl decay characteristics in turbulent flow and the experiments conducted were... concentrations of the Polyox were put into the water in a uniform procedure in order to obtain consist. ent results. A venturi mixer was designed and used to di perse the polymer particles into the water in the mixing tank. The vigorous stir- ring bv the jet...

Neeley, Patrick Foster

2012-06-07T23:59:59.000Z

49

Cryogenic heat exchanger with turbulent flows  

Science Journals Connector (OSTI)

An evaporator-type cryogenic heat exchanger is designed and built for introducing fluidsolid heat exchange phenomena to undergraduates in a practical and efficient way. The heat exchanger functions at liquid nitrogen temperature and enables cooling of N2and He gases from room temperatures. We present first the experimental results of various parameters which characterize the heat exchanger (efficiency, number of transfer units, heat exchange coefficient, etc) as a function of the mass flow rate of the gas to be cooled. An analysis of the NuRe diagram is also presented. All experiments were conducted with N2gas. The scope of this tool is readily extended to research purposes.

Jay Amrit; Christelle Douay; Francis Dubois; Grard Defresne

2012-01-01T23:59:59.000Z

50

Solid particle deposition during turbulent flow production operations  

SciTech Connect

The production and transportation of petroleum fluids could be severely affected by deposition of suspended particles (i.e., asphaltene, paraffin/wax, sand, and/or diamondoid) in the production wells and/or transfer pipelines. In many instances the amount of precipitation is rather large causing complete plugging of these conduits. Therefore, it is important to understand the behavior of suspended particles during flow conditions. In this paper the authors present an analysis of the diffusional effects on the rate of solid particle deposition during turbulent flow conditions (crude oil production generally falls within this regime). The turbulent boundary layer theory and the concepts of mass transfer have been utilized to calculate the particle deposition rates on the walls of the flowing conduit. The developed model accounts for the eddy and Brownian diffusivities as well as for inertial effects. The analysis presented in this paper shows that rates of solid-particle deposition (during crude oil production) on the walls of the flowing channel due solely to diffusional effects are small. It is also shown that deposition rates decrease with increasing particle size. However, when the process is momentum controlled (large particle sizes) higher deposition rates are expected.

Escobedo, J.; Mansoori, G.A. [Univ. of Illinois, Chicago, IL (United States)

1995-12-31T23:59:59.000Z

51

Coherent structures in ion temperature gradient turbulence-zonal flow  

SciTech Connect

Nonlinear stationary structure formation in the coupled ion temperature gradient (ITG)-zonal flow system is investigated. The ITG turbulence is described by a wave-kinetic equation for the action density of the ITG mode, and the longer scale zonal mode is described by a dynamic equation for the m?=?n?=?0 component of the potential. Two populations of trapped and untrapped drift wave trajectories are shown to exist in a moving frame of reference. This novel effect leads to the formation of nonlinear stationary structures. It is shown that the ITG turbulence can self-consistently sustain coherent, radially propagating modulation envelope structures such as solitons, shocks, and nonlinear wave trains.

Singh, Rameswar, E-mail: rameswar.singh@lpp.polytechnique.fr [Laboratoire de Physique des Plasmas, Ecole Polytechnique, Route de Saclay, 91128 Palaiseau Cedex (France); Institute for Plasma Research, Bhat, Gandhinagar 382 428 (India); Singh, R. [Institute for Plasma Research, Bhat, Gandhinagar 382 428 (India); WCI Center for Fusion Theory, National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of); Kaw, P. [Institute for Plasma Research, Bhat, Gandhinagar 382 428 (India); Grcan, . D. [Laboratoire de Physique des Plasmas, Ecole Polytechnique, Route de Saclay, 91128 Palaiseau Cedex (France); Diamond, P. H. [WCI Center for Fusion Theory, National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of); CMTFO and CASS, University of California, San Diego, California 92093 (United States)

2014-10-15T23:59:59.000Z

52

FliHy experimental facilities for studying open channel turbulent flows and heat transfer  

E-Print Network (OSTI)

FliHy experimental facilities for studying open channel turbulent flows and heat transfer B. Freeze) facility was constructed at UCLA to study open channel turbulent flow and heat transfer of low supercritical flow regimes (Fr /1), in which the surface waves are amplified and heat transfer is enhanced due

Abdou, Mohamed

53

Progress in Simulating Turbulent Electron Thermal Transport in NSTX  

SciTech Connect

Nonlinear simulations based on multiple NSTX discharge scenarios have progressed to help differentiate unique instability mechanisms and to validate with experimental turbulence and transport data. First nonlinear gyrokinetic simulations of microtearing (MT) turbulence in a high-beta NSTX H-mode discharge predict experimental levels of electron thermal transport that are dominated by magnetic flutter and increase with collisionality, roughly consistent with energy confinement times in dimensionless collisionality scaling experiments. Electron temperature gradient (ETG) simulations predict significant electron thermal transport in some low and high beta discharges when ion scales are suppressed by E x B shear. Although the predicted transport in H-modes is insensitive to variation in collisionality (inconsistent with confinement scaling), it is sensitive to variations in other parameters, particularly density gradient stabilization. In reversed shear (RS) Lmode discharges that exhibit electron internal transport barriers, ETG transport has also been shown to be suppressed nonlinearly by strong negative magnetic shear, s<<0. In many high beta plasmas, instabilities which exhibit a stiff beta dependence characteristic of kinetic ballooning modes (KBM) are sometimes found in the core region. However, they do not have a distinct finite beta threshold, instead transitioning gradually to a trapped electron mode (TEM) as beta is reduced to zero. Nonlinear simulations of this "hybrid" TEM/KBM predict significant transport in all channels, with substantial contributions from compressional magnetic perturbations. As multiple instabilities are often unstable simultaneously in the same plasma discharge, even on the same flux surface, unique parametric dependencies are discussed which may be useful for distinguishing the different mechanisms experimentally.

Guttenfelder, Walter; Kaye, S. M.; Ren, Y.; Bell, R. E.; Hammett, G. W.; LeBlanc, B. P.; Mikkelsen, D. R. [Princeton Plasma Physics Lab., Princeton, NJ (United States); Peterson, J. L.; Nevins, W. M. [Lawrence Livermore National Lab., Livermore, CA (United States); Candy, J. [General Atomics, San Diego, CA (United States); Yuh, H. [Nova Photonics, Princeton, NJ (United States)

2013-07-17T23:59:59.000Z

54

Friction factor for turbulent flow in rough pipes from Heisenberg's closure hypothesis  

E-Print Network (OSTI)

We show that the main results of the analysis of the friction factor for turbulent pipe flow reported in G. Gioia and P. Chakraborty (GC), Phys. Rev. Lett. 96, 044502 (1996) can be recovered by assuming the Heisenberg closure hypothesis for the turbulent spectrum. This highlights the structural features of the turbulent spectrum underlying GC's analysis.

Esteban Calzetta

2009-01-02T23:59:59.000Z

55

Convective stability of turbulent Boussinesq flow in the dissipative range and flow around small particles  

E-Print Network (OSTI)

We consider arbitrary, possibly turbulent, Boussinesq flow which is smooth below a dissipative scale $l_d$. It is demonstrated that the stability of the flow with respect to growth of fluctuations with scale smaller than $l_d$ leads to a non-trivial constraint. That involves the dimensionless strength $Fl$ of fluctuations of the gradients of the scalar in the direction of gravity and the Rayleigh scale $L$ depending on the Rayleigh number $Ra$, the Nusselt number $Nu$ and $l_d$. The constraint implies that the stratified fluid at rest, which is linearly stable, develops instability in the limit of large $Ra$. This limits observability of solution for the flow around small swimmer in quiescent stratified fluid that has closed streamlines at scale $L$ [A. M. Ardekani and R. Stocker, Phys. Rev. Lett. 105, 084502 (2010)]. Correspondingly to study the flow at scale $L$ one has to take turbulence into account. We demonstrate that the resulting turbulent flow around small particles or swimmers can be described by scalar integro-differential advection-diffusion equation. Describing the solutions we show that closed streamlines persist with finite probability. Our results seem to be the necessary basis in understanding flows around small swimmers.

Itzhak Fouxon; Alexander Leshansky

2014-07-24T23:59:59.000Z

56

Flame-wall interaction simulation in a turbulent channel flow  

SciTech Connect

The interaction between turbulent premixed flames and channel walls is studied. Combustion is represented by a simple irreversible reaction with a large activation temperature. A low heat release assumption is used, but feedback to the flowfield can be allowed through viscosity changes. The effect of wall distance on local and global flame structure is investigated. Quenching distances and maximum wall heat fluxed computed in laminar cases are compared to DNS results. It is found that quenching distances decrease and maximum heat fluxes increase relative to laminar flame values, scaling with the turbulent strain rate. It is shown that these effects are due to large coherent structures which push flame elements towards the wall. The effect of wall strain in flame-wall interaction is studied in a stagnation line flow; this is used to explain the DNS results. The effects of the flame on the flow through viscosity changes is studied. It is also shown that remarkable flame events are produced by flame interaction with a horseshoe vortex: burned gases are pushed towards the wall at high speed and induce quenching and high wall heat flux while fresh gases are expelled from the wall region and form finger-like structures. Effects of the wall on flame surface density are investigated.

Bruneaux, G.; Akselvoll, K.; Poinsot, T.; Ferziger, J.H.

1996-10-01T23:59:59.000Z

57

Single particle resuspension experiments in turbulent channel flows  

Science Journals Connector (OSTI)

Abstract The resuspension of a monolayer of spherical glass and polypropylene particles from a channel floor by a dry and turbulent airflow was investigated. Special attention was given to the influence of the particle size, the particle and wall material, the wall surface roughness and the critical friction velocity. The experiments were performed in an air-driven small-scale test facility and the channel floor was made of interchangeable glass and steel wall segments. The turbulent channel flow was recorded using a planar Particle Image Velocimetry system. Prior to the experiments the spherical particles were classified using Scanning Electron Microscopy techniques. The particles on the channel floor were detected and classified by means of an optical microscope combined with a digital camera. A statistically sufficient particle monolayer was generated on the channel floor by dispersing the particles into the flow during a pure deposition regime. Afterwards, particle resuspension was induced by stepwise increase of the fluid velocity. The resuspension was quantified by the fraction of remaining particles against the friction velocity for a particle diameter range between 3m and 45m. It was found that particles instantly resuspend once a critical friction velocity is exceeded. Larger particles require lower fluid velocities for the removal than smaller particles. The wall surface roughness seems to scatter the resuspension process with respect to the friction velocity.

T. Barth; J. Preu; G. Mller; U. Hampel

2014-01-01T23:59:59.000Z

58

Heat Transfer at Low Temperatures between Tube Walls and Gases in Turbulent Flow  

Science Journals Connector (OSTI)

...September 1947 research-article Heat Transfer at Low Temperatures between Tube...counter-flow system to study heat transfer between tube walls and gases at...Determinations on friction accompanying heat transfer with gases in turbulent flow at...

1947-01-01T23:59:59.000Z

59

Convective stability of turbulent Boussinesq flow in the dissipative range and flow around small particles  

E-Print Network (OSTI)

We consider arbitrary, possibly turbulent, Boussinesq flow which is smooth below a dissipative scale $l_d$. It is demonstrated that the stability of the flow with respect to growth of fluctuations with scale smaller than $l_d$ leads to a non-trivial constraint. That involves the dimensionless strength $Fl$ of fluctuations of the gradients of the scalar in the direction of gravity and the Rayleigh scale $L$ depending on the Rayleigh number $Ra$, the Nusselt number $Nu$ and $l_d$. The constraint implies that the stratified fluid at rest, which is linearly stable, develops instability in the limit of large $Ra$. This limits observability of solution for the flow around small swimmer in quiescent stratified fluid that has closed streamlines at scale $L$ [A. M. Ardekani and R. Stocker, Phys. Rev. Lett. 105, 084502 (2010)]. Correspondingly to study the flow at scale $L$ one has to take turbulence into account. We demonstrate that the resulting turbulent flow around small particles or swimmers can be described by sc...

Fouxon, Itzhak

2014-01-01T23:59:59.000Z

60

Gyrokinetic and Gyrofluid Models for Zonal Flow Dynamics in Ion and Electron Temperature Gradient Turbulence  

SciTech Connect

Collisionless time evolution of zonal flows in ion and electron temperature gradient turbulence in toroidal plasmas is investigated. The responses of the zonal-flow potential to the initial perturbation and to the turbulence source are determined from the gyrokinetic equations combined with the Poisson equation, A novel gyrofluid model is presented, which properly describes the zonal-flow time evolution and reproduces the same residual zonal-flow levels as predicted by the gyrokinetic model.

Sugama, H.; Watanabe, T.-H. [National Institute for Fusion Science, Toki, Gifu, 509-5292 (Japan); Graduate University for Advanced Studies, Toki, Gifu, 509-5292 (Japan); Ferrando i Margalet, S. [National Institute for Fusion Science, Toki, Gifu, 509-5292 (Japan)

2006-11-30T23:59:59.000Z

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


61

Turbulence effects on the wake flow and power production of a horizontal-axis wind turbine  

Science Journals Connector (OSTI)

Abstract This study experimentally investigated the effects of ambient turbulence on the wake flows and power production of a horizontal-axis wind turbine. The approaching flows included low-turbulence smooth flow and grid-generated turbulent flow. The profiles of time-averaged velocity, turbulence intensity and Reynolds stress from the intermediate to the far-wake regions were measured and compared for smooth and turbulent flows. Based on the measured data, prediction models for the centerline velocity deficit, turbulence intensity, wake radius and velocity profile were proposed. In addition, the experimental results showed that the power productions in the grid-generated turbulent flows were slightly higher than that in the smooth flow. But the power loss due to the velocity deficit in the wake flow was larger than 50% when the downwind distance was less than 12D (D is the rotor diameter). An empirical relation between the power production and the downwind distance x and lateral distance y was proposed.

Chia-Ren Chu; Pei-Hung Chiang

2014-01-01T23:59:59.000Z

62

Experimental study of vortex generators effects on low Reynolds number airfoils in turbulent flow  

Science Journals Connector (OSTI)

In the present work, we study the aerodynamic effects of triangular vortex generators, as passive flow control devices, placed on the upper surface of an airfoil submitted to a low Reynolds number turbulent flow. In the experiments, different configurations of those devices have been studied. An Eppler 387 airfoil was used. The tests were performed in a turbulent boundary layer wind tunnel using a two component aerodynamic balance and flow visualisation systems. Turbulent flow characterisation was made by means of hot wire anemometry. Calculations of local turbulent intensity as well as temporal and spatial turbulent scales were made. Vortex generators were located at 10% and 20% of the airfoil chord from the leading edge, modifying its angle of incidence refereed to the free stream. The results show changes in the aerodynamic section coefficients, C1, Cd and C1, for the different vortex generator configurations. Neither hysteresis effects, nor leading edge bubbles were found in the experiments.

Juan Sebastián Delnero; Julio Marañon Di Leo; Mauricio Ezequiel Camocardi; Mariano A. Martinez; Jorge L. Colman Lerner

2012-01-01T23:59:59.000Z

63

Turbulence prediction in two- and three-dimensional bundle flows using Large Eddy Simulation  

E-Print Network (OSTI)

TURBULENCE PREDICTION IN TWO- AND THREE-DIMENSIONAL BUNDLE FLOWS USING LARGE EDDY SIMULATION A Thesis by WAEL ABDUL-HAMID IBRAHIM Submitted to Texas A&M University in partial fulfillment of the requirements for the degree of MASTER... Prediction in Two- and Three-Dimensional Bundle Flows Using Large Eddy Simulation. (May 1994) Wael Abdul-Hamid Ibrahim, B. S. Alexandria University Chair of Advisory Committee: Dr. Yassin A. Hassan Flow turbulence is a familiar phenomenon in everyday life...

Ibrahim, Wael Abdul-Hamid

1994-01-01T23:59:59.000Z

64

Drag, turbulence, and diffusion in flow through emergent vegetation  

E-Print Network (OSTI)

Aquatic plants convert mean kinetic energy into turbulent kinetic energy at the scale of the plant stems and branches. This energy transfer, linked to wake generation, affects vegetative drag and turbulence intensity. ...

Nepf, Heidi

65

On the validation of magnetic resonance velocimetry in single-phase turbulent pipe flows  

SciTech Connect

A nuclear magnetic resonance imaging technique is used to measure velocity distributions in turbulent pipe flows up to Re = 24580. While turbulent intensity is usually determined from signal attenuation, we deduce turbulent intensity from velocity distribution with no need to suppose a Gaussian distribution for velocity fluctuations. Skewness and flatness measurements are also presented in this paper. Comparison with DNS show good agreement and we show that NMR data is sufficiently accurate to provide turbulent viscosity profile. The low field system used in this study allow the suppression of susceptibility artifacts and thus open its use for studying two-phase flows. We postulate that the method used here could be applied to two-phase flows and would thus provide valuable information on turbulent viscosity models. (authors)

Jullien, P.; Lemonnier, H. [CEA Grenoble, DTN LITA SE2T, F-38054 Grenoble 9, (France)

2012-03-15T23:59:59.000Z

66

EXPERIMENTAL INVESTIGATION OF TURBULENT HEAT TRANSFER OF HIGH PRANDTL NUMBER FLUID FLOW UNDER STRONG MAGNETIC FIELD  

E-Print Network (OSTI)

EXPERIMENTAL INVESTIGATION OF TURBULENT HEAT TRANSFER OF HIGH PRANDTL NUMBER FLUID FLOW UNDER to the heat transfer characteristic: Flibe is a high Prandtl number fluid. For high Prandtl number fluid, there is a severe limitation of temperature window due to its high melting point. The turbulent heat transfer is

Abdou, Mohamed

67

IMECE2009-13258 SIMULATION OF OPEN CHANNEL TURBULENT FLOW OVER BRIDGE  

E-Print Network (OSTI)

surface above channel bed * h - Inundation ratio k m2 /s2 Turbulence kinetic energy bridgeL m LengthIMECE2009-13258 SIMULATION OF OPEN CHANNEL TURBULENT FLOW OVER BRIDGE DECKS AND FORMATION OF SCOUR HOLE BENEATH THE BRIDGE UNDER FLOODING CONDITIONS Bishwadipa Adhikary, Pradip Majumdar, and Milivoje

Kostic, Milivoje M.

68

Turbulent models of ice giant internal dynamics: Dynamos, heat transfer, and zonal flows  

E-Print Network (OSTI)

Turbulent models of ice giant internal dynamics: Dynamos, heat transfer, and zonal flows K Magnetic fields a b s t r a c t The ice giant planets, Uranus and Neptune, have magnetic fields to yield small-scale and disorganized turbulence. In agreement with ice giant observations, both

69

Development of Interfacial Structure in a Confined Air-Water Cap-Turbulent and Churn-Turbulent Flow  

SciTech Connect

The objective of the present work is to study and model the interfacial structure development of air-water two-phase flow in a confined test section. Experiments of a total of 9 flow conditions in cap-turbulent and churn-turbulent flow regimes are carried out in a vertical air-water upward two-phase flow experimental loop with a test section of 200-mm in width and 10-mm in gap. Miniaturized four-sensor conductivity probes are used to measure local two-phase parameters at three different elevations for each flow condition. The bubbles captured by the probes are categorized into two groups in view of the two-group interfacial area transport equation, i.e., spherical/distorted bubbles as Group 1 and cap/churn-turbulent bubbles as Group 2. The acquired parameters are time-averaged local void fraction, interfacial velocity, bubble number frequency, interfacial area concentration, and bubble Sauter mean diameter for both groups of bubbles. Also, the line-averaged and area-averaged data are presented and discussed. The comparisons of these parameters at different elevations demonstrate the development of interfacial structure along the flow direction due to bubble interactions. (authors)

Xiaodong Sun; Seungjin Kim; Ling Cheng; Mamoru Ishii [Purdue University, West Lafayette, IN 47907 (United States); Beus, Stephen G. [Bechtel Bettis, Inc., Bettis Atomic Power Laboratory, Post Office Box 79, West Mifflin, PA 15122-0079 (United States)

2002-07-01T23:59:59.000Z

70

High resolution numerical study of Rayleigh-Taylor turbulence using a thermal lattice Boltzmann scheme  

E-Print Network (OSTI)

We present results of a high resolution numerical study of two dimensional (2d) Rayleigh-Taylor turbulence using a recently proposed thermal lattice Boltzmann method (LBT). The goal of our study is both methodological and physical. We assess merits and limitations concerning small- and large-scale resolution/accuracy of the adopted integration scheme. We discuss quantitatively the requirements needed to keep the method stable and precise enough to simulate stratified and unstratified flows driven by thermal active fluctuations at high Rayleigh and high Reynolds numbers. We present data with spatial resolution up to 4096 x 10000 grid points and Rayleigh number up to Ra ~ 10^11 . The statistical quality of the data allows us to investigate velocity and temperature fluctuations, scale-by-scale, over roughly four decades. We present a detailed quantitative analysis of scaling laws in the viscous, inertial and integral range, supporting the existence of a Bolgiano-like inertial scaling, as expected in 2d systems. We also discuss the presence of small/large intermittent deviation to the scaling of velocity/temperature fluctuations and the Rayleigh dependency of gradients flatness.

L. Biferale; F. Mantovani; M. Sbragaglia; A. Scagliarini; F. Toschi; R. Tripiccione

2010-09-28T23:59:59.000Z

71

Simulation of Turbulent Flow Inside and Above Wind Farms: Model Validation and Layout Effects  

Science Journals Connector (OSTI)

A recently-developed large-eddy simulation framework is validated and used to investigate turbulent flow within and above wind farms under neutral conditions. Two different layouts are considered, consisting of t...

Yu-Ting Wu; Fernando Port-Agel

2013-02-01T23:59:59.000Z

72

Quantitative visualization of compressible turbulent shear flows using condensate-enhanced Rayleigh scattering  

E-Print Network (OSTI)

was based on laser scattering from particles of H2O or CO2 condensate that form in the wind tunnel nozzleQuantitative visualization of compressible turbulent shear flows using condensate-enhanced Rayleigh

Miles, Richard

73

Efficient Parallel Implementation of a Hybrid Finite-Volume/Particle Method for the PDF Equations of Turbulent Reactive Flows  

E-Print Network (OSTI)

combustion engines, gas turbines, furnaces etc. The computational modelling of turbulent reacting flows pollutant emissions, reduce design costs and development times. However, turbulent combustion remains one strategies: multiple independent simulations, particle partitioning and mesh work partitioning are described

74

Implications of turbulence interactions: A path toward addressing very high Reynolds number flows  

SciTech Connect

The classical 'turbulence problem' is narrowed down and redefined for scientific and engineering applications. From an application perspective, accurate computation of large-scale transport of the turbulent flows is needed. In this paper, a scaling analysis that allows for the large-scales of very high Reynolds number turbulent flows - to be handled by the available supercomputers is proposed. Current understanding of turbulence interactions of incompressible turbulence, which forms the foundation of our argument, is reviewed. Furthermore, the data redundancy in the inertial range is demonstrated. Two distinctive interactions, namely, the distance and near-grid interactions, are inspected for large-scale simulations. The distant interactions in the subgrid scales in an inertial range can be effectively modelled by an eddy damping. The near-grid interactions must be carefully incorporated.

Zhou, Y

2006-05-15T23:59:59.000Z

75

Fine-Scale Zonal Flow Suppression of Electron Temperature Gradient Turbulence  

SciTech Connect

It is found in collisionless Electron Temperature Gradient (ETG) turbulence simulations that, while zonal flows are weak at early times, the zonal flows continue to grow algebraically (proportional to time). These fine-scale zonal flows have a radial wave number such that kr{rho}i > 1 and kr{rho}e < 1. Eventually, the zonal flows grow to a level that suppresses the turbulence due to ExB shearing. The final electron energy flux is found to be relatively low. These conclusions are based on particle convergence studies with adiabatic ion electrostatic flux-tube gyrokinetic {delta}f particle simulations run for long times. The Rosenbluth-Hinton random walk mechanism is given as an explanation for the long time build up of the zonal flow in ETG turbulence and it is shown that the generation is (k perpendicular {rho}e)2 smaller than for isomorphic Ion Temperature Gradient (ITG) problem. This mechanism for zonal flow generation here is different than the modulational instability mechanism for ITG turbulence. These results are important because previous results indicated zonal flows were unimportant for ETG turbulence. Weak collisional damping of the zonal flow is also shown to be a n important effect.

Parker, S. E.; Kohut, J. J.; Chen, Y. [Center for Integrated Plasma Studies, University of Colorado, Boulder, C0 (United States); Lin, Z. [University of Californian, Irvine, CA (United States); Hinton, F. L. [Hinton Associates, Escondido, CA (United States); Lee, W. W. [Princeton Plasma Physics Laboratory, Princeton, NJ (United States)

2006-11-30T23:59:59.000Z

76

SYMPOSIUM ON TURBULENCE AND COMBUSTION - SPECIAL SYMPOSIUM TO BRING TOGETHER TOP RESEARCHERS IN THE FIELDS OF FLUID TURBULENCE AND COMBUSTION TO PROMOTE ADVANCES IN TURBULENT, REACTING FLOWS  

SciTech Connect

A Symposium on Turbulence and Combustion was held at Cornell University on August 3-4, 2009. The overall goal of the Symposium was to promote future advances in the study of turbulence and combustion, through an unique forum intended to foster interactions between leading members of these two research communities. The Symposium program consisted of twelve invited lectures given by world-class experts in these fields, two poster sessions consisting of nearly 50 presentations, an open forum, and other informal activities designed to foster discussion. Topics covered in the lectures included turbulent dispersion, wall-bounded flows, mixing, finite-rate chemistry, and others, using experiment, modeling, and computations, and included perspectives from an international community of leading researchers from academia, national laboratories, and industry.

Caughey, David

2010-10-08T23:59:59.000Z

77

Magnetohydrodynamic lattice Boltzmann simulations of turbulence and rectangular jet flow  

E-Print Network (OSTI)

relaxation time (SRT) parameter for the Maxwells stress tensor is developed for this study. In the MHD homogeneous turbulence studies, the kinetic/magnetic energy and enstrophy decays, kinetic enstrophy evolution, and vorticity alignment with the strain...

Riley, Benjamin Matthew

2009-05-15T23:59:59.000Z

78

Solutions of turbulent backward-facing step flow with heat transfer using the finite volume method  

SciTech Connect

The heated turbulent flow over a backward-facing step is numerically solved using the commercial computational fluid dynamics program FLUENT. The methods used here consist of the default power-law upwinding scheme, default multigrid equation solution method and a standard k-{var_epsilon} turbulence model with wall functions. A total of four separate cases are reported. The four cases consist of combinations of partially and fully developed flow at the inlet with uniform or developed temperature profiles. Three mesh refinements are reported for each flow.

Horstman, R.H. [Boeing Commercial Airplane, Seattle, WA (United States). Environmental Control Systems R& D; Cochran, R.J. [Sandia National Labs., Albuquerque, NM (United States); Emergy, A.F. [Univ. of Washington, Seattle, WA (United States). Dept. of Mechanical Engineering

1995-12-31T23:59:59.000Z

79

Experimental study of turbulent unconfined groundwater flow in a single fracture  

E-Print Network (OSTI)

Experimental study of turbulent unconfined groundwater flow in a single fracture Jiazhong Qiana groundwater flow in a single fracture under the conditions of different surface roughness and apertures. We found that the gradient of the Reynolds number versus the average velocity in a single fracture

Zhan, Hongbin

80

A phenomenological model to describe turbulent friction in permeable-wall flows  

E-Print Network (OSTI)

A phenomenological model to describe turbulent friction in permeable-wall flows C. Manes,1 L impermeable rough boundaries. A novel phenomenological model that describes such anomalous behavior), A phenomenological model to describe tur- bulent friction in permeable-wall flows, Geophys. Res. Lett., 39, L14403

Katul, Gabriel

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


81

Current trends in modelling research for turbulent aerodynamic flows  

Science Journals Connector (OSTI)

...specific heats (c p/c v) and R is the gas constant. The presence of the turbulent...over and downstream of airfoils, wings, turbine blades or aerodynamic bodies. It is necessary...Navier-Stokes equations: properties of the residual stress. Phys. Fluids. 15, 2127-2140...

2007-01-01T23:59:59.000Z

82

Current trends in modelling research for turbulent aerodynamic flows  

Science Journals Connector (OSTI)

...standpoint in RANS model development, the task is to characterize...motivation behind the development of turbulent closure...wing-body junctions or turbine blades where separation...c v) and R is the gas constant. The presence...equations. 3. Closure strategies for RANS The closure...

2007-01-01T23:59:59.000Z

83

Computational analysis of incompressible turbulent flow in an idealised swirl combustor  

Science Journals Connector (OSTI)

Isothermal turbulent swirling flow in a water test rig, representing an idealised swirl combustor, has been investigated experimentally and numerically. The Reynolds number based on combustor inlet diameter and mean axial velocity was 4600. Two cases were investigated at two different swirl intensities. Time-averaged velocities and RMS turbulence intensities were measured by Laser Doppler Anemometer (LDA), along radial traverses at different axial stations. In the three-dimensional, transient computations, Large Eddy Simulations (LES) and URANS Reynolds Stress Models (RSM) have basically been employed as modelling strategies for turbulence. To model subgrid-scale (SGS) turbulence for LES, the models owing to Smagorinsky and Voke were used. In one of the cases, Detached Eddy Simulations (DES) were also applied. The predictions have been compared with the measurements. It has been observed that LES provides the best overall accuracy, where no significant differences between the Smagorinsky and Voke models could be discerned.

A.C. Benim; M.P. Escudier; A. Nahavandi; A.K. Nickson; K.J. Syed; F. Joos

2011-01-01T23:59:59.000Z

84

Coherent Structures in Turbulent Flows: Experimental Studies on the Turbulence of Multiphase Plumes and Tidal Vortices  

E-Print Network (OSTI)

Akker 1999), and ocean CO2 sequestration (Adams and Wannamaker 2005; Adams and Wannamaker 2006). In particular, ocean CO2 sequestration has been noted by the Intergovernmental Panel on Climate Change in its 2005 special report on Carbon Dioxide... for direct carbon sequestration in the oceans have been considered as a means to mitigate the effects on global warming of burning fossil fuels. While the concept of CO2 sequestration is promising, the turbulent structures in multiphase plumes...

Bryant, Duncan Burnette

2011-08-08T23:59:59.000Z

85

Turbulent Flow Effects on the Biological Performance of Hydro-Turbines  

SciTech Connect

The hydro-turbine industry uses Computational Fluid Dynamics (CFD) tools to predict the flow conditions as part of the design process for new and rehabilitated turbine units. Typically the hydraulic design process uses steady-state simulations based on Reynolds-Averaged Navier-Stokes (RANS) formulations for turbulence modeling because these methods are computationally efficient and work well to predict averaged hydraulic performance, e.g. power output, efficiency, etc. However, in view of the increasing emphasis on environmental concerns, such as fish passage, the consideration of the biological performance of hydro-turbines is also required in addition to hydraulic performance. This leads to the need to assess whether more realistic simulations of the turbine hydraulic environment ?those that resolve unsteady turbulent eddies not captured in steady-state RANS computations? are needed to better predict the occurrence and extent of extreme flow conditions that could be important in the evaluation of fish injury and mortality risks. In the present work, we conduct unsteady, eddy-resolving CFD simulations on a Kaplan hydro-turbine at a normal operational discharge. The goal is to quantify the impact of turbulence conditions on both the hydraulic and biological performance of the unit. In order to achieve a high resolution of the incoming turbulent flow, Detached Eddy Simulation (DES) turbulence model is used. These transient simulations are compared to RANS simulations to evaluate whether extreme hydraulic conditions are better captured with advanced eddy-resolving turbulence modeling techniques. The transient simulations of key quantities such as pressure and hydraulic shear flow that arise near the various components (e.g. wicket gates, stay vanes, runner blades) are then further analyzed to evaluate their impact on the statistics for the lowest absolute pressure (nadir pressures) and for the frequency of collisions that are known to cause mortal injury in fish passing through hydro-turbines.

Richmond, Marshall C.; Romero Gomez, Pedro DJ

2014-08-25T23:59:59.000Z

86

A SIMPLE PREDICTION ALGORITHM FOR THE LAGRANGIAN MOTION IN TWO-DIMENSIONAL TURBULENT FLOWS  

E-Print Network (OSTI)

with the mean square error of a prediction algorithm. The mathematical framework we set up here is as followsA SIMPLE PREDICTION ALGORITHM FOR THE LAGRANGIAN MOTION IN TWO-DIMENSIONAL TURBULENT FLOWS LEONID I Vol. 63, No. 1, pp. 116­148 Abstract. A new algorithm is suggested for prediction of a Lagrangian

Ozgökmen, Tamay M.

87

Turbulent Flow Analysis and Coherent Structure Identification in Experimental Models with Complex Geometries  

E-Print Network (OSTI)

through the core of an annular pebble bed VHTR. The complex geometry of the core and the highly turbulent nature of the coolant flow passing through the gaps of fuel pebbles make this case quite challenging. In this experiment, a high frequency Hot Wire...

Amini, Noushin

2012-02-14T23:59:59.000Z

88

Thermal shallow water models of geostrophic turbulence in Jovian atmospheres  

SciTech Connect

Conventional shallow water theory successfully reproduces many key features of the Jovian atmosphere: a mixture of coherent vortices and stable, large-scale, zonal jets whose amplitude decreases with distance from the equator. However, both freely decaying and forced-dissipative simulations of the shallow water equations in Jovian parameter regimes invariably yield retrograde equatorial jets, while Jupiter itself has a strong prograde equatorial jet. Simulations by Scott and Polvani [Equatorial superrotation in shallow atmospheres, Geophys. Res. Lett. 35, L24202 (2008)] have produced prograde equatorial jets through the addition of a model for radiative relaxation in the shallow water height equation. However, their model does not conserve mass or momentum in the active layer, and produces mid-latitude jets much weaker than the equatorial jet. We present the thermal shallow water equations as an alternative model for Jovian atmospheres. These equations permit horizontal variations in the thermodynamic properties of the fluid within the active layer. We incorporate a radiative relaxation term in the separate temperature equation, leaving the mass and momentum conservation equations untouched. Simulations of this model in the Jovian regime yield a strong prograde equatorial jet, and larger amplitude mid-latitude jets than the Scott and Polvani model. For both models, the slope of the non-zonal energy spectra is consistent with the classic Kolmogorov scaling, and the slope of the zonal energy spectra is consistent with the much steeper spectrum observed for Jupiter. We also perform simulations of the thermal shallow water equations for Neptunian parameter values, with a radiative relaxation time scale calculated for the same 25 mbar pressure level we used for Jupiter. These Neptunian simulations reproduce the broad, retrograde equatorial jet and prograde mid-latitude jets seen in observations. The much longer radiative time scale for the colder planet Neptune explains the transition from a prograde to a retrograde equatorial jet, while the broader jets are due to the deformation radius being a larger fraction of the planetary radius.

Warneford, Emma S., E-mail: emma.warneford@maths.ox.ac.uk; Dellar, Paul J., E-mail: dellar@maths.ox.ac.uk [OCIAM, Mathematical Institute, University of Oxford, Radcliffe Observatory Quarter, Oxford OX2 6GG (United Kingdom)

2014-01-15T23:59:59.000Z

89

Energy flux fluctuations in a finite volume of turbulent flow  

E-Print Network (OSTI)

The flux of turbulent kinetic energy from large to small spatial scales is measured in a small domain B of varying size R. The probability distribution function of the flux is obtained using a time-local version of Kolmogorov's four-fifths law. The measurements, made at a moderate Reynolds number, show frequent events where the flux is backscattered from small to large scales, their frequency increasing as R is decreased. The observations are corroborated by a numerical simulation based on the motion of many particles and on an explicit form of the eddy damping.

Mahesh Bandi; Walter Goldburg; John Cressman Jr.; Alain Pumir

2006-07-19T23:59:59.000Z

90

DNS on turbulent heat transfer of viscoelastic fluid flow in a plane channel with transverse rectangular orifices  

Science Journals Connector (OSTI)

Heat-transfer characteristics of a viscoelastic turbulence past rectangular orifices were investigated in the context of the reduction effects of fluid elasticity on drag and heat transfer. To simulate the fully-developed channel flow through transverse orifices located periodically at intervals of 6.4 times channel height, we imposed periodic conditions at the upstream and downstream boundaries. To discuss the dissimilarity between the velocity and thermal fields, the molecular Prandtl number was set to be 1.0 and any temperature dependence of the fluid and rheological properties was not considered. In the present condition, the ratio of the reduction rates in drag and heat transfer was found to be 2.8:1.0, revealing that the present flow configuration is better than a smooth channel for avoiding the heat-transfer reduction. This phenomenon was attributed to the sustainment of the quasi-streamwise vortex downstream of the reattachment point despite the absence of strong spanwise vortices emanating from the orifice edge in the viscoelastic fluid. The longitudinal vortices behind the reattachment point caused a high turbulent heat flux and increased the local Nusselt number.

Takahiro Tsukahara; Tomohiro Kawase; Yasuo Kawaguchi

2013-01-01T23:59:59.000Z

91

Structure of Turbulence in Katabatic Flows below and above the Wind-Speed Maximum  

E-Print Network (OSTI)

Measurements of small-scale turbulence made over the complex-terrain atmospheric boundary layer during the MATERHORN Program are used to describe the structure of turbulence in katabatic flows. Turbulent and mean meteorological data were continuously measured at multiple levels at four towers deployed along the East lower slope (2-4 deg) of Granite Mountain. The multi-level observations made during a 30-day long MATERHORN-Fall field campaign in September-October 2012 allowed studying of temporal and spatial structure of katabatic flows in detail, and herein we report turbulence and their variations in katabatic winds. Observed vertical profiles show steep gradients near the surface, but in the layer above the slope jet the vertical variability is smaller. It is found that the vertical (normal to the slope) momentum flux and horizontal (along the slope) heat flux in a slope-following coordinate system change their sign below and above the wind maximum of a katabatic flow. The vertical momentum flux is directed...

Grachev, Andrey A; Di Sabatino, Silvana; Fernando, Harindra J S; Pardyjak, Eric R; Fairall, Christopher W

2015-01-01T23:59:59.000Z

92

Assessment of One- and Two-Equation Turbulence Models for Hypersonic Transitional Flows  

SciTech Connect

Many Navier-Stokes codes require that the governing equations be written in conservation form with a source term. The Spalart-Allmaras one-equation model was originally developed in substantial derivative form and when rewritten in conservation form, a density gradient term appears in the source term. This density gradient term causes numerical problems and has a small influence on the numerical predictions. Further work has been performed to understand and to justify the neglect of this term. The transition trip term has been included in the one-equation eddy viscosity model of Spalart-Allmaras. Several problems with this model have been discovered when applied to high-speed flows. For the Mach 8 flat plate boundary layer flow with the standard transition method, the Baldwin-Barth and both k-{omega} models gave transition at the specified location. The Spalart-Allmaras and low Reynolds number k-{var_epsilon} models required an increase in the freestream turbulence levels in order to give transition at the desired location. All models predicted the correct skin friction levels in both the laminar and turbulent flow regions. For Mach 8 flat plate case, the transition location could not be controlled with the trip terms as given in the Spalart-Allmaras model. Several other approaches have been investigated to allow the specification of the transition location. The approach that appears most appropriate is to vary the coefficient that multiplies the turbulent production term in the governing partial differential equation for the eddy viscosity (Method 2). When this coefficient is zero, the flow remains laminar. The coefficient is increased to its normal value over a specified distance to crudely model the transition region and obtain fully turbulent flow. While this approach provides a reasonable interim solution, a separate effort should be initiated to address the proper transition procedure associated with the turbulent production term. Also, the transition process might be better modeled with the Spalart-Allmaras turbulence model with modification of the damping function f{sub v1}. The damping function could be set to zero in the laminar flow region and then turned on through the transition flow region.

ROY,CHRISTOPHER J.; BLOTTNER,FREDERICK G.

2000-01-14T23:59:59.000Z

93

SciTech Connect: Thermal Hydraulic Characteristics of Fuel Defects...  

Office of Scientific and Technical Information (OSTI)

VA at www.ntis.gov. Thermal Hydraulic Characteristics of Fuel Defects in Plate Type Nuclear Research Reactors Turbulent flow coupled with heat transfer is investigated for a...

94

Inflow turbulence generation for eddy-resolving simulations of turbomachinery flows  

E-Print Network (OSTI)

A simple variant of recycling and rescaling method to generate inflow turbulence using unstructured grid CFD codes is presented. The method has been validated on large eddy simulation of spatially developing flat plate turbulent boundary layer. The proposed rescaling algorithm is based on the momentum thickness which is more robust and essentially obviates the need of finding the edge of the turbulent boundary layer in unstructured grid codes. Extension of this algorithm to hybrid RANS/LES type of approaches and for wall-bounded turbomachinery flows is also discussed. Results from annular diffuser with different inflow boundary layer characteristics is presented as an example application to show the utility of such an algorithm.

Arolla, Sunil K

2014-01-01T23:59:59.000Z

95

On integrating large eddy simulation and laboratory turbulent flow experiments  

Science Journals Connector (OSTI)

...effective simulation strategy mostly by necessity...its analysis and development, further understanding...directed research and development program at Los...multi-swirl gas turbine combustor. Proc...simulation of a gas turbine combustor flow...

2009-01-01T23:59:59.000Z

96

The Effect of Vertical Upward Flow on Thermal Plumes  

NLE Websites -- All DOE Office Websites (Extended Search)

The Effect of Vertical Upward Flow on Thermal Plumes The Effect of Vertical Upward Flow on Thermal Plumes Speaker(s): Pierre S. Farrugia Date: November 18, 2010 - 12:05pm Location: 90-3122 Seminar Host/Point of Contact: David Lorenzetti Thermal plumes have been widely investigated in a variety of scenarios, including natural convection and stratified environments. The resulting theory may be used to predict ventilation flow rates in, for example, natural and displacement ventilation, and under-floor air distribution (UFAD) systems. However, there has been little effort in investigating how uniform upward flows affect the plume velocity, rate of growth, and thermal profile. Such situations can arise if, for example, the diffusers of a UFAD system are evenly distributed. In order to study such situations, analytical expressions for the velocity and temperature profiles of a plume

97

Heat transfer and temperature distribution in a turbulent flow over a flat plate with an unheated starting length  

SciTech Connect

The present study is a numerical investigation of heat transfer and temperature distribution in a boundary layer formed by a flow with nonzero free stream turbulence over a flat plate with an unheated starting length. The numerical method is based on the Reynolds-averaged equations of motion and energy. As a closure for the Reynolds- averaged equations the Hinze relations for turbulent shear stresses and for turbulent heat flux are used. The Hinze equations are used instead of the usually employed Boussinesq eddy-viscosity hypothesis, because the latter does not work properly for flows with high free stream turbulence. It is shown in the present study that the influence of an unheated starting length on a temperature profile has manifested itself similarly to the influence of the free stream turbulence and resulted in a temperature profile with negative profile parameter. Unlike the flow with zero free stream turbulence, a heat transfer coefficient for the part of the plate with an unheated starting length can be less than for the fully heated plate. This difference increases with increasing level of the free stream turbulence. The family of functions that describe the influence of an unheated starting length for flows with nonzero free stream turbulence is presented.

Fridman, E.

1997-07-01T23:59:59.000Z

98

Nonlinear transverse cascade and two-dimensional magnetohydrodynamic subcritical turbulence in plane shear flows  

E-Print Network (OSTI)

We find and investigate via numerical simulations self-sustained two-dimensional turbulence in a magnetohydrodynamic flow with a maximally simple configuration: plane, noninflectional (with a constant shear of velocity) and threaded by a parallel uniform background magnetic field. This flow is spectrally stable, so the turbulence is subcritical by nature and hence it can be energetically supported just by transient growth mechanism due to shear flow nonnormality. This mechanism appears to be essentially anisotropic in spectral (wavenumber) plane and operates mainly for spatial Fourier harmonics with streamwise wavenumbers less than a ratio of flow shear to the Alfv\\'{e}n speed, $k_y < S/u_A$ (i.e., the Alfv\\'{e}n frequency is lower than the shear rate). We focused on the analysis of the character of nonlinear processes and underlying self-sustaining scheme of the turbulence, i.e., on the interplay between linear transient growth and nonlinear processes, in spectral plane. Our study, being concerned with a ...

Mamatsashvili, G R; Chagelishvili, G D; Horton, W

2014-01-01T23:59:59.000Z

99

Response Relationship Between Juvenile Salmon and an Autonomous Sensor in Turbulent Flows  

SciTech Connect

Juvenile fall chinook salmon (Oncorhynchus tshawythscha) and an autonomous sensor device (Sensor Fish) were exposed to turbulent shear flows in order to determine how hydraulic conditions effected fish injury response. Studies were designed to establish correlation metrics between Sensor Fish device measurements and live fish injuries by conducting concurrent releases in a range of turbulent shear flows. Comparisons were made for two exposure scenarios. In the fast-fish-to-slow-water scenario, test fish were carried by the fast-moving water of a submerged turbulent jet and exposed into the standing water of a flume. In the slow-fish-to-fast-water scenario, test fish were introduced into a turbulent jet from standing water through an introduction tube placed just outside the edge of the jet. Motion-tracking analysis was performed on high-speed, high-resolution digital videos of all the releases at water jet velocities ranging from 3 to 22.9 m s?1. Velocities of the Sensor Fish were very similar to those of live fish, but maximum accelerations of live fish were larger than those by Sensor Fish for all the nozzle velocities of both cenarios. A 10% probability of major injury threshold was found to occur at sensor fish accelerations of 513 and 260 (m s?2) for the fast-fish-to-slow-water and slow-fish-to-fast-water scenarios, respectively. The findings provide a linkage between laboratory experiments of fish injury, field survival studies, and numerical modeling.

Richmond, Marshall C.; Deng, Zhiqun; McKinstry, Craig A.; Mueller, Robert P.; Carlson, Thomas J.; Dauble, Dennis D.

2009-04-01T23:59:59.000Z

100

Rossby and Drift Wave Turbulence and Zonal Flows: the Charney-Hasegawa-Mima model and its extensions  

E-Print Network (OSTI)

A detailed study of the Charney-Hasegawa-Mima model and its extensions is presented. These simple nonlinear partial differential equations suggested for both Rossby waves in the atmosphere and also drift waves in a magnetically-confined plasma exhibit some remarkable and nontrivial properties, which in their qualitative form survive in more realistic and complicated models, and as such form a conceptual basis for understanding the turbulence and zonal flow dynamics in real plasma and geophysical systems. Two idealised scenarios of generation of zonal flows by small-scale turbulence are explored: a modulational instability and turbulent cascades. A detailed study of the generation of zonal flows by the modulational instability reveals that the dynamics of this zonal flow generation mechanism differ widely depending on the initial degree of nonlinearity. A numerical proof is provided for the extra invariant in Rossby and drift wave turbulence -zonostrophy and the invariant cascades are shown to be characterised by the zonostrophy pushing the energy to the zonal scales. A small scale instability forcing applied to the model demonstrates the well-known drift wave - zonal flow feedback loop in which the turbulence which initially leads to the zonal flow creation, is completely suppressed and the zonal flows saturate. The turbulence spectrum is shown to diffuse in a manner which has been mathematically predicted. The insights gained from this simple model could provide a basis for equivalent studies in more sophisticated plasma and geophysical fluid dynamics models in an effort to fully understand the zonal flow generation, the turbulent transport suppression and the zonal flow saturation processes in both the plasma and geophysical contexts as well as other wave and turbulence systems where order evolves from chaos.

Colm Connaughton; Sergey Nazarenko; Brenda Quinn

2014-07-07T23:59:59.000Z

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


101

Steady state whistler turbulence and stability of thermal barriers in tandem mirrors  

Science Journals Connector (OSTI)

The effect of the whistler turbulence on anisotropic electrons in a thermal barrier is examined. The electron distribution function is derived self?consistently by solving the steady state quasilinear diffusion equation. Saturated amplitudes are computed using the resonance broadening theory or convective stabilization. Estimated power levels necessary for sustaining the steady state of a strongly anisotropic electron population are found to exceed by orders of magnitude the estimates based on FokkerPlanck calculations for the range of parameters of tandem mirror (TMX?U and MFTF?B) experiments [Nucl. Fusion 2 5 1205 (1985)]. Upper limits on the allowed degree of anisotropy for existing power densities are calculated.

C. Litwin; R. N. Sudan

1986-01-01T23:59:59.000Z

102

Steady state whistler turbulence and stability of thermal barriers in tandem mirrors  

SciTech Connect

The effect of the whistler turbulence on anisotropic electrons in a thermal barrier is examined. The electron distribution function is derived self-consistently by solving the steady state quasilinear diffusion equation. Saturated amplitudes are computed using the resonance broadening theory or convective stabilization. Estimated power levels necessary for sustaining the steady state of a strongly anisotropic electron population are found to exceed by orders of magnitude the estimates based on Fokker--Planck calculations for the range of parameters of tandem mirror (TMX-U and MFTF-B) experiments (Nucl. Fusion 25, 1205 (1985)). Upper limits on the allowed degree of anisotropy for existing power densities are calculated.

Litwin, C.; Sudan, R.N.

1986-11-01T23:59:59.000Z

103

Turbulence  

NLE Websites -- All DOE Office Websites (Extended Search)

Turbulence Turbulence in Alcator C-Mod and Wendelstein 7-AS plasmas during controlled confinement transitions N.P.Basse, E.M.Edlund, C.L.Fiore, M.J.Greenwald, A.E.Hubbard, J.W.Hughes, J.H.Irby, G.J.Kramer 1 , L.Lin, Y.Lin, A.G.Lynn 2 , E.S.Marmar, D.R.Mikkelsen 1 , D.Mossessian, P.E.Phillips 2 , M.Porkolab, J.E.Rice, W.L.Rowan 2 , J.A.Snipes, J.L.Terry, S.M.Wolfe, S.J.Wukitch, K.Zhurovich, S.Zoletnik 3 and the C-Mod and W7-AS 4 Teams MIT Plasma Science and Fusion Center, Cambridge, USA 1 Princeton Plasma Physics Laboratory, Princeton, USA 2 University of Texas at Austin, Austin, USA 3 KFKI-RMKI, EURATOM Association, Budapest, Hungary 4 Max-Planck-Institut f¨ ur Plasmaphysik, EURATOM Association, Greifswald, Germany At certain values of the edge rotational transform, ι a = 1/q a , the confinement time of plasmas in the Wendelstein 7-AS (W7-AS) stellarator was found to

104

Mean and Turbulent Flow Downstream of a Low-Intensity Fire: Influence of Canopy and Background Atmospheric Conditions  

Science Journals Connector (OSTI)

This study examines the sensitivity of mean and turbulent flow in the planetary boundary layer (PBL) and roughness sub-layer to a low-intensity fire and evaluates whether the sensitivity is dependent on canopy and background atmospheric ...

Michael T. Kiefer; Warren E. Heilman; Shiyuan Zhong; Joseph J. Charney; Xindi Bian

105

A GENERALIZED ALGEBRAIC RELATION FOR PREDICTING DEVELOPING CURVED CHANNEL FLOW WITH A k-t MODEL OF TURBULENCE  

E-Print Network (OSTI)

S. V. , "Numerical Heat Transfer and Fluid Flow," HemisphereCurvature on Heat Transfer to Incompressible Fluids," Trans.Heat Transfer in a Turbulent Boundary Layer," Journal of Fluid

Humphrey, Joseph A.C.

2014-01-01T23:59:59.000Z

106

Rossby and Drift Wave Turbulence and Zonal Flows: the Charney-Hasegawa-Mima model and its extensions  

E-Print Network (OSTI)

A detailed study of the Charney-Hasegawa-Mima model and its extensions is presented. These simple nonlinear partial differential equations suggested for both Rossby waves in the atmosphere and also drift waves in a magnetically-confined plasma exhibit some remarkable and nontrivial properties, which in their qualitative form survive in more realistic and complicated models, and as such form a conceptual basis for understanding the turbulence and zonal flow dynamics in real plasma and geophysical systems. Two idealised scenarios of generation of zonal flows by small-scale turbulence are explored: a modulational instability and turbulent cascades. A detailed study of the generation of zonal flows by the modulational instability reveals that the dynamics of this zonal flow generation mechanism differ widely depending on the initial degree of nonlinearity. A numerical proof is provided for the extra invariant in Rossby and drift wave turbulence -zonostrophy and the invariant cascades are shown to be characterised...

Connaughton, Colm; Quinn, Brenda

2014-01-01T23:59:59.000Z

107

Development of analytical and numerical models predicting the deposition rate of electrically charged particles in turbulent channel flows  

E-Print Network (OSTI)

An analytical model is established to predict an electrostatically charged particle deposition as a function of particle size in fully-developed turbulent pipe flow. The convectivediffusion flux equation is solved for the particle concentration as a...

Ko, Hanseo

2012-06-07T23:59:59.000Z

108

Wavelet-based Adaptive Techniques Applied to Turbulent Hypersonic Scramjet Intake Flows  

E-Print Network (OSTI)

The simulation of hypersonic flows is computationally demanding due to large gradients of the flow variables caused by strong shock waves and thick boundary or shear layers. The resolution of those gradients imposes the use of extremely small cells in the respective regions. Taking turbulence into account intensives the variation in scales even more. Furthermore, hypersonic flows have been shown to be extremely grid sensitive. For the simulation of three-dimensional configurations of engineering applications, this results in a huge amount of cells and prohibitive computational time. Therefore, modern adaptive techniques can provide a gain with respect to computational costs and accuracy, allowing the generation of locally highly resolved flow regions where they are needed and retaining an otherwise smooth distribution. An h-adaptive technique based on wavelets is employed for the solution of hypersonic flows. The compressible Reynolds averaged Navier-Stokes equations are solved using a differential Reynolds s...

Frauholz, Sarah; Reinartz, Birgit U; Mller, Siegfried; Behr, Marek

2013-01-01T23:59:59.000Z

109

The effect of diamagnetic flows on turbulent driven ion toroidal rotation  

SciTech Connect

Turbulent momentum redistribution determines the radial profile of rotation in a tokamak. The momentum transport driven by diamagnetic flow effects is an important piece of the radial momentum transport for sub-sonic rotation, which is often observed in experiments. In a non-rotating state, the diamagnetic flow and the E B flow must cancel. The diamagnetic flow and the E B flow have different effects on the turbulent momentum flux, and this difference in behavior induces intrinsic rotation. The momentum flux is evaluated using gyrokinetic equations that are corrected to higher order in the ratio of the poloidal Larmor radius to the minor radius, which requires evaluation of the diamagnetic corrections to Maxwellian equilibria. To study the momentum transport due to diamagnetic flow effects, three experimental observations of ion rotation are examined. First, a strong pressure gradient at the plasma edge is shown to result in a significant inward momentum transport due to the diamagnetic effect, which may explain the observed peaking of rotation in a high confinement mode. Second, the direction of momentum transport is shown to change as collisionality increases, which is qualitatively consistent with the observed reversal of intrinsic rotation by varying plasma density and current. Last, the dependence of the intrinsic momentum flux on the magnetic shear is found, and it may explain the observed rotation changes in the presence of lower hybrid current drive.

Lee, J. P. [Courant Institute of Mathematical Sciences, New York University, New York, New York 10003 (United States)] [Courant Institute of Mathematical Sciences, New York University, New York, New York 10003 (United States); Barnes, M. [Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712 (United States)] [Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712 (United States); Parra, F. I. [Rudolf Peierls Centre for Theoretical Physics, Oxford University, Oxford OX1 3NP (United Kingdom)] [Rudolf Peierls Centre for Theoretical Physics, Oxford University, Oxford OX1 3NP (United Kingdom); Belli, E. A.; Candy, J. [General Atomics, San Diego, California 92121 (United States)] [General Atomics, San Diego, California 92121 (United States)

2014-05-15T23:59:59.000Z

110

Momentum and heat fluxes in a turbulent air flow over a wet, smooth boundary  

E-Print Network (OSTI)

are negligible in directions other than those normal to the boundary surface. Such equa? tions were first employed by Boussinesq (5* 6). For turbulent flow, he suggested the equatiisns, ? IS ^7/ (momentum flux)/ - U and ^ =. Kh (beat flux) where KM and c... of a pre? cision potentiometer. Continuous, uniform water supply to the test surface was achieved by a distilled water supply system composed of glass bottles and copper tubing arranged to supply water at any required rate without attention from...

Rice, Warren

2013-10-04T23:59:59.000Z

111

Morphological Evolution of Thermal Plumes in Turbulent Rayleigh-Bnard Convection  

Science Journals Connector (OSTI)

An experimental study of the morphological evolution of thermal plumes in turbulent thermal convection is presented. Individual sheetlike plumes are extracted and their area, circumference, and heat content are found to all exhibit log-normal distributions. As the sheetlike plumes move across the plate they collide and convolute into spiraling swirls. These swirls then spiral away from the plates to become mushroomlike plumes which are accompanied by strong vertical vorticity. The measured profiles of plume numbers and of vertical vorticity quantify the morphological transition of sheetlike plumes to mushroomlike ones and the mixing and merging or clustering of mushroomlike plumes. The fluctuating vorticity is found to have the same exponential distribution and scaling behavior as the fluctuating temperature.

Quan Zhou; Chao Sun; Ke-Qing Xia

2007-02-12T23:59:59.000Z

112

Modification of turbulent structure in channel flows by microbubble injection close to the wall  

E-Print Network (OSTI)

mass production N Total number of realizations N T Number of velocity fields P Turbulent energy production P Pressure Q a Air flow rate Q w Water flow rate R(s) Autocorrelation of I(X) R b Bubble radius Re Reynolds number Re... through the porous section Re x Reynolds number based on the free stream velocity and distance x viii R ij (?r) Two-point correlation coefficient R ij (?t) Autocorrelation coefficient s Riblet spacing s + Riblet spacing in wall units S ij...

Gutierrez Torres, Claudia del Carmen

2005-11-01T23:59:59.000Z

113

MODELING STRATEGIES FOR UNSTEADY TURBULENT FLOWS IN THE LOWER PLENUM OF THE VHTR  

SciTech Connect

Validation simulations are presented for turbulent flow in a staggered tube bank, geometry similar to that in the lower plenum of a block very high temperature reactor. Steady 2D RANS predictions are compared to unsteady 2D RANS results and experiment. The unsteady calculations account for the fact that nonturbulent fluctuations (due to vortex-shedding) are present in the flow. The unsteady computations are shown to predict the mean variables and the total shear stress quite well. Previous workers have presented results that indicated that 3D simulations were necessary to obtain reasonable results. Best practices are based on requirements for the ASME Journal of Fluids Engineering.

Richard W. Johnson

2006-09-01T23:59:59.000Z

114

Simulations of Turbulent Flows with Strong Shocks and Density Variations: Final Report  

SciTech Connect

The target of this SciDAC Science Application was to develop a new capability based on high-order and high-resolution schemes to simulate shock-turbulence interactions and multi-material mixing in planar and spherical geometries, and to study Rayleigh-Taylor and Richtmyer-Meshkov turbulent mixing. These fundamental problems have direct application in high-speed engineering flows, such as inertial confinement fusion (ICF) capsule implosions and scramjet combustion, and also in the natural occurrence of supernovae explosions. Another component of this project was the development of subgrid-scale (SGS) models for large-eddy simulations of flows involving shock-turbulence interaction and multi-material mixing, that were to be validated with the DNS databases generated during the program. The numerical codes developed are designed for massively-parallel computer architectures, ensuring good scaling performance. Their algorithms were validated by means of a sequence of benchmark problems. The original multi-stage plan for this five-year project included the following milestones: 1) refinement of numerical algorithms for application to the shock-turbulence interaction problem and multi-material mixing (years 1-2); 2) direct numerical simulations (DNS) of canonical shock-turbulence interaction (years 2-3), targeted at improving our understanding of the physics behind the combined two phenomena and also at guiding the development of SGS models; 3) large-eddy simulations (LES) of shock-turbulence interaction (years 3-5), improving SGS models based on the DNS obtained in the previous phase; 4) DNS of planar/spherical RM multi-material mixing (years 3-5), also with the two-fold objective of gaining insight into the relevant physics of this instability and aiding in devising new modeling strategies for multi-material mixing; 5) LES of planar/spherical RM mixing (years 4-5), integrating the improved SGS and multi-material models developed in stages 3 and 5. This final report is outlined as follows. Section 2 shows an assessment of numerical algorithms that are best suited for the numerical simulation of compressible flows involving turbulence and shock phenomena. Sections 3 and 4 deal with the canonical shock-turbulence interaction problem, from the DNS and LES perspectives, respectively. Section 5 considers the shock-turbulence inter-action in spherical geometry, in particular, the interaction of a converging shock with isotropic turbulence as well as the problem of the blast wave. Section 6 describes the study of shock-accelerated mixing through planar and spherical Richtmyer-Meshkov mixing as well as the shock-curtain interaction problem In section 7 we acknowledge the different interactions between Stanford and other institutions participating in this SciDAC project, as well as several external collaborations made possible through it. Section 8 presents a list of publications and presentations that have been generated during the course of this SciDAC project. Finally, section 9 concludes this report with the list of personnel at Stanford University funded by this SciDAC project.

Sanjiva Lele

2012-10-01T23:59:59.000Z

115

PhD scholarship on "Particle transport and clustering in stratified turbulent flows" funded by the Research  

E-Print Network (OSTI)

production in thermal power plants. Additionally, there will also be a coupling between this work, and the phenomenon of turbulent thermal diffusion (TTD). The research work will focus both on computer simulations (Direct Numerical Simulations) and on modelling of the particle-embedded fluid-solid interfaces

Brandenburg, Axel

116

Experimental and numerical investigation of turbulent flow and heat (mass) transfer in a two-pass trapezoidal channel with turbulence promoters  

E-Print Network (OSTI)

of three-dimensional flow and heat transfer also were performed for the trapezoidal channel with and without 90 ribs tested by Lee et al. (2007). Reynolds stress turbulence model (RSM) in the FLUENT CFD code was used to calculate the heat transfer...

Oh, Sung Hyuk

2009-05-15T23:59:59.000Z

117

Distributions of velocity and turbulence in a parallel flow along an asymmetric rod bundle  

SciTech Connect

An experimental investigation was performed to obtain detailed information on the velocity and turbulence distributions in a parallel turbulent flow through an asymmetric rod bundle. The rod bundle consisted of four parallel rods arranged asymmetrically in a rectangular channel. The pitch-to-diameter (P/D) ratio of the rods was P/D = 1.072. Experimental results were obtained in two wall subchannels with wall-to-diameter (W/D) ratios of W/D = 1.096 and 1.048, respectively. The experimental results showed high anisotropy of the momentum transport, particularly in the gaps of the rod bundle. Comparisons between the measured wall shear stresses and data computed by the VELASCO code show considerable differences, particularly for the wall subchannel with W/D = 1.048.

Rehme, K.

1982-10-01T23:59:59.000Z

118

3-D Numerical Simulation of Heat Transfer and Turbulent Flow in a Receiver Tube of Solar Parabolic Trough Concentrator with Louvered Twisted-tape Inserts  

Science Journals Connector (OSTI)

Abstract High temperature and higher-thermal efficiency for CSP cycles are main goals to improve trough collector's technologies. For a parabolic trough collector the major factor for optimum heat transfer from sun to the heat transfer fluid passing in the absorber tube is to have high convection heat transfer coefficient. Literature shows that absorber tubes with various tape inserts are used and recommended to produce high convection coefficient. Typical twisted-tape (TT) enhances heat exchange between tube surface and working fluid by generating turbulent swirling flow. In this study, enhancement of convection coefficient in the receiver tube of a solar parabolic trough concentrator that the absorber tube is equipped with a new perforated louvered twisted- tape (LTT) is studied numerically. For numerical simulations three different twist ratios (TR), TR=y/W= 2.67, 4, 5.33 (y is the length required for one twist and W is the width of the tape) are used in an experimental laboratory trough collector. Flow is assumed turbulent due to louvered perforated surface and rotational shape of the tape. For thermal boundary condition, non- uniform wall solar heat flux is determined by Soltrace code on the outer surface of the absorber tube. Heat transfer rate and pressure drop are determined for fully developed condition for several Reynolds numbers based on the tube diameter and flow mean velocity. Results show that the heat transfer coefficient and pressure drop increase significantly in comparison with a typical plain twisted-tape in the tube and a plain tube.

Sh. Ghadirijafarbeigloo; A.H. Zamzamian; M. Yaghoubi

2014-01-01T23:59:59.000Z

119

The friction factor of two-dimensional rough-boundary turbulent soap film flows  

E-Print Network (OSTI)

We use momentum transfer arguments to predict the friction factor $f$ in two-dimensional turbulent soap-film flows with rough boundaries (an analogue of three-dimensional pipe flow) as a function of Reynolds number Re and roughness $r$, considering separately the inverse energy cascade and the forward enstrophy cascade. At intermediate Re, we predict a Blasius-like friction factor scaling of $f\\propto\\textrm{Re}^{-1/2}$ in flows dominated by the enstrophy cascade, distinct from the energy cascade scaling of $\\textrm{Re}^{-1/4}$. For large Re, $f \\sim r$ in the enstrophy-dominated case. We use conformal map techniques to perform direct numerical simulations that are in satisfactory agreement with theory, and exhibit data collapse scaling of roughness-induced criticality, previously shown to arise in the 3D pipe data of Nikuradse.

Nicholas Guttenberg; Nigel Goldenfeld

2008-08-11T23:59:59.000Z

120

Non-Oberbeck-Boussinesq effects in turbulent thermal convection in ethane close to the critical point  

Science Journals Connector (OSTI)

As shown in earlier work [Ahlers et al., J. Fluid Mech. 569, 409 (2006)], non-Oberbeck-Boussinesq (NOB) corrections to the center temperature in turbulent Rayleigh-Bnard convection in water and also in glycerol are governed by the temperature dependences of the kinematic viscosity and the thermal diffusion coefficient. If the working fluid is ethane close to the critical point, the origin of non-Oberbeck-Boussinesq corrections is very different, as will be shown in the present paper. Namely, the main origin of NOB corrections then lies in the strong temperature dependence of the isobaric thermal expansion coefficient ?(T). More precisely, it is the nonlinear T dependence of the density ?(T) in the buoyancy force that causes another type of NOB effect. We demonstrate this through a combination of experimental, numerical, and theoretical work, the last in the framework of the extended Prandtl-Blasius boundary-layer theory developed by Ahlers et al. as cited above. The theory comes to its limits if the temperature dependence of the thermal expension coefficient ?(T) is significant. The measurements reported here cover the ranges 2.1?Pr?3.9 and 5109?Ra?21012 and are for cylindrical samples of aspect ratios 1.0 and 0.5.

Guenter Ahlers; Enrico Calzavarini; Francisco Fontenele Araujo; Denis Funfschilling; Siegfried Grossmann; Detlef Lohse; Kazuyasu Sugiyama

2008-04-08T23:59:59.000Z

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


121

IMPACT OF BOUNDARY-LAYER CUTTING AND FLOW CONDITIONING ON FREE-SURFACE BEHAVIOR IN TURBULENT LIQUID SHEETS  

E-Print Network (OSTI)

IMPACT OF BOUNDARY-LAYER CUTTING AND FLOW CONDITIONING ON FREE-SURFACE BEHAVIOR IN TURBULENT LIQUID dimension) = 1 cm into ambient air are compared with empirical correlations at a nearly prototypical term, for a well- conditioned jet but is not a substitute for well-designed flow conditioning. I

California at San Diego, University of

122

ACCRETION OF GAS ONTO GAP-OPENING PLANETS AND CIRCUMPLANETARY FLOW STRUCTURE IN MAGNETIZED TURBULENT DISKS  

SciTech Connect

We have performed three-dimensional magnetohydrodynamical simulations of stellar accretion disks, using the PLUTO code, and studied the accretion of gas onto a Jupiter-mass planet and the structure of the circumplanetary gas flow after opening a gap in the disk. We compare our results with simulations of laminar, yet viscous disks with different levels of an {alpha}-type viscosity. In all cases, we find that the accretion flow across the surface of the Hill sphere of the planet is not spherically or azimuthally symmetric, and is predominantly restricted to the mid-plane region of the disk. Even in the turbulent case, we find no significant vertical flow of mass into the Hill sphere. The outer parts of the circumplanetary disk are shown to rotate significantly below Keplerian speed, independent of viscosity, while the circumplanetary disk density (therefore the angular momentum) increases with viscosity. For a simulation of a magnetized turbulent disk, where the global averaged alpha stress is {alpha}{sub MHD} = 10{sup -3}, we find the accretion rate onto the planet to be M-dot {approx}2 Multiplication-Sign 10{sup -6}M{sub J} yr{sup -1} for a gap surface density of 12 g cm{sup -2}. This is about a third of the accretion rate obtained in a laminar viscous simulation with equivalent {alpha} parameter.

Uribe, A. L. [University of Chicago, Chicago, IL 60637 (United States); Klahr, H.; Henning, Th., E-mail: uribe@oddjob.uchicago.edu [Max-Planck-Institut fuer Astronomie, Heidelberg (Germany)

2013-06-01T23:59:59.000Z

123

Comparison of analytical models for zonal flow generation in ion-temperature-gradient mode turbulence  

SciTech Connect

During the past years the understanding of the multi scale interaction problems have increased significantly. However, at present there exists a flora of different analytical models for investigating multi scale interactions and hardly any specific comparisons have been performed among these models. In this work two different models for the generation of zonal flows from ion-temperature-gradient (ITG) background turbulence are discussed and compared. The methods used are the coherent mode coupling model and the wave kinetic equation model (WKE). It is shown that the two models give qualitatively the same results even though the assumption on the spectral difference is used in the (WKE) approach.

Anderson, J.; Miki, K.; Uzawa, K.; Li, J.; Kishimoto, Y. [Dept. Fundamental Energy Science, School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto, 611-0011 (Japan)

2006-11-30T23:59:59.000Z

124

Inviscid Limits for a Stochastically Forced Shell Model of Turbulent Flow  

E-Print Network (OSTI)

We establish the anomalous mean dissipation rate of energy in the inviscid limit for a stochastic shell model of turbulent fluid flow. The proof relies on viscosity independent bounds for stationary solutions and on establishing ergodic and mixing properties for the viscous model. The shell model is subject to a degenerate stochastic forcing in the sense that noise acts directly only through one wavenumber. We show that it is hypo-elliptic (in the sense of Hormander) and use this property to prove a gradient bound on the Markov semigroup.

Susan Friedlander; Nathan Glatt-Holtz; Vlad Vicol

2014-04-03T23:59:59.000Z

125

Heat transfer deterioration in tubes caused by bulk flow acceleration due to thermal and frictional influences  

SciTech Connect

Severe deterioration of forced convection heat transfer can be encountered with compressible fluids flowing through strongly heated tubes of relatively small bore as the flow accelerates and turbulence is reduced because of the fluid density falling (as the temperature rises and the pressure falls due to thermal and frictional influence). The model presented here throws new light on how the dependence of density on both temperature and pressure can affect turbulence and heat transfer and it explains why the empirical equations currently available for calculating effectiveness of forced convection heat transfer under conditions of strong non-uniformity of fluid properties sometimes fail to reproduce observed behaviour. It provides a criterion for establishing the conditions under which such deterioration of heat transfer might be encountered and enables heat transfer coefficients to be determined when such deterioration occurs. The analysis presented here is for a gaseous fluid at normal pressure subjected strong non-uniformity of fluid properties by the application of large temperature differences. Thus the model leads to equations which describe deterioration of heat transfer in terms of familiar parameters such as Mach number, Reynolds number and Prandtl number. It is applicable to thermal power plant systems such as rocket engines, gas turbines and high temperature gas-cooled nuclear reactors. However, the ideas involved apply equally well to fluids at supercritical pressure. Impairment of heat transfer under such conditions has become a matter of growing interest with the active consideration now being given to advanced water-cooled nuclear reactors designed to operate at pressures above the critical value. (authors)

Jackson, J. D. [Univ. of Manchester, Manchester (United Kingdom)

2012-07-01T23:59:59.000Z

126

Chaotic mean wind in turbulent thermal convection and long-term correlations in solar activity  

E-Print Network (OSTI)

It is shown that correlation function of the mean wind velocity in a turbulent thermal convection (Rayleigh number $Ra \\sim 10^{11}$) exhibits exponential decay with a very long correlation time, while corresponding largest Lyapunov exponent is certainly positive. These results together with the reconstructed phase portrait indicate presence of a chaotic component in the examined mean wind. Telegraph approximation is also used to study relative contribution of the chaotic and stochastic components to the mean wind fluctuations and an equilibrium between these components has been studied. Since solar activity is based on the thermal convection processes, it is reasoned that the observed solar activity long-term correlations can be an imprint of the mean wind chaotic properties. In particular, correlation function of the daily sunspots number exhibits exponential decay with a very long correlation time and corresponding largest Lyapunov exponent is certainly positive, also relative contribution of the chaotic and stochastic components follows the same pattern as for the convection mean wind.

A. Bershadskii

2009-08-27T23:59:59.000Z

127

Asymptotic results for backwards two-particle dispersion in a turbulent flow  

E-Print Network (OSTI)

We derive an exact equation governing two-particle backwards mean-squared dispersion for both deterministic and stochastic tracer particles in turbulent flows. For the deterministic trajectories, we probe the consequences of our formula for short times and arrive at approximate expressions for the mean-squared dispersion which involve second order structure functions of the velocity and acceleration fields. For the stochastic trajectories, we analytically compute an exact $t^3$ contribution to the squared separation of stochastic paths. We argue that this contribution appears also for deterministic paths at long times and present direct numerical simulation results for incompressible Navier-Stokes flows to support this claim. We also numerically compute the probability distribution of particle separations for the deterministic paths and the stochastic paths and show their strong self-similar nature.

Damien Benveniste; Theodore D. Drivas

2014-04-17T23:59:59.000Z

128

Numerical simulation of swirling flow in complex hydroturbine draft tube using unsteady statistical turbulence models  

SciTech Connect

A numerical method is developed for carrying out unsteady Reynolds-averaged Navier-Stokes (URANS) simulations and detached-eddy simulations (DESs) in complex 3D geometries. The method is applied to simulate incompressible swirling flow in a typical hydroturbine draft tube, which consists of a strongly curved 90 degree elbow and two piers. The governing equations are solved with a second-order-accurate, finite-volume, dual-time-stepping artificial compressibility approach for a Reynolds number of 1.1 million on a mesh with 1.8 million nodes. The geometrical complexities of the draft tube are handled using domain decomposition with overset (chimera) grids. Numerical simulations show that unsteady statistical turbulence models can capture very complex 3D flow phenomena dominated by geometry-induced, large-scale instabilities and unsteady coherent structures such as the onset of vortex breakdown and the formation of the unsteady rope vortex downstream of the turbine runner. Both URANS and DES appear to yield the general shape and magnitude of mean velocity profiles in reasonable agreement with measurements. Significant discrepancies among the DES and URANS predictions of the turbulence statistics are also observed in the straight downstream diffuser.

Paik, Joongcheol [University of Minnesota; Sotiropoulos, Fotis [University of Minnesota; Sale, Michael J [ORNL

2005-06-01T23:59:59.000Z

129

Notes 10. A thermohydrodynamic bulk-flow model for fluid film bearings  

E-Print Network (OSTI)

The complete set of bulk-flow equations for the analysis of turbulent flow fluid film bearings. Importance of thermal effects in process fluid applications. A CFD method for solution of the bulk-flow equations....

San Andres, Luis

2009-01-01T23:59:59.000Z

130

The mathematical structure of multiphase thermal models of flow in porous media  

E-Print Network (OSTI)

The mathematical structure of multiphase thermal models of flow in porous media By Daniel E.A. van with the formulation and numerical solution of equations for modelling multicomponent, two-phase, thermal fluid flow typical flow behaviour that occurs during fluid injection into a reservoir. Keywords: porous media flow

131

Gas flow driven by thermal creep in dusty plasma T. M. Flanagan and J. Goree  

E-Print Network (OSTI)

Gas flow driven by thermal creep in dusty plasma T. M. Flanagan and J. Goree Department of Physics 2009 Thermal creep flow TCF is a flow of gas driven by a temperature gradient along a solid boundary to the bulk gas, causing the bulk gas to flow, thereby stirring the suspension of dust particles. This result

Goree, John

132

Experiments measuring particle deposition from fully developed turbulent flow in ventilation ducts  

SciTech Connect

Particle deposition in ventilation ducts influences particle exposures of building occupants and may lead to a variety of indoor air quality concerns. Experiments have been performed in a laboratory to study the effects of particle size and air speed on deposition rates of particles from turbulent air flows in galvanized steel and internally insulated ducts with hydraulic diameters of 15.2 cm. The duct systems were constructed of materials typically found in commercial heating, ventilating and air conditioning (HVAC) systems. In the steel duct system, experiments with nominal particle sizes of 1, 3, 5, 9 and 16 {micro}m were conducted at each of three nominal air speeds: 2.2, 5.3 and 9.0 m/s. In the insulated duct system, deposition rates of particles with nominal sizes of 1, 3, 5, 8 and 13 {micro}m were measured at nominal air speeds of 2.2, 5.3 and 8.8 m/s. Fluorescent techniques were used to directly measure the deposition velocities of monodisperse fluorescent particles to duct surfaces (floor, wall and ceiling) at two straight duct sections where the turbulent flow profile was fully developed. In steel ducts, deposition rates were higher to the duct floor than to the wall, which were, in turn, greater than to the ceiling. In insulated ducts, deposition was nearly the same to the duct floor, wall and ceiling for a given particle size and air speed. Deposition to duct walls and ceilings was greatly enhanced in insulated ducts compared to steel ducts. Deposition velocities to each of the three duct surface orientations in both systems were found to increase with increasing particle size or air velocity over the ranges studied. Deposition rates measured in the current experiments were in general agreement with the limited observations of similar systems by previous researchers.

Sippola, Mark R.; Nazaroff, William W.

2003-08-01T23:59:59.000Z

133

Heat transfer and friction factor of water based TiO2 and SiO2 nanofluids under turbulent flow in a tube  

Science Journals Connector (OSTI)

Abstract The heat transfer coefficient and friction factor of TiO2 and SiO2 water based nanofluids flowing in a circular tube under turbulent flow are investigated experimentally under constant heat flux boundary condition. TiO2 and SiO2 nanofluids with an average particle size of 50nm and 22nm respectively are used in the working fluid for volume concentrations up to 3.0%. Experiments are conducted at a bulk temperature of 30C in the turbulent Reynolds number range of 5000 to 25,000. The enhancements in viscosity and thermal conductivity of TiO2 are greater than SiO2 nanofluid. However, a maximum enhancement of 26% in heat transfer coefficients is obtained with TiO2 nanofluid at 1.0% concentration, while SiO2 nanofluid gave 33% enhancement at 3.0% concentration. The heat transfer coefficients are lower at all other concentrations. The particle concentration at which the nanofluids give maximum heat transfer has been determined and validated with property enhancement ratio. It is observed that the pressure drop is directly proportional to the density of the nanoparticle.

W.H. Azmi; K.V. Sharma; P.K. Sarma; Rizalman Mamat; G. Najafi

2014-01-01T23:59:59.000Z

134

Studies of turbulence and flows in the DIII-D tokamak  

E-Print Network (OSTI)

The DIII-D tokamak . . . . . . . . . . . . . . . .2 Turbulence in tokamaks: background and review of existingscale instabilities in tokamaks . . . . . . . . . . . .

Hillesheim, Jon Clark

2012-01-01T23:59:59.000Z

135

Flow, Turbulence and Combustion 62: 295333, 1999. 1999 Kluwer Academic Publishers. Printed in the Netherlands.  

E-Print Network (OSTI)

in the Netherlands. 295 Application of PDF Modeling to Swirling and Nonswirling Turbulent Jets P.R. VAN SLOOTEN

136

Validation Analysis for the Calculation of a Turbulent Free Jet in Water Using CFDS-FLOW 3-D and FLUENT  

SciTech Connect

The application of computational fluid dynamics methods to the analysis of mixing in the high level waste tanks at the Savannah River Site requires a demonstration that the computer codes can properly represent the behavior of fluids in the tanks. The motive force for mixing the tanks is a set of jet pumps taking suction from the tank fluid and discharging turbulent jets near the bottom of the tank. The work described here focuses on the free turbulent jet in water as the simplest case of jet behavior for which data could be found in the open literature. Calculations performed with both CFDS-FLOW3D and FLUENT were compared with data as well as classical jet theory. Results showed both codes agreed reasonably well with each other and with the data, but that results were sensitive to the computational mesh and, to a lesser degree, the selection of turbulence models.

Dimenna, R.A.; Lee, S.Y.

1995-05-01T23:59:59.000Z

137

Effects of Magnetic Field on the Turbulent Wake of a Cylinder in MHD Channel Flow  

SciTech Connect

Results from a free-surface MHD flow experiment are presented detailing the modi cation of vortices in the wake of a circular cylinder with its axis parallel to the applied magnetic fi eld. Experiments were performed with a Reynolds number near Re ~ 104 as the interaction parameter, N = |j x#2; B| / |? (? ? ?), was increased through unity. By concurrently sampling the downstream fluid velocity at sixteen cross-stream locations in the wake, it was possible to extract an ensemble of azimuthal velocity profi les as a function of radius for vortices shed by the cylinder at varying strengths of magnetic field. Results indicate a signi cant change in vortex radius and rotation as N is increased. The lack of deviations from the vortex velocity pro file at high magnetic fi elds suggests the absence of small-scale turbulent features. By sampling the wake at three locations downstream in subsequent experiments, the decay of the vortices was examined and the effective viscosity was found to decrease as N-0490.4. This reduction in effective viscosity is due to the modi cation of the small-scale eddies by the magnetic fi eld. The slope of the energy spectrum was observed to change from a k-1.8 power-law at low N to a k-3.5 power-law for N > 1. Together, these results suggest the flow smoothly transitioned to a quasi-two-dimensional state in the range 0 < N < 1.

John Rhoads, Eric Edlund and Hantao Ji

2013-04-17T23:59:59.000Z

138

The divergence of neighboring magnetic field lines and fast-particle diffusion in strong magnetohydrodynamic turbulence, with application to thermal conduction in galaxy clusters  

E-Print Network (OSTI)

We investigate field-line separation in strong MHD turbulence using direct numerical simulations. We find that in the static-magnetic-field approximation the thermal conductivity in galaxy clusters is reduced by a factor of about 50 relative to the Spitzer thermal conductivity of a non-magnetized plasma. This value is too small for heat conduction to balance radiative cooling in clusters.

Jason L. Maron; Benjamin D. G. Chandran; Eric G. Blackman

2003-03-11T23:59:59.000Z

139

Thermal analysis and two-directional air flow thermal management for lithium-ion battery pack  

Science Journals Connector (OSTI)

Abstract Thermal management is a routine but crucial strategy to ensure thermal stability and long-term durability of the lithium-ion batteries. An air-flow-integrated thermal management system is designed in the present study to dissipate heat generation and uniformize the distribution of temperature in the lithium-ion batteries. The system contains of two types of air ducts with independent intake channels and fans. One is to cool the batteries through the regular channel, and the other minimizes the heat accumulations in the middle pack of batteries through jet cooling. A three-dimensional anisotropic heat transfer model is developed to describe the thermal behavior of the lithium-ion batteries with the integration of heat generation theory, and validated through both simulations and experiments. Moreover, the simulations and experiments show that the maximum temperature can be decreased to 33.1C through the new thermal management system in comparison with 42.3C through the traditional ones, and temperature uniformity of the lithium-ion battery packs is enhanced, significantly.

Kuahai Yu; Xi Yang; Yongzhou Cheng; Changhao Li

2014-01-01T23:59:59.000Z

140

Final Technical Report: Numerical and Experimental Investigation of Turbulent Transport Control via Shaping of Radial Plasma Flow Profiles  

SciTech Connect

The strong coupling between the different physical variables involved in the plasma transport phenomenon and the high complexity of its dynamics call for a model-based, multivariable approach to profile control where those predictive models could be exploited. The overall objective of this project has been to extend the existing body of work by investigating numerically and experimentally active control of unstable fluctuations, including fully developed turbulence and the associated cross-field particle transport, via manipulation of flow profiles in a magnetized laboratory plasma device. Fluctuations and particle transport can be monitored by an array of electrostatic probes, and Ex#2;B flow profiles can be controlled via a set of biased concentric ring electrodes that terminate the plasma column. The goals of the proposed research have been threefold: i- to develop a predictive code to simulate plasma transport in the linear HELCAT (HELicon-CAThode) plasma device at the University of New Mexico (UNM), where the experimental component of the proposed research has been carried out; ii- to establish the feasibility of using advanced model-based control algorithms to control cross-field turbulence-driven particle transport through appropriate manipulation of radial plasma flow profiles, iii- to investigate the fundamental nonlinear dynamics of turbulence and transport physics. Lehigh University (LU), including Prof. Eugenio Schuster and one full-time graduate student, has been primarily responsible for control-oriented modeling and model-based control design. Undergraduate students have also participated in this project through the National Science Foundation Research Experience for Undergraduate (REU) program. The main goal of the LU Plasma Control Group has been to study the feasibility of controlling turbulence-driven transport by shaping the radial poloidal flow profile (i.e., by controlling flow shear) via biased concentric ring electrodes.

Schuster, Eugenio

2014-05-02T23:59:59.000Z

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


141

Effects of turbulence model on convective heat transfer of coolant flow in a prismatic very high temperature reactor core  

SciTech Connect

The existing study of Spall et al. shows that only {nu}{sup 2}-f turbulence model well matches with the experimental data of Shehata and McEligot which were obtained under strongly heated gas flows. Significant over-predictions in those literatures were observed in the convective heat transfer with the other famous turbulence models such as the k-{epsilon} and k-{omega} models. In spite of such good evidence about the performance of the{nu}{sup 2}-f model, the application of the {nu}{sup 2}-f model to the thermo-fluid analysis of a prismatic core is very rare. In this paper, therefore, the convective heat transfer of the coolant flow in a prismatic core has been investigated using the {nu}{sup 2}-f model. Computational fluid dynamics (CFD) calculations have been carried out for the typical unit cell geometry of a prismatic fuel column with typical operating conditions of prismatic designs. The tested Reynolds numbers of the coolant flow are 10,000, 20,000, 30,000 and 50,000. The predicted Nusselt numbers with the {nu}{sup 2}-f model are compared with the results by the other turbulence models (k-{epsilon} and SST) as well as the empirical correlations. (authors)

Lee, S. N.; Tak, N. I.; Kim, M. H.; Noh, J. M. [Korea Atomic Energy Research Inst., Daedeok-daero 989-11, Yuseong-gu, Daejeon (Korea, Republic of)

2012-07-01T23:59:59.000Z

142

Thermal end effects on electroosmotic flow in a capillary Xiangchun Xuan, David Sinton, Dongqing Li *  

E-Print Network (OSTI)

Thermal end effects on electroosmotic flow in a capillary Xiangchun Xuan, David Sinton, Dongqing Li [16,17] etc.). Using caged-dye based flow visualization, Sinton and Li [18] found a slight curvature

Xuan, Xiangchun "Schwann"

143

Enhanced thermal and gas flow performance in a three-way catalytic...  

Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

flow performance in a three-way catalytic converter through use of insulation within the ceramic monolith Enhanced thermal and gas flow performance in a three-way catalytic...

144

Application of the velocity-dissipation probability density function model to inhomogeneous turbulent flows  

E-Print Network (OSTI)

Application of the velocity-dissipation probability density function model to inhomogeneous. Fluids A 2, 1437 ( 1990) ] developed a turbulence model based on the one-point Eulerian joint probability were constructed by reference to the known statistics of homogenous turbulence, and the applicability

145

An experimental investigation on turbulent flow through symmetric wall subchannels of two rod bundles  

SciTech Connect

Measurements of the mean velocity, wall shear stresses, and turbulent Reynolds stresses have been performed in wall subchannels of two rod bundles. The rod bundle of four parallel rods was arranged symmetrically in a rectangular channel. The pitch-to-diameter ratio was 1.148, and the wall-to-diameter ratios were 1.045 and 1.074, respectively. The Reynolds numbers in these investigations were 6.11 {times} 10{sup 4} and 7.07 {times} 10{sup 4}, respectively. The experimental results demonstrate that the structure of turbulence in rod bundles differs greatly from the structure in circular tubes. Especially in the narrow gaps between the rods and channel walls, there are increased levels of turbulence intensities in both the axial and azimuthal directions and, hence, of the kinetic energy of turbulence, caused by a strong turbulent momentum transport through the gaps.

Wu, S.R. (Inst. of Nuclear Energy Technology, Tsinghua Univ., P.O. Box 1021, Beijing (CN)); Rehme, K. (Kernforschungszentrum Karlsruhe GmbH (Germany, F.R.). Inst. fuer Neutronenphysik und Reaktortechnik)

1990-01-01T23:59:59.000Z

146

Contribution to the numerical study of turbulence in high intensity discharge lamps  

SciTech Connect

We present in this paper a comparison between results obtained with a laminar and turbulent models for high-pressure mercury arc. The two models are based on the resolution of bidimensional time-dependent equations by a semi-implicit finite-element code. The numerical computation of turbulent model is solved with large eddy simulation model; this approach takes into account the various scales of turbulence by a filtering method on each scale. The results show the quantitative influence of turbulence on the flow fields and also the difference between laminar and turbulent effects on the dynamic thermal behaviour and on the characteristics of the discharge.

Kaziz, S.; Ben Ahmed, R.; Helali, H.; Gazzah, H.; Charrada, K. [Unite d'Etude des Milieux Ionises et Reactifs, IPEIM, 5019 route de Kairouan Monastir (Tunisia)

2011-07-15T23:59:59.000Z

147

Numerical study of fluid flow and heat transfer characteristics inanintermittent turbulent impinging round jet  

Science Journals Connector (OSTI)

Abstract The flow structure and heat transfer of the air pulsed turbulent impinging jet are studied numerically. The gas turbulence is modelled with the Reynolds stress model. The effects of pulse frequency, ratio of on time to total cycle time, distance between pipe outlet and impinging flat plate and Reynolds number on heat transfer are numerically studied. The impingement heat transfer increases with distance from the pipe edge and target surface. The heat transfer decreases at high distance from the pipe edge and target surface. An increase in the Reynolds number causes reduction of heat transfer enhancement. Reduced heat transfer in comparison with the steady-state impinging jet is typical in the range of low frequencies of the pulse impinging jet.

M.A. Pakhomov; V.I. Terekhov

2015-01-01T23:59:59.000Z

148

Dispersion of swimming algae in laminar and turbulent channel flows: consequences for photobioreactors  

Science Journals Connector (OSTI)

...24 30 18 Dispersion of swimming algae in laminar and turbulent channel...affects the transport of swimming algae in suspension. For example, viscous...SA Scott, and AG Smith. 2010 Biodiesel from algae: challenges and prospects. Energy...

2013-01-01T23:59:59.000Z

149

Analysis and identification of vortices within a turbulent channel boundary layer flow  

E-Print Network (OSTI)

understanding of the drag reduction mechanism is still lacking. Vortices play an important role in turbulence structure. Nevertheless, the identification of vortices is still unclear, not even a universal definition of a vortex is accepted. In the present study...

Maroni Veiga, Adrian Gaston

2006-08-16T23:59:59.000Z

150

Measurement of wall pressure fluctuations in the presence of vibrations induced by a turbulent flow  

Science Journals Connector (OSTI)

A systematic study of the methods of measuring wall pressure fluctuations against a background of intense vibrations is carried out. The method of separating the turbulent signal from noise on the basis of mon...

E. B. Kudashev

2003-03-01T23:59:59.000Z

151

Divergence of Neighboring Magnetic-Field Lines and Fast-Particle Diffusion in Strong Magnetohydrodynamic Turbulence, with Application to Thermal Conduction in Galaxy Clusters  

Science Journals Connector (OSTI)

Using direct numerical simulations, we calculate the rate of divergence of neighboring magnetic-field lines in different types of strong magnetohydrodynamic turbulence. In the static-magnetic-field approximation, our results imply that tangled magnetic fields in galaxy clusters reduce the electron diffusion coefficient and thermal conductivity by a factor of ?510, relative to their values in a nonmagnetized plasma.

Jason Maron; Benjamin D. G. Chandran; Eric Blackman

2004-01-27T23:59:59.000Z

152

Wake Turbulence of Two NREL 5-MW Wind Turbines Immersed in a Neutral Atmospheric Boundary-Layer Flow  

E-Print Network (OSTI)

The fluid dynamics video considers an array of two NREL 5-MW turbines separated by seven rotor diameters in a neutral atmospheric boundary layer (ABL). The neutral atmospheric boundary-layer flow data were obtained from a precursor ABL simulation using a Large-Eddy Simulation (LES) framework within OpenFOAM. The mean wind speed at hub height is 8m/s, and the surface roughness is 0.2m. The actuator line method (ALM) is used to model the wind turbine blades by means of body forces added to the momentum equation. The fluid dynamics video shows the root and tip vortices emanating from the blades from various viewpoints. The vortices become unstable and break down into large-scale turbulent structures. As the wakes of the wind turbines advect further downstream, smaller-scale turbulence is generated. It is apparent that vortices generated by the blades of the downstream wind turbine break down faster due to increased turbulence levels generated by the wake of the upstream wind turbine.

Bashioum, Jessica L; Schmitz, Sven; Duque, Earl P N

2013-01-01T23:59:59.000Z

153

Geothermal Resource-Reservoir Investigations Based On Heat Flow And Thermal  

Open Energy Info (EERE)

Resource-Reservoir Investigations Based On Heat Flow And Thermal Resource-Reservoir Investigations Based On Heat Flow And Thermal Gradient Data For The United States Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Report: Geothermal Resource-Reservoir Investigations Based On Heat Flow And Thermal Gradient Data For The United States Details Activities (2) Areas (2) Regions (0) Abstract: Several activities related to geothermal resources in the western United States are described in this report. A database of geothermal site-specific thermal gradient and heat flow results from individual exploration wells in the western US has been assembled. Extensive temperature gradient and heat flow exploration data from the active exploration of the 1970's and 1980's were collected, compiled, and synthesized, emphasizing previously unavailable company data. Examples of

154

Comparative study of laminar and turbulent flow model with different operating parameters for radio frequency-inductively coupled plasma torch working at 3??MHz frequency at atmospheric pressure  

Science Journals Connector (OSTI)

This paper provides 2D comparative study of results obtained using laminar and turbulent flow model for RF (radio frequency) Inductively Coupled Plasma (ICP) torch. The study was done for the RF-ICP torch operating at 50?kW DC power and 3?MHz frequency located at BARC. The numerical modeling for this RF-ICP torch is done using ANSYS software with the developed User Defined Function. A comparative study is done between laminar and turbulent flow model to investigate how temperature and flow fields change when using different operating conditions such as (a) swirl and no swirl velocity for sheath gas flow rate (b) variation in sheath gas flow rate and (c) variation in plasma gas flow rate. These studies will be useful for different material processing applications.

Sangeeta B. Punjabi; S. N. Sahasrabudhe; N. K. Joshi; H. A. Mangalvedekar; A. K. Das; D. C. Kothari

2014-01-01T23:59:59.000Z

155

Wall-bounded turbulent shear flow: Analytic result for a universal amplitude  

Science Journals Connector (OSTI)

In the turbulent boundary layer above a flat plate, the velocity profile is known to have the form v=v0[(1/?)ln z+const]. The distance from the wall in dimensionless units is z and v0 is a uniquely defined velocity scale. The number ? is universal, and measurements over several decades have shown that it is nearly 0.42. We use a randomly stirred model of turbulence to derive the above law and find ?=108/125??0.52.

Amit Kr. Chattopadhyay and Jayanta K. Bhattacharjee

2000-12-21T23:59:59.000Z

156

Numerical simulation of air/H2 combustion processes in a scramjet turbulent flow  

Science Journals Connector (OSTI)

The aim of this work is to develop a numerical approach, based on the Favre's averaged Navier-Stokes equations coupled with a turbulence model and with a complex finite rate Air/Hydrogen combustion kinetic model to simulate the unsteady axisymetric supersonic hydrogen-air mixing processes. The main application is dedicated to the scramjet hypersonic air-breathing propulsion engine. To achieve this goal the Spalart-Allmaras turbulence model (SA) with correction terms to model the compressibility effects and the complete finite rate chemistry model of Jachimowsky involving 13 species and 153 reactions have been implemented in a finite volume code.

Y. Burtschell; S. Seror; J.D. Parisse; D. Zeitoun

2008-01-01T23:59:59.000Z

157

Comparative study of the vorticity field in turbulent flows: Theory, experiments, computations  

SciTech Connect

The Goal of the project was to understand the role of topology vortex lines in general and the helicity invariant (inviscid) in particular for turbulent dynamics. The project consisted of three main ingredients: theoretical, numerical and experimental. The achievements and failures of the above are separately reported in this paper.

Levich, E.

1991-09-01T23:59:59.000Z

158

Comparative study of the vorticity field in turbulent flows: Theory, experiments, computations. Final report  

SciTech Connect

The Goal of the project was to understand the role of topology vortex lines in general and the helicity invariant (inviscid) in particular for turbulent dynamics. The project consisted of three main ingredients: theoretical, numerical and experimental. The achievements and failures of the above are separately reported in this paper.

Levich, E.

1991-09-01T23:59:59.000Z

159

Rapid Solar-thermal Dissociation of Natural Gas in an Aerosol Flow Reactor  

E-Print Network (OSTI)

/or hydrogen powered fuel cell vehicles could help to mitigate the energy supply and environmental problems black production. For solar-thermal processing, where carbon black is sold, fossil energy usageRapid Solar-thermal Dissociation of Natural Gas in an Aerosol Flow Reactor Jaimee Dahl a , Karen

160

An analog analysis of transient heat flow in solids with temperature-dependent thermal properties  

E-Print Network (OSTI)

) used a nonlinear material known as Metrosil to simulate the nonlinear variations of thermal properties for combined conductive and radiant heat transfer. Since that time, Friedmann (8) has used nonlinear resistances in conjunction with an electronic... at end of this thesis. K = thermal conductivity of heat conducting media, and K and S are functions of the temperature t. Since the formation of these equations, solutions of transient heat flow problems involving materials in which the thermal...

Lee, Dwain Edward

2012-06-07T23:59:59.000Z

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


161

A New Aerosol Flow System for Photochemical and Thermal Studies...  

NLE Websites -- All DOE Office Websites (Extended Search)

be applied simultaneously. The residence time is of the order of an hour, and sampling ports located along the length of the flow tube allow for time-resolved measurements of...

162

Thermal boundary layer development in dispersed flow film boiling  

E-Print Network (OSTI)

Dispersed flow film boiling consists of a dispersion of droplets which are carried over a very hot surface by their vapor. This process occurs in cryogenic equipment and wet steam turbines. It is also of interest in the ...

Hull, Lawrence M.

1982-01-01T23:59:59.000Z

163

On Challenges for Hypersonic Turbulent Simulations  

SciTech Connect

This short note discusses some of the challenges for design of suitable spatial numerical schemes for hypersonic turbulent flows, including combustion, and thermal and chemical nonequilibrium flows. Often, hypersonic turbulent flows in re-entry space vehicles and space physics involve mixed steady strong shocks and turbulence with unsteady shocklets. Material mixing in combustion poses additional computational challenges. Proper control of numerical dissipation in numerical methods beyond the standard shock-capturing dissipation at discontinuities is an essential element for accurate and stable simulations of the subject physics. On one hand, the physics of strong steady shocks and unsteady turbulence/shocklet interactions under the nonequilibrium environment is not well understood. On the other hand, standard and newly developed high order accurate (fourth-order or higher) schemes were developed for homogeneous hyperbolic conservation laws and mixed hyperbolic and parabolic partial differential equations (PDEs) (without source terms). The majority of finite rate chemistry and thermal nonequilibrium simulations employ methods for homogeneous time-dependent PDEs with a pointwise evaluation of the source terms. The pointwise evaluation of the source term might not be the best choice for stability, accuracy and minimization of spurious numerics for the overall scheme.

Yee, H C; Sjogreen, B

2009-01-14T23:59:59.000Z

164

AN ASSESSMENT OF THE ACCURACY OF MAGENTIC RESONANCE PHASE VELOCITY MAPPING IN TURBULENT FLOW THROUGH ORIFICES.  

E-Print Network (OSTI)

?? Magnetic resonance phase velocity mapping (MRPVM) is an established clinical technique to measure blood flow. The acquired information can be used to diagnose a (more)

Pidaparthi, Sahitya

2011-01-01T23:59:59.000Z

165

Numerical and experimental investigations on vibration of simulated CANDU fuel bundles subjected to turbulent fluid flow.  

E-Print Network (OSTI)

??Vibration of simulated CANDU fuel bundles induced by coolant flow is investigated in this thesis through experiments and numerical simulations. Two simulated bundles and a (more)

Zhang, Xuan

2011-01-01T23:59:59.000Z

166

A Numerical Method for DNS/LES of Turbulent Reacting Flows Jeff Doom, Yucheng Hou & Krishnan Mahesh  

E-Print Network (OSTI)

of the solution. Turbulent combustion can occur at very low Mach numbers (e.g. gas-turbine combustors at low thicknesses. Turbulence introduces its own range of length and time-scales. Furthermore the nonlinear nature

Mahesh, Krishnan

167

JOURNAL OF COMPUTATIONAL PHYSICS 26, 197-217 (1978) The Calculation of Turbulent Recirculating Flows  

E-Print Network (OSTI)

is more suited to the calculation of the flow in gas-turbine com- bustion chambers of varying radius Flows in General Orthogonal Coordinates s. B. POPE' Imperial College of Science and Technology in Cartesian coordinates. A calculation procedure is developed by representing the conservation equations

168

Turbulent combustion  

SciTech Connect

Turbulent combustion is the dominant process in heat and power generating systems. Its most significant aspect is to enhance the burning rate and volumetric power density. Turbulent mixing, however, also influences the chemical rates and has a direct effect on the formation of pollutants, flame ignition and extinction. Therefore, research and development of modern combustion systems for power generation, waste incineration and material synthesis must rely on a fundamental understanding of the physical effect of turbulence on combustion to develop theoretical models that can be used as design tools. The overall objective of this program is to investigate, primarily experimentally, the interaction and coupling between turbulence and combustion. These processes are complex and are characterized by scalar and velocity fluctuations with time and length scales spanning several orders of magnitude. They are also influenced by the so-called {open_quotes}field{close_quotes} effects associated with the characteristics of the flow and burner geometries. The authors` approach is to gain a fundamental understanding by investigating idealized laboratory flames. Laboratory flames are amenable to detailed interrogation by laser diagnostics and their flow geometries are chosen to simplify numerical modeling and simulations and to facilitate comparison between experiments and theory.

Talbot, L.; Cheng, R.K. [Lawrence Berkeley Laboratory, CA (United States)

1993-12-01T23:59:59.000Z

169

New models for wind noise measured in a flat surface under turbulent flow.  

Science Journals Connector (OSTI)

We have previously developed models for predicting the power spectral density of the wind noisepressuremeasured in a flat plate outdoors from the measured power spectral density of the turbulence and the measured wind velocity profile above the plate [Yu et al. Proceedings of NCAD 2008 NoiseCon2008?ASME NCAD]. Recently we have corrected an error in the model for the logarithmic profile wind velocity gradient results and have developed an improved integration method. Also we have developed a prediction for arbitrary wind velocity profiles using the previous single exponential model. Typical results comparing our predictions with our measurements are presented and analyzed. A simple algebraic fit to the prediction for the logarithmic profile fit form is also provided for use by others. [Research supported by the U.S. Army TACOM?ARDEC at Picatinny Arsenal NJ.

2009-01-01T23:59:59.000Z

170

Heat-transfer mechanism in turbulent flow of fluid at supercritical pressures  

Science Journals Connector (OSTI)

A hypothetical physical model of the heat-transfer process accompanying a forced flow of liquid at supercritical pressures is proposed. This model accounts for the anomalous improvements and deteriorations in ...

Sh. G. Kaplan

1971-09-01T23:59:59.000Z

171

A thermal distribution function for relativistic magnetically insulated electron flows  

SciTech Connect

A distribution function is presented that may be used to study the effects of finite temperature on the equilibrium and stability properties of magnetically insulated electron flows. This distribution function has the useful property that it generates the thoroughly studied class of constant Q = ..omega../sup 2//sub p//..cap omega../sup 2/ equilibria in its zero-temperature limit. Analytic solutions are given for the general, constant Q, zero-temperature equilibria.

Desjarlais, M.P.; Sudan, R.N.

1986-05-01T23:59:59.000Z

172

A thermal distribution function for relativistic magnetically insulated electron flows  

Science Journals Connector (OSTI)

A distribution function is presented that may be used to study the effects of finite temperature on the equilibrium and stability properties of magnetically insulated electron flows. This distribution function has the useful property that it generates the thoroughly studied class of constant Q=?2 p /?2 equilibria in its zero?temperature limit. Analytic solutions are given for the general constant Q zero?temperature equilibria.

M. P. Desjarlais; R. N. Sudan

1986-01-01T23:59:59.000Z

173

Usage of turbulence for superresolved imaging  

Science Journals Connector (OSTI)

We have used the turbulent flow of hot air to improve the diffraction limits of resolution in an imaging system. A time-multiplexing approach was applied and used the turbulent flow...

Zalevsky, Zeev; Rozental, Shay; Meller, Moshe

2007-01-01T23:59:59.000Z

174

Radiative Transfer of Sound Waves in a Random Flow: Turbulent Scattering and ModeCoupling  

E-Print Network (OSTI)

systematically to derive the radiative transport equations that describe the evolution of acoustic correlation : : : : : : : : : : : : : : : : : : : : 8 3.2 The radiative transport equations : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 9 of the radiative transport equations 21 B Derivation of the diffusion equation without flow­straining 23 C

Ryzhik, Lenya

175

Modeling evaporation from porous medium influenced by turbulent free flow Thomas Fetzer  

E-Print Network (OSTI)

toolbox freeflow (1p2c) direct numerical simulation Reynolds-averaged- Navier-Stokes (RANS) Stokes flow medium (2p2c) direct numerical simulation pore network modeling representative elementary volume (REV as a one-phase, two-component system (1p2c), the porous medium as a two-phase, two-component system (2p2c

Cirpka, Olaf Arie

176

Flow distribution analysis on the cooling tube network of ITER thermal shield  

SciTech Connect

Thermal shield (TS) is to be installed between the vacuum vessel or the cryostat and the magnets in ITER tokamak to reduce the thermal radiation load to the magnets operating at 4.2K. The TS is cooled by pressurized helium gas at the inlet temperature of 80K. The cooling tube is welded on the TS panel surface and the composed flow network of the TS cooling tubes is complex. The flow rate in each panel should be matched to the thermal design value for effective radiation shielding. This paper presents one dimensional analysis on the flow distribution of cooling tube network for the ITER TS. The hydraulic cooling tube network is modeled by an electrical analogy. Only the cooling tube on the TS surface and its connecting pipe from the manifold are considered in the analysis model. Considering the frictional factor and the local loss in the cooling tube, the hydraulic resistance is expressed as a linear function with respect to mass flow rate. Sub-circuits in the TS are analyzed separately because each circuit is controlled by its own control valve independently. It is found that flow rates in some panels are insufficient compared with the design values. In order to improve the flow distribution, two kinds of design modifications are proposed. The first one is to connect the tubes of the adjacent panels. This will increase the resistance of the tube on the panel where the flow rate is excessive. The other design suggestion is that an orifice is installed at the exit of tube routing where the flow rate is to be reduced. The analysis for the design suggestions shows that the flow mal-distribution is improved significantly.

Nam, Kwanwoo; Chung, Wooho; Noh, Chang Hyun; Kang, Dong Kwon; Kang, Kyoung-O; Ahn, Hee Jae; Lee, Hyeon Gon [ITER Korea, National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of)

2014-01-29T23:59:59.000Z

177

Turbulence Structure and Wall Signature in Hypersonic Turbulent Boundary Layer  

E-Print Network (OSTI)

Turbulence Structure and Wall Signature in Hypersonic Turbulent Boundary Layer Yin-Chiu Kan , Clara and hypersonic turbulent boundary layer datasets from direct numerical simulation (DNS). Contour plots and Marusic5 and Mathis, Hutchins and Marusic16 ). In contrast to supersonic and hypersonic flow regimes

Martín, Pino

178

Thermal anomalies indicate preferential flow along faults in unconsolidated sedimentary aquifers  

E-Print Network (OSTI)

Thermal anomalies indicate preferential flow along faults in unconsolidated sedimentary aquifers V in unconsolidated siliciclastic aquifers off-set by normal-faults in the Lower Rhine Embayment, Germany. High plane. Most current models of fault hydrology in unconsolidated sedimentary sequences assume faults

Bense, Victor

179

Heat flow determinations and implied thermal regime of the Coso geothermal  

Open Energy Info (EERE)

determinations and implied thermal regime of the Coso geothermal determinations and implied thermal regime of the Coso geothermal area, California Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Conference Proceedings: Heat flow determinations and implied thermal regime of the Coso geothermal area, California Details Activities (1) Areas (1) Regions (0) Abstract: Obvious surface manifestations of an anomalous concentration of geothermal energy at the Coso Geothermal Area, California, include fumarolic activity, active hot springs, and associated hydrothermally altered rocks. Abundant Pleistocene volcanic rocks, including a cluster of thirty-seven rhyolite domes, occupy a north-trending structural and topographic ridge near the center of an oval-shaped zone of late Cenozoic ring faulting. In an investigation of the thermal regime of the geothermal

180

LATERAL HEAT FLOW INFRARED THERMOGRAPHY FOR THICKNESS INDEPENDENT DETERMINATION OF THERMAL DIFFUSIVITY IN CFRP  

SciTech Connect

In conventional infrared thermography, determination of thermal diffusivity requires thickness information. Recently GE has been experimenting with the use of lateral heat flow to determine thermal diffusivity without thickness information. This work builds on previous work at NASA Langley and Wayne State University but we incorporate thermal time of flight (tof) analysis rather than curve fitting to obtain quantitative information. We have developed appropriate theoretical models and a tof based data analysis framework to experimentally determine all components of thermal diffusivity from the time-temperature measurements. Initial validation was carried out using finite difference simulations. Experimental validation was done using anisotropic carbon fiber reinforced polymer (CFRP) composites. We found that in the CFRP samples used, the in-plane component of diffusivity is about eight times larger than the through-thickness component.

Tralshawala, Nilesh; Howard, Don; Knight, Bryon; Plotnikov, Yuri; Ringermacher, Harry [Nondestructive Technologies Laboratory, GE--Global Research Center, Niskayuna, NY 12309 (United States)

2008-02-28T23:59:59.000Z

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


181

The flow and heat transfer characteristics of multi-thermal fluid in horizontal wellbore coupled with flow in heavy oil reservoirs  

Science Journals Connector (OSTI)

Abstract As a new improved oil-recovery technique, multi-thermal fluid injection technology through a horizontal well has been widely used in the development process of heavy oil reservoirs. The flow and heat transfer characteristic of multi-thermal fluid in horizontal wellbore is significantly important for the productivity evaluation and parameters design of the horizontal well. Considering the specific physical properties of multi-thermal fluid, fluid absorption in perforation holes and pressure drop characteristics along the horizontal wellbore, this paper developed the flow and heat transfer model of multi-thermal fluid in perforated horizontal wellbore. In order to evaluate the heating effect of the multi-thermal fluid, a concept of effective heating length of a horizontal well is proposed. Then, a sensitivity analysis process is performed to study the influence of reservoir/fluid parameters and operating parameters on the flowing process of multi-thermal fluid in horizontal wellbore. Simultaneously, using the method of orthogonal numerical test, differential analysis and variance analysis are also conducted. Results show that the flowing process of multi-thermal fluid in horizontal wellbore includes a single-phase flowing process and a gasliquid two-phase flowing process. The influence of oil viscosity on the flow and heat transfer characteristics of multi-thermal fluid in horizontal wellbore is most significant. Thereafter, the solution of our semi-analytical model is compared against the test results of an actual horizontal well from an oilfield in China. It is shown that the model results are in good agreement with the real test results. This model could be used to calculate and predict the flow and heat transfer characteristics of multi-thermal fluid (or saturated steam) in a perforated horizontal wellbore.

Xiaohu Dong; Huiqing Liu; Zhaoxiang Zhang; Changjiu Wang

2014-01-01T23:59:59.000Z

182

Turbulent heat transfer characteristics in a circular tube and thermal properties of n-decane-in-water nanoemulsion fluids and micelles-in-water fluids  

Science Journals Connector (OSTI)

Abstract We carry out experimental studies of turbulent convective heat transfer of several n-decane-in-water nanoemulsions and micelles-in-water fluids. We characterize the viscosity and thermal properties of the nanofluids, and the nanoparticle distributions and shapes with various techniques, including transmission electron microscopy. We find that the thermal conductivity of the nanofluids is lower than that of the base fluid, and the conductivity shows no anomalous behavior. Despite this we find that the average Nusselt numbers and convective heat transfer coefficients are enhanced for low volume fractions when the Reynolds number Re>7000, in agreement with solid particle nanofluids. However, when the pressure losses are taken into account, we find that the nanofluids studied have a practical efficiency equal to or less than that of the base fluid. The highest heat transfer enhancements were obtained with volume fractions considerably smaller than those for the solid particle nanofluids. Our results indicate that the improved heat transfer is due to enhancement of turbulence in the large Re regime.

Sampo Saarinen; Salla Puupponen; Arttu Merilinen; Aliakbar Joneidi; Ari Seppl; Kari Saari; Tapio Ala-Nissila

2015-01-01T23:59:59.000Z

183

A Generic Model for the Resuspension of Multilayer Aerosol Deposits by Turbulent Flow  

SciTech Connect

An idealized lattice structure is considered of multilayer aerosol deposits, where every particle at the deposit surface is associated with a resuspension rate constant depending on a statistically distributed particle parameter and on flow conditions. The response of this generic model is represented by a set of integrodifferential equations. As a first application of the general formalism, the behavior of Fromentin's multilayer model is analyzed, and the model parameters are adapted to experimental data. In addition, improved relations between model parameters and physical input parameters are proposed. As a second application, a method is proposed for building multilayer models by using resuspension rate constants of existing monolayer models. The method is illustrated by a sample of monolayer data resulting from the model of Reeks, Reed, and Hall. Also discussed is the error to be expected if a monolayer resuspension model, which works well for thin aerosol deposits, is applied to thick deposits under the classical monolayer assumption that all deposited particles interact with the fluid at all times.

Friess, H.; Yadigaroglu, G. [Swiss Federal Institute of Technology (Switzerland)

2001-06-15T23:59:59.000Z

184

Dynamic electro-thermal modeling of all-vanadium redox flow battery with forced cooling strategies  

Science Journals Connector (OSTI)

Abstract The present study focuses on the dynamic electro-thermal modeling for the all-vanadium redox flow battery (VRB) with forced cooling strategies. The Foster network is adopted to dynamically model the heat dissipation of VRB with heat exchangers. The parameters of Foster network are extracted by fitting the step response of it to the results of linearized CFD model. Then a complete electro-thermal model is proposed by coupling the heat generation model, Foster network and electrical model. Results show that the established model has nearly the same accuracy with the nonlinear CFD model in electrolyte temperature prediction but drastically improves the computational efficiency. The modeled terminal voltage is also benchmarked with the experimental data under different current densities. The electrolyte temperature is found to be significantly influenced by the flow rate of coolant. As compared, although the electrolyte flow rate has unremarkable impact on electrolyte temperature, its effect on system pressure drop and battery efficiency is significant. Increasing the electrolyte flow rate improves the coulombic efficiency, voltage efficiency and energy efficiency simultaneously but at the expense of higher pump power demanded. An optimal flow rate exists for each operating condition to maximize the system efficiency.

Zhongbao Wei; Jiyun Zhao; Binyu Xiong

2014-01-01T23:59:59.000Z

185

Global simulations of magnetorotational turbulence II. Turbulent energetics  

Science Journals Connector (OSTI)

......Importantly, as we are using an ideal MHD simulation, this shows that...construct a simplified energy flow diagram, which is shown in Fig...the heart of self-sustaining MHD turbulence in accretion discs. Figure 14. Energy flow diagram for turbulence in a global disc......

E. R. Parkin

2014-01-01T23:59:59.000Z

186

Detailed numerical modeling of chemical and thermal nonequilibrium in hypersonic flows  

SciTech Connect

Interest in hypersonic flows has created a large demand for physicochemical models for air flow computations around reentry bodies. Detailed physicochemical models for air in chemical and thermal nonequilibrium are needed for a realistic prediction of hypersonic flowfields. In this paper we develop a model, based on elementary physicochemical processes, for a detailed description of chemical nonequilibrium together with the excitation of internal DOFs. This model is implemented in a 2D Navier-Stokes code in order to show the strong influence of thermal nonequilibrium on the flowfields. The algorithm presented here is based on a fully conservative discretization of the inviscid fluxes in the conservation equations and uses the chain rule conservation law form for the viscous fluxes. The large system of ordinary differential and algebraic equations resulting from the spatial discretization is solved by a time-accurate semiimplicit extrapolation method. 34 refs.

Riedel, U.; Maas, U.; Warnatz, J. (Stuttgart Univ. (Germany))

1993-03-01T23:59:59.000Z

187

Heat release effects on decaying homogeneous compressible turbulence  

E-Print Network (OSTI)

turbulence. A good understanding of high-enthalpy compressible turbulence is crucial for analyzing the flow around re-entry spacecrafts and hypersonic flight vehicles, and inside scramjet engines. One main factor affecting turbulence in these high...

Lee, Kurn Chul

2009-05-15T23:59:59.000Z

188

23.11.2014bo Akademi Univ -Thermal and Flow Engineering Piispankatu 8, 20500 Turku 1/36 7. Air conditioning, cooling towers  

E-Print Network (OSTI)

23.11.2014?bo Akademi Univ - Thermal and Flow Engineering Piispankatu 8, 20500 Turku 1/36 7. Air conditioning, cooling towers Ron Zevenhoven ?bo Akademi University Thermal and Flow Engineering Laboratory Engineering Piispankatu 8, 20500 Turku 2/36 7.1 Humid air #12;23.11.2014 ?bo Akademi Univ - Thermal and Flow

Zevenhoven, Ron

189

Effect of the forcing term in the pseudopotential lattice Boltzmann modeling of thermal flows  

E-Print Network (OSTI)

The pseudopotential lattice Boltzmann (LB) model is a popular model in the LB community for simulating multiphase flows. Recently, several thermal LB models, which are based on the pseudopotential LB model and constructed within the framework of the double-distribution-function LB method, were proposed to simulate thermal multiphase flows [G. H\\'azi and A. M\\'arkus, Phys. Rev. E 77, 026305 (2008); L. Biferale et al., Phys. Rev. Lett. 108, 104502 (2012); S. Gong and P. Cheng, Int. J. Heat Mass Transfer 55, 4923 (2012)]. The objective of the present paper is to show that the effect of the forcing term on the temperature equation must be eliminated in the pseudopotential LB modeling of thermal flows. First, the effect of the forcing term on the temperature equation is shown via the Chapman-Enskog analysis. For comparison, alternative treatments that are free from the forcing-term effect are provided. Subsequently, numerical investigations are performed for two benchmark tests. The numerical results clearly show ...

Li, Q

2014-01-01T23:59:59.000Z

190

A New Aerosol Flow System for Photochemical and Thermal Studies of Tropospheric Aerosols  

SciTech Connect

For studying the formation and photochemical/thermal reactions of aerosols relevant to the troposphere, a unique, high-volume, slow-flow, stainless steel aerosol flow system equipped with 5 UV lamps has been constructed and characterized experimentally. The total flow system length 6 is 8.5 m and includes a 1.2 m section used for mixing, a 6.1 m reaction section and a 1.2 m 7 transition cone at the end. The 45.7 cm diameter results in a smaller surface to volume ratio than is found in many other flow systems and thus reduces the potential contribution from wall reactions. The latter are also reduced by frequent cleaning of the flow tube walls which is made feasible by the ease of disassembly. The flow tube is equipped with ultraviolet lamps for photolysis. This flow system allows continuous sampling under stable conditions, thus increasing the amount of sample available for analysis and permitting a wide variety of analytical techniques to be applied simultaneously. The residence time is of the order of an hour, and sampling ports located along the length of the flow tube allow for time-resolved measurements of aerosol and gas-phase products. The system was characterized using both an inert gas (CO2) and particles (atomized NaNO3). Instruments interfaced directly to this flow system include a NOx analyzer, an ozone analyzer, relative humidity and temperature probes, a scanning mobility particle sizer spectrometer, an aerodynamic particle sizer spectrometer, a gas chromatograph-mass spectrometer, an integrating nephelometer, and a Fourier transform infrared spectrophotometer equipped with a long path (64 m) cell. Particles collected with impactors and filters at the various sampling ports can be analyzed subsequently by a variety of techniques. Formation of secondary organic aerosol from ?-pinene reactions (NOx photooxidation and ozonolysis) are used to demonstrate the capabilities of this new system.

Ezell, Michael J.; Johnson, Stanley N.; Yu, Yong; Perraud, Veronique; Bruns, Emily; Alexander, M. L.; Zelenyuk, Alla; Dabdub, Donald; Finlayson-Pitts, Barbara J.

2010-05-01T23:59:59.000Z

191

List of Publications A Numerical Study of Transient Mixed Convection Flows in a Thermal Storage Tank, J. Solar  

E-Print Network (OSTI)

List of Publications A Numerical Study of Transient Mixed Convection Flows in a Thermal Storage Tank, J. Solar Energy Eng. 105, 246­253 (1983) (with A.M.C. Chan & D. Giusti) An Approximate Analytical

Smereka, Peter

192

Oxygen sorption and thermal regeneration of sorption centers on catalysts of ammonia synthesis in helium and hydrogen flow  

Science Journals Connector (OSTI)

The interaction of oxygen with catalysts for ammonia synthesis in helium and hydrogen flow has been studied. Various catalysts sorb from 7 to 12 oxygen layers. 2 to 4 layers can be removed by thermal activatio...

A. V. Krylova; V. V. Morozov; S. S. Lachinov

193

Flightcrash events in turbulence  

Science Journals Connector (OSTI)

...Institute of Science, Rehovot 76100...Mechanical and Aerospace Engineering, Cornell...14). The recent advances in our ability...turbulent flow . Science 311 ( 5762 ): 835...turbulence: recent results...Cooperation in Science and Technology...

Haitao Xu; Alain Pumir; Gregory Falkovich; Eberhard Bodenschatz; Michael Shats; Hua Xia; Nicolas Francois; Guido Boffetta

2014-01-01T23:59:59.000Z

194

Holographic Vortex Liquids and Superfluid Turbulence  

Science Journals Connector (OSTI)

...of Kelvin waves flowing along vortex strings in 3D quantum turbulence...theory correlators from non-critical string theory . Phys. Lett. B...S. , Emergence of turbulence in an oscillating Bose-Einstein condensate . Phys. Rev...

Paul M. Chesler; Hong Liu; Allan Adams

2013-07-26T23:59:59.000Z

195

Effect of Finite-rate Chemical Reactions on Turbulence in Hypersonic Turbulent Boundary Layers  

E-Print Network (OSTI)

Effect of Finite-rate Chemical Reactions on Turbulence in Hypersonic Turbulent Boundary Layers Lian on future air-breathing hypersonic cruise vehicles will be turbulent and chemically reacting. To aid the design of such vehicles, a greater understanding of turbulent hypersonic flows is needed. Although

Martín, Pino

196

Thermalization, Isotropization and Elliptic Flow from Nonequilibrium Initial Conditions with a Saturation Scale  

E-Print Network (OSTI)

In this article we report on our results about the computation of the elliptic flow of the quark-gluon-plasma produced in relativistic heavy ion collisions, simulating the expansion of the fireball by solving the relativistic Boltzmann equation for the parton distribution function tuned at a fixed shear viscosity to entropy density ratio $\\eta/s$. Our main goal is to put emphasis on the role of a saturation scale in the initial gluon spectrum, which makes the initial distribution far from a thermalized one. We find that the presence of the saturation scale reduces the efficiency in building-up the elliptic flow, even if the thermalization process is quite fast $\\tau_{therm} \\approx 0.8 \\,\\rm fm/c$ and the pressure isotropization even faster $\\tau_{isotr} \\approx 0.3 \\,\\rm fm/c$. The impact of the non-equilibrium implied by the saturation scale manifests for non-central collisions and can modify the estimate of the viscosity respect to the assumption of full thermalization in $p_T$-space. We find that the estimate of $\\eta/s$ is modified from $\\eta/s \\approx 2/4\\pi$ to $\\eta/s \\approx 1/4\\pi$ at RHIC and from $\\eta/s \\approx 3/4\\pi$ to $\\eta/s \\approx 2/4\\pi$ at LHC. We complete our investigation by a study of the thermalization and isotropization times of the fireball for different initial conditions and values of $\\eta/s$ showing how the latter affects both isotropization and thermalization. Lastly, we have seen that the range of values explored by the phase-space distribution function $f$ is such that at $p_T<0.5\\, \\rm GeV$ the inner part of the fireball stays with occupation number significantly larger than unity despite the fast longitudinal expansion, which might suggest the possibility of the formation of a transient Bose-Einstein Condensate.

Marco Ruggieri; Francesco Scardina; Salvatore Plumari; Vincenzo Greco

2014-07-09T23:59:59.000Z

197

Heat transfer and fluid flow in microchannels and nanochannels at high Knudsen number using thermal lattice-Boltzmann method  

Science Journals Connector (OSTI)

The present paper deals with the two-dimensional numerical simulation of gaseous flow and heat transfer in planar microchannel and nanochannel with different wall temperatures in transitional regime 0.1?Kn?1. An atomistic molecular simulation method is used known as thermal lattice-Boltzmann method. The results of simulation are presented in four cases corresponding to the Fourier flow, shear-driven flow (Couette flow), pressure-driven flow (Poiseuille flow), and mixed shearpressure-driven flow in the developing and fully developed regions. The mixed shearpressure-driven flow is divided into two subcases with shear stress and pressure gradient acting in the same and the opposite directions. Normalized temperature and velocity profiles across the channel, distribution of local wall Nusselt number, and friction coefficient are illustrated. Using this method, nonlinear pressure distribution in the streamwise direction, reduction in mass flow rate, Cf?Re, and Nu by increasing the Knudsen number are studied. It is seen that for Couette flow, Nu over the hotter plate is greater than the cooler plate, but for the pressure-driven flow with stationary wall temperature dependency of viscosity and thermal conductivity causes this trend to be reversed. The reversed flow appearance in the velocity profile is captured in the case of opposite shearpressure-driven flow.

J. Ghazanfarian and A. Abbassi

2010-08-13T23:59:59.000Z

198

10.2.2013bo Akademi Univ -Thermal and Flow Engineering Piispankatu 8, 20500 Turku 1/32 Irreversible thermodynamics,  

E-Print Network (OSTI)

University Thermal and Flow Engineering Laboratory / Värme- och strömningsteknik tel. 3223 ; ron.zevenhoven@abo.fi Process EngineeringThermodynamics course # 424304.0 v. 2013 ?A 424304 10.2.2013?bo Akademi Univ - Thermal is more common than equilibrium state (also in nature as a result of the constant energy influx from

Zevenhoven, Ron

199

On self-sustaining processes in Rayleigh-stable rotating plane Couette flows and subcritical transition to turbulence in accretion disks  

E-Print Network (OSTI)

Subcritical transition to turbulence in Keplerian accretion disks is still a controversial issue and some theoretical progress is required in order to determine whether or not this scenario provides a plausible explanation for the origin of angular momentum transport in non-magnetized accretion disks. Motivated by the recent discoveries of exact nonlinear steady self-sustaining solutions in linearly stable non-rotating shear flows, we attempt to compute similar solutions in Rayleigh-stable rotating plane Couette flows and to identify transition mechanisms in such flows by combining nonlinear continuation methods and asymptotic theory. We obtain exact nonlinear solutions for Rayleigh-stable cyclonic regimes but show that it is not possible to compute solutions for Rayleigh-stable anticyclonic regimes, including Keplerian flow, using similar techniques. We also present asymptotic descriptions of these various problems at large Reynolds numbers that provide some insight into the differences between the non-rotating and Rayleigh-stable anticyclonic regimes and derive some necessary conditions for mechanisms analogous to the non-rotating self-sustaining process to be present in flows on the Rayleigh line. Our results demonstrate that subcritical transition mechanisms cannot be identified in wall-bounded Rayleigh-stable anticyclonic shear flows by transposing directly the phenomenology of subcritical transition in cyclonic and non-rotating wall-bounded shear flows. Asymptotic developments, however, leave open the possibility that nonlinear self-sustaining solutions may exist in unbounded or periodic flows on the Rayleigh line. These could serve as a starting point to discover solutions in Rayleigh-stable flows, but the nonlinear stability of Keplerian accretion disks remains to be determined.

F. Rincon; G. I. Ogilvie; C. Cossu

2006-12-07T23:59:59.000Z

200

Numerical study of unsteady, thermally stratified flow in an idealized thermoacoustic stack  

Science Journals Connector (OSTI)

A computational model for the simulation of unsteady thermally stratified flow within an idealized thermoacoustic stack is developed. The model is based on a vorticity?based formulation of the low?Mach?number conservation equations. The numerical scheme combines fast Poisson solvers with domain decomposition/boundary Greens?function techniques. The model is applied to analyze the response of the stack to imposed finite?amplitude acoustic oscillations. Computed results are used to visualize the essential features of the vorticity field and temperature distribution quantify the heat transfer between the gas and plates and analyze thermal and mechanical energy losses. [The work of A.S.W. and O.M.K. is supported by the Office of Naval Research. R.K. is partially supported by Deutsche Forschungsgemeinschaft (DFG).

Aniruddha S. Worlikar; Omar M. Knio; Rupert Klein

1996-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


201

Culture of selected organisms in recirculating and flow-through systems using thermal effluent  

E-Print Network (OSTI)

&M University; Chairman of Advisory Committee: Dr. Kirk Strawn Twenty species were cultured in tanks on flow-through and recirculating systems. Water source was the thermal effluent from the discharge can 1 of Houston Lighting a Power Company's Cedar Bayou..., pH and Turbidity Levels for Monitored Tanks Table Al Daily Temperature i Conductivity i Di s- solved Oxygen, pH and Turbidity Levels for Monitored Tanks Figures Al through A72 80 86 vu APPENDIX B ? Summary of Monthly Survival, L ngth...

Berry, Terri Layne

1978-01-01T23:59:59.000Z

202

Advances in compressible turbulent mixing  

SciTech Connect

This volume includes some recent additions to original material prepared for the Princeton International Workshop on the Physics of Compressible Turbulent Mixing, held in 1988. Workshop participants were asked to emphasize the physics of the compressible mixing process rather than measurement techniques or computational methods. Actual experimental results and their meaning were given precedence over discussions of new diagnostic developments. Theoretical interpretations and understanding were stressed rather than the exposition of new analytical model developments or advances in numerical procedures. By design, compressibility influences on turbulent mixing were discussed--almost exclusively--from the perspective of supersonic flow field studies. The papers are arranged in three topical categories: Foundations, Vortical Domination, and Strongly Coupled Compressibility. The Foundations category is a collection of seminal studies that connect current study in compressible turbulent mixing with compressible, high-speed turbulent flow research that almost vanished about two decades ago. A number of contributions are included on flow instability initiation, evolution, and transition between the states of unstable flow onset through those descriptive of fully developed turbulence. The Vortical Domination category includes theoretical and experimental studies of coherent structures, vortex pairing, vortex-dynamics-influenced pressure focusing. In the Strongly Coupled Compressibility category the organizers included the high-speed turbulent flow investigations in which the interaction of shock waves could be considered an important source for production of new turbulence or for the enhancement of pre-existing turbulence. Individual papers are processed separately.

Dannevik, W.P.; Buckingham, A.C.; Leith, C.E. [eds.

1992-01-01T23:59:59.000Z

203

Gyrokinetic particle simulation for thermonuclear plasma turbulence studies in magnetic confinement.  

E-Print Network (OSTI)

??Thermal transport in a magnetised plasma is believed to be substantially enhanced due to turbulence. The ELMFIRE code has been developed fortokamak plasma turbulence studies (more)

Janhunen, Salomon

2013-01-01T23:59:59.000Z

204

Comprehensive Approaches to Multiphase Flows in Geophysics - Application to nonisothermal, nonhomogenous, unsteady, large-scale, turbulent dusty clouds I. Hydrodynamic and Thermodynamic RANS and LES Models  

SciTech Connect

The objective of this manuscript is to fully derive a geophysical multiphase model able to ''accommodate'' different multiphase turbulence approaches; viz., the Reynolds Averaged Navier-Stokes (RANS), the Large Eddy Simulation (LES), or hybrid RANSLES. This manuscript is the first part of a larger geophysical multiphase project--lead by LANL--that aims to develop comprehensive modeling tools for large-scale, atmospheric, transient-buoyancy dusty jets and plume (e.g., plinian clouds, nuclear ''mushrooms'', ''supercell'' forest fire plumes) and for boundary-dominated geophysical multiphase gravity currents (e.g., dusty surges, diluted pyroclastic flows, dusty gravity currents in street canyons). LES is a partially deterministic approach constructed on either a spatial- or a temporal-separation between the large and small scales of the flow, whereas RANS is an entirely probabilistic approach constructed on a statistical separation between an ensemble-averaged mean and higher-order statistical moments (the so-called ''fluctuating parts''). Within this specific multiphase context, both turbulence approaches are built up upon the same phasic binary-valued ''function of presence''. This function of presence formally describes the occurrence--or not--of any phase at a given position and time and, therefore, allows to derive the same basic multiphase Navier-Stokes model for either the RANS or the LES frameworks. The only differences between these turbulence frameworks are the closures for the various ''turbulence'' terms involving the unknown variables from the fluctuating (RANS) or from the subgrid (LES) parts. Even though the hydrodynamic and thermodynamic models for RANS and LES have the same set of Partial Differential Equations, the physical interpretations of these PDEs cannot be the same, i.e., RANS models an averaged field, while LES simulates a filtered field. In this manuscript, we also demonstrate that this multiphase model fully fulfills the second law of thermodynamics and fulfills the necessary requirements for a well-posed initial-value problem. In the next manuscripts, we will further develop specific closures for multiphase RANS, LES, and hybrid-LES.

S. Dartevelle

2005-09-05T23:59:59.000Z

205

turbulent heat International Journal of Numerical  

E-Print Network (OSTI)

Enhanced turbulent heat transfer 47 International Journal of Numerical Methods for Heat & Fluid, Hsinchu,Taiwan Keywords Heat transfer, Fluids, Flow, Turbulence, Numerical methods Abstract This study evaluates low Reynolds number models of turbulence for numerical computations on the heat transfer and fluid

Lin, Wen-Wei

206

TURBULENCE IN SUPERSONIC AND HYPERSONIC BOUNDARY LAYERS  

E-Print Network (OSTI)

TURBULENCE IN SUPERSONIC AND HYPERSONIC BOUNDARY LAYERS Alexander J. Smits and M. Pino Martin in supersonic and hypersonic flow where the effects of compressibility have a direct influence on the turbulence. Experimental and DNS results are presented and compared. Key words: Turbulence, supersonic, hypersonic, shocks

Martín, Pino

207

Information Content of Turbulence  

E-Print Network (OSTI)

We treat a turbulent velocity field as a message in the same way as a book or a picture. All messages can be described by their entropy per symbol $h$, defined as in Shannon's theory of communication. In a turbulent flow, as the Reynolds number $Re$ increases, more correlated degrees of freedom are excited and participate in the turbulent cascade. Experiments in a turbulent soap film suggest that the spatial entropy density $h$ is a decreasing function of $Re$, namely $h \\propto -\\log Re$ + const. In the logistic map, also analyzed here, increasing the control parameter $r$ increases $h$. A modified logistic map with additional coupling to past iterations suggests the significance of correlations.

Rory Cerbus; Walter Goldburg

2013-07-03T23:59:59.000Z

208

Notes 09. Fluid inertia and turbulence in fluid film bearings  

E-Print Network (OSTI)

When fluid inertia effects are important. Bulk-flow model for inertial flows. Turbulence and inertia in short length journal bearings and open end dampers....

San Andres, Luis

2009-01-01T23:59:59.000Z

209

Wind Effect, Recirculation and Thermal Flow Field of a Direct Air?cooled Condenser for a Large Power Plant  

Science Journals Connector (OSTI)

The thermal effect experiments were carried out of a direct air?cooled system in the low speed wind tunnel. The influence of effect factors on recirculation is also discussion after that the relationship between the thermal flow field structure and recirculation ratio under the cooling tower is analyzed. At last the engineering measures to reduce or avoid recirculation are proposed. For certain conditions the experimental measurement shows close agreement with numerical values.

W. L. Zhao; P. Q. Liu; H. S. Duan; J. Y. Zhu

2011-01-01T23:59:59.000Z

210

Comprehensive model to determine the effects of temperature and species fluctuations on reaction rates in turbulent reaction flows  

SciTech Connect

The use of silane (SiH4) as an effective ignitor and flame stabilizing pilot fuel is well documented. A reliable chemical kinetic mechanism for prediction of its behavior at the conditions encountered in the combustor of a SCRAMJET engine was calculated. The effects of hydrogen addition on hydrocarbon ignition and flame stabilization as a means for reduction of lengthy ignition delays and reaction times were studied. The ranges of applicability of chemical kinetic models of hydrogen-air combustors were also investigated. The CHARNAL computer code was applied to the turbulent reaction rate modeling.

Magnotti, F.; Diskin, G.; Matulaitis, J.; Chinitz, W.

1984-01-01T23:59:59.000Z

211

Lattice Boltzmann Methods for thermal flows: continuum limit and applications to compressible Rayleigh-Taylor systems  

E-Print Network (OSTI)

We compute the continuum thermo-hydrodynamical limit of a new formulation of lattice kinetic equations for thermal compressible flows, recently proposed in [Sbragaglia et al., J. Fluid Mech. 628 299 (2009)]. We show that the hydrodynamical manifold is given by the correct compressible Fourier- Navier-Stokes equations for a perfect fluid. We validate the numerical algorithm by means of exact results for transition to convection in Rayleigh-B\\'enard compressible systems and against direct comparison with finite-difference schemes. The method is stable and reliable up to temperature jumps between top and bottom walls of the order of 50% the averaged bulk temperature. We use this method to study Rayleigh-Taylor instability for compressible stratified flows and we determine the growth of the mixing layer at changing Atwood numbers up to At ~ 0.4. We highlight the role played by the adiabatic gradient in stopping the mixing layer growth in presence of high stratification and we quantify the asymmetric growth rate for spikes and bubbles for two dimensional Rayleigh- Taylor systems with resolution up to Lx \\times Lz = 1664 \\times 4400 and with Rayleigh numbers up to Ra ~ 2 \\times 10^10.

Andrea Scagliarini; Luca Biferale; Mauro Sbragaglia; Kazuyasu Sugiyama; Federico Toschi

2010-05-20T23:59:59.000Z

212

Information theoretical characterization of turbulence  

Science Journals Connector (OSTI)

A method of describing turbulence in terms of dynamical connectivity in the wave-number space is proposed. The connectivity is quantified by the information theoretical quantities, i.e., mutual information and cross information flow rate. This method is applied to the analysis of two simple examples of turbulence in one spatial dimension. Although the examples have quite different physical origins, the information structures of the wave-number space turn out to be quite similar: The wave-number space consists of several regions generating information in different ways, and how information flows between these regions reflects the dynamical structure of turbulence.

K. Ikeda and K. Matsumoto

1989-05-08T23:59:59.000Z

213

A STUDY OF ATES THERMAL BEHAVIOR USING A STEADY FLOW MODEL  

E-Print Network (OSTI)

and Warman, J.c. , "Thermal energy storage in a confinedProceedings of Thermal Energy Storage in Aquifers Workshop,c.F. , ~Aquifer thermal energy storage- parameter study,~

Doughty, Christine

2013-01-01T23:59:59.000Z

214

7 feb 13bo Akademi Univ -Thermal and Flow Engineering Piispankatu 8, 20500 Turku 1/82 Thermodynamics of separation  

E-Print Network (OSTI)

Laboratory / Värme- och strömningsteknik tel. 3223 ; ron.zevenhoven@abo.fi Process EngineeringThermodynamics course # 424304.0 v. 2013 ?A 424304 7 feb 13?bo Akademi Univ - Thermal and Flow Engineering Piispankatu 8/desorption, extraction), or 2) by adding or removing energy (e.g. heat) (distillation, crystallisation) Creating an "un

Zevenhoven, Ron

215

A Mountain-Scale Thermal Hydrologic Model for Simulating FluidFlow and Heat Transfer in Unsaturated Fractured Rock  

SciTech Connect

A multidimensional, mountain-scale, thermal-hydrologic (TH) numerical model is presented for investigating unsaturated flow behavior in response to decay heat from the radioactive waste repository in the Yucca Mountain unsaturated zone (UZ), Nevada. The model, consisting of both two-dimensional (2-D) and three-dimensional (3-D) representations of the UZ repository system, is based on the current repository design, drift layout, thermal loading scenario, and estimated current and future climate conditions. This mountain-scale TH model evaluates the coupled TH processes related to mountain-scale UZ flow. It also simulates the impact of radioactive waste heat release on the natural hydrogeological system, including heat-driven processes occurring near and far away from the emplacement tunnels or drifts. The model simulations predict thermally perturbed liquid saturation, gas- and liquid-phase fluxes, and water and rock temperature elevations, as well as the changes in water flux driven by evaporation/condensation processes and drainage between drifts. These simulations provide mountain-scale thermally perturbed flow fields for assessing the repository performance under thermal loading conditions.

Wu, Yu-Shu; Mukhopadhyay, Sumit; Zhang, Keni; Bodvarsson,Gudmundur S.

2005-05-25T23:59:59.000Z

216

EVOLUTION OF SHOCKS AND TURBULENCE IN MAJOR CLUSTER MERGERS  

SciTech Connect

We performed a set of cosmological simulations of major mergers in galaxy clusters, in order to study the evolution of merger shocks and the subsequent injection of turbulence in the post-shock region and in the intra-cluster medium (ICM). The computations have been performed with the grid-based, adaptive mesh refinement hydrodynamical code Enzo, using a refinement criterion especially designed for refining turbulent flows in the vicinity of shocks. When a major merger event occurs, a substantial amount of turbulence energy is injected in the ICM of the newly formed cluster. Our simulations show that the shock launched after a major merger develops an ellipsoidal shape and gets broken by the interaction with the filamentary cosmic web around the merging cluster. The size of the post-shock region along the direction of shock propagation is of the order of 300 kpc h{sup -1}, and the turbulent velocity dispersion in this region is larger than 100 km s{sup -1}. We performed a scaling analysis of the turbulence energy within our cluster sample. The best fit for the scaling of the turbulence energy with the cluster mass is consistent with M{sup 5/3}, which is also the scaling law for the thermal energy in the self-similar cluster model. This clearly indicates the close relation between virialization and injection of turbulence in the cluster evolution. As for the turbulence in the cluster core, we found that within 2 Gyr after the major merger (the timescale for the shock propagation in the ICM), the ratio of the turbulent to total pressure is larger than 10%, and after about 4 Gyr it is still larger than 5%, a typical value for nearly relaxed clusters. Turbulence at the cluster center is thus sustained for several gigayears, which is substantially longer than typically assumed in the turbulent re-acceleration models, invoked to explain the statistics of observed radio halos. Striking similarities in the morphology and other physical parameters between our simulations and the 'symmetrical radio relics' found at the periphery of the merging cluster A3376 are finally discussed. In particular, the interaction between the merger shock and the filaments surrounding the cluster could explain the presence of 'notch-like' features at the edges of the double relics.

Paul, S.; Mannheim, K. [Institut fuer Theoretische Physik und Astrophysik, Universitaet Wuerzburg, Am Hubland, D-97074 Wuerzburg (Germany); Iapichino, L. [Zentrum fuer Astronomie der Universitaet Heidelberg, Institut fuer Theoretische Astrophysik, Albert-Ueberle-Strasse 2, D-69120 Heidelberg (Germany); Miniati, F. [Physics Department, Wolfgang-Pauli-Strasse 27, ETH-Zuerich, CH-8093 Zuerich (Switzerland); Bagchi, J. [Inter-University Center for Astronomy and Astrophysics, Pune University Campus, Pune 411 007 (India)

2011-01-01T23:59:59.000Z

217

23.11.2014bo Akademi Univ -Thermal and Flow Engineering Piispankatu 8, 20500 Turku 1/28 6. Food cooling and freezing  

E-Print Network (OSTI)

air affects moisture loss from products, etc. Picture: ?B98 23.11.2014 ?bo Akademi Univ - Thermal - Thermal and Flow Engineering Piispankatu 8, 20500 Turku 3/28 Food products /1 About 15-20% of world and Flow Engineering Piispankatu 8, 20500 Turku 4/28 Food products /2 Food deteriorates fastest at 20 - 60

Zevenhoven, Ron

218

Study of turbulence-chemistry interaction in hypersonic turbulent boundary layers  

E-Print Network (OSTI)

Study of turbulence-chemistry interaction in hypersonic turbulent boundary layers Lian Duan and M of the turbulence-chemistry interaction (TCI) are performed in hypersonic tur- bulent boundary layers using direct numerical simulation (DNS) flow fields under typical hypersonic conditions representative of blunt

Martín, Pino

219

Atmospheric Flow Development and Associated Changes in Turbulent Sensible Heat Flux over a Patchy Mountain Snow Cover  

Science Journals Connector (OSTI)

In this study we numerically investigated the small-scale boundary layer dynamics and the energy balance over a fractional snow-cover. The atmospheric boundary layer flows over a patchy snow-cover were calculated with an atmospheric model (...

Rebecca Mott; Michael Lehning; Megan Daniels; Michael Lehning

220

AIAA-92-5101 Hypersonic Turbulent  

E-Print Network (OSTI)

AIAA-92-5101 Hypersonic Turbulent Expansion-Corner Flow with Impingement K. Chung & F. Lu;HYPERSONIC TURBULENT EXPANSION-CORNER FLOW WITH SHOCK IMPINGEMENT ICung-Ming Chung* and Frank IC. Lut of considcrablc research.' Recently, renewed in- tcrcst in supersonic and hypersonic flight vehicles has

Texas at Arlington, University of

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


221

Progress in sub-grid scale modeling of shock-turbulence interaction  

SciTech Connect

The authors report on progress in the development of sub grid scale (SGS) closure relationships for the unresolved motion scales in compressible large eddy simulations (LES). At present they are refining the SGS model and overall LES procedure to include: a linearized viscoelastic model for finite thickness shock distortions and shocked turbulence field response; multiple scale asymptotic considerations to improve predictions of average near-wall surface behavior; and a spectral statistical model simulating the effects of high wave number stochastic feed-back from the unresolved SGS nonlinear motion influences on the explicitly resolved grid scale motions. Predicted amplification levels, modal energy partition, shock translational to turbulence kinetic energy transfer, and viscoelastic spatio-temporal response of turbulence to shock interaction are examined in comparison with available experimental evidence. Supplemental hypersonic compressible turbulence experimental information is developed from sub nanosecond interval pulsed shadowgraph evidence of laser impulse generated hypervelocity shocks interacting with intense, previously developed and carefully characterized initial turbulence. Accurate description of the influence of shock-turbulence interactions is vital for predicting their influence on: Supersonic/hypersonic flow field analysis, aerodynamic design, and aerostructural materials selection. Practical applications also include interior supersonic combustion analysis and combustion chamber design. It is also the essential foundation for accurately predicting the development and evolution of flow-field generated thermal and electromagnetic radiation important to hypersonic flight vehicle survivability, detection and communication.

Buckingham, A.C. [Lawrence Livermore National Lab., CA (United States). Center for Advanced Fluid Dynamics Applications; Grun, J. [Naval Research Lab., Washington, DC (United States). Plasma Physics Div.

1994-12-01T23:59:59.000Z

222

Complete Numerical Simulation of Subcooled Flow Boiling in the Presence of Thermal and Chemical Interactions  

SciTech Connect

At present, guidelines for fuel cycle designs to prevent axial offset anomalies (AOA) in pressurized water reactor (PWR) cores are based on empirical data from several operating reactors. Although the guidelines provide an ad-hoc solution to the problem, a unified approach based on simultaneous modeling of thermal-hydraulics, chemical, and nuclear interactions with vapor generation at the fuel cladding surface does not exist. As a result, the fuel designs are overly constrained with a resulting economic penalty. The objective of present project is to develop a numerical simulation model supported by laboratory experiments that can be used for fuel cycle design with respect to thermal duty of the fuel to avoid economic penalty, as well as, AOA. At first, two-dimensional numerical simulation of the growth and departure of a bubble in pool boiling with chemical interaction is considered. A finite difference scheme is used to solve the equations governing conservation of mass, momentum, energy, and species concentration. The Level Set method is used to capture the evolving liquid-vapor interface. A dilute aqueous boron solution is considered in the simulation. From numerical simulations, the dynamic change in concentration distribution of boron during the bubble growth shows that the precipitation of boron can occur near the advancing and receding liquid-vapor interface when the ambient boron concentration level is 3,000 ppm by weight. Secondly, a complete three-dimensional numerical simulation of inception, growth and departure of a single bubble subjected to forced flow parallel to the heater surface was developed. Experiments on a flat plate heater with water and with boron dissolved in the water were carried out. The heater was made out of well-polished silicon wafer. Numbers of nucleation sites and their locations were well controlled. Bubble dynamics in great details on an isolated nucleation site were obtained while varying the wall superheat, liquid subcooling and flow velocity parametrically. Concentration variation of boron near the liquid-vapor interface was detected successfully with a newly developed miniature concentration sensor. The measured concentration variations at different radial locations from the center of cavity have the same trend as given by the numerical simulations. The deposition of boron was found near the nucleation site on the heater surface, which validates the numerical simulation. Subcooled flow boiling experiments at three pressures were performed on a nine-rod bundle with water and with boron dissolved in the water. The test runs were conducted with a wide range of mass fluxes (186 to 2800 kg/m2s) and heat fluxes (1.0 to 30.0 W/ cm2). Not only the variables required to develop mechanistic models for subcooled flow boiling were measured, but also the crud formation during boiling and its effect on the heat transfer process were investigated. (B204)

V.K. Dhir

2003-04-28T23:59:59.000Z

223

Imaging Fluid Flow in Geothermal Wells Using Distributed Thermal Perturbation Sensing  

E-Print Network (OSTI)

Imaging Fluid Flow in Geothermal Wells Using Distributed16 Imaging Fluid Flow in Geothermal Wells Using Distributedflow processes near a geothermal well under heating and

Freifeld, B.

2011-01-01T23:59:59.000Z

224

Observations of turbulence caused by a combination of tides and mean baroclinic flow over a fjord sill  

Science Journals Connector (OSTI)

Here we investigate the dissipation rates and flow conditions at the Drbak Sill in the Oslofjord. The area was transected 13 times with a free falling microstructure shear probe during 4 days in June 2011. At the same time an ADCP was deployed ...

Andre Staalstrm; Lars Arneborg; Bengt Liljebladh; Gran Brostrm

225

Plasma turbulence  

SciTech Connect

The origin of plasma turbulence from currents and spatial gradients in plasmas is described and shown to lead to the dominant transport mechanism in many plasma regimes. A wide variety of turbulent transport mechanism exists in plasmas. In this survey the authors summarize some of the universally observed plasma transport rates.

Horton, W. [Univ. of Texas, Austin, TX (United States). Inst. for Fusion Studies; Hu, G. [Globalstar LP, San Jose, CA (United States)

1998-07-01T23:59:59.000Z

226

First order particle acceleration in magnetically-driven flows  

E-Print Network (OSTI)

We demonstrate that particles are regularly accelerated while experiencing curvature drift in flows driven by magnetic tension. Some examples of such flows include spontaneous turbulent reconnection and decaying magnetohydrodynamic (MHD) turbulence, where magnetic field relaxes to a lower-energy configuration and transfers part of its energy to kinetic motions. The opposite process, such as dynamo, will actually result in the net cooling of particles by the curvature drift. Being very generic, this acceleration mechanism is likely to be responsible in production of non-thermal particle distribution in magnetically-dominant environments such as solar chromosphere, pulsar magnetosphere, jets from supermassive black holes, $\\gamma$-ray bursts, etc.

Beresnyak, Andrey

2014-01-01T23:59:59.000Z

227

Numerical Investigations of Magnetohydrodynamic Hypersonic Flows.  

E-Print Network (OSTI)

??Numerical simulations of magnetohydrodynamic (MHD) hypersonic flow are presented for both laminar and turbulent flow over a cylinder and flow entering a scramjet inlet. ANSYS (more)

Guarendi, Andrew N

2013-01-01T23:59:59.000Z

228

Three-dimensional coupled ground water flow, thermal transport and/or migration of nuclides analysis by boundary element method  

SciTech Connect

In the safety analyses of radioactive waste disposal, it is important and indispensable to analyze coupled problems of ground water flow, thermal transport and/or migration of nuclides. The three-dimensional coupled problems is solved by boundary element method in this paper. The results of this method are compared with those experiments of JAERI and STRIPA SWEDEN on the thermal problem, and with those analyses of analytical and FEM results on the migration problem. In this formulation, natural convection is considered by Boussinesq approximation. An example of coupled ground water flow and migration of nuclides with decay chain U{sup 234} {yields} Th{sup 230} {yields} Ra{sup 226} is also tried.

Kawamura, Ryuji [Information and Mathematical Science Lab., Inc., Kanagawa (Japan)

1994-12-31T23:59:59.000Z

229

3.12.2014bo Akademi Univ -Thermal and Flow Engineering Piispankatu 8, 20500 Turku 1/56 9. Solar cooling  

E-Print Network (OSTI)

.iea.org/publications/freepublications/publication/Solar_Heating_Cooling_Road map_2012_WEB.pdf 3.12.2014 ?bo Akademi Univ - Thermal and Flow Engineering - Piispankatu 8, 20500.iea.org/publications/freepublications/publication/Solar_Heating_Cooling_Road map_2012_WEB.pdf #12;3.12.2014?bo Akademi Univ - Thermal and Flow Engineering - Piispankatu 8, 20500.12.2014?bo Akademi Univ - Thermal and Flow Engineering - Piispankatu 8, 20500 Turku 8/56 http://www.brighton-webs

Zevenhoven, Ron

230

Bacteria in shear flow  

E-Print Network (OSTI)

Bacteria are ubiquitous and play a critical role in many contexts. Their environment is nearly always dynamic due to the prevalence of fluid flow: creeping flow in soil, highly sheared flow in bodily conduits, and turbulent ...

Marcos, Ph.D. Massachusetts Institute of Technology

2011-01-01T23:59:59.000Z

231

Protostellar Outflow Evolution in Turbulent Environments  

SciTech Connect

The link between turbulence in star formatting environments and protostellar jets remains controversial. To explore issues of turbulence and fossil cavities driven by young stellar outflows we present a series of numerical simulations tracking the evolution of transient protostellar jets driven into a turbulent medium. Our simulations show both the effect of turbulence on outflow structures and, conversely, the effect of outflows on the ambient turbulence. We demonstrate how turbulence will lead to strong modifications in jet morphology. More importantly, we demonstrate that individual transient outflows have the capacity to re-energize decaying turbulence. Our simulations support a scenario in which the directed energy/momentum associated with cavities is randomized as the cavities are disrupted by dynamical instabilities seeded by the ambient turbulence. Consideration of the energy power spectra of the simulations reveals that the disruption of the cavities powers an energy cascade consistent with Burgers-type turbulence and produces a driving scale-length associated with the cavity propagation length. We conclude that fossil cavities interacting either with a turbulent medium or with other cavities have the capacity to sustain or create turbulent flows in star forming environments. In the last section we contrast our work and its conclusions with previous studies which claim that jets can not be the source of turbulence.

Cunningham, A; Frank, A; Carroll, J; Blackman, E; Quillen, A

2008-04-11T23:59:59.000Z

232

Nonlinear closures for scale separation in supersonic magnetohydrodynamic turbulence  

E-Print Network (OSTI)

Turbulence in compressible plasma plays a key role in many areas of astrophysics and engineering. The extreme plasma parameters in these environments, e.g. high Reynolds numbers, supersonic and super-Alfvenic flows, however, make direct numerical simulations computationally intractable even for the simplest treatment -- magnetohydrodynamics (MHD). To overcome this problem one can use subgrid-scale (SGS) closures -- models for the influence of unresolved, subgrid-scales on the resolved ones. In this work we propose and validate a set of constant coefficient closures for the resolved, compressible, ideal MHD equations. The subgrid-scale energies are modeled by Smagorinsky-like equilibrium closures. The turbulent stresses and the electromotive force (EMF) are described by expressions that are nonlinear in terms of large scale velocity and magnetic field gradients. To verify the closures we conduct a priori tests over 137 simulation snapshots from two different codes with varying ratios of thermal to magnetic pre...

Grete, Philipp; Schmidt, Wolfram; Schleicher, Dominik R G; Federrath, Christoph

2015-01-01T23:59:59.000Z

233

Tempest in a Teapot - Surface and Volume Turbulence in a Closed System  

Science Journals Connector (OSTI)

Turbulence can be generated by oscillating a grid in a volume of water. The turbulent flow thus created has minimal mean shear and mean flow. We have studied the motion of small floating particles on the surfa...

Walter I. Goldburg; Cecil Cheung

1997-01-01T23:59:59.000Z

234

Gyro-water-bag approach in nonlinear gyrokinetic turbulence  

Science Journals Connector (OSTI)

Turbulent transport is a key issue for controlled thermonuclear fusion based on magnetic confinement. The thermal confinement of a magnetized fusion plasma is essentially determined by the turbulent heat conduction across the equilibrium magnetic field. ... Keywords: 65M15, 65P40, 83C05, Discontinuous Galerkin methods, Gyrokinetic equations, Plasma turbulence, Quasilinear theory, Semi-Lagrangian methods, Water-bag model

Nicolas Besse; Pierre Bertrand

2009-06-01T23:59:59.000Z

235

THE INFLUENCE OF REPOSITORY THERMAL LOAD ON MULTIPHASE FLOW AND HEAT TRANSFER IN THE UNSATURATED ZONE OF YUCCA MOUNTAIN  

SciTech Connect

This paper investigates the impact of proposed repository thermal-loading on mountain-scale flow and heat transfer in the unsaturated fractured rock of Yucca Mountain, Nevada. In this context, a model has been developed to study the coupled thermal-hydrological (TH) processes at the scale of the entire Yucca Mountain. This mountain-scale TH model implements the current geological framework and hydrogeological conceptual models, and incorporates the latest rock thermal and hydrological properties. The TH model consists of a two-dimensional north-south vertical cross section across the entire unsaturated zone model domain and uses refined meshes near and around the proposed repository block, based on the current repository design, drift layout, thermal loading scenario, and estimated current and future climatic conditions. The model simulations provide insights into thermally affected liquid saturation, gas- and liquid-phase fluxes, and elevated water and rock temperature, which in turn allow modelers to predict the changes in water flux driven by evaporation/condensation processes, and drainage between drifts.

Yu-Shu Wu, Sumit Mukhopadhyay, Keni Zhang, and G. S. Bodvarsson

2006-04-16T23:59:59.000Z

236

Thermal Stratification Effects on Hiemenz Flow of Nanofluid Over a Porous Wedge Sheet in the Presence of Suction/Injection Due to Solar Energy: Lie Group Transformation  

Science Journals Connector (OSTI)

The objective of the present work is to investigate theoretically the Hiemenz flow and heat transfer of an incompressible viscous nanofluid past a porous wedge sheet in the presence of thermal stratification due ...

R. Kandasamy; I. Muhaimin; N. Siva Ram; K. K. Sivagnana Prabhu

2012-08-01T23:59:59.000Z

237

A new technique to analyze simultaneous sandface flow rate and pressure measurements of gas wells with turbulence and damage  

SciTech Connect

Most of the problems associated with conventional gas well test are related to the nonlinearity of the equations describing real gas flow, the presence of the rate dependent (non-Darcy) skin, and the long shut-in time periods required to collect the data for the analysis in tight reservoirs in which the wellbore storage period can be excessively long. This paper presents a new pressure buildup technique that reduces the wellbore storage effects, eliminates the long shut-in periods experienced with conventional tests by using afterflow rate and pressure data, and most importantly provides a direct method to estimate non-Darcy skin. The proposed technique uses normalized pseudofunctions to avoid the nonlinearities of the governing equations and involves using two different plots. The formation permeability is obtained from the slope of the first plot. The mechanical and non-Darcy skin factors are obtained respectively from the slope and intercept of the second plot. A field example and two simulated cases are presented to illustrate the application of the new technique.

Nashawi, I.S. [Kuwait Univ. (Kuwait); Al-Mehaideb, R.A.

1995-10-01T23:59:59.000Z

238

On applicability of the thermalized potential solver in simulations of the plasma flow in Hall thrusters  

SciTech Connect

In Hall thrusters, the potential distribution plays an important role in discharge processes and ion acceleration. This paper presents a 2D potential solver in the Hall thruster instead of the thermalized potential, and compares equipotential contours solved by these two methods for different magnetic field conditions. The comparison results reveal that the expected thermalized potential works very well when the magnetic field is nearly uniform and electron temperature is constant along the magnetic field lines. However for the case with a highly non-uniform magnetic field or variable electron temperature along the magnetic field lines, the thermalized potential is not accurate. In some case with magnetic separatrix inside the thruster channel, the thermalized potential model cannot be applied at all. In those cases, a full 2D potential solver must be applied. Overall, this paper shows the limit of applicability of the thermalized potential model.

Geng, Jinyue [School of Astronautics, Beijing University of Aeronautics and Astronautics, Beijing 100191 (China) [School of Astronautics, Beijing University of Aeronautics and Astronautics, Beijing 100191 (China); Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, District of Columbia 20052 (United States); Brieda, Lubos [Particle in Cell Consulting LLC, Falls Church, Virginia 22046 (United States)] [Particle in Cell Consulting LLC, Falls Church, Virginia 22046 (United States); Rose, Laura; Keidar, Michael [Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, District of Columbia 20052 (United States)] [Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, District of Columbia 20052 (United States)

2013-09-14T23:59:59.000Z

239

1.12.2014bo Akademi Univ -Thermal and Flow Engineering Piispankatu 8, 20500 Turku 1/24 8. Heat pumps, heat pipes,  

E-Print Network (OSTI)

pumps, heat pipes, cold thermal energy storage Ron Zevenhoven ?bo Akademi University Thermal and Flow for heating is referred to as a heat pump (mostly based on a vapour-compression cycle) Heat pumps make use electricity!) for heating and air conditioning purposes Heat pumps became popular in the 1970s

Zevenhoven, Ron

240

Turbulent phenomena in protein folding  

Science Journals Connector (OSTI)

Protein folding and hydrodynamic turbulence are two long-standing challenges, in molecular biophysics and fluid dynamics, respectively. The theories of these phenomena have been developed independently and used different formalisms. Here we show that the protein folding flows can be surprisingly similar to turbulent fluid flows. Studying a benchmark model protein (an SH3 domain), we have found that the flows for the slow folding trajectories of the protein, in which a partly formed N- and C-terminal ? sheet hinders the RT loop from attaching to the protein core, have many properties of turbulent flows of a fluid. The flows are analyzed in a three-dimensional (3D) space of collective variables, which are the numbers of native contacts between the terminal ? strands, between the RT loop and the protein core, and the rest of the native contacts. We have found that the flows have fractal nature and are filled with 3D eddies; the latter contain strange attractors, at which the tracer flow paths behave as saddle trajectories. Two regions of the space increment have been observed, in which the flux variations are self-similar with the scaling exponent h=1/3, in surprising agreement with the Kolmogorov inertial range theory of turbulence. In one region, the cascade of protein rearrangements is directed from larger to smaller scales (net folding), and in the other, it is oppositely directed (net unfolding). Folding flows for the fast trajectories are essentially laminar and do not have the property of self-similarity. Based on the results of our study, we infer, and support this inference by simulations, that the origin of the similarity between the protein folding and turbulent motion of a fluid is in a cascade mechanism of structural transformations in the systems that underlies these phenomena.

Igor V. Kalgin and Sergei F. Chekmarev

2011-01-31T23:59:59.000Z

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


241

On the dynamics of magnetorotational turbulent stresses  

Science Journals Connector (OSTI)

......C 5= 1 are adopted.The diagram is self-similar and therefore...corresponding to a state of steady MHD turbulence. A typical result...state of statistically steady MHD turbulence.The solution approached...stable. Figure 4 Stability diagram for rotating plane Couette flow......

G.I. Ogilvie

2003-04-11T23:59:59.000Z

242

Modulation of homogeneous turbulence seeded with finite size ...  

E-Print Network (OSTI)

Nov 10, 2009 ... of the energy spectrum of the turbulent velocity fluctuations with a uniform ..... collect within the cores of vortex tubes that may form in the flow.

"K. Yeo; S. Dong; E. Climent; M.R. Maxey"

2010-01-30T23:59:59.000Z

243

Thermal non-equilibrium in dispersed flow film boiling in a vertical tube  

E-Print Network (OSTI)

The departure from thermal equilibrium between a dispersed liquid phase and its vapor at high quality during film boiling is investigated, The departure from equilibruim is manifested by the high resistance to heat transfer ...

Forslund, Robert Paul

1966-01-01T23:59:59.000Z

244

Buoyancy-generated variable-density turbulence  

SciTech Connect

Because of the importance of turbulence mixing in many applications, a number of turbulence mixing models have been proposed for variable- density flows. These engineering models (one- point statistical models) typically include the transport of the turbulent kinetic energy and the turbulent energy dissipation rate (i.e., k - {epsilon} models). The model presented by Besnard, Harlow, Rauenzahn and Zemach (1992) (herein referred to as BHRZ) is a one-point model intended to describe variable-density turbulent flows. Transport equations for the Reynolds stress tensor, R{sub ij}, and the turbulent energy dissipation rate, the density-velocity correlation, a{sub i}, and the density-specific volume correlation, b are derived. This model employs- techniques and concepts from incompressible, constant- density turbulence modeling and incorporates ideas from two-phase flow models. Clark and Spitz (1994) present a two-point model for variable-density turbulence. Their derivation is based on transport equations that, are based 0481 on two-point- generalizations of R{sub ij}, a{sub ij}, and b. These equations are Fourier transformed with respect to the separation distance between the two points. Transport equations are derived for R{sub ij}, a{sub i}, b. As in the one-point model, this model contains many ad-hoc assumptions and unknown model coefficients that must be determined by comparison with experimental and numerical data. However, the two-point formalism requires fewer equilibrium assumptions then does a single-point model. Our primary concern in this paper lies in the nonlinear processes of turbulence and the influence of large density variations (not within the Boussinesq limit) on these processes. To. isolate the effects of variable-density on the turbulence we restrict our flow to be incompressible, statistically homogeneous buoyancy-generated. turbulence. To our knowledge there have not been any simulations reported for this problem.

Sandoval, D.L.; Clark, T.T.; Riley, J.J.

1996-07-01T23:59:59.000Z

245

Elevated thermal maturation in Pennsylvanian rocks, Cherokee basin, southeastern Kansas: Importance of regional fluid flow  

SciTech Connect

Thermal history of sedimentary basins is commonly assumed to be dominated by burial heating. Marked contrast between reconstructed burial temperatures and other temperature determinations would suggest alternative processes. In the Cherokee basin of southeastern Kansas, reconstruction of burial and thermal history indicates that basal Pennsylvanian strata were not buried more than 1.8 km, and should have reached only about 90C. However, the study of Pennsylvanian rocks of the Cherokee basin indicates that higher temperatures were reached and that the pattern of thermal maturation is inconsistent with simple burial heating. Regional pattern of vitrinite reflectance reveals several warm spots' where thermal maturation is elevated above the regional background. Primary fluid inclusions in late Ca-Mg-Fe carbonate cements yield homogenization-temperature modes or petrographically consistent populations ranging from 100 to 150C. These data suggest that the samples experienced at least those temperatures, hence fluid inclusions closely agree with vitrinite and Rock-Eval. Elevated temperatures, warm spots, confined thermal spikes, a low R{sub m} gradient argue against simple burial heating. These observations are consistent with regional invasion of warm fluids, probably from the Ouachita-Arkoma system, and their subsequent upward migration into Pennsylvanian strata through faults and fractures. Petroleum exploration should consider the possibility of regionally elevated thermal maturation levels with even more elevated local maxima. Consequences may include local generation of hydrocarbons or local changes in diagenetic patterns.

Wojcik, K.M.; Goldstein, R.H.; Walton, A.W. (Univ. of Kansas, Lawrence (United States)); Barker, C.E. (Geological Survey, Denver, CO (United States))

1991-03-01T23:59:59.000Z

246

Modular High-Temperature Gas-Cooled Reactor short term thermal response to flow and reactivity transients  

SciTech Connect

The analyses reported here have been conducted at the Oak Ridge National Laboratory (ORNL) for the US Nuclear Regulatory Commission's (NRC's) Division of Regulatory Applications of the Office of Nuclear Regulatory Research. The short-term thermal response of the Modular High-Temperature Gas-Cooled Reactor (MHTGR) is analyzed for a range of flow and reactivity transients. These include loss of forced circulation (LOFC) without scram, moisture ingress, spurious withdrawal of a control rod group, hypothetical large and rapid positive reactivity insertion, and a rapid core cooling event. The coupled heat transfer-neutron kinetics model is also described.

Cleveland, J.C.

1988-01-01T23:59:59.000Z

247

Active skin for turbulent drag reduction  

E-Print Network (OSTI)

evidence that spanwise traveling waves of the right amplitude, wavelength and frequency can result in significant turbulent drag reduction. Such traveling waves can be induced in the smart skin via active-material actuation. The flow control technique...

Mani, Raghavendran

2002-01-01T23:59:59.000Z

248

Large eddy simulation of turbulence within heat exchangers  

E-Print Network (OSTI)

be problematic if the turbulent energy is near the tubes natural frequency. However, as compared to the drag force exerted by the fluid, vortex shedding and turbulent buffeting are are of lesser significance than fluid elastic instability. Fluid elastic... on turbulent statistics. Is is widely accepted that there are four basic sources of cross-flow excitation in tube banks: vortex shedding, turbulent buffeting, fluid-elastic instability, and acoustic resonance (Grover et aL 1978). Vortex shedding is a...

Pruitt, John Myron

2012-06-07T23:59:59.000Z

249

Dependence of thermal destabilization of electric-arc plasma in an air flow on discharge conditions  

Science Journals Connector (OSTI)

The effect of the conditions of electric-arc burning in an air flow on the ... processes in the development of instability in an arc-discharge column is shown.

V. N. Borisyuk; S. V. Goncharik

1997-03-01T23:59:59.000Z

250

Caged Molecular Fluorescence Velocimetry to measure meso-to micro-scale thermal flow fields  

E-Print Network (OSTI)

Velocimetry Concept . . . 16 Figure 9. Bulk Region Flow in D = 5 mm Scale; (a) with the Heater Oriented Above (Left of) the Meniscus, (b) with the Heater Oriented Below (Right of) the Meniscus . 20 Figure 10 Meniscus Region Flow in 6 & I mm Scale; (a...) with the Heater Oriented Above (Left of) the Meniscus, (b) with the Heater Oriented Below (Rightof)the Meniscus . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . 22 Figure 11 Two Velocity Profiles...

Park, Jaesung

2012-06-07T23:59:59.000Z

251

Turbulence Considerations for Comparing Ecosystem Exchange over Old-Growth and Clear-Cut Stands For Limited Fetch and Complex Canopy Flow Conditions  

SciTech Connect

Carbon dioxide, water vapor and energy fluxes were measured using eddy covariance (EC) methodology over three adjacent forests in southern Washington State to identify stand-level age-effects on ecosystem exchange. The sites represent Douglas-fir forest ecosystems at two contrasting successional stages: old-growth (OG) and early seral (ES). Here we present eddy flux and meteorological data from two early seral stands and the Wind River AmeriFlux old-growth forest during the growing season (March-October) in 2006 and 2007. We show an alternative approach to the usual friction velocity (u*) method for determining periods of adequate atmospheric boundary layer (ABL) mixing based on the ratio of mean horizontal ({bar u}) and vertical ({bar w}) wind flow to a modified turbulent kinetic energy scale (uTKE). This new parameter in addition to footprint modeling showed that daytime CO{sub 2} fluxes (F{sub NEE}) in small clear-cuts (< 10 hectares) can be measured accurately with EC if micrometeorological conditions are carefully evaluated. Peak midday CO{sub 2} fluxes (F{sub NEE} = -14.0 to -12.3 {micro}mol m{sup -2} s{sup -1}) at OG were measured in April in both 2006 and 2007 before bud break when air and soil temperatures and vapor pressure deficit were relatively low, and soil moisture and light levels were favorable for photosynthesis. At the early seral stands, peak midday CO{sub 2} fluxes (F{sub NEE} = -11.0 to -8.7 {micro}mol m{sup -2} s{sup -1}) were measured in June and July while spring-time CO{sub 2} fluxes were much smaller (F{sub NEE} = -3.8 to -3.6 {micro}mol m{sup -2} s{sup -1}). Overall, we measured lower evapotranspiration (OG = 230 mm; ES = 297 mm) higher midday F{sub NEE} (OG F{sub NEE} = -9.0 {micro}mol m{sup -2} s{sup -1}; ES F{sub NEE} = -7.3 {micro}mol m{sup -2} s{sup -1}) and higher Bowen ratios (OG {beta} = 2.0. ES {beta} = 1.2) at the old-growth forest than at the ES sites during the summer months (May-August). Eddy covariance studies such as ours add critical land-atmosphere exchange data for an abundant, but rarely studied Douglas-fir age class.

Wharton, S; Schroeder, M; Paw U, K T; Falk, M; Bible, K

2009-01-08T23:59:59.000Z

252

Setup of Particle Image Velocimetry (PIV) in Hypersonic Flows.  

E-Print Network (OSTI)

??The accuracy of numerical methods in calculating the flow of backward facing steps in turbulent hypersonic flows is limited due to a lack of flow (more)

Anwar, Moazzam

2008-01-01T23:59:59.000Z

253

On the heat flux vector for flowing granular materials--Part I: effective thermal conductivity and background  

SciTech Connect

Heat transfer plays a major role in the processing of many particulate materials. The heat flux vector is commonly modelled by the Fouriers law of heat conduction and for complex materials such as nonlinear fluids, porous media, or granular materials, the coeffcient of thermal conductivity is generalized by assuming that it would depend on a host of material and kinematical parameters such as temperature, shear rate, porosity or concentration, etc. In Part I, we will give a brief review of the basic equations of thermodynamics and heat transfer to indicate the importance of the modelling of the heat flux vector. We will also discuss the concept of effective thermal conductivity (ETC) in granular and porous media. In Part II, we propose and subsequently derive a properly frame-invariant constitutive relationship for the heat flux vector for a (single phase) flowing granular medium. Standard methods in continuum mechanics such as representation theorems and homogenization techniques are used. It is shown that the heat flux vector in addition to being proportional to the temperature gradient (the Fouriers law), could also depend on the gradient of density (or volume fraction), and D (the symmetric part of the velocity gradient) in an appropriate manner. The emphasis in this paper is on the idea that for complex non-linear materials it is the heat flux vector which should be studied; obtaining or proposing generalized form of the thermal conductivity is not always appropriate or suffcient.

Massoudi, Mehrdad

2006-09-10T23:59:59.000Z

254

Flow and heat transfer in porous micro heat sink for thermal management of high power LEDs  

Science Journals Connector (OSTI)

A novel porous micro heat sink system is presented for thermal management of high power LEDs, which has high heat transport capability. The operational principle and heat transfer characteristics of porous micro heat sink are analyzed. Numerical model ... Keywords: Heat dissipation, High heat flux, High power LEDs, Porous media, Porous micro heat sink

Z. M. Wan; J. Liu; K. L. Su; X. H. Hu; S. S. M

2011-05-01T23:59:59.000Z

255

DRAIN-BACK PROTECTED LOW-FLOW SOLAR HEATING SYSTEM WITH DISTRIBUTED ELEVATED THERMALLY STRATIFIED STORAGE  

Science Journals Connector (OSTI)

ABSTRACT Design considerations concerning a drain-back freeze and overheat protection system are given with emphasis on nitrogen management and thermal stratification of an elevated distributed storage. The actual system of GNT in Berg, Federal Republic of Germany is described. KEYWORDS Solar Heating; Freeze Protection; Overheat Protection; Drain-Back System;

W.B. VELTKAMP; J. VAN BERKEL; A.T. KEESMAN

1990-01-01T23:59:59.000Z

256

Turbulence of a Unidirectional Flow  

E-Print Network (OSTI)

66(4):12151223, 1961. [17] J. Hack. Studies of longitudinalscaling laws. These are Hacks law in one dimension, thelaws of river basins is Hacks law [17] that states that the

Birnir, Bjorn

2007-01-01T23:59:59.000Z

257

Magnetic Reconnection and Turbulent Mixing: From ISM to Clusters of Galaxies  

E-Print Network (OSTI)

Magnetic reconnection, or the ability of the magnetic field lines that are frozen in plasma to change their topology, is a fundamental problem of magnetohydrodynamics (MHD). We briefly examine the problem starting with the well-known Sweet-Parker scheme, discuss effects of tearing modes, anomalous resistivity and the concept of hyperresistivity. We show that the field stochasticity by itself provides a way to enable fast reconnection even if, at the scale of individual turbulent wiggles, the reconnection happens at the slow Sweet-Parker rate. We show that fast reconnection allows efficient mixing of magnetic field in the direction perpendicular to the local direction of magnetic field. While the idea of stochastic reconnection still requires numerical confirmation, our numerical simulations testify that mixing motions perpendicular to the local magnetic field are up to high degree hydrodynamical. This suggests that the turbulent heat transport should be similar to that in non-magnetized turbulent fluid, namely, should have a diffusion coefficient \\sim LV_L, where V_L is the amplitude of the turbulent velocity and L is the scale of the turbulent motions. We present numerical simulations which support this conclusion. The application of this idea to thermal conductivity in clusters of galaxies shows that this mechanism may dominate the diffusion of heat and may be efficient enough to prevent cooling flow formation.

A. Lazarian; J. Cho

2003-02-05T23:59:59.000Z

258

Imaging Fluid Flow in Geothermal Wells Using Distributed Thermal Perturbation Sensing  

Energy.gov (U.S. Department of Energy (DOE))

Project objective: A New Geothermal Well Imaging Tool. 1.To develop a robust and easily deployable DTPS for monitoring in geothermal wells; and 2. Develop the associated analysis methodology for flow imaging; and?when possible by wellbore conditions?to determine in situthermal conductivity and basal heat flux.

259

A study of flow in stratified reservoirs by use of the thermal analogy  

E-Print Network (OSTI)

of Calculated and Experimental Diffusivities for Various Metal Plates. . . . . . 17 Effective Thermal Diffusivities of Bimetallic Plates. 19 The Change in Diffusivity with Time of Multilayered Linear Metal Plates. 20 Change in Diffusivity with Time... for Bimetallic Plates. 23 The Change in Diffusivity with Time for Multi- laye red Plates. 24 Effect of a Layer of Low Conductivity on Effective The rmal Diffusivity. 30 10 A and B- The Effect of Varying the Thickness of a Low Conductive Material Between...

Pickering, Charles William

2012-06-07T23:59:59.000Z

260

Measurement of the Rates of Production and Dissipation of Turbulent Kinetic Energy in an Energetic Tidal Flow: Red Wharf Bay Revisited  

Science Journals Connector (OSTI)

Simultaneous measurements of the rates of turbulent kinetic energy (TKE) dissipation (?) and production (P) have been made over a period of 24 h at a tidally energetic site in the northern Irish Sea in water of 25-m depth. Some ? profiles from ?5 ...

Tom P. Rippeth; John H. Simpson; Eirwen Williams; Mark E. Inall

2003-09-01T23:59:59.000Z

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


261

9.11.2014bo Akademi Univ -Thermal and Flow Engineering -Piispankatu 8, 20500 Turku 1/65 2. Vapour-compression refrigeration  

E-Print Network (OSTI)

. Vapour-compression refrigeration processes Ron Zevenhoven ?bo Akademi University Thermal and Flow") Refrigeration course # 424503.0 v. 2014 ?A 424503 Refrigeration / Kylteknik 9.11.2014?bo Akademi Univ - Thermal of a refrigerant fluid Picture: ?B98 liquid-vapour saturation dome 1-2 and 3-4: reversible and isothermal 2-3 and 4

Zevenhoven, Ron

262

Dependence of thermal diffusivity on organic content for Green River oil shalesExtension of the modified Cheng?Vachon model to the parallel heat?flow case  

Science Journals Connector (OSTI)

In an earlier paper [J. Appl. Phys. 50 2776 (1979)] the modified Cheng?Vachon model was found to give good agreement with experimental data on the variation of thermal diffusivity with organic content for Green River oil shales. Calculations using the model were carried out for the case where heat flows in directions perpendicular to the shale stratigraphic planes. In the present paper the above model is modified to account for experimental trends in the parallel heat?flow case. The modified model provides a self?consistent explanation for the lower degree of anisotropy (relative to theory) that has been experimentally observed for the thermal diffusivity of Green River oil shales.

Y. Wang; K. Rajeshwar; J. DuBow

1980-01-01T23:59:59.000Z

263

Lattice Boltzmann simulation of mass transfer in thermally driven cavity flows  

Science Journals Connector (OSTI)

We study mass transfer in 2D thermally driven cavity using lattice Boltzmann method. Simulations are performed to investigate various effects on enhancement of oxygen mass transfer in lead/lead bismuth eutectic. It is shown that oxygen transfer is dominated by convection although diffusion plays a role. Comparative studies demonstrate that side heating and top-cooling configuration is more efficient than side-heating/cooling and oxygen transfers more rapidly in a square than rectangular cavity with same area. This work supplies supportive information for developing active oxygen control technique in experiments to prevent or reduce corrosion in liquid metal cooled nuclear reactors.

Huidan Yu; Jinsuo Zhang; Ning Li

2008-01-01T23:59:59.000Z

264

Thermal effects on FarleyBuneman waves at nonzero aspect and flow angles. II. Behavior near threshold  

Science Journals Connector (OSTI)

Based on the linear dispersion relation of Kissack et al. Phys. Plasmas 15 022901 (2008) the physical processes that define altitude behavior of marginally stable FarleyBuneman waves in the equatorial electrojet are investigated. The expressions derived for the angular frequency and growth rate are presented in such a way as to make it easy to track the dominant physical processes and to see the relation with earlier work. Two dimensionless parameters are identified that are helpful in showing the transition between altitude and wavelength domains where different thermal processes dominate. The difference in phase velocity between vertical and off-vertical transmissions (zero versus nonzero flow angles) is found to be due to DimantSudan effects which are preferentially less important at higher altitudes and shorter wavelengths.

R. S. Kissack; L. M. Kagan; J.-P. St.-Maurice

2008-01-01T23:59:59.000Z

265

Thermal effects on Farley-Buneman waves at nonzero aspect and flow angles. II. Behavior near threshold  

SciTech Connect

Based on the linear dispersion relation of Kissack et al., Phys. Plasmas 15, 022901 (2008), the physical processes that define altitude behavior of marginally stable Farley-Buneman waves in the equatorial electrojet are investigated. The expressions derived for the angular frequency and growth rate are presented in such a way as to make it easy to track the dominant physical processes and to see the relation with earlier work. Two dimensionless parameters are identified that are helpful in showing the transition between altitude and wavelength domains where different thermal processes dominate. The difference in phase velocity between vertical and off-vertical transmissions (zero versus nonzero flow angles) is found to be due to Dimant-Sudan effects, which are preferentially less important at higher altitudes and shorter wavelengths.

Kissack, R. S.; Kagan, L. M. [Department of Physics and Astronomy, University of Western Ontario, London, Ontario N6A 3K7 (Canada); St-Maurice, J.-P. [Department of Physics, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2 (Canada)

2008-02-15T23:59:59.000Z

266

An h-adaptive finite element method for turbulent heat transfer  

SciTech Connect

A two-equation turbulence closure model (k-{omega}) using an h-adaptive grid technique and finite element method (FEM) has been developed to simulate low Mach flow and heat transfer. These flows are applicable to many flows in engineering and environmental sciences. Of particular interest in the engineering modeling areas are: combustion, solidification, and heat exchanger design. Flows for indoor air quality modeling and atmospheric pollution transport are typical types of environmental flows modeled with this method. The numerical method is based on a hybrid finite element model using an equal-order projection process. The model includes thermal and species transport, localized mesh refinement (h-adaptive) and Petrov-Galerkin weighting for the stabilizing the advection. This work develops the continuum model of a two-equation turbulence closure method. The fractional step solution method is stated along with the h-adaptive grid method (Carrington and Pepper, 2002). Solutions are presented for 2d flow over a backward-facing step.

Carriington, David B [Los Alamos National Laboratory

2009-01-01T23:59:59.000Z

267

Computational simulation of liquid-fuelled HVOF thermal spraying  

Science Journals Connector (OSTI)

Liquid-fuelled high-velocity oxygenfuel (HVOF) thermal spraying systems are gaining more attentions due to their advantage of producing denser coatings in comparison to their gas-fuelled counterparts. The flow through a HVOF gun is characterized by a complex array of thermodynamic phenomena involving combustion, turbulence and compressible flow. Advanced computational models have been developed to gain insight to the thermochemical processes of thermal spraying, however little work has been reported for the liquid-fuelled systems. This investigation employs a commercial finite volume CFD code to simulate the flow field through the most widely used liquid-fuel HVOF gun, JP5000 (Praxair, US). By combining numerical combustion and discrete phase models the turbulent spray flame is captured and the development of supersonic gas flow is revealed. The flow field is thoroughly examined by adjusting the nozzle throat diameter and combustion chamber size. The influence of fuel droplet size on the flame shame shape and combusting gas flow is also examined.

H. Tabbara; S. Gu

2009-01-01T23:59:59.000Z

268

9.11.2014bo Akademi Univ -Thermal and Flow Engineering Piispankatu 8, 20500 Turku 1/44 3. Absorption, gas expansion and  

E-Print Network (OSTI)

Thermal and Flow Engineering Laboratory / Värme- och strömningsteknik tel. 3223 ; ron.zevenhoven@abo.fi Kylteknik ("KYL") Refrigeration course # 424503.0 v. 2014 ?A 424503 Refrigeration / Kylteknik 9.11.2014?bo energy, solar energy, biogas fuel, etc. Absorption refrigeration involves absorption of refrigerant

Zevenhoven, Ron

269

Turbulent structures and budgets behind permeable ribs  

SciTech Connect

Different rib geometries are traditionally used to improve heat transfer and enhance mixing in different industrial applications, i.e. heat exchangers, cooling passages of gas turbine blades and fuel elements of nuclear reactors, etc. Permeable ribs have been proposed in literature for passive control of the reattaching flow past surface mounted ribs leading to superior performance. The flow past different surface mounted permeable rib geometries, i.e. solid, slit, split-slit and inclined split-slit ribs have been investigated in this study. Both two components and stereo particle image velocimetry (PIV) have been used in streamwise and cross stream planes to study the underlying flow structures. The detailed turbulent statistics, i.e. mean and rms velocity, higher order moments, quadrant decomposition of turbulent shear stress producing motions, skewness and components of the turbulent kinetic energy budgets have been compared for different rib geometries. Coherent structures are identified based on the invariant of velocity gradient tensor invariant and wavelet transform. The skewness results demonstrate the intermittency of quadrant motions. The reattachment length of the inclined split-slit rib is lowest among all rib geometries. The average Reynolds stresses and the production of turbulent kinetic energy are highest for the inclined split-slit rib. The pressure transport calculated as residual of the turbulent kinetic energy budget equation is highest for the inclined split-slit rib. This is attributed to the smaller reattachment length leading to greater adverse pressure gradient for the inclined split-slit rib. The quadrant motions, turbulent fluxes, skewness and kinetic energy budgets at post reattachment region compares well with that of flat plate turbulent boundary layer from hot wire measurements in literature. Overall, this study demonstrates the effectiveness of PIV technique for the detailed turbulent structures characterization of complex flows. (author)

Panigrahi, P.K. [Department of Mechanical Engineering, IIT Kanpur, UP 208016 (India); Schroeder, A.; Kompenhans, J. [Institute of Aerodynamics and Flow Technology, German Aerospace Center (DLR), Goettingen (Germany)

2008-02-15T23:59:59.000Z

270

Fluid flow in the resurgent dome of Long Valley Caldera: implications from thermal data and deep electrical sounding  

Science Journals Connector (OSTI)

Temperatures of 100C are measured at 3 km depth in a well located on the resurgent dome in the center of Long Valley Caldera, California, despite an assumed >800C magma chamber at 68 km depth. Local downflow of cold meteoric water as a process for cooling the resurgent dome is ruled out by a Peclt-number analysis of temperature logs. These analyses reveal zones with fluid circulation at the upper and lower boundaries of the Bishop Tuff, and an upflow zone in the metasedimentary rocks. Vertical Darcy velocities range from 10 to 70 cm a?1. A 21-km-long geoelectrical profile across the caldera provides resistivity values to the order of 100 to >103 ?m down to a depth of 6 km, as well as variations of self-potential. Interpretation of the electrical data with respect to hydrothermal fluid movement confirms that there is no downflow beneath the resurgent dome. To explain the unexpectedly low temperatures in the resurgent dome, we challenge the common view that the caldera as a whole is a regime of high temperatures and the resurgent dome is a local cold anomaly. Instead, we suggest that the caldera was cooled to normal thermal conditions by vigorous hydrothermal activity in the past, and that a present-day hot water flow system is responsible for local hot anomalies, such as Hot Creek and the area of the Casa Diablo geothermal power plant. The source of hot water has been associated with recent shallow intrusions into the West Moat. The focus of planning for future power plants should be to locate this present-day flow system instead of relying on heat from the old magma chamber.

Daniel F.C Pribnow; Claudia Schtze; Suzanne J Hurter; Christina Flechsig; John H Sass

2003-01-01T23:59:59.000Z

271

On specification of initial conditions in turbulence models  

SciTech Connect

Recent research has shown that initial conditions have a significant influence on the evolution of a flow towards turbulence. This important finding offers a unique opportunity for turbulence control, but also raises the question of how to properly specify initial conditions in turbulence models. We study this problem in the context of the Rayleigh-Taylor instability. The Rayleigh-Taylor instability is an interfacial fluid instability that leads to turbulence and turbulent mixing. It occurs when a light fluid is accelerated in to a heavy fluid because of misalignment between density and pressure gradients. The Rayleigh-Taylor instability plays a key role in a wide variety of natural and man-made flows ranging from supernovae to the implosion phase of Inertial Confinement Fusion (ICF). Our approach consists of providing the turbulence models with a predicted profile of its key variables at the appropriate time in accordance to the initial conditions of the problem.

Rollin, Bertrand [Los Alamos National Laboratory; Andrews, Malcolm J [Los Alamos National Laboratory

2010-12-01T23:59:59.000Z

272

THEORY-BASED MODELS OF TURBULENCE AND ANOMALOUS TRANSPORT IN FUSION PLASMAS  

E-Print Network (OSTI)

: studying ways to reduce turbulence and the cost of a fusion energy power plant. General Atomics (San Diego '94 · Based on nonlinear gyrofluid simulations of ITG turbulence to map out struc- ture of ion thermal prevent honey from dripping. #12;Cut-away view of tokamak turbulence simulation Waltz (General Atomics

Hammett, Greg

273

A Mountain-Scale Thermal Hydrologic Model for Simulating Fluid Flow and Heat Transfer in Unsaturated Fractured Rock  

E-Print Network (OSTI)

for Simulating Fluid Flow and Heat Transfer in Unsaturatedcomplex multiphase fluid flow and heat-transfer processes.of the coupled fluid-flow and heat-transfer processes has

Wu, Yu-Shu; Mukhopadhyay, Sumit; Zhang, Keni; Bodvarsson, Gudmundur S.

2005-01-01T23:59:59.000Z

274

Modelling suspended sediment in environmental turbulent fluids  

E-Print Network (OSTI)

Modelling sediment transport in environmental turbulent fluids is a challenge. This article develops a sound model of the lateral transport of suspended sediment in environmental fluid flows such as floods and tsunamis. The model is systematically derived from a 3D turbulence model based on the Smagorinski large eddy closure. Embedding the physical dynamics into a family of problems and analysing linear dynamics of the system, centre manifold theory indicates the existence of slow manifold parametrised by macroscale variables. Computer algebra then constructs the slow manifold in terms of fluid depth, depth-averaged lateral velocities, and suspended sediment concentration. The model includes the effects of sediment erosion, advection, dispersion, and also the interactions between the sediment and turbulent fluid flow. Vertical distributions of the velocity and concentration in steady flow agree with the established experimental data. Numerical simulations of the suspended sediment under large waves show that ...

Cao, Meng

2014-01-01T23:59:59.000Z

275

In vivo wall shear stress and flow reversal in canine thoracic aortae  

E-Print Network (OSTI)

stress in a stable flow regime may become an area of high shear if the flow becomes un- stable or turbulent [15]. The arterial blood flow is not steady, nor is it fully developed. Flow disturbances such as turbulence, flow separation and flow... stress in a stable flow regime may become an area of high shear if the flow becomes un- stable or turbulent [15]. The arterial blood flow is not steady, nor is it fully developed. Flow disturbances such as turbulence, flow separation and flow...

Dunn, Carl Anthony

2012-06-07T23:59:59.000Z

276

43rd AIAA Aerospace Sciences Meeting and Exhibit, Jan 10Jan 13, Reno, Nevada Analysis of Shockwave/Turbulent Boundary Layer  

E-Print Network (OSTI)

, for example, in scramjet engines, where the turbulent flow inside the engine is characterized by complex shock

Martín, Pino

277

Recent results on analytical plasma turbulence theory: Realizability, intermittency, submarginal turbulence, and self-organized criticality  

SciTech Connect

Recent results and future challenges in the systematic analytical description of plasma turbulence are described. First, the importance of statistical realizability is stressed, and the development and successes of the Realizable Markovian Closure are briefly reviewed. Next, submarginal turbulence (linearly stable but nonlinearly self-sustained fluctuations) is considered and the relevance of nonlinear instability in neutral-fluid shear flows to submarginal turbulence in magnetized plasmas is discussed. For the Hasegawa-Wakatani equations, a self-consistency loop that leads to steady-state vortex regeneration in the presence of dissipation is demonstrated and a partial unification of recent work of Drake (for plasmas) and of Waleffe (for neutral fluids) is given. Brief remarks are made on the difficulties facing a quantitatively accurate statistical description of submarginal turbulence. Finally, possible connections between intermittency, submarginal turbulence, and self-organized criticality (SOC) are considered and outstanding questions are identified.

Krommes, J.A.

2000-01-18T23:59:59.000Z

278

Thermal and flow analysis of the Fluor Daniel, Inc., Nuclear Material Storage Facility renovation design (initial 30% effort of Title 1)  

SciTech Connect

The computational fluid dynamics code CFX4.2 was used to evaluate steady-state thermal-hydraulic conditions in the Fluor Daniel, Inc., Nuclear Material Storage Facility renovation design (initial 30% of Title 1). Thirteen facility cases were evaluated with varying temperature dependence, drywell-array heat-source magnitude and distribution, location of the inlet tower, and no-flow curtains in the drywell-array vault. Four cases of a detailed model of the inlet-tower top fixture were evaluated to show the effect of the canopy-cruciform fixture design on the air pressure and flow distributions.

Steinke, R.G.; Mueller, C.; Knight, T.D.

1998-03-01T23:59:59.000Z

279

On predicting the transition to turbulence in stably stratified fluids  

SciTech Connect

The development of turbulence in stratified fluids has historically been studied using the flux, Ri{sub f}, and the gradient Richardson no., Ri, whereas the simpler shear flow transition in homogeneous fluids has been studied using the Reynolds no. A complete dimensional analysis dimensional analysis of the relevant linearized conservation equations in the Boussinesq approximation predicts that the physical processes in stably stratified boundary layers should depend on as many as five dimensionless parameters, namely, the Rayleigh no, Ra, the Reynolds no., Re, the Taylor no., Ta, the Prandtl no., Pr, and the Radiation no., Rd. The Radiation no. is very similar to Pr, but includes thermal radiative transfer instead of molecular heat conduction.

ReVelle, D.O.

1997-08-01T23:59:59.000Z

280

Advanced battery thermal management for electrical-drive vehicles using reciprocating cooling flow and spatial-resolution, lumped-capacitance thermal model.  

E-Print Network (OSTI)

?? The thermal management of traction battery systems for electrical-drive vehicles directly affects vehicle dynamic performance, long-term durability and cost of the battery systems. The (more)

Mahamud, Rajib

2011-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


281

Reaction and diffusion in turbulent combustion  

SciTech Connect

The motivation for this project is the need to obtain a better quantitative understanding of the technologically-important phenomenon of turbulent combustion. In nearly all applications in which fuel is burned-for example, fossil-fuel power plants, furnaces, gas-turbines and internal-combustion engines-the combustion takes place in a turbulent flow. Designers continually demand more quantitative information about this phenomenon-in the form of turbulent combustion models-so that they can design equipment with increased efficiency and decreased environmental impact. For some time the PI has been developing a class of turbulent combustion models known as PDF methods. These methods have the important virtue that both convection and reaction can be treated without turbulence-modelling assumptions. However, a mixing model is required to account for the effects of molecular diffusion. Currently, the available mixing models are known to have some significant defects. The major motivation of the project is to seek a better understanding of molecular diffusion in turbulent reactive flows, and hence to develop a better mixing model.

Pope, S.B. [Mechanical and Aerospace Engineering, Ithaca, NY (United States)

1993-12-01T23:59:59.000Z

282

Turbulence-Chemistry Interaction in Lean Premixed Hydrogen Combustion  

E-Print Network (OSTI)

Turbulence-Chemistry Interaction in Lean Premixed Hydrogen Combustion A. J. Aspden1,2 , M. S. Day2 between fuel consumption and heat release. Keywords: turbulent premixed combustion, low Mach number flow or hydrogen-rich mixtures obtained from gasi- fication of coal or biomass. These types of fuels provide clean

Bell, John B.

283

Turbulent diffusion with rotation or magnetic fields  

E-Print Network (OSTI)

The turbulent diffusion tensor describing the evolution of the mean concentration of a passive scalar is investigated for forced turbulence either in the presence of rotation or a magnetic field. With rotation the Coriolis force causes a sideways deflection of the flux of mean concentration. Within the magnetohydrodynamics approximation there is no analogous effect from the magnetic field because the effects on the flow do not depend on the sign of the field. Both rotation and magnetic fields tend to suppress turbulent transport, but this suppression is weaker in the direction along the magnetic field. Turbulent transport along the rotation axis is not strongly affected by rotation, except on shorter length scales, i.e. when the scale of the variation of the mean field becomes comparable with the scale of the energy-carrying eddied.

Brandenburg, Axel; Vasil, Geoffrey M

2009-01-01T23:59:59.000Z

284

Inhomogeneous distribution of droplets in cloud turbulence  

E-Print Network (OSTI)

We solve the problem of spatial distribution of inertial particles that sediment in turbulent flow with small ratio of acceleration of fluid particles to acceleration of gravity $g$. The particles are driven by linear drag and have arbitrary inertia. The pair-correlation function of concentration obeys a power-law in distance with negative exponent. Divergence at zero signifies singular distribution of particles in space. Independently of particle size the exponent is ratio of integral of energy spectrum of turbulence times the wavenumber to $g$ times numerical factor. We find Lyapunov exponents and confirm predictions by direct numerical simulations of Navier-Stokes turbulence. The predictions include typical case of water droplets in clouds. This significant progress in the study of turbulent transport is possible because strong gravity makes the particle's velocity at a given point unique.

Itzhak Fouxon; Yongnam Park; Roei Harduf; Changhoon Lee

2014-10-30T23:59:59.000Z

285

Thermal Energy Measurement with Tangential Paddlewheel Flow Meters: Summary of Experimental Results and in-situ Diagnostics  

E-Print Network (OSTI)

paddlewheel flow meters, and several new methods for in-situ diagnostic measures for ascertaining whether or not a flow meter is experiencing fluctuating flow conditions or if a flow meter is suffering a degraded signal due to shaft wear. INTRODUCTION Flow... section where it passes across the candidate sensor that is placed in the inter-changeable test section, through the orifice plate and finally into the is combined with Btu meter the threshold can be much higher than the published threshold of the flow...

Haberl, J. S.; Watt, J. B.

1994-01-01T23:59:59.000Z

286

The Influence of Proposed Repository Thermal Load on Multiphase Flow and Heat Transfer in the Unsaturated Zone of Yucca Mountain  

E-Print Network (OSTI)

development of fluid flow and heat transfer models at otherTOUGH2 code [22]. Fluid flow and heat-transfer processes inand heat transfer through fractured rock is based on the DKM method. This approach considers global fluid and

Wu, Y.-S.; Mukhopadhyay, Sumit; Zhang, Keni; Bodvarsson, G.S.

2006-01-01T23:59:59.000Z

287

Using large eddy simulations to understand flow mixing | Argonne National  

NLE Websites -- All DOE Office Websites (Extended Search)

large eddy simulations to understand flow mixing large eddy simulations to understand flow mixing March 4, 2013 Tweet EmailPrint In nuclear power plants, turbulent flow streams of different velocity and density mix rapidly at right angles in pipes. If those mixing flow streams are of different temperatures, thermal fluctuations result on the pipe wall. Such fluctuations can damage a pipe's structure and, ultimately, cause its failure. To better understand this phenomenon and to predict the effects, scientists have developed modeling methods known as large eddy simulations (LES). LES models only the energy-carrying large scales of motion, using a filtering mechanism to account for subgrid-scale motion. Thanks to recent advances in high-performance computing, the technique has become increasingly popular for simulating unsteady flows, allowing high fidelity

288

Turbulence attenuation by large neutrally buoyant particles  

E-Print Network (OSTI)

Turbulence modulation by inertial-range-size, neutrally-buoyant particles is investigated experimentally in a von K\\'arm\\'an flow. Increasing the particle volume fraction $\\Phi_\\mathrm{v}$, maintaining constant impellers Reynolds number attenuates the fluid turbulence. The inertial-range energy transfer rate decreases as $\\propto\\Phi_\\mathrm{v}^{2/3}$, suggesting that only particles located on a surface affect the flow. Small-scale turbulent properties, such as structure functions or acceleration distribution, are unchanged. Finally, measurements hint at the existence of a transition between two different regimes occurring when the average distance between large particles is of the order of the thickness of their boundary layers.

Cisse, Mamadou; Gibert, Mathieu; Bodenschatz, Eberhard; Bec, Jeremie

2015-01-01T23:59:59.000Z

289

CONTROL OF COHERENT STRUCTURE IN COAXIAL SWIRLING TURBULENT JETS  

E-Print Network (OSTI)

stronger effect than the pilot jet itself, leading to an almost entire removal of coherent structures. 2.2. Flow Instability Swirl is naturally presented in the exhaust from a turbine or an axial flow pump, and may be deliberately generated... ............................................................................................. 1 2. REVIEW OF LITERATURE............................................................................. 6 2.1. Turbulent Jets with Swirl................................................................................ 7 2.2. Flow Instability...

Lee, Wonjoong

2008-01-01T23:59:59.000Z

290

A Mountain-Scale Thermal Hydrologic Model for Simulating Fluid Flow and Heat Transfer in Unsaturated Fractured Rock  

E-Print Network (OSTI)

Studies Using the Yucca Mountain Unsaturated Zone Model,Unsaturated Zone at Yucca Mountain, Nevada, to Thermal LoadUnsaturated Zone, Yucca Mountain, Nevada, Water-Resources

Wu, Yu-Shu; Mukhopadhyay, Sumit; Zhang, Keni; Bodvarsson, Gudmundur S.

2005-01-01T23:59:59.000Z

291

The Influence of Proposed Repository Thermal Load on Multiphase Flow and Heat Transfer in the Unsaturated Zone of Yucca Mountain  

E-Print Network (OSTI)

Studies Using the Yucca Mountain Unsaturated Zone Model,Unsaturated Zone at Yucca Mountain, Nevada, to Thermal LoadLarge Block Test at Yucca Mountain, Nevada, Water Resources

Wu, Y.-S.; Mukhopadhyay, Sumit; Zhang, Keni; Bodvarsson, G.S.

2006-01-01T23:59:59.000Z

292

Cup Anemometer Behavior in Turbulent Environments  

Science Journals Connector (OSTI)

The behavior of the cup anemometer rotor in turbulent atmospheric flow is discussed in terms of a general equation of motion. This equates the rate of change s?? of the rotation rate s? of the rotor to a forcing F(s?, h?, w?), which is proportional ...

Leif Kristensen

1998-02-01T23:59:59.000Z

293

OF HEALTH CARE IN TURBULENT TIMES  

E-Print Network (OSTI)

FIXING THE FLOW OF HEALTH CARE IN TURBULENT TIMES INNOVATION REPORT 2014 #12;Since 2012, Algorithms facing health care today. We believe there's an unprecedented opportunity to invent a new vision for health care, and academic medicine is poised to lead the way. Algorithms for Innovations is designed

Feschotte, Cedric

294

NO concentration imaging in turbulent nonpremixed flames  

SciTech Connect

The importance of NO as a pollutant species is well known. An understanding of the formation characteristics of NO in turbulent hydrocarbon flames is important to both the desired reduction of pollutant emissions and the validation of proposed models for turbulent reacting flows. Of particular interest is the relationship between NO formation and the local flame zone, in which the fuel is oxidized and primary heat release occurs. Planar imaging of NO provides the multipoint statistics needed to relate NO formation to the both the flame zone and the local turbulence characteristics. Planar imaging of NO has been demonstrated in turbulent flames where NO was seeded into the flow at high concentrations (2000 ppm) to determine the gas temperature distribution. The NO concentrations in these experiments were significantly higher than those expected in typical hydrocarbon-air flames, which require a much lower detectability limit for NO measurements. An imaging technique based on laser-induced fluorescence with sufficient sensitivity to study the NO formation mechanism in the stabilization region of turbulent lifted-jet methane flames.

Schefer, R.W. [Sandia National Laboratories, Livermore, CA (United States)

1993-12-01T23:59:59.000Z

295

The Temperature of Interstellar Clouds from Turbulent Heating  

E-Print Network (OSTI)

To evaluate the effect of turbulent heating in the thermal balance of interstellar clouds, we develop an extension of the log-Poisson intermittency model to supersonic turbulence. The model depends on a parameter, d, interpreted as the dimension of the most dissipative structures. By comparing the model with the probability distribution of the turbulent dissipation rate in a simulation of supersonic and super-Alfvenic turbulence, we find a best-fit value of d=1.64. We apply this intermittency model to the computation of the mass-weighted probability distribution of the gas temperature of molecular clouds, high-mass star-forming cores, and cold diffuse HI clouds. Our main results are: i) The mean gas temperature in molecular clouds can be explained as the effect of turbulent heating alone, while cosmic ray heating may dominate only in regions where the turbulent heating is low; ii) The mean gas temperature in high-mass star-forming cores with typical FWHM of ~6 km/s (corresponding to a 1D rms velocity of 2.5 km/s) may be completely controlled by turbulent heating, which predicts a mean value of approximately 36 K, two to three times larger than the mean gas temperature in the absence of turbulent heating; iii) The intermittency of the turbulent heating can generate enough hot regions in cold diffuse HI clouds to explain the observed CH+ abundance, if the rms velocity on a scale of 1 pc is at least 3 km/s, in agreement with previous results based on incompressible turbulence. Because of its importance in the thermal balance of molecular clouds and high-mass star-forming cores, the process of turbulent heating may be central in setting the characteristic stellar mass and in regulating molecular chemical reactions.

Liubin Pan; Paolo Padoan

2008-06-30T23:59:59.000Z

296

Liquid Salts as Media for Process Heat Transfer from VHTR's: Forced Convective Channel Flow Thermal Hydraulics, Materials, and Coating  

SciTech Connect

The goal of this NERI project was to perform research on high temperature fluoride and chloride molten salts towards the long-term goal of using these salts for transferring process heat from high temperature nuclear reactor to operation of hydrogen production and chemical plants. Specifically, the research focuses on corrosion of materials in molten salts, which continues to be one of the most significant challenges in molten salts systems. Based on the earlier work performed at ORNL on salt properties for heat transfer applications, a eutectic fluoride salt FLiNaK (46.5% LiF-11.5%NaF-42.0%KF, mol.%) and a eutectic chloride salt (32%MgCl2-68%KCl, mole %) were selected for this study. Several high temperature candidate Fe-Ni-Cr and Ni-Cr alloys: Hastelloy-N, Hastelloy-X, Haynes-230, Inconel-617, and Incoloy-800H, were exposed to molten FLiNaK with the goal of understanding corrosion mechanisms and ranking these alloys for their suitability for molten fluoride salt heat exchanger and thermal storage applications. The tests were performed at 850????????C for 500 h in sealed graphite crucibles under an argon cover gas. Corrosion was noted to occur predominantly from dealloying of Cr from the alloys, an effect that was particularly pronounced at the grain boundaries Alloy weight-loss due to molten fluoride salt exposure correlated with the initial Cr-content of the alloys, and was consistent with the Cr-content measured in the salts after corrosion tests. The alloys???¢???????? weight-loss was also found to correlate to the concentration of carbon present for the nominally 20% Cr containing alloys, due to the formation of chromium carbide phases at the grain boundaries. Experiments involving molten salt exposures of Incoloy-800H in Incoloy-800H crucibles under an argon cover gas showed a significantly lower corrosion for this alloy than when tested in a graphite crucible. Graphite significantly accelerated alloy corrosion due to the reduction of Cr from solution by graphite and formation on Cr-carbide on the graphite surface. Ni-electroplating dramatically reduced corrosion of alloys, although some diffusion of Fe and Cr were observed occur through the Ni plating. A pyrolytic carbon and SiC (PyC/SiC) CVD coating was also investigated and found to be effective in mitigating corrosion. The KCl-MgCl2 molten salt was less corrosive than FLiNaK fluoride salts for corrosion tests performed at 850oC. Cr dissolution in the molten chloride salt was still observed and consequently Ni-201 and Hastelloy N exhibited the least depth of attack. Grain-boundary engineering (GBE) of Incoloy 800H improved the corrosion resistance (as measured by weight loss and maximum depth of attack) by nearly 50% as compared to the as-received Incoloy 800H sample. Because Cr dissolution is an important mechanism of corrosion, molten salt electrochemistry experiments were initiated. These experiments were performed using anodic stripping voltammetry (ASV). Using this technique, the reduction potential of Cr was determined against a Pt quasi-reference electrode as well as against a Ni(II)-Ni reference electrode in molten FLiNaK at 650 oC. The integrated current increased linearly with Cr-content in the salt, providing for a direct assessment of the Cr concentration in a given salt of unknown Cr concentration. To study heat transfer mechanisms in these molten salts over the forced and mixed convection regimes, a forced convective loop was constructed to measure heat transfer coefficients, friction factors and corrosion rates in different diameter tubes in a vertical up flow configuration in the laminar flow regime. Equipment and instrumentation for the forced convective loop was designed, constructed, and tested. These include a high temperature centrifugal pump, mass flow meter, and differential pressure sensing capabilities to an uncertainty of < 2 Pa. The heat transfer coefficient for the KCl-MgCl2 salt was measured in t

Kumar Sridharan; Mark Anderson; Todd Allen; Michael Corradini

2012-01-30T23:59:59.000Z

297

Odor Landscapes in Turbulent Environments  

Science Journals Connector (OSTI)

The olfactory system of male moths is exquisitely sensitive to pheromones emitted by females and transported in the environment by atmospheric turbulence. Moths respond to minute amounts of pheromones, and their behavior is sensitive to the fine-scale structure of turbulent plumes where pheromone concentration is detectible. The signal of pheromone whiffs is qualitatively known to be intermittent, yet quantitative characterization of its statistical properties is lacking. This challenging fluid dynamics problem is also relevant for entomology, neurobiology, and the technological design of olfactory stimulators aimed at reproducing physiological odor signals in well-controlled laboratory conditions. Here, we develop a Lagrangian approach to the transport of pheromones by turbulent flows and exploit it to predict the statistics of odor detection during olfactory searches. The theory yields explicit probability distributions for the intensity and the duration of pheromone detections, as well as their spacing in time. Predictions are favorably tested by using numerical simulations, laboratory experiments, and field data for the atmospheric surface layer. The resulting signal of odor detections lends itself to implementation with state-of-the-art technologies and quantifies the amount and the type of information that male moths can exploit during olfactory searches.

Antonio Celani; Emmanuel Villermaux; Massimo Vergassola

2014-10-28T23:59:59.000Z

298

Heat Generation and Flow and Thermal Effects on Optical Spectra in Laser Diode Pumped Thulium-doped Vanadate Crystals  

Science Journals Connector (OSTI)

Optical spectra, excited state relaxation dynamics and thermal conductivity in a wide temperature region for thulium-doped YVO4, GdVO4 and LuVO4 have been measured and analyzed to...

Lisiecki, Radoslaw; Stachowiak, Piotr; Jezowski, Andrzej; Solarz, Piotr; Dominiak-Dzik, Grazyna; Ryba-Romanowski, Witold; Lukasiewicz, Tadeusz

299

Wind- and thermal-driven air flows and the buoyancy and advection effects on air exchange within urban environments  

E-Print Network (OSTI)

Human exposure to air pollutants and thermal stress in urban areas are public health concerns. The year 2008 was the first year when more than half of the human population lived in urban areas. Studies of the urban air ...

Magnusson, Sigurur Ptur

2014-01-01T23:59:59.000Z

300

Large-eddy simulation of a wind turbine wake in turbulent  

E-Print Network (OSTI)

Large-eddy simulation of a wind turbine wake in turbulent neutral shear flow Shengbai Xie, Cristina-similar velocity profile existing in the wake after a wind turbine? How does the wake influence the vertical? Motivation #12; Large-eddy simulation for turbulent flow field Actuator-line model for wind turbine ui

Firestone, Jeremy

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


301

Analyzing Transient Turbulence in a Stenosed Carotid Artery by Proper Orthogonal Decomposition  

E-Print Network (OSTI)

rate, a transitional and intermittent flow between laminar and turbulent states was established. Time in the clinical setting--was also investigated. Keywords--CFD, Transitional flow, Windowed-POD. INTRODUCTION We. The stenosis may trigger transition to turbu- lence, and onset of turbulence downstream of severe occlusions

Yakhot, Alexander

302

Rhines scale and spectra of the -plane turbulence with bottom drag Sergey Danilov1,2  

E-Print Network (OSTI)

,7­10 . The Rhines definition involves, however, the undeter- mined energy content of the flow, which depends and dissipation. Clearly, turbulent flows stabilized by the friction have their energy content, hence rms velocity the jet number and the energy peak of the -plane turbulence for strong . The intermediate cases show

Gurarie, David

303

Mixed convection in the thermal entrance region of symmetrically and asymmetrically heated vertical flat duct with upward or downward air-flow  

SciTech Connect

A numerical investigation has been conducted on the effect of body force on pure forced convection of the upward or downward air-flow in the thermal entrance region between vertical parallel plates with uniform wall temperature. The governing equations based on the usual Boussinesq approximation are solved for the symmetrically and asymmetrically heated parallel plates. Numerically predicted friction factors C{sub f} and local Nusselt numbers Nu{sub x} are compared with their counterparts, C*{sub f} and Nu*{sub x}, for pure forced convection.

Naito, Etsuro; Nagano, Yasutaka

1999-07-01T23:59:59.000Z

304

Reply to Comment on Heat transfer and fluid flow in microchannels and nanochannels at high Knudsen number using thermal lattice-Boltzmann method  

Science Journals Connector (OSTI)

In this reply to the Comment by Li-Shi Luo, we discuss the results of the lattice Bhatnagar-Gross-Krook (LBGK) model for high-Knudsen-number (Kn) flow and heat transfer, in the range of Kn?1. We present various studies employing the LBGK model for high-Kn flow and heat transfer simulations. It is concluded that, with the use of the LBGK model in the thermal lattice Boltzmann method for Kn?0.8, some approximations appear in the negative pressure deviation from the linear distribution along the channel. But for Kn<0.8, the velocity and temperature profiles, compressibility effects, Knudsen layer capturing, and Knudsen paradox phenomenon can be predicted by the LBGK model. We also reject Li-Shi Luos claim about the nonconvergence of our numerical scheme by presenting a velocity profile across the channel corresponding to three different high-resolution meshes.

J. Ghazanfarian and A. Abbassi

2011-10-25T23:59:59.000Z

305

Turbulent drag reduction through oscillating discs  

E-Print Network (OSTI)

The changes of a turbulent channel flow subjected to oscillations of wall flush-mounted rigid discs are studied by means of direct numerical simulations. The Reynolds number is $R_\\tau$=$180$, based on the friction velocity of the stationary-wall case and the half channel height. The primary effect of the wall forcing is the sustained reduction of wall-shear stress, which reaches a maximum of 20%. A parametric study on the disc diameter, maximum tip velocity, and oscillation period is presented, with the aim to identify the optimal parameters which guarantee maximum drag reduction and maximum net energy saving, computed by taking into account the power spent to actuate the discs. This may be positive and reaches 6%. The Rosenblat viscous pump flow is used to predict the power spent for disc motion in the turbulent channel flow and to estimate localized and transient regions over the disc surface subjected to the turbulent regenerative braking effect, for which the wall turbulence exerts work on the discs. The...

Wise, Daniel J

2014-01-01T23:59:59.000Z

306

Enhancement and suppression of heat transfer by MHD turbulence  

E-Print Network (OSTI)

We study of the effect of turbulence on heat transfer within magnetized plasmas for energy injection velocities both larger and smaller that the Alfven speed. We find that in the latter regime the heat transfer is partially suppressed, while in the former regime the effects of turbulence depend on the intensity of driving. In fact, the scale l at which the turbulent velocity is equal the Alfven velocity is a new important parameter. When the electron mean free path is larger than l, the stronger the the turbulence, the lower thermal conductivity by electrons is. The turbulent motions, however, induces their own advective heat transport, which, for the parameters of intracluster medium (ICM) provides effective heat diffusivity that exceeds the classical Spitzer value.

A. Lazarian

2006-08-02T23:59:59.000Z

307

Characterization of Fuego for laminar and turbulent natural convection heat transfer.  

SciTech Connect

A computational fluid dynamics (CFD) analysis is conducted for internal natural convection heat transfer using the low Mach number code Fuego. The flow conditions under investigation are primarily laminar, transitional, or low-intensity level turbulent flows. In the case of turbulent boundary layers at low-level turbulence or transitional Reynolds numbers, the use of standard wall functions no longer applies, in general, for wall-bounded flows. One must integrate all the way to the wall in order to account for gradients in the dependent variables in the viscous sublayer. Fuego provides two turbulence models in which resolution of the near-wall region is appropriate. These models are the v2-f turbulence model and a Launder-Sharma, low-Reynolds number turbulence model. Two standard geometries are considered: the annulus formed between horizontal concentric cylinders and a square enclosure. Each geometry emphasizes wall shear flow and complexities associated with turbulent or near turbulent boundary layers in contact with a motionless core fluid. Overall, the Fuego simulations for both laminar and turbulent flows compared well to measured data, for both geometries under investigation, and to a widely accepted commercial CFD code (FLUENT).

Francis, Nicholas Donald, Jr. (,; .)

2005-08-01T23:59:59.000Z

308

Distributed Energy Resources On-Site Optimization for Commercial Buildings with Electric and Thermal Storage Technologies  

E-Print Network (OSTI)

lead/acid battery, and thermal storage, capabilities, withhour electrical flow battery 8 thermal Not all constraintslifetime ( a) thermal storage 11 flow battery absorption

Stadler, Michael

2008-01-01T23:59:59.000Z

309

Generalized universal instability: Transient linear amplification and subcritical turbulence  

E-Print Network (OSTI)

In this work we numerically demonstrate both significant transient (i.e. non-modal) linear amplification and sustained nonlinear turbulence in a kinetic plasma system with no unstable eigenmodes. The particular system considered is an electrostatic plasma slab with magnetic shear, kinetic electrons and ions, weak collisions, and a density gradient, but with no temperature gradient. In contrast to hydrodynamic examples of non-modal growth and subcritical turbulence, here there is no sheared flow in the equilibrium. Significant transient linear amplification is found when the magnetic shear and collisionality are weak. It is also demonstrated that nonlinear turbulence can be sustained if initialized at sufficient amplitude. We prove these two phenomena are related: when sustained turbulence occurs without unstable eigenmodes, states that are typical of the turbulence must yield transient linear amplification of the gyrokinetic free energy.

Landreman, Matt; Dorland, William

2015-01-01T23:59:59.000Z

310

The energetic coupling of scales in gyrokinetic plasma turbulence  

SciTech Connect

In magnetized plasma turbulence, the couplings of perpendicular spatial scales that arise due to the nonlinear interactions are analyzed from the perspective of the free-energy exchanges. The plasmas considered here, with appropriate ion or electron adiabatic electro-neutrality responses, are described by the gyrokinetic formalism in a toroidal magnetic geometry. Turbulence develops due to the electrostatic fluctuations driven by temperature gradient instabilities, either ion temperature gradient (ITG) or electron temperature gradient (ETG). The analysis consists in decomposing the system into a series of scale structures, while accounting separately for contributions made by modes possessing special symmetries (e.g., the zonal flow modes). The interaction of these scales is analyzed using the energy transfer functions, including a forward and backward decomposition, scale fluxes, and locality functions. The comparison between the ITG and ETG cases shows that ETG turbulence has a more pronounced classical turbulent behavior, exhibiting a stronger energy cascade, with implications for gyrokinetic turbulence modeling.

Teaca, Bogdan, E-mail: bogdan.teaca@coventry.ac.uk [Applied Mathematics Research Centre, Coventry University, Coventry CV1 5FB (United Kingdom); Max-Planck fr Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Gttingen (Germany); Max-Planck-Institut fr Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Max-Planck/Princeton Center for Plasma Physics (Germany); Navarro, Alejandro Ban, E-mail: alejandro.banon.navarro@ipp.mpg.de [Max-Planck-Institut fr Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Jenko, Frank, E-mail: frank.jenko@ipp.mpg.de [Max-Planck-Institut fr Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Max-Planck/Princeton Center for Plasma Physics (Germany)

2014-07-15T23:59:59.000Z

311

Statistical models for spatial patterns of inertial particles in turbulence  

E-Print Network (OSTI)

The dynamics of particles suspended in turbulent flows is of fundamental importance for a wide range of questions in astrophysics, cloud physics, oceanography, and in technology. Laboratory experiments and direct numerical simulations have demonstrated that heavy particles respond in intricate ways to turbulent fluctuations of the carrying fluid: independent particles may cluster together and form spatial patterns even though the fluid is incompressible, and the relative speeds of nearby particles may fluctuate strongly. Both phenomena depend sensitively on the parameters of the system, affect collision rates and outcomes, and thus the long-term fate of the system. This is a hard problem to describe theoretically: the turbulence determines the particle paths, but at the same time the turbulent fluctuations encountered by a particle depend sensitively upon its path through the medium. In recent years it has become clear that important aspects of the particle dynamics in turbulence can be understood in terms of...

Gustavsson, K

2014-01-01T23:59:59.000Z

312

Integrated thermal treatment system study: Phase 1 results. Appendix B, Flow sheets and material balances: Volume 2  

SciTech Connect

This document accompanies a full report which describes the testing and evaluation of ten different methods for incinerating mixed low-level radioactive wastes. It consists of flowsheets and diagrams of a rotary kiln, pyrolysis methods, a plasma furnace, a fixed hearth, and thermal desorption methods.

Feizollahi, F.; Quapp, W.J.; Hempill, H.G.; Groffie, F.J.

1994-07-01T23:59:59.000Z

313

Experimental Analysis of the Effect of Vibrational Non-Equilibrium on the Decay of Grid-Generated Turbulence  

E-Print Network (OSTI)

the fundamental scientific question: ?Does thermal non-equilibrium alter the decay rate of turbulence?? The results of this study show that the answer is ?Yes.? The results demonstrate a clear coupling between thermal non-equilibrium and turbulence transport... ................................................................... 86 2.70 Macor-aluminum test section (exploded view) ....................................... 87 2.71 Upwind flange .......................................................................................... 88 2.72 Macor slab...

Fuller, T. J.

2010-10-12T23:59:59.000Z

314

Turbulence intensity pulse propagation with self-consistent nonlinear noise  

SciTech Connect

A model of turbulence intensity spreading with self-consistent nonlinear noise is derived systematically for the simple dynamical model of resistivity gradient driven turbulence. Local effective drive, thermal conduction damping, nonlinear coupling, and spatial scattering effects are included. As a consequence of nonlinear mode coupling processes (i.e., triad mode interactions), turbulence energy can be spatially scattered, leading to turbulence propagation and spreading. However, the range of any nonlinear mode interactions of the background with a test mode is restricted to within a few mode scale widths from the test mode rational surface. The speed of a turbulent spreading front is calculated. This front speed is effectively constant on macroscopic scales. We show that the effect of self-consistent nonlinear noise on the intensity front speed is modest, as a consequence of the ordering {Delta}{sub c}turbulence correlation length and L{sub f} is the scale length of the front's leading edge. The implications of these results for turbulence spreading models and the important differences between self-consistent mode coupling noise and ad hoc external noise are discussed. The broader implications of these results for turbulence front propagation are identified and explained.

Wang, Z. H. [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Department of Physics and Center for Astrophysics and Space Sciences, University of California at San Diego, La Jolla, California 92093-0424 (United States); Diamond, P. H. [Department of Physics and Center for Astrophysics and Space Sciences, University of California at San Diego, La Jolla, California 92093-0424 (United States); WCI Center for Fusion Theory, National Fusion Research Institute, Gwahangno 113, Yuseong-gu, Daejeon 305-333 (Korea, Republic of); Guercan, Oe. D. [Laboratoire de Physique des Plasmas, Ecole Polytechnique-CNRS, 91128 Palaiseau Cedex (France); Garbet, X. [CEA, IRFM, F-13108 Saint Paul Lez Durance (France); Wang, X. G. [School of Physics, Peking University, Beijing 100871 (China)

2011-03-15T23:59:59.000Z

315

Ambient aerosol sampling inlet for flow rates of 100 and 400 l/min  

E-Print Network (OSTI)

across the cross section of the wind tunnel. Downstream from that is a flow straightener that eliminates large-scale turbulence and flow swirl. A TSI VelociCalc thermal anemometer (TSI Inc., St. Paul, MN) is used to measure the wind speed in the wind... on the slide through use of a coefficient similar 7 to that of Olan-Figuroa et al. (1982), but with a value of 1.29, which is appropriate for the Nyebar K. An Aerodynamic Particle Sizer (APS, Model 3321, TSI Inc., St. Paul, MN) is used to monitor...

Baehl, Michael Matthew

2009-05-15T23:59:59.000Z

316

Low flow fume hood  

DOE Patents (OSTI)

A fume hood is provided having an adequate level of safety while reducing the amount of air exhausted from the hood. A displacement flow fume hood works on the principal of a displacement flow which displaces the volume currently present in the hood using a push-pull system. The displacement flow includes a plurality of air supplies which provide fresh air, preferably having laminar flow, to the fume hood. The displacement flow fume hood also includes an air exhaust which pulls air from the work chamber in a minimally turbulent manner. As the displacement flow produces a substantially consistent and minimally turbulent flow in the hood, inconsistent flow patterns associated with contaminant escape from the hood are minimized. The displacement flow fume hood largely reduces the need to exhaust large amounts of air from the hood. It has been shown that exhaust air flow reductions of up to 70% are possible without a decrease in the hood's containment performance. The fume hood also includes a number of structural adaptations which facilitate consistent and minimally turbulent flow within a fume hood.

Bell, Geoffrey C. (Pleasant Hill, CA); Feustel, Helmut E. (Albany, CA); Dickerhoff, Darryl J. (Berkeley, CA)

2002-01-01T23:59:59.000Z

317

A theory for radial jet reattachment flow  

E-Print Network (OSTI)

, the velocity profile and mass entrainment are given accordrng to Goertler's t. wo- dimensional free jet theory. His analysrs of a free jet also assumes that. the turbulent eddy viscosity is constant ar ross the jet. (6) For the case of laminar flow... of total jet momentum. Laminar jet flow is approximated using Schlichting's velocity profile, whereas turbulent flow calculations are made assuming Goertler's velocity profile. Momentum integral principles are applied to the flow at reattachment...

Hadden, Lynne Loise

2012-06-07T23:59:59.000Z

318

Simulation Strategies for Shock-Turbulence Interactions  

SciTech Connect

The computational challenge of predicting shock-turbulence interactions stems from the fundamentally different physics at play. Shock waves are microscopically thin regions wherein flow properties change rapidly over a distance roughly equal to the molecular mean free path; hence, they are essentially strong discontinuities in the flow field. Turbulence, on the other hand, is a chaotic phenomenon with broadband spatial and temporal scales of motion. Most shock-capturing methods rely on strong numerical dissipation to artificially smooth the discontinuity, such that it can be resolved on the computational grid. Unfortunately, the artificial dissipation necessary for capturing shocks has a deleterious effect on turbulence. An additional problem is the fact that shock-capturing schemes are typically based on one-dimensional Riemann solutions that are not strictly valid in multiple dimensions. This can lead to anisotropy errors and grid-seeded perturbations. Other complications arising from upwinding, flux limiting, operator splitting etc., can seriously degrade performance and generate significant errors, especially in multiple dimensions. The purpose of this work is to design improved algorithms, capable of capturing both shocks and turbulence, which also scale to tens of thousands of processors. We have evaluated two new hydrodynamic algorithms, in relation to the widely used WENO method, on a suite of test cases. The new methods, referred to as the 'Compact' and 'Hybrid' schemes, show very promising results.

Cook, A; Larsson, J; Cabot, W; Lele, S K

2008-02-20T23:59:59.000Z

319

Turbulent transport of energetic ions  

SciTech Connect

Approaching ITER operation, the issue of anomalous transport of fast particles becomes more and more important. This is partly because the ITER heating and current drive system relies heavily on neutral beam injection. Moreover burning plasmas are heated by fast fusion {alpha} particles.Fusion {alpha} particles are characterised by a fixed energy and an isotropic velocity distribution. Therefore they have gyroradii one magnitude larger than the thermal ions. The dependency of the particle diffusion of {alpha} test particles on the Kubo number K = VExB{tau}c/{lambda}c (VExB mean E x B velocity, {tau}c, {lambda}c correlation time and length of the turbulent potential) is presented. For different turbulent regimes, different dependency of the diffusion on the gyroradius is found. For large Kubo numbers, the transport is found to remain constant for gyroradii up to the correlation length of the potential, whereas it is drastically reduced in the small Kubo number regime.In the second part, a model for beam ions injected along the equilibrium magnetic field is described. The beam ions are treated gyrokinetically in a self-consistent way with the equilibrium distribution function taken as a shifted Maxwellian. The implications of such a model for the Vlasov equation, the field equations, and the calculation of moments and fluxes are discussed. Linear and nonlinear results, obtained with the gyrokinetic flux tube code GENE show the existence of a new instability driven by fast beam ions. The instability has a maximum growth rate at perpendicular wave numbers of ky{rho}s {approx} 0.15 and depends mainly on the beam velocity and the density gradient of the beam ions. This instability leads to a replacement of bulk ion particle transport by fast ion particle transport, connected to a strongly enhanced heat flux. In the presence of this instability, the turbulent particle and heat transport is dominated by fast ions.

Dannert, Tilman; Hauff, Thilo; Jenko, Frank; Guenter, Sibylle [Max-Planck-Institut fuer Plasmaphysik, Garching (Germany)

2006-11-30T23:59:59.000Z

320

PERPENDICULAR ION HEATING BY REDUCED MAGNETOHYDRODYNAMIC TURBULENCE  

SciTech Connect

Recent theoretical studies argue that the rate of stochastic ion heating in low-frequency Alfvn-wave turbulence is given by Q = c{sub 1}((?u){sup 3}/?)exp ( c{sub 2}/?), where ?u is the rms turbulent velocity at the scale of the ion gyroradius ?, ? = ?u/v{sub i}, v{sub i} is the perpendicular ion thermal speed, and c{sub 1} and c{sub 2} are dimensionless constants. We test this theoretical result by numerically simulating test particles interacting with strong reduced magnetohydrodynamic (RMHD) turbulence. The heating rates in our simulations are well fit by this formula. The best-fit values of c{sub 1} are ?1. The best-fit values of c{sub 2} decrease (i.e., stochastic heating becomes more effective) as the Reynolds number and the number of grid points in the RMHD simulations increase. As an example, in a 1024{sup 2} 256 RMHD simulation with a dissipation wavenumber of the order of the inverse ion gyroradius, we find c{sub 2} = 0.21. We show that stochastic heating is significantly stronger in strong RMHD turbulence than in a field of randomly phased Alfvn waves with the same power spectrum, because coherent structures in strong RMHD turbulence increase orbit stochasticity in the regions where ions are heated most strongly. We find that c{sub 1} increases by a factor of ?3 while c{sub 2} changes very little as the ion thermal speed increases from values <

Xia, Qian; Perez, Jean C.; Chandran, Benjamin D. G. [Space Science Center and Department of Physics, University of New Hampshire, Durham, NH (United States); Quataert, Eliot, E-mail: qdy2@unh.edu, E-mail: benjamin.chandran@unh.edu, E-mail: jeanc.perez@unh.edu, E-mail: eliot@astro.berkeley.edu [Astronomy Department and Theoretical Astrophysics Center, 601 Campbell Hall, The University of California, Berkeley, CA 94720 (United States)

2013-10-20T23:59:59.000Z

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


321

Kinetic Effects on Turbulence Driven by the Magnetorotational Instability in Black Hole Accretion  

E-Print Network (OSTI)

Magnetorotational Instability (MRI), the instability causing turbulent transport in accretion disks, is studied in the kinetic regime. Radiatively Inefficient Accretion Flows (RIAFs), like the one around the supermassive black hole in the center of our Galaxy, are believed to be collisionless. Kinetic MHD formalism, based on the moments of the Vlasov equation, is used for linear analysis and nonlinear simulations. ZEUS MHD code is modified to include key kinetic MHD terms: anisotropic pressure tensor and anisotropic thermal conduction. Simulations use the local shearing box approximation. Pressure anisotropy is created, because of the adiabatic invariance ($\\mu=p_\\perp/B$), as magnetic field is amplified by the MRI. Larmor radius scale instabilities--mirror, ion-cyclotron, and firehose--are excited at large pressure anisotropy. Pressure isotropization due to pitch angle scattering by these instabilities is included as a subgrid model. A key result of the kinetic MHD simulations is that the anisotropic (viscous) stress can be as large as the Maxwell stress. A new numerical method to simulate anisotropic thermal conduction with large temperature gradients is suggested. Simple tests show that the centered differencing of anisotropic thermal conduction can result in heat flowing from lower to higher temperatures, giving rise to negative temperatures. Limiting of transverse temperature gradients does not accentuate temperature extrema.

Prateek Sharma

2007-03-20T23:59:59.000Z

322

Acceleration and vortex filaments in turbulence  

E-Print Network (OSTI)

We report recent results from a high resolution numerical study of fluid particles transported by a fully developed turbulent flow. Single particle trajectories were followed for a time range spanning more than three decades, from less than a tenth of the Kolmogorov time-scale up to one large-eddy turnover time. We present some results concerning acceleration statistics and the statistics of trapping by vortex filaments.

F. Toschi; L. Biferale; G. Boffetta; A. Celani; B. J. Devenish; A. Lanotte

2005-01-23T23:59:59.000Z

323

Terascale High-Fidelity Simulations of Turbulent Combustion with Detailed Chemistry: Spray Simulations  

SciTech Connect

The Terascale High-Fidelity Simulations of Turbulent Combustion (TSTC) project is a multi-university collaborative effort to develop a high-fidelity turbulent reacting flow simulation capability utilizing terascale, massively parallel computer technology. The main paradigm of the approach is direct numerical simulation (DNS) featuring the highest temporal and spatial accuracy, allowing quantitative observations of the fine-scale physics found in turbulent reacting flows as well as providing a useful tool for development of sub-models needed in device-level simulations. Under this component of the TSTC program the simulation code named S3D, developed and shared with coworkers at Sandia National Laboratories, has been enhanced with new numerical algorithms and physical models to provide predictive capabilities for turbulent liquid fuel spray dynamics. Major accomplishments include improved fundamental understanding of mixing and auto-ignition in multi-phase turbulent reactant mixtures and turbulent fuel injection spray jets.

Rutland, Christopher J.

2009-04-26T23:59:59.000Z

324

Non-thermal Plasma Chemistry Non-thermal Thermal  

E-Print Network (OSTI)

automotive industry optics biomedical technology environmental technology Plasma Technology Quote from: Pla-thermal Plasma Chemical Flow Reactor #12;Werner von Siemens ,, ... construction of an apparatus generation (1857) pollution control volatile organic components, NOx reforming, ... radiation sources excimer

Greifswald, Ernst-Moritz-Arndt-Universität

325

Observations of Edge Turbulence  

NLE Websites -- All DOE Office Websites (Extended Search)

Edge Turbulence Edge Turbulence near the X-point of Alcator C-Mod APS-2007 (1) J.L. Terry, S.J. Zweben*, B. LaBombard, I. Cziegler, O. Grulke + , D.P. Stotler* MIT - Plasma Science and Fusion Center *Princeton Plasma Physics Laboratory + MPI for Plasma Physics, EURATOM Assoc., Greifswald, Germany American Physical Society - Div. of Plasma Physics Orlando, FL Nov. 12 - Nov. 16, 2007 APS-2007 (2) Background and Motivation for "Xpt-region" View Strong edge turbulence has been observed in nearly all magnetic confinement devices. Desire predictive capability Most previous measurements made near outboard midplane where the turbulence has the following main features: - generation is ballooning-like (absent at inboard midplane, etc.) - filaments/blobs moves radially outward with some poloidal motion

326

ARM - Measurement - Atmospheric turbulence  

NLE Websites -- All DOE Office Websites (Extended Search)

turbulence turbulence ARM Data Discovery Browse Data Comments? We would love to hear from you! Send us a note below or call us at 1-888-ARM-DATA. Send Measurement : Atmospheric turbulence High frequency velocity fluctuations that lead to turbulent transport of momentum, heat, mositure, and passive scalars, and often expressed in terms of variances and covariances. Categories Atmospheric State, Surface Properties Instruments The above measurement is considered scientifically relevant for the following instruments. Refer to the datastream (netcdf) file headers of each instrument for a list of all available measurements, including those recorded for diagnostic or quality assurance purposes. ARM Instruments CO2FLX : Carbon Dioxide Flux Measurement Systems ECOR : Eddy Correlation Flux Measurement System

327

Lattice Boltzmann simulations of flow past a cylindrical obstacle  

Science Journals Connector (OSTI)

We present lattice Boltzmann simulations of flow past a cylindrical obstacle. ... the Lvy walk model of turbulence in a lattice Boltzmann model. We discuss pressure around the cylinder...

Lukas Wagner; Fernand Hayot

1995-10-01T23:59:59.000Z

328

The dynamics of variable-density turbulence  

SciTech Connect

The dynamics of variable-density turbulent fluids are studied by direct numerical simulation. The flow is incompressible so that acoustic waves are decoupled from the problem, and implying that density is not a thermodynamic variable. Changes in density occur due to molecular mixing. The velocity field, is in general, divergent. A pseudo-spectral numerical technique is used to solve the equations of motion. Three-dimensional simulations are performed using a grid size of 128{sup 3} grid points. Two types of problems are studied: (1) the decay of isotropic, variable-density turbulence, and (2) buoyancy-generated turbulence in a fluid with large density fluctuations. In the case of isotropic, variable-density turbulence, the overall statistical decay behavior, for the cases studied, is relatively unaffected by the presence of density variations when the initial density and velocity fields are statistically independent. The results for this case are in quantitative agreement with previous numerical and laboratory results. In this case, the initial density field has a bimodal probability density function (pdf) which evolves in time towards a Gaussian distribution. The pdf of the density field is symmetric about its mean value throughout its evolution. If the initial velocity and density fields are statistically dependent, however, the decay process is significantly affected by the density fluctuations. For the case of buoyancy-generated turbulence, variable-density departures from the Boussinesq approximation are studied. The results of the buoyancy-generated turbulence are compared with variable-density model predictions. Both a one-point (engineering) model and a two-point (spectral) model are tested against the numerical data. Some deficiencies in these variable-density models are discussed and modifications are suggested.

Sandoval, D.L.

1995-11-01T23:59:59.000Z

329

Modeling variable density effects in turbulent flames -- Some basic considerations  

SciTech Connect

The paper discusses the basic physical phenomena involved in pressure-density interactions, and presents models of pressure-velocity, pressure-scalar, baroclinic and dilatation effects for variable density low Mach-number turbulence. Their implementation in the {kappa}-{epsilon} framework is then described and their performance evaluated. The models assume that both scalar transport and turbulence generation arising from pressure-density interactions in flames are caused by the motion of large scale turbulent thermals superposed on the normal turbulence mechanism. The velocity of the thermals is related directly to the mean pressure gradient and local density differences in the flames. It is furthermore assumed that the correction for dilatation effects in the {kappa}-{epsilon} system can be determined from the constraint of conservation of the angular momentum of turbulence per unit mass. Simple corrections of the {kappa}-{epsilon} system are proposed for fast chemistry diffusion and premixed flames subject to variable pressure gradients, which offer substantial improvements in the predictions of the flames. some problems remain, particularly in predictions of turbulence in premixed flames, owing to large scale instabilities of the flames observed in the experiments.

Chomiak, J.; Nisbet, J.R. [Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Thermo and Fluid Dynamics] [Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Thermo and Fluid Dynamics

1995-08-01T23:59:59.000Z

330

A spray-suppression model for turbulent combustion  

SciTech Connect

A spray-suppression model that captures the effects of liquid suppressant on a turbulent combusting flow is developed and applied to a turbulent diffusion flame with water spray suppression. The spray submodel is based on a stochastic separated flow approach that accounts for the transport and evaporation of liquid droplets. Flame extinguishment is accounted for by using a perfectly stirred reactor (PSR) submodel of turbulent combustion. PSR pre-calculations of flame extinction times are determined using CHEMKIN and are compared to local turbulent time scales of the flow to determine if local flame extinguishment has occurred. The PSR flame extinguishment and spray submodels are incorporated into Sandia's flow fire simulation code, VULCAN, and cases are run for the water spray suppression studies of McCaffrey for turbulent hydrogen-air jet diffusion flames. Predictions of flame temperature decrease and suppression efficiency are compared to experimental data as a function of water mass loading using three assumed values of drop sizes. The results show that the suppression efficiency is highly dependent on the initial droplet size for a given mass loading. A predicted optimal suppression efficiency was observed for the smallest class of droplets while the larger drops show increasing suppression efficiency with increasing mass loading for the range of mass loadings considered. Qualitative agreement to the experiment of suppression efficiency is encouraging, however quantitative agreement is limited due to the uncertainties in the boundary conditions of the experimental data for the water spray.

DESJARDIN,PAUL E.; TIESZEN,SHELDON R.; GRITZO,LOUIS A.

2000-02-14T23:59:59.000Z

331

Wing tucks are a response to atmospheric turbulence in the soaring flight of the steppe eagle Aquila nipalensis  

Science Journals Connector (OSTI)

...bottom of the thermal column. Thermal turbulence increases with the...rate [16]. In addition, thermals actually magnify the vertical...nipalensis (Hodgson)-a typical thermal-soaring migrant [18-20...weighed less than 0.075 kg with battery. This represents less than...

2014-01-01T23:59:59.000Z

332

Generation of Geodesic Acoustic Modes in ITG turbulence  

SciTech Connect

The generation of geodesic acoustic modes (GAM) is studied by means of numerical simulations of a 3D fluid global model, describing flux-driven electrostatic ITG (Ion Temperature Gradient) turbulence in the core of tokamak plasmas. The model evolves the equilibrium and the perturbed fields as a whole. The coupling of poloidal harmonics induced by the curvature thus results in the presence of both turbulent and neoclassical transport effects in the system. The neoclassical thermal conductivity, which is linked to the time-independent component of the poloidal modulation of the equilibrium fields, is observed to be of the order of the turbulent one, in a system driven by strong injected heat fluxes. The frequency spectrum of the electrostatic potential fluctuations exhibits a peak near the theoretical GAM frequency. In the turbulent stationary state of the simulations a downshift of the GAM frequency is observed.

Falchetto, G. L.; Garbet, X.; Ottaviani, M. [Association EURATOM-CEA, CEA/DSM/DRFC, Centre de Cadarache, 13108 Saint Paul lez Durance (France); Smolyakov, A. [Department of Physics and Engineering Physics, University of Saskatchewan, SK (Canada)

2006-11-30T23:59:59.000Z

333

A turbulent transport network model in MULTIFLUX coupled with TOUGH2  

SciTech Connect

A new numerical method is described for the fully iterated, conjugate solution of two discrete submodels, involving (a) a transport network model for heat, moisture, and airflows in a high-permeability, air-filled cavity; and (b) a variably saturated fractured porous medium. The transport network submodel is an integrated-parameter, computational fluid dynamics solver, describing the thermal-hydrologic transport processes in the flow channel system of the cavity with laminar or turbulent flow and convective heat and mass transport, using MULTIFLUX. The porous medium submodel, using TOUGH2, is a solver for the heat and mass transport in the fractured rock mass. The new model solution extends the application fields of TOUGH2 by integrating it with turbulent flow and transport in a discrete flow network system. We present demonstrational results for a nuclear waste repository application at Yucca Mountain with the most realistic model assumptions and input parameters including the geometrical layout of the nuclear spent fuel and waste with variable heat load for the individual containers. The MULTIFLUX and TOUGH2 model elements are fully iterated, applying a programmed reprocessing of the Numerical Transport Code Functionalization model-element in an automated Outside Balance Iteration loop. The natural, convective airflow field and the heat and mass transport in a representative emplacement drift during postclosure are explicitly solved in the new model. The results demonstrate that the direction and magnitude of the air circulation patterns and all transport modes are strongly affected by the heat and moisture transport processes in the surrounding rock, justifying the need for a coupled, fully iterated model solution such as the one presented in the paper.

Danko, G.; Bahrami, D.; Birkholzer, J.T.

2011-02-15T23:59:59.000Z

334

Thermal-fluid and electrochemical modeling and performance study of a planar solid oxide electrolysis cell : analysis on SOEC resistances, size, and inlet flow conditions.  

SciTech Connect

Argonne National Laboratory and Idaho National Laboratory researchers are analyzing the electrochemical and thermal-fluid behavior of solid oxide electrolysis cells (SOECs) for high temperature steam electrolysis using computational fluid dynamics (CFD) techniques. The major challenges facing commercialization of steam electrolysis technology are related to efficiency, cost, and durability of the SOECs. The goal of this effort is to guide the design and optimization of performance for high temperature electrolysis (HTE) systems. An SOEC module developed by FLUENT Inc. as part of their general CFD code was used for the SOEC analysis by INL. ANL has developed an independent SOEC model that combines the governing electrochemical mechanisms based on first principals to the heat transfer and fluid dynamics in the operation of SOECs. The ANL model was embedded into the commercial STAR-CD CFD software, and is being used for the analysis of SOECs by ANL. The FY06 analysis performed by ANL and reported here covered the influence of electrochemical properties, SOEC component resistances and their contributing factors, SOEC size and inlet flow conditions, and SOEC flow configurations on the efficiency and expected durability of these systems. Some of the important findings from the ANL analysis are: (1) Increasing the inlet mass flux while going to larger cells can be a compromise to overcome increasing thermal and current density gradients while increasing the cell size. This approach could be beneficial for the economics of the SOECs; (2) The presence of excess hydrogen at the SOEC inlet to avoid Ni degradation can result in a sizeable decrease in the process efficiency; (3) A parallel-flow geometry for SOEC operation (if such a thing be achieved without sealing problems) yields smaller temperature gradients and current density gradients across the cell, which is favorable for the durability of the cells; (4) Contact resistances can significantly influence the total cell resistance and cell temperatures over a large range of operating potentials. Thus it is important to identify and avoid SOEC stack conditions leading to such high resistances due to poor contacts.

Yildiz, B.; Smith, J.; Sofu, T.; Nuclear Engineering Division

2008-06-25T23:59:59.000Z

335

A Second Order Thermal and Momentum Immersed Boundary Method for Conjugate Heat Transfer in a Cartesian Finite Volume Solver  

E-Print Network (OSTI)

A conjugate heat transfer (CHT) immersed boundary (IB and CHTIB) method is developed for use with laminar and turbulent flows with low to moderate Reynolds numbers. The method is validated with the canonical flow of two co-annular rotating cylinders at $Re=50$ which shows second order accuracy of the $L_{2}$ and $L_{\\infty}$ error norms of the temperature field over a wide rage of solid to fluid thermal conductivities, $\\kappa_{s}/\\kappa_{f} = \\left(9-100\\right)$. To evaluate the CHTIBM with turbulent flow a fully developed, heated, turbulent channel $\\left(Re_{u_{\\tau}}=150\\text{ and } \\kappa_{s}/\\kappa_{f}=4 \\right)$ is used which shows near perfect correlation to previous direct numerical simulation (DNS) results. The CHTIB method is paired with a momentum IB method (IBM), both of which use a level set field to define the wetted boundaries of the fluid/solid interfaces and are applied to the flow solver implicitly with rescaling of the difference operators of the finite volume (FV) method (FVM).

Crocker, Ryan; Desjardins, Olivier

2014-01-01T23:59:59.000Z

336

The influence of a magnetic field on turbulent heat transfer of a high Prandtl number fluid  

E-Print Network (OSTI)

The influence of a magnetic field on turbulent heat transfer of a high Prandtl number fluid H magnetic field on the local and average heat transfer of an electrically conducting, turbulent fluid flow with high Prandtl number was studied experimentally. The mechanism of heat transfer modification due

Abdou, Mohamed

337

Under consideration for publication in J. Fluid Mech. 1 Realizing turbulent statistics  

E-Print Network (OSTI)

be reproduced at the inflow?". We present a technique able to produce a random field with the exact two on our system. Suppose that we are interested in the wake of a cylinder in a fully turbulent flow, as could be realized experimentally by placing a turbulence generating grid in a wind tunnel, upstream

Hoepffner, Jérôme

338

Waves and Mirror Symmetry in Rotating and Stratified Turbulence Pablo D. Mininni  

E-Print Network (OSTI)

Fisica, Facultad de Cs. Exactas y Naturales, Universidad de Buenos Aires, Argentina, and National Center in the behavior of turbulent flows. The cascade of energy (a transfer of energy to small scales) in three dimensional hydrodynamic turbulence, associated with the conservation of energy in the ideal case, is a well

339

Atmospheric and Wake Turbulence Impacts on Wind Turbine Fatigue Loadings  

SciTech Connect

Large-eddy simulations of atmospheric boundary layers under various stability and surface roughness conditions are performed to investigate the turbulence impact on wind turbines. In particular, the aeroelastic responses of the turbines are studied to characterize the fatigue loading of the turbulence present in the boundary layer and in the wake of the turbines. Two utility-scale 5-MW turbines that are separated by seven rotor diameters are placed in a 3 km by 3 km by 1 km domain. They are subjected to atmospheric turbulent boundary layer flow and data is collected on the structural response of the turbine components. The surface roughness was found to increase the fatigue loads while the atmospheric instability had a small influence. Furthermore, the downstream turbines yielded higher fatigue loads indicating that the turbulent wakes generated from the upstream turbines have significant impact.

Lee, S.; Churchfield, M.; Moriarty, P.; Jonkman, J.; Michalakes, J.

2012-01-01T23:59:59.000Z

340

Holographic thermalization patterns  

E-Print Network (OSTI)

We investigate the behaviour of various correlators in N=4 super Yang Mills theory, taking finite coupling corrections into account. In the thermal limit we investigate the flow of the quasinormal modes as a function of the 't Hooft coupling. Then by using a specific model of holographic thermalization we investigate the deviation of the spectral densities from their thermal limit in an out-of-equilibrium situation. The main focus lies on the thermalization pattern with which the various plasma constituents of different energies approach their final thermal distribution as the coupling constant decreases from the infinite coupling limit. All results point towards the weakening of the usual top down thermalization pattern.

Stefan Stricker

2014-03-11T23:59:59.000Z

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


341

Holographic thermalization patterns  

E-Print Network (OSTI)

We investigate the behaviour of various correlators in N=4 super Yang Mills theory, taking finite coupling corrections into account. In the thermal limit we investigate the flow of the quasinormal modes as a function of the 't Hooft coupling. Then by using a specific model of holographic thermalization we investigate the deviation of the spectral densities from their thermal limit in an out-of-equilibrium situation. The main focus lies on the thermalization pattern with which the various plasma constituents of different energies approach their final thermal distribution as the coupling constant decreases from the infinite coupling limit. All results point towards the weakening of the usual top down thermalization pattern.

Stricker, Stefan

2014-01-01T23:59:59.000Z

342

Turbulent convection in liquid metal with and without rotation  

E-Print Network (OSTI)

is the efficiency of convective heat transfer (Nu). In general, we find that the convective behavior of liquid metal=ðkT?, where q is total heat flux and k is the fluid's thermal conductivity. Heat flux q is total heat power P by turbulent, rotating convection in liquid metal. Liquid metals are peculiar in that they diffuse heat more

343

Toward a wave turbulence formulation of statistical nonlinear optics  

E-Print Network (OSTI)

Toward a wave turbulence formulation of statistical nonlinear optics Josselin Garnier,1, * Mietek optical waves have been reported in the literature. This article is aimed at providing a generalized wave, the process of optical wave thermalization to thermo- dynamic equilibrium, which slows down significantly

Garnier, Josselin

344

NUMERICAL SIMULATIONS OF DRIVEN RELATIVISTIC MAGNETOHYDRODYNAMIC TURBULENCE  

SciTech Connect

A wide variety of astrophysical phenomena involve the flow of turbulent magnetized gas with relativistic velocity or energy density. Examples include gamma-ray bursts, active galactic nuclei, pulsars, magnetars, micro-quasars, merging neutron stars, X-ray binaries, some supernovae, and the early universe. In order to elucidate the basic properties of the relativistic magnetohydrodynamical (RMHD) turbulence present in these systems, we present results from numerical simulations of fully developed driven turbulence in a relativistically warm, weakly magnetized and mildly compressible ideal fluid. We have evolved the RMHD equations for many dynamical times on a uniform grid with 1024{sup 3} zones using a high-order Godunov code. We observe the growth of magnetic energy from a seed field through saturation at {approx}1% of the total fluid energy. We compute the power spectrum of velocity and density-weighted velocity U = {rho}{sup 1/3} v and conclude that the inertial scaling is consistent with a slope of -5/3. We compute the longitudinal and transverse velocity structure functions of order p up to 11 and discuss their possible deviation from the expected scaling for non-relativistic media. We also compute the scale-dependent distortion of coherent velocity structures with respect to the local magnetic field, finding a weaker scale dependence than is expected for incompressible non-relativistic flows with a strong mean field.

Zrake, Jonathan; MacFadyen, Andrew I. [Center for Cosmology and Particle Physics, Physics Department, New York University, New York, NY 10003 (United States)

2012-01-01T23:59:59.000Z

345

turbulence | OpenEI  

Open Energy Info (EERE)

turbulence turbulence Dataset Summary Description This raw data reflects readings from instruments mounted on or near a 82 meter meteorological tower located at the National Wind Technology Center (NWTC), approximately 5 miles south of Boulder, CO (specifically: 39.9107 N, 105.2348 W, datum WGS84). Source NREL Date Released Unknown Date Updated Unknown Keywords DOE irradiance NREL NWTC temperature turbulence wind wind direction wind speed Data text/plain icon Raw data (txt, 82 KiB) application/vnd.openxmlformats-officedocument.spreadsheetml.sheet icon Raw data field descriptions (xlsx, 52.5 KiB) Quality Metrics Level of Review Some Review Comment Data have not been reviewed for accuracy or completeness; disclaimer available (http://www.nrel.gov/disclaimer.html). Temporal and Spatial Coverage

346

Intermittent Turbulence in the Very Stable Ekman Layer  

SciTech Connect

INTERMITTENT TURBULENCE IN THE VERY STABLE EKMAN LAYER This study describes a Direct Numerical Simulation (DNS) of a very stable Ekman layer in which a constant downward heat flux is applied at the lower boundary, thus cooling the fluid above. Numerical experiments were performed in which the strength of the imposed heat flux was varied. For downward heat fluxes above a certain critical value the turbulence becomes intermittent and, as the heat flux increases beyond this value, the flow tends to relaminarize because of the very strong ambient stratification. We adopt Mahrt?s (1999) definition of the very stable boundary layer as a boundary layer in which intermittent, rather than continuous turbulence, is observed. Numerical experiments were used to test various hypothesis of where in ?stability parameter space? the very stable boundary layer is found. These experiments support the findings of Howell and Sun (1999) that the boundary layer will exhibit intermittency and therefore be categorized as ?very stable?, when the stability parameter, z/L, exceeds unity. Another marker for the very stable boundary layer, Derbyshire?s (1990) maximum heat flux criterion, was also examined. Using a case study drawn from the simulations where turbulence intermittency was observed, the mechanism that causes the intermittence was investigated. It was found that patchy turbulence originates from a vigorous inflectional, Ekman-like instability -- a roll cell -- that lifts colder air over warmer air. The resulting convective instability causes an intense burst of turbulence. This turbulence is short-lived because the lifting motion of the roll cell, as well as the roll cell itself, is partially destroyed after the patchy turbulence is generated. Examples of intermittent turbulence obtained from the simulations appear to be consistent with observations of intermittency even though the Reynolds number of the DNS is relatively low (400).

Barnard, James C.

2001-01-05T23:59:59.000Z

347

The translation of turbulent wind energy to individual corn plant motion during senescense  

Science Journals Connector (OSTI)

Wind flow within inflexible plant canopies is turbulent and leads to an oscillatory motion of individual plants. A study was conducted to describe the motion of corn (Zea mays...L.) stalks in the wind using a tra...

T. K. Flesch; R. H. Grant

1991-04-01T23:59:59.000Z

348

Dynamics on the Laminar-Turbulent Boundary and the Origin of the Maximum Drag Reduction Asymptote  

E-Print Network (OSTI)

Dynamical trajectories on the boundary in state space between laminar and turbulent plane channel flowedge statesare computed for Newtonian and viscoelastic fluids. Viscoelasticity has a negligible effect on the properties ...

Graham, Michael D.

349

Subcritical dynamos in shear flows  

E-Print Network (OSTI)

Identifying generic physical mechanisms responsible for the generation of magnetic fields and turbulence in differentially rotating flows is fundamental to understand the dynamics of astrophysical objects such as accretion disks and stars. In this paper, we discuss the concept of subcritical dynamo action and its hydrodynamic analogue exemplified by the process of nonlinear transition to turbulence in non-rotating wall-bounded shear flows. To illustrate this idea, we describe some recent results on nonlinear hydrodynamic transition to turbulence and nonlinear dynamo action in rotating shear flows pertaining to the problem of turbulent angular momentum transport in accretion disks. We argue that this concept is very generic and should be applicable to many astrophysical problems involving a shear flow and non-axisymmetric instabilities of shear-induced axisymmetric toroidal velocity or magnetic fields, such as Kelvin-Helmholtz, magnetorotational, Tayler or global magnetoshear instabilities. In the light of several recent numerical results, we finally suggest that, similarly to a standard linear instability, subcritical MHD dynamo processes in high-Reynolds number shear flows could act as a large-scale driving mechanism of turbulent flows that would in turn generate an independent small-scale dynamo.

F. Rincon; G. I. Ogilvie; M. R. E. Proctor; C. Cossu

2008-05-09T23:59:59.000Z

350

Causality detection and turbulence in fusion plasmas  

E-Print Network (OSTI)

This work explores the potential of an information-theoretical causality detection method for unraveling the relation between fluctuating variables in complex nonlinear systems. The method is tested on some simple though nonlinear models, and guidelines for the choice of analysis parameters are established. Then, measurements from magnetically confined fusion plasmas are analyzed. The selected data bear relevance to the all-important spontaneous confinement transitions often observed in fusion plasmas, fundamental for the design of an economically attractive fusion reactor. It is shown how the present method is capable of clarifying the interaction between fluctuating quantities such as the turbulence amplitude, turbulent flux, and Zonal Flow amplitude, and uncovers several interactions that were missed by traditional methods.

van Milligen, B Ph; Ramisch, M; Estrada, T; Hidalgo, C; Alonso, A

2013-01-01T23:59:59.000Z

351

On the relevance of subcritical hydrodynamic turbulence to accretion disk transport  

E-Print Network (OSTI)

Hydrodynamic unstratified keplerian flows are known to be linearly stable at all Reynolds numbers, but may nevertheless become turbulent through nonlinear mechanisms. However, in the last ten years, conflicting points of view have appeared on this issue. We have revisited the problem through numerical simulations in the shearing sheet limit. It turns out that the effect of the Coriolis force in stabilizing the flow depends on whether the flow is cyclonic (cooperating shear and rotation vorticities) or anticyclonic (competing shear and rotation vorticities); keplerian flows are anticyclonic. We have obtained the following results: i/ The Coriolis force does not quench turbulence in subcritical flows; ii/ The resolution demand, when moving away from the marginal stability boundary, is much more severe for anticyclonic flows than for cyclonic ones. Presently available computer resources do not allow numerical codes to reach the keplerian regime. iii/ The efficiency of turbulent transport is directly correlated to the Reynolds number of transition to turbulence $Rg$, in such a way that the Shakura-Sunyaev parameter $\\alpha\\sim 1/Rg$. iv/ Even the most optimistic extrapolations of our numerical data show that subcritical turbulent transport would be too inefficient in keplerian flows by several orders of magnitude for astrophysical purposes. v/ Our results suggest that the data obtained for keplerian-like flows in a Taylor-Couette settings are largely affected by secondary flows, such as Ekman circulation.

G. Lesur; P-Y. Longaretti

2005-09-19T23:59:59.000Z

352

Asymptotic expansion and statistical description of turbulent systems  

SciTech Connect

A new approach to studying turbulent systems is presented in which an asymptotic expansion of the general dynamical equations is performed prior to the application of statistical methods for describing the evolution of the system. This approach has been applied to two specific systems: anomalous drift wave turbulence in plasmas and homogeneous, isotropic turbulence in fluids. For the plasma case, the time and length scales of the turbulent state result in the asymptotic expansion of the Vlasov/Poisson equations taking the form of nonlinear gyrokinetic theory. Questions regarding this theory and modern Hamiltonian perturbation methods are discussed and resolved. A new alternative Hamiltonian method is described. The Eulerian Direct Interaction Approximation (EDIA) is slightly reformulated and applied to the equations of nonlinear gyrokinetic theory. Using a similarity transformation technique, expressions for the thermal diffusivity are derived from the EDIA equations for various geometries, including a tokamak. In particular, the unique result for generalized geometry may be of use in evaluating fusion reactor designs and theories of anomalous thermal transport in tokamaks. Finally, a new and useful property of the EDIA is pointed out. For the fluid case, an asymptotic expansion is applied to the Navier-Stokes equation and the results lead to the speculation that such an approach may resolve the problem of predicting the Kolmogorov inertial range energy spectrum for homogeneous, isotropic turbulence. 45 refs., 3 figs.

Hagan, W.K. III

1986-01-01T23:59:59.000Z

353

Asymptotic expansion and statistical description of turbulent systems  

SciTech Connect

A new approach to studying turbulent systems is presented in which an asymptotic expansion of the general dynamical equations is performed prior to the application of statistical methods for describing the evolution of the system. This approach was applied to two specific systems: anomalous drift wave turbulence in plasmas and homogeneous, isotropic turbulence in fluids. For the plasma case, the time and length scales of the turbulent states result in the asymptotic expansion of the Vlasov/Poisson equations taking the form of nonlinear gyrokinetic theory. A new alternative Hamiltonian method is described. The Eulerian Direct Interaction Approximation (EDIA) is slightly reformulated and applied to the equation of nonlinear gyrokinetic theory. Using a similarity transformation technique, expressions for the thermal diffusivity are derived from the EDIA equations for various geometries, including a tokamak. In particular, the unique result for generalized geometry may be of use in evaluating fusion reaction designs and theories of anomalous thermal transport in tokamaks. Finally, a new and useful property of the EDIA is pointed out. For the fluid case, an asymptotic expansion is applied to the Navier-Stokes equation and the results, in combination with the efforts of other workers on the problem, lead to the speculation that such an approach may resolve the problem of predicting the Kolmogorov intertial range energy spectrum for homogeneous, isotropic turbulence.

Hagan, W.K. III

1986-01-01T23:59:59.000Z

354

Characterization of Relativistic MHD Turbulence  

E-Print Network (OSTI)

The objective of this work is to understand if and how the characteristics of relativistic MHD turbulence may differ from those of nonrelativistic MHD turbulence. We accomplish this by studying the invariants in the relativistic case and comparing them to what we know of nonrelativistic turbulence. Although much work has been done to understand the dynamics of nonrelativistic systems (mostly for ideal incompressible fluids), there is minimal literature explicitly describing the dynamics of relativistic MHD turbulence. Many authors simply assume that relativistic turbulence has the same invariants and obeys the same inverse energy cascade as non-relativistic systems.

Garrison, David

2015-01-01T23:59:59.000Z

355

Zonal flow as pattern formation  

SciTech Connect

Zonal flows are well known to arise spontaneously out of turbulence. We show that for statistically averaged equations of the stochastically forced generalized Hasegawa-Mima model, steady-state zonal flows, and inhomogeneous turbulence fit into the framework of pattern formation. There are many implications. First, the wavelength of the zonal flows is not unique. Indeed, in an idealized, infinite system, any wavelength within a certain continuous band corresponds to a solution. Second, of these wavelengths, only those within a smaller subband are linearly stable. Unstable wavelengths must evolve to reach a stable wavelength; this process manifests as merging jets.

Parker, Jeffrey B.; Krommes, John A. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)] [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)

2013-10-15T23:59:59.000Z

356

A commotion over turbulence  

Science Journals Connector (OSTI)

... calculations) of dimensionless parameters of the reactor setup9. This has led to the IFS/PPPL model, named after the main institutions involved in its development. The basis for this ... other components besides the turbulence-induced diffusivity. Dorland and Kotschen-reuther have combined the IFS/PPPL diffusivity model with an assumed prescription for the density evolution and the boundary temperatures, ...

Benjamin A. Carreras

1997-01-23T23:59:59.000Z

357

Muffler Theory Considering Flow  

Science Journals Connector (OSTI)

The effect of a steady subsonic flow component upon the acoustical properties of pipes and of laminar and turbulent flow resistances is accounted for in an elementary fashion. The effect of the alternating or acoustic component upon the steady?flow properties is treated likewise. Acoustic transmission loss referred to the end radiation from a pipe is related to back pressure (increase in steady pressure due to the muffler). Equivalent circuits and diagrams of transmission loss vs back pressure are presented for some simple arrangements of pipes volumes irises and flow resistances.

Ewald Eichler

1962-01-01T23:59:59.000Z

358

Transition and self-sustained turbulence in dilute suspensions of finite-size particles  

E-Print Network (OSTI)

We study the transition to turbulence of channel flow of finite-size particle suspensions at low volume fraction, i.e. $\\Phi \\approx 0.001$. The critical Reynolds number above which turbulence is sustained reduces to $Re \\approx 1675$, in the presence of few particles, independently of the initial condition, a value lower than that of the corresponding single-phase flow, i.e. $Re\\approx1775$. In the dilute suspension, the initial arrangement of the particles is important to trigger the transition at a fixed Reynolds number and particle volume fraction. As in single phase flows, streamwise elongated disturbances are initially induced in the flow. If particles can induce oblique disturbances with high enough energy within a certain time, the streaks breakdown, flow experiences the transition to turbulence and the particle trajectories become chaotic. Otherwise, the streaks decay in time and the particles immigrate towards the channel core in a laminar flow.

Lashgari, Iman; Brandt, Luca

2015-01-01T23:59:59.000Z

359

Development of one-equation transition/turbulence models  

SciTech Connect

This paper reports on the development of a unified one-equation model for the prediction of transitional and turbulent flows. An eddy viscosity--transport equation for nonturbulent fluctuation growth based on that proposed by Warren and Hassan is combined with the Spalart-Allmaras one-equation model for turbulent fluctuation growth. Blending of the two equations is accomplished through a multidimensional intermittency function based on the work of Dhawan and Narasimha. The model predicts both the onset and extent of transition. Low-speed test cases include transitional flow over a flat plate, a single element airfoil, and a multi-element airfoil in landing configuration. High-speed test cases include transitional Mach 3.5 flow over a 5{degree} cone and Mach 6 flow over a flared-cone configuration. Results are compared with experimental data, and the grid-dependence of selected predictions is analyzed.

Edwards, J.R.; Roy, C.J.; Blottner, F.G.; Hassan, H.A.

2000-01-14T23:59:59.000Z

360

Numerical simulation of turbulent jet primary breakup in Diesel engines  

E-Print Network (OSTI)

Numerical simulation of turbulent jet primary breakup in Diesel engines Peng Zeng1 Marcus Herrmann and Aerospace Engineering Arizona State University "Micro-Macro Modelling and Simulation of Liquid-Vapour Flows" IRMA Strasbourg, 23.Jan.2008 #12;Introduction DNS of Primary Breakup in Diesel Injection Phase

Helluy, Philippe

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


361

Turbulence Structure and Wall Signature in Hypersonic Boundary Layer  

E-Print Network (OSTI)

Turbulence Structure and Wall Signature in Hypersonic Boundary Layer Yin-Chiu Kan , Beekman Izaak and low- speed features, found in subsonic experiments, are present in our supersonic and hypersonic and hypersonic regimes due to the lack of detailed flow field data, and the studies have been mostly restricted

Martín, Pino

362

Nathan Holmberg Modeling of Turbulent Water over Natural Terrain  

E-Print Network (OSTI)

Nathan Holmberg 2514355 1 Modeling of Turbulent Water over Natural Terrain Project Report Abstract of this project is to try to model flowing water in rivers, over waterfalls etc with the intent that the model can to represent certain effects, such as the motion of deep water waves to the exclusion of all else, to more

Goodman, James R.

363

The Symmetry Properties of the Flow in a Nuclear Reactor Vessel  

Science Journals Connector (OSTI)

The turbulent flow in a Pressurized Water Reactor vessel is modeled in a small scale experiment. Careful observations and flow control experiments, driven by considerations of symmetry, show that this flow of ...

Pierre Albarde

1996-01-01T23:59:59.000Z

364

Thermally driven circulation  

E-Print Network (OSTI)

Several problems connected by the theme of thermal forcing are addressed herein. The main topic is the stratification and flow field resulting from imposing a specified heat flux on a fluid that is otherwise confined to a ...

Nelken, Haim

1987-01-01T23:59:59.000Z

365

3-D turbulent particle dispersion submodel development. Quarterly progress report No. 1, 5 April--5 July 1991  

SciTech Connect

The lack of a mathematical description of the interactions of fluid turbulence with other physics-chemical processes is a major obstacle in modeling many industrial program. Turbulent two-phase flow is a phenomenon that is of significant practical importance to coal combustion as well as other disciplines. The interactions of fluid turbulence with the particulate phase has yet to be accurately and efficiently modeled for these industrial applications. On 15 May 1991 work was initiated to cover four major tasks toward the development of a computational submodel for turbulent particle dispersion that would be applicable to coal combustion simulations. Those four tasks are: 1. A critical evaluation of the 2-D Lagrangian particle dispersion submodel, 2. Development of a 3-D submodel for turbulent particle dispersion, 3. Evaluation of the 3-D submodel for turbulent particle dispersion, 4.Exploration of extensions of the Lagrangian dispersion theory to other applications including chemistry-turbulence interactions.

Smith, P.J.

1991-12-31T23:59:59.000Z

366

Numerical simulations of heat transfer in plane channel flow Najla EL GHARBI 1, 3, a  

E-Print Network (OSTI)

Numerical simulations of heat transfer in plane channel flow Najla EL GHARBI 1, 3, a , Rafik ABSI 2 abenzaoui@gmail.com Keywords: turbulent flows, heat transfer, forced convection, low Reynolds number model data for Re = 150. Introduction Turbulent flow with heat transfer mechanism is of great importance from

Paris-Sud XI, Université de

367

Transition to turbulence in ferrofluids  

E-Print Network (OSTI)

It is known that in classical fluids turbulence typically occurs at high Reynolds numbers. But can turbulence occur at low Reynolds numbers? Here we investigate the transition to turbulence in the classic Taylor-Couette system in which the rotating fluids are manufactured ferrofluids with magnetized nanoparticles embedded in liquid carriers. We find that, in the presence of a magnetic field turbulence can occur at Reynolds numbers that are at least one order of magnitude smaller than those in conventional fluids. This is established by extensive computational ferrohydrodynamics through a detailed bifurcation analysis and characterization of behaviors of physical quantities such as the energy, the wave number, and the angular momentum through the bifurcations. A striking finding is that, as the magnetic field is increased, the onset of turbulence can be determined accurately and reliably. Our results imply that experimental investigation of turbulence can be greatly facilitated by using ferrofluids, opening up...

Altmeyer, Sebastian; Lai, Ying-Cheng

2015-01-01T23:59:59.000Z

368

Study of natural circulation in a VHTR after a LOFA using different turbulence models  

SciTech Connect

Natural convection currents in the core are anticipated in the event of the failure of the gas circulator in a prismatic gas-cooled very high temperature reactor (VHTR). The paths that the helium coolant takes in forming natural circulation loops and the effective heat transport are of interest. The heated flow in the reactor core is turbulent during normal operating conditions and at the beginning of the LOFA with forced convection, but the flow may significantly be slowed down after the event and laminarized with mixed convection. In the present study, the potential occurrence and effective heat transport of natural circulation are demonstrated using computational fluid dynamic (CFD) calculations with different turbulence models as well as laminar flow. Validations and recommendation on turbulence model selection are conducted. The study concludes that large loop natural convection is formed due to the enhanced turbulence levels by the buoyancy effect and the turbulent regime near the interface of upper plenum and flow channels increases the flow resistance for channel flows entering upper plenum and thus less heat can be removed from the core than the prediction by laminar flow assumption.

Yu-Hsin Tung; Yuh-Ming Ferng; Richard W. Johnson; Ching-Chang Chieng

2013-10-01T23:59:59.000Z

369

Dynamics of quasi-two-dimensional turbulent jets  

E-Print Network (OSTI)

In turbulent jets, fluid is driven by momentum from an orifice into an environ- ment filled with similar fluid. The complexity of this flow, which has been studied for more than 80 years (see e.g. List, 1982, for a detailed review), resides in its turbulent... in time with an accuracy of approximately 1 %. We conducted two distinct sets of experiments using two qualitatively different techniques: dye tracking and particle image velocimetry (PIV). 7 2 Meandering and self-similarity of quasi-two-dimensional jets x...

Landel, Julien Rmy Dominique Grard

2012-11-13T23:59:59.000Z

370

Quantum ghost imaging through turbulence  

SciTech Connect

We investigate the effect of turbulence on quantum ghost imaging. We use entangled photons and demonstrate that for a specific experimental configuration the effect of turbulence can be greatly diminished. By decoupling the entangled photon source from the ghost-imaging central image plane, we are able to dramatically increase the ghost-image quality. When imaging a test pattern through turbulence, this method increases the imaged pattern visibility from V=0.15{+-}0.04 to 0.42{+-}0.04.

Dixon, P. Ben; Howland, Gregory A.; Howell, John C. [Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627 (United States); Chan, Kam Wai Clifford [Rochester Optical Manufacturing Company, Rochester, New York 14606 (United States); O'Sullivan-Hale, Colin; Rodenburg, Brandon [Institute of Optics, University of Rochester, Rochester, New York 14627 (United States); Hardy, Nicholas D.; Shapiro, Jeffrey H. [Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Simon, D. S.; Sergienko, A. V. [Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts 02215 (United States); Boyd, R. W. [Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627 (United States); Institute of Optics, University of Rochester, Rochester, New York 14627 (United States)

2011-05-15T23:59:59.000Z

371

The dynamics of variable-density turbulence  

SciTech Connect

The dynamics of variable-density turbulent fluids are studied by direct numerical simulation. The flow is incompressible so that acoustic waves are decoupled from the problem, and implying that density is not a thermodynamic variable. Changes in density occur due to molecular mixing. The velocity field is, in general, divergent. A pseudo-spectral numerical technique is used to solve the equations of motion. Three-dimensional simulations are performed using a grid size of 128{sup 3} grid points. Two types of problems are studied: (1) the decay of isotropic, variable-density turbulence, and (2) buoyancy-generated turbulence in a fluid with large density fluctuations (such that the Boussinesq approximation is not valid). In the case of isotropic, variable-density turbulence, the overall statistical decay behavior, for the cases studied, is relatively unaffected by the presence of density variations when the initial density and velocity fields are statistically independent. The results for this case are in quantitative agreement with previous numerical and laboratory results. In this case, the initial density field has a bimodal probability density function (pdf) which evolves in time towards a Gaussian distribution. The pdf of the density field is symmetric about its mean value throughout its evolution. If the initial velocity and density fields are statistically dependent, however, the decay process is significantly affected by the density fluctuations. For this case, the pdf of the density becomes asymmetric about its mean value during the early stages of its evolution. It is argued that these asymmetries in the pdf of the density field are due to different entrainment rates, into the mixing region, that favor the high speed fluid.

Sandoval, D.L.

1995-11-01T23:59:59.000Z

372

E-Print Network 3.0 - artery flow velocity Sample Search Results  

NLE Websites -- All DOE Office Websites (Extended Search)

Artery by Proper Orthogonal Decomposition Summary: employ computational fluid dynamics (CFD) to investigate blood flow in a carotid artery, which has... to turbulence is expected...

373

Non-Newtonian Fluids, Mudflows, and Debris Flows: A Rheological Approach  

Science Journals Connector (OSTI)

Just as examples: Pengcheng (1992) describes the turbulent debris flows of the the Jiangja ravine in China in terms of a Chezy-like formula $...

Fabio Vittorio De Blasio

2011-01-01T23:59:59.000Z

374

THE STATE OF THE ART OF NUMERICAL MODELING OF THERMOHYDROLOGIC FLOW IN FRACTURED ROCK MASSES  

E-Print Network (OSTI)

At normal rates of geothermal wells, turbulent flow is fullyeffects in two- phase geothermal well tests were studied (of salt precipitation around geothermal wells and of methane

Wang, J.S.Y.

2013-01-01T23:59:59.000Z

375

Turbulence radiation interaction modeling in hydrocarbon pool fire simulations  

SciTech Connect

The importance of turbulent fluctuations in temperature and species concentration in thermal radiation transport modeling for combustion applications is well accepted by the radiation transport and combustion communities. A number of experimental and theoretical studies over the last twenty years have shown that fluctuations in the temperature and species concentrations may increase the effective emittance of a turbulent flame by as much as 50% to 300% over the value that would be expected from the mean temperatures and concentrations. With the possibility of such a large effect on the principal mode of heat transfer from a fire, it is extremely important for fire modeling efforts that turbulence radiation interaction be well characterized and possible modeling approaches understood. Toward this end, this report seeks to accomplish three goals. First, the principal turbulence radiation interaction closure terms are defined. Second, an order of magnitude analysis is performed to understand the relative importance of the various closure terms. Finally, the state of the art in turbulence radiation interaction closure modeling is reviewed. Hydrocarbon pool fire applications are of particular interest in this report and this is the perspective from which this review proceeds. Experimental and theoretical analysis suggests that, for this type of heavily sooting flame, the turbulent radiation interaction effect is dominated by the nonlinear dependence of the Planck function on the temperature. Additional effects due to the correlation between turbulent fluctuations in the absorptivity and temperature may be small relative to the Planck function effect for heavily sooting flames. This observation is drawn from a number of experimental and theoretical discussions. Nevertheless, additional analysis and data is needed to validate this observation for heavily sooting buoyancy dominated plumes.

BURNS,SHAWN P.

1999-12-01T23:59:59.000Z

376

Bypass Flow Study  

SciTech Connect

The purpose of the fluid dynamics experiments in the MIR (Matched Index of-Refraction) flow system at Idaho National Laboratory (INL) is to develop benchmark databases for the assessment of Computational Fluid Dynamics (CFD) solutions of the momentum equations, scalar mixing, and turbulence models for the flow ratios between coolant channels and bypass gaps in the interstitial regions of typical prismatic standard fuel element (SFE) or upper reflector block geometries of typical Modular High-temperature Gas-cooled Reactors (MHTGR) in the limiting case of negligible buoyancy and constant fluid properties. The experiments use Particle Image Velocimetry (PIV) to measure the velocity fields that will populate the bypass flow study database.

Richard Schultz

2011-09-01T23:59:59.000Z

377

Supercomputers Capture Turbulence in the Solar Wind  

NLE Websites -- All DOE Office Websites (Extended Search)

Capture Turbulence in the Solar Wind Supercomputers Capture Turbulence in the Solar Wind Berkeley Lab visualizations could help scientists forecast destructive space weather...

378

Turbulent flame speed for syngas at gas turbine relevant conditions  

Science Journals Connector (OSTI)

Modifications of conventional natural-gas-fired burners for operation with syngas fuels using lean premixed combustion is challenging due to the different physicochemical properties of the two fuels. A key differentiating parameter is the turbulent flame velocity, ST, commonly expressed as its ratio to the laminar flame speed, SL. This paper reports an experimental investigation of premixed syngas combustion at gas turbine like conditions, with emphasis on the determination of ST/SL derived as global fuel consumption per unit time. Experiments at pressures up to 2.0MPa, inlet temperatures and velocities up to 773K and 150m/s, respectively, and turbulence intensity to laminar flame speed ratios, u?/SL, exceeding 100 are presented for the first time. Comparisons between different syngas mixtures and methane clearly show much higher ST/SL for the former fuel. It is shown that ST/SL is strongly dependent on preferential diffusive-thermal (PDT) effects, co-acting with hydrodynamic effects, even for very high u?/SL. ST/SL increases with rising hydrogen content in the fuel mixture and with increasing pressure. A correlation for ST/SL valid for all investigated fuel mixtures, including methane, is proposed in terms of turbulence properties (turbulence intensity and integral length scale), combustion properties (laminar flame speed and laminar flame thickness) and operating conditions (pressure and inlet temperature). The correlation captures effects of preferential diffusive-thermal and hydrodynamic instabilities.

S. Daniele; P. Jansohn; J. Mantzaras; K. Boulouchos

2011-01-01T23:59:59.000Z

379

Wind noise and the spectrum of atmospheric turbulence pressure fluctuations  

Science Journals Connector (OSTI)

Previous research [S. Morgan and R. Raspet J. Acoust. Soc. Am. 92 11801183 (1992)] has shown that wind noise is predominantly caused by pressure fluctuations intrinsic to the turbulent atmospheric flow. Therefore it should be possible to predict wind noise from models for turbulent pressure spectra in the atmosphere. Based on simple dimensional analysis and an application of Taylors hypothesis the inertial?subrange power spectrum for turbulent pressure fluctuations should be proportional to f ?7/3 where f is frequency. But more recent atmospheric observations and theoretical arguments [J. D. Albertson G. G. Katul M. B. Parlange and W. E. Eichinger Phys. Fluids 10 17251732 (1998)] suggest that the power spectrum actually goes as f ?3/2. In this paper it is shown that the f ?3/2 dependence predicts a much slower decay in wind noise with increasing acoustic frequency than is typically observed. Possible reasons for this discrepancy are discussed.

2003-01-01T23:59:59.000Z

380

Reconnection outflow generated turbulence in the solar wind  

E-Print Network (OSTI)

Petschek-type time-dependent reconnection (TDR) and quasi-stationary reconnection (QSR) models are considered to understand reconnection outflow structures and the features of the associated locally generated turbulence in the solar wind. We show that the outflow structures, such as discontinuites, Kelvin-Helmholtz (KH) unstable flux tubes or continuous space filling flows cannot be distinguished from one-point WIND measurements. In both models the reconnection outflows can generate more or less spatially extended turbulent boundary layers (TBDs). The structure of an unique extended reconnection outflow is investigated in detail. The analysis of spectral scalings and break locations show that reconnection outflows can control the local field and plasma conditions which may play in favor of one or another turbulent dissipation mechanisms with their characteristic scales and wavenumbers.

Vrs, Z; Semenov, V S; Zaqarashvili, T V; Bruno, R; Khodachenko, M

2014-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


381

Flow visualization around cylinders in a channel flow using Particle Image Velocimetry  

E-Print Network (OSTI)

The objective of the undertaken study was to apply state-of the-art Particle Image Velocimetry to measure full field turbulent flow around cylinders, starting with one cylinder and eventually to a quad cylinder arrangement. Particle Image...

Martinez, Ramiro Serna

2012-06-07T23:59:59.000Z

382

Thermal Recovery Methods  

SciTech Connect

Thermal Recovery Methods describes the basic concepts of thermal recovery and explains the injection patterns used to exploit reservoir conditions. Basic reservoir engineering is reviewed with an emphasis on changes in flow characteristics caused by temperature. The authors discuss an energy balance for steam and combustion drive, and they explain in situ reactions. Heat loss, combustion drive, and steam displacement also are examined in detail, as well as cyclic steam injection, downhole ignition, well heating, and low-temperature oxidation. Contents: Thermal processes; Formation and reservoir evaluations; Well patterns and spacing; Flow and process equations; Laboratory simulation of thermal recovery; Heat loss and transmission; Displacement and production; Equipment; Basic data for field selection; Laboratory evaluation of combustion characteristics; Thermal properties of reservoirs and fluids.

White, P.D.; Moss, J.T.

1983-01-01T23:59:59.000Z

383

Towards Understanding the Poor Thermal Stability of V5+ Electrolyte...  

NLE Websites -- All DOE Office Websites (Extended Search)

the Poor Thermal Stability of V5+ Electrolyte Solution in Vanadium Redox Flow Batteries. Towards Understanding the Poor Thermal Stability of V5+ Electrolyte Solution in...

384

Turbulent Magnetic Reconnection Near a  

E-Print Network (OSTI)

Turbulent Magnetic Reconnection Near a 3D Magnetic Null C. S. Ng Space Science Center Institute for the Study of Earth, Oceans, and Space University of New Hampshire, Durham, NH 03824 #12;Turbulent Magnetic Reconnection Near a 3D Magnetic Null C. S. Ng, chung-sang.ng@unh.edu, Space Science Center, Institute

Ng, Chung-Sang

385

Rossby waves and two-dimensional turbulence in the presence of a large-scale zonal jet  

E-Print Network (OSTI)

This dissertation represents a theoretical, numerical, and observational study of barotropic waves and turbulence in an inhomogeneous background flow environment. The theoretical aspects of the work are simplified by ...

Shepherd, Theodore Gordon

1984-01-01T23:59:59.000Z

386

The Local Structure of Atmospheric Turbulence and Its Effect on the Smagorinsky Model for Large Eddy Simulation  

Science Journals Connector (OSTI)

Phenomena such as large-scale shear, buoyancy, and the proximity to the ground surface significantly affect interactions among scales in atmospheric boundary layer turbulent flows. Hence, these phenomena impact parameters that enter subgrid-scale ...

Marcelo Chamecki; Charles Meneveau; Marc B. Parlange

2007-06-01T23:59:59.000Z

387

Investigation of the effect of a circular patch of vegetation on turbulence generation and sediment deposition using four case studies  

E-Print Network (OSTI)

This study describes the spatial distribution of sediment deposition in the wake of a circular patch of model vegetation and the effect of the patch on turbulence and mean flow. Two difference types pf vegetation were used ...

Ortiz, Alejandra C

2012-01-01T23:59:59.000Z

388

Theory of shear suppression of edge turbulence by externally driven radio-frequency waves  

Science Journals Connector (OSTI)

Here, we propose and analyze a technique for active suppression of tokamak edge turbulence. Suppression occurs due to the effects of a sheared radial electric field generated by externally driven radio-frequency waves. Plasma flow is induced by radially varying wave-driven Reynolds and magnetic stresses, and opposed by neoclassical damping. For Alfvnic flow drive, the predicted shear flow profile is determined by ion inertia and electron dissipation effects. Results indicate that a modest amount of absorbed power is required for edge-turbulence suppression. More generally, several novel results in the theory of momentum transport by electromagnetic fluctuations are presented.

G. G. Craddock and P. H. Diamond

1991-09-16T23:59:59.000Z

389

High-density turbidity currents: Are they sandy debris flows?  

SciTech Connect

Conventionally, turbidity currents are considered as fluidal flows in which sediment is supported by fluid turbulence, whereas debris flows are plastic flows in which sediment is supported by matrix strength, dispersive pressure, and buoyant lift. The concept of high-density turbidity current refers to high-concentration, commonly non-turbulent, flows of fluids in which sediment is supported mainly by matrix strength, dispersive pressure, and buoyant lift. The conventional wisdom that traction carpets with entrained turbulent clouds on top represent high-density turbidity currents is a misnomer because traction carpets are neither fluidal nor turbulent. Debris flows may also have entrained turbulent clouds on top. The traction carpet/debris flow and the overriding turbulent clouds are two separate entities in terms of flow rheology and sediment-support mechanism. In experimental and theoretical studies, which has linked massive sands and floating clasts to high-density turbidity currents, the term high-density turbidity current has actually been used for laminar flows. In alleviating this conceptual problem, sandy debris flow is suggested as a substitute for high-density turbidity current. Sandy debris flows represent a continuous spectrum of processes between cohesive and cohesionless debris flows. Commonly they are rheologically plastic. They may occur with or without entrained turbulent clouds on top. Their sediment-support mechanisms include matrix strength, dispersive pressure, and buoyant lift. They are characterized by laminar flow conditions, a moderate to high grain concentration, and a low to moderate mud content. Although flows evolve and transform during the course of transport in density-stratified flows, the preserved features in a deposit are useful to decipher only the final stages of deposition. At present, there are no established criteria to decipher transport mechanism from the depositional record.

Shanmugam, G. [Mobil Exploration and Producing Technical Center, Dallas, TX (United States)

1996-01-01T23:59:59.000Z

390

Mathematical modelling of Inconel 718 particles in HVOF thermal spraying  

Science Journals Connector (OSTI)

High velocity oxygen fuel (HVOF) thermal spray technology is able to produce very dense coating without over-heating powder particles. The quality of coating is directly related to the particle parameters such as velocity, temperature and state of melting or solidification. In order to obtain this particle data, mathematical models are developed to predict particle dynamic behaviour in a liquid fuelled high velocity oxy-fuel thermal spray gun. The particle transport equations are solved in a Lagrangian manner and coupled with the three-dimensional, chemically reacting, turbulent gas flow. The melting and solidification within particles as a result of heat exchange with the surrounding gas flow is solved numerically. The in-flight particle characteristics of Inconel 718 are studied and the effects of injection parameters on particle behavior are examined. The computational results show that the particles smaller than 10?m undergo melting and solidification prior to impact while the particle larger than 20?m never reach liquid state during the process.

S. Kamnis; S. Gu; N. Zeoli

2008-01-01T23:59:59.000Z

391

Terascale High-Fidelity Simulations of Turbulent Combustion with Detailed Chemistry  

SciTech Connect

The TSTC project is a multi-university collaborative effort to develop a high-fidelity turbulent reacting flow simulation capability utilizing terascale, massively parallel computer technology. The main paradigm of our approach is direct numerical simulation (DNS) featuring highest temporal and spatial accuracy, allowing quantitative observations of the fine-scale physics found in turbulent reacting flows as well as providing a useful tool for development of sub-models needed in device-level simulations. The code named S3D, developed and shared with Chen and coworkers at Sandia National Laboratories, has been enhanced with new numerical algorithms and physical models to provide predictive capabilities for spray dynamics, combustion, and pollutant formation processes in turbulent combustion. Major accomplishments include improved characteristic boundary conditions, fundamental studies of auto-ignition in turbulent stratified reactant mixtures, flame-wall interaction, and turbulent flame extinction by water spray. The overarching scientific issue in our recent investigations is to characterize criticality phenomena (ignition/extinction) in turbulent combustion, thereby developing unified criteria to identify ignition and extinction conditions. The computational development under TSTC has enabled the recent large-scale 3D turbulent combustion simulations conducted at Sandia National Laboratories.

Hong G. Im; Arnaud Trouve; Christopher J. Rutland; Jacqueline H. Chen

2009-02-02T23:59:59.000Z

392

Convective heat transfer enhancement of laminar flow of latent functionally thermal fluid in a circular tube with constant heat flux: internal heat source model and its application  

Science Journals Connector (OSTI)

This paper analyzes the convective heat transfer enhancement mechanism of latent heat functionally thermal fluid. By using the proposed internal heat source model, the influence of each factor affecting the heat

Yinping Zhang; Xianxu Hu; Qing Hao; Xin Wang

2003-04-01T23:59:59.000Z

393

Power-Law Wrinkling Turbulence-Flame Interaction Model for Astrophysical Flames  

E-Print Network (OSTI)

We extend a model for turbulence-flame interactions (TFI) to consider astrophysical flames with a particular focus on combustion in type Ia supernovae. The inertial range of the turbulent cascade is nearly always under-resolved in simulations of astrophysical flows, requiring the use of a model in order to quantify the effects of subgrid-scale wrinkling of the flame surface. We provide implementation details to extend a well-tested TFI model to low-Prandtl number flames for use in the compressible hydrodynamics code FLASH. A local, instantaneous measure of the turbulent velocity is calibrated for FLASH and verification tests are performed. Particular care is taken to consider the relation between the subgrid rms turbulent velocity and the turbulent flame speed, especially for high-intensity turbulence where the turbulent flame speed is not expected to scale with the turbulent velocity. Finally, we explore the impact of different TFI models in full-star, three-dimensional simulations of type Ia supernovae.

Jackson, Aaron P; Calder, Alan C

2014-01-01T23:59:59.000Z

394

Coupled multi-body dynamics and CFD for wind turbine simulation including explicit wind turbulence  

Science Journals Connector (OSTI)

Abstract A high fidelity approach for wind turbine aero-elastic simulations including explicit representation of the atmospheric wind turbulence is presented. The approach uses a dynamic overset computational fluid dynamics (CFD) code for the aerodynamics coupled with a multi-body dynamics (MBD) code for the motion responses to the aerodynamic loads. Mann's wind turbulence model was implemented into the CFD code as boundary and initial conditions. The wind turbulence model was validated by comparing the theoretical one-point spectrum for the three components of the velocity fluctuations, and by comparing the expected statistics from the CFD simulated wind turbulent field with the explicit wind turbulence inlet boundary from Mann model. Extensive simulations based on the proposed coupled approach were conducted with the conceptual NREL 5-MW offshore wind turbine in an increasing level of complexity, analyzing the turbine behavior as elasticity, wind shear and atmospheric wind turbulence are added to the simulations. Results are compared with the publicly available simulations results from OC3 participants, showing good agreement for the aerodynamic loads and blade tip deflections in time and frequency domains. Wind turbulence/turbine interaction was examined for the wake flow. It was found that explicit turbulence addition results in considerably increased wake diffusion. The coupled CFD/MBD approach can be extended to include multibody models of the shaft, bearings, gearbox and generator, resulting in a promising tool for wind turbine design under complex operational environments.

Y. Li; A.M. Castro; T. Sinokrot; W. Prescott; P.M. Carrica

2015-01-01T23:59:59.000Z

395

Memory effects in turbulent transport  

E-Print Network (OSTI)

In the mean-field theory of magnetic fields, turbulent transport, i.e. the turbulent electromotive force, is described by a combination of the alpha effect and turbulent magnetic diffusion, which are usually assumed to be proportional respectively to the mean field and its spatial derivatives. For a passive scalar there is just turbulent diffusion, where the mean flux of concentration depends on the gradient of the mean concentration. However, these proportionalities are approximations that are valid only if the mean field or the mean concentration vary slowly in time. Examples are presented where turbulent transport possesses memory, i.e. where it depends crucially on the past history of the mean field. Such effects are captured by replacing turbulent transport coefficients with time integral kernels, resulting in transport coefficients that depend effectively on the frequency or the growth rate of the mean field itself. In this paper we perform numerical experiments to find the characteristic timescale (or memory length) of this effect as well as simple analytical models of the integral kernels in the case of passive scalar concentrations and kinematic dynamos. The integral kernels can then be used to find self-consistent growth or decay rates of the mean fields. In mean-field dynamos the growth rates and cycle periods based on steady state values of alpha effect and turbulent diffusivity can be quite different from the actual values.

Alexander Hubbard; Axel Brandenburg

2008-11-17T23:59:59.000Z

396

RETRAN-02: A program for transient thermal-hydraulic analysis of complex fluid flow systems: Volume 5, Modeling guidelines: Computer code manual  

SciTech Connect

RETRAN is a computer code designed to perform overall system response analyses of reactor power plants. The RETRAN code uses plant geometry, initial thermal-hydraulic states, component data, control function descriptions, and physics data as input to calculate the overall plant system thermal-hydraulic response during a transient. Where additional detail is required, the overall system response calculated by RETRAN can be used as a boundary condition for the detailed analysis.

Harrison, J.F.; Farman, R.F.; Peterson, C.E.; Jensen, P.J.

1987-11-01T23:59:59.000Z

397

THE IPOS FRAMEWORK: LINKING FISH SWIMMING PERFORMANCE IN ALTERED FLOWS FROM LABORATORY EXPERIMENTS TO RIVERS  

SciTech Connect

Current understanding of the effects of turbulence on the swimming performance of fish 32 is primarily derived from laboratory experiments under pressurized flow swim tunnels 33 and open channel flow facilities. These studies have produced valuable information on 34 the swimming mechanics and behavior of fish in turbulent flow. However, laboratory 35 studies have limited representation of the flows fish experience in nature. The complex 36 flow structure in rivers is imparted primarily by the highly heterogeneous and non37 uniform bed and planform geometry. Our goal is to direct future laboratory and field 38 studies to adopt a common framework that will shape the integration of both approaches. 39 This paper outlines four characteristics of turbulent flow, which we suggest should be 40 evaluated when generalizing results from fish turbulent studies in both the laboratory and 41 the field. The framework is based on four turbulence characteristics that are summarized 42 under the acronym IPOS: Intensity, Periodicity, Orientation, and Scale.

Neary, Vincent S [ORNL

2011-01-01T23:59:59.000Z

398

Thermal Storage and Advanced Heat Transfer Fluids (Fact Sheet)  

SciTech Connect

Fact sheet describing NREL CSP Program capabilities in the area of thermal storage and advanced heat transfer fluids: measuring thermophysical properties, measuring fluid flow and heat transfer, and simulating flow of thermal energy and fluid.

Not Available

2010-08-01T23:59:59.000Z

399

Transient simulation for large scale flow in bubble columns  

Science Journals Connector (OSTI)

Abstract The transient simulation of large scale bubbly flow in bubble columns using the unsteady Reynolds averaged Navier Stokes (URANS) equations is investigated in the present paper. An extensive set of bubble forces is used with different models for the bubble induced turbulence. Criteria are given to assess the independence of the simulation time and the time step length. Using these criteria it is shown that a simulation time, time step length and mesh independent solution can be obtained for complex bubbly flows using URANS equations under certain requirements. With the obtained setup the contribution of the resolved turbulence to the total turbulence and the influence of the bubble induced turbulence modeling on the resolved turbulence is investigated. Further, it is pointed out that the virtual mass force is not negligible. The simulations are compared to data from the literature at two different superficial velocities, which cover monodisperse and polydisperse bubbly flows.

T. Ziegenhein; R. Rzehak; D. Lucas

2015-01-01T23:59:59.000Z

400

Turbulence-Flame Interactions in Type Ia Supernovae  

E-Print Network (OSTI)

The large range of time and length scales involved in type Ia supernovae (SN Ia) requires the use of flame models. As a prelude to exploring various options for flame models, we consider, in this paper, high-resolution three-dimensional simulations of the small-scale dynamics of nuclear flames in the supernova environment in which the details of the flame structure are fully resolved. The range of densities examined, 1 to $8 \\times 10^7$ g cm$^{-3}$, spans the transition from the laminar flamelet regime to the distributed burning regime where small scale turbulence disrupts the flame. The use of a low Mach number algorithm facilitates the accurate resolution of the thermal structure of the flame and the inviscid turbulent kinetic energy cascade, while implicitly incorporating kinetic energy dissipation at the grid-scale cutoff. For an assumed background of isotropic Kolmogorov turbulence with an energy characteristic of SN Ia, we find a transition density between 1 and $3 \\times 10^7$ g cm$^{-3}$ where the nature of the burning changes qualitatively. By $1 \\times 10^7$ g cm$^{-3}$, energy diffusion by conduction and radiation is exceeded, on the flame scale, by turbulent advection. As a result, the effective Lewis Number approaches unity. That is, the flame resembles a laminar flame, but is turbulently broadened with an effective diffusion coefficient, $D_T \\sim u' l$, where $u'$ is the turbulent intensity and $l$ is the integral scale. For the larger integral scales characteristic of a real supernova, the flame structure is predicted to become complex and unsteady. Implications for a possible transition to detonation are discussed.

A. J. Aspden; J. B. Bell; M. S. Day; S. E. Woosley; M. Zingale

2008-11-17T23:59:59.000Z

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


401

Observations of turbulent fluxes and turbulence dynamics in the ocean surface boundary layer  

E-Print Network (OSTI)

This study presents observations of turbulence dynamics made during the low winds portion of the Coupled Boundary Layers and Air-Sea Transfer experiment (CBLAST-Low). Observations were made of turbulent fluxes, turbulent ...

Gerbi, Gregory Peter

2008-01-01T23:59:59.000Z

402

Experimental evidence of accelerated energy transfer in turbulence  

Science Journals Connector (OSTI)

We investigate the vorticity dynamics in a turbulent vortex using scattering of acoustic waves. Two ultrasonic beams are adjusted to probe simultaneously two spatial scales in a given volume of the flow, thus allowing a dual channel recording of the dynamics of coherent vorticity structures. Our results show that this allows one to measure the average energy transfer time between different spatial length scales, and that such transfer goes faster at smaller scales.

R. Labb; C. Baudet; G. Bustamante

2007-01-19T23:59:59.000Z

403

Fluid Flow, Thermal History, and Diagenesis of the Cambrian-Ordovician Arbuckle Group and Overlying Units in South-Central Kansas  

E-Print Network (OSTI)

A diagenetic study of the Cambrian-Ordovician Arbuckle Group to the Middle Pennsylvanian Cherokee Group in south-central Kansas produced evidence of regional advective fluid flow and more localized fracture-controlled fluid ...

King, Bradley Donald

2013-12-31T23:59:59.000Z

404

Study of active control of instability in a boundary layer over a flat plate flow  

E-Print Network (OSTI)

A feasibility study of utilizing synthetic jet actuators as a mean to mitigate disturbances that can cause instability and turbulent flow is described. Prediction of flow transition via linear stability theory was performed by solving the Orr...

Oryu, Hiroshi

2012-06-07T23:59:59.000Z

405

The conservative cascade of kinetic energy in compressible turbulence  

E-Print Network (OSTI)

The physical nature of compressible turbulence is of fundamental importance in a variety of astrophysical settings. We present the first direct evidence that mean kinetic energy cascades conservatively beyond a transitional "conversion" scale-range despite not being an invariant of the compressible flow dynamics. We use high-resolution three-dimensional simulations of compressible hydrodynamic turbulence on $512^3$ and $1024^3$ grids. We probe regimes of forced steady-state isothermal flows and of unforced decaying ideal gas flows. The key quantity we measure is pressure dilatation cospectrum, $E^{PD}(k)$, where we provide the first numerical evidence that it decays at a rate faster than $k^{-1}$ as a function of wavenumber. This is sufficient to imply that mean pressure dilatation acts primarily at large-scales and that kinetic and internal energy budgets statistically decouple beyond a transitional scale-range. Our results suggest that an extension of Kolmogorov's inertial-range theory to compressible turbulence is possible.

Hussein Aluie; Shengtai Li; Hui Li

2011-07-28T23:59:59.000Z

406

The Dimits Shift in More Realistic Gyrokinetic Plasma Turbulence Simulations  

SciTech Connect

In simulations of turbulent plasma transport due to long wavelength, (k?pi ? 1), electrostatic drift-type instabilities we find that a nonlinear upshift of the effective threshold persists. This `Dimits shift' represents the difference between the linear threshold, at the onset of instability, and the nonlinear threshold, where transport increases suddenly as the driving temperature gradient is increased. As the drive increases, the magnitudes of turbulent eddies and zonal ows grow until the zonal flows become nonlinearly unstable to 'tertiary' modes and their sheared ows no longer grow fast enough to strongly limit eddy size. The tertiary mode threshold sets the effective nonlinear threshold for the heat transport, and the Dimits shift arises when this occurs at a zonal flow magnitude greater than that needed to limit transport near the linear threshold. Nextgeneration tokamaks will likely benefit from the higher effective threshold for turbulent transport, and transport models should incorporate suitable corrections to linear thresholds. These gyrokinetic simulations are more realistic than previous reports of a Dimits shift because they include nonadiabatic electron dynamics, strong collisional damping of zonal flows, and finite electron and ion collisionality together with realistic shaped magnetic geometry. Reversing previously reported results based on idealized adiabatic electrons, we find that increasing collisionality reduces the heat flux because collisionality reduces the nonadiabatic electron drive.

D.R. Mikkelsen and W. Dorland

2008-07-23T23:59:59.000Z

407

Flame front geometry in premixed turbulent flames  

SciTech Connect

Experimental and numerical determinations of flame front curvature and orientation in premixed turbulent flames are presented. The experimental data is obtained from planar, cross sectional images of stagnation point flames at high Damkoehler number. A direct numerical simulation of a constant energy flow is combined with a zero-thickness, constant density flame model to provide the numerical results. The computational domain is a 32{sup 3} cube with periodic boundary conditions. The two-dimensional curvature distributions of the experiments and numerical simulations compare well at similar q{prime}/S{sub L} values with means close to zero and marked negative skewness. At higher turbulence levels the simulations show that the distributions become symmetric about zero. These features are also found in the three dimensional distributions of curvature. The simulations support assumptions which make it possible to determine the mean direction cosines from the experimental data. This leads to a reduction of 12% in the estimated flame surface area density in the middle of the flame brush. 18 refs.

Shepherd, I.G. (Lawrence Berkeley Lab., CA (United States)); Ashurst, W.T. (Sandia National Labs., Livermore, CA (United States))

1991-12-01T23:59:59.000Z

408

Invariant Gibbs measures of the energy for shell models of turbulence; the inviscid and viscous cases  

E-Print Network (OSTI)

Gaussian measures of Gibbsian type are associated with some shell models of 3D turbulence; they are constructed by means of the energy, a conserved quantity for the 3D inviscid and unforced shell model. We prove the existence of a unique global flow for a stochastic viscous shell model and a global flow for the deterministic inviscid shell model, with the property that these Gibbs measures are invariant for these flows.

Hakima Bessaih; Benedetta Ferrario

2011-03-10T23:59:59.000Z

409

Interfaces and inhomogeneous turbulence  

Science Journals Connector (OSTI)

...argued that these local distortion mechanisms...meteorological model WRF [58]. This is...anabatic and katabatic winds. The thermal forcing...wind, the cross-wind horizontal breeze...This leads to a local vortex form with...the length of the wind tunnel where the...10], using the local RMS velocity and...

2011-01-01T23:59:59.000Z

410

Turbulence radiation interaction in Reynolds-averaged Navier-Stokes simulations of nonpremixed piloted turbulent laboratory-scale flames  

SciTech Connect

Numerical simulation results are presented for two axisymmetric, nonluminous turbulent piloted jet diffusion flames: Sandia Flame D (SFD) and Delft Flame III (DFIII). Turbulence is represented by a Reynolds stress transport model, while chemistry is modeled by means of steady laminar flamelets. We use the preassumed PDF approach for turbulence-chemistry interaction. A weighted sum of gray gases model is used for the gas radiative properties. The radiative transfer equation is solved using the discrete ordinates method in the conservative finite-volume formulation. The radiative loss leads to a decrease in mean temperature, but does not significantly influence the flow and mixing fields, in terms either of mean values or of rms values of fluctuations. A systematic analysis of turbulence-radiation interaction (TRI) is carried out. By considering five different TRI formulations, and comparing also with a simple optically thin model, individual TRI contributions are isolated and quantified. For both flames, effects are demonstrated of (1) influence of temperature fluctuations on the mean Planck function, (2) temperature and composition fluctuations on the mean absorption coefficient, and (3) correlation between absorption coefficient and Planck function. The strength of the last effect is stronger in DFIII than in SFD, because of stronger turbulence-chemistry interaction and lower mean temperature in DFIII. The impact of the choice of TRI model on the prediction of the temperature-sensitive minor species NO is determined in a postprocessing step with fixed flow and mixing fields. Best agreement for NO is obtained using the most complete representation of TRI. (author)

Habibi, A.; Merci, B. [Department of Flow, Heat and Combustion Mechanics, Ghent University, B-9000 Ghent (Belgium); Roekaerts, D. [Delft University of Technology, Delft (Netherlands)

2007-10-15T23:59:59.000Z

411

12.11.2014bo Akademi Univ -Thermal and Flow Engineering Piispankatu 8, 20500 Turku 1/32 4. Refrigeration process comparison;  

E-Print Network (OSTI)

Engineering Laboratory / Värme- och strömningsteknik tel. 3223 ; ron.zevenhoven@abo.fi Kylteknik ("KYL") Refrigeration course # 424503.0 v. 2014 ?A 424503 Refrigeration / Kylteknik 12.11.2014?bo Akademi Univ - Thermal voltage part for T-E) see ---- boundaries in the figures below The energy input occurs at the point where

Zevenhoven, Ron

412

Center for Turbulence Research Proceedings of the Summer Program 2008  

E-Print Network (OSTI)

of plasmas in thermal and chemical non-equilibrium. Finally, derivation of the Saha equation, describing chem. Massot a suitable thermodynamics for plasmas and extend the Saha equation to thermal non- equilibrium plasmas for atmospheric entry flows based on kinetic theory By B. Graille, T. E. Magin AND M. Massot We

Prinz, Friedrich B.

413

Tunable thermal link  

DOE Patents (OSTI)

Disclosed is a device whereby the thermal conductance of a multiwalled nanostructure such as a multiwalled carbon nanotube (MWCNT) can be controllably and reversibly tuned by sliding one or more outer shells with respect to the inner core. As one example, the thermal conductance of an MWCNT dropped to 15% of the original value after extending the length of the MWCNT by 190 nm. The thermal conductivity returned when the tube was contracted. The device may comprise numbers of multiwalled nanotubes or other graphitic layers connected to a heat source and a heat drain and various means for tuning the overall thermal conductance for applications in structure heat management, heat flow in nanoscale or microscale devices and thermal logic devices.

Chang, Chih-Wei; Majumdar, Arunava; Zettl, Alexander K.

2014-07-15T23:59:59.000Z

414

Mobile Window Thermal Test  

NLE Websites -- All DOE Office Websites (Extended Search)

Mobile Window Thermal Test (MoWiTT) Facility Mobile Window Thermal Test (MoWiTT) Facility winter.jpg (469135 bytes) The window has come a long way since the days when it was a single pane of glass in a wood frame. Low-emissivity windows were designed to help buildings retain some of the energy that would have leaked out of less efficient windows. Designing efficient window-and-frame systems is one strategy for reducing the energy use of buildings. But the net energy flowing through a window is a combination of temperature- driven thermal flows and transmission of incident solar energy, both of which vary with time. U-factor and solar heat gain coefficient (SHGC), the window properties that control these flows, depend partly on ambient conditions. Window energy flows can affect how much energy a building uses, depending on when the window flows are available to help meet other energy demands within the building, and when they are adverse, adding to building energy use. This leads to a second strategy for reducing building energy use: using the beneficial solar gain available through a window, either for winter heating or for daylighting, while minimizing adverse flows.

415

Neutrino and Cosmic-Ray Emission and Cumulative Background from Radiatively Inefficient Accretion Flows in Low-Luminosity Active Galactic Nuclei  

E-Print Network (OSTI)

We study high-energy neutrino and cosmic-ray (CR) emission from the cores of low-luminosity active galactic nuclei (LLAGN). In LLAGN, the thermalization of particles is expected to be incomplete in radiatively inefficient accretion flows (RIAFs), allowing the existence of non-thermal particles. In this work, assuming stochastic particle acceleration due to turbulence in RIAFs, we solve the Fokker-Planck equation and calculate spectra of escaping neutrinos and CRs. The RIAF in LLAGN can emit CR protons with $\\gtrsim10$ PeV energies and TeV-PeV neutrinos generated via $pp$ and/or $p\\gamma$ reactions. We find that, if $\\sim1$% of the accretion luminosity is carried away by non-thermal ions, the diffuse neutrino intensity from the cores of LLAGN may be as high as $E_\

Shigeo S. Kimura; Kohta Murase; Kenji Toma

2014-11-13T23:59:59.000Z

416

Thermal Insulation for Energy Conservation  

Science Journals Connector (OSTI)

The use of thermal insulations to reduce heat flow across the building ... decades. Materials available for use as building insulation include naturally occurring fibers and particles, man ... plastics, evacuated...

Dr. David W. Yarbrough Ph.D.; PE

2012-01-01T23:59:59.000Z

417

Turbulent Friction in Rough Pipes and the Energy Spectrum of the Phenomenological Theory  

E-Print Network (OSTI)

The classical experiments on turbulent friction in rough pipes were performed by J. Nikuradse in the 1930's. Seventy years later, they continue to defy theory. Here we model Nikuradse's experiments using the phenomenological theory of Kolmog\\'orov, a theory that is widely thought to be applicable only to highly idealized flows. Our results include both the empirical scalings of Blasius and Strickler, and are otherwise in minute qualitative agreement with the experiments; they suggest that the phenomenological theory may be relevant to other flows of practical interest; and they unveil the existence of close ties between two milestones of experimental and theoretical turbulence.

G. Gioia; Pinaki Chakraborty

2005-07-08T23:59:59.000Z

418

Turbulent Rivers Bjorn Birnir  

E-Print Network (OSTI)

) function gives rise to Hack's law [16]; stating that the length of the main river, in mature river basins, scales with the area of the basin l Ah, h = 0.568 being Hack's exponent. 1 Introduction The flow]. One of the best known scaling laws of river basins is Hack's law [16] that states that the area

Birnir, Björn

419

19 `eme Congr`es Francais de Mecanique Marseille, 24-28 ao^ut 2009 Transition to turbulence in globally subcritical systems  

E-Print Network (OSTI)

in globally subcritical systems P. MANNEVILLEa , J. ROLLANDa,b a. LadHyX, ´Ecole Polytechnique, 91128 our current understanding of the transition to turbulence in globally subcritical systems, pointing to turbulence, subcritical systems, plane Couette flow 1 General setting Understanding the transition

Boyer, Edmond

420

34th AIAA Fluid Dynamics Conference and Exhibit, June 28July 1, 2004/Portland, OR DNS of Hypersonic Turbulent Boundary Layers  

E-Print Network (OSTI)

of Hypersonic Turbulent Boundary Layers M. Pino Martin Department of Mechanical and Aerospace Engineering and hypersonic turbu- lent boundary layers. The systematic procedure for initializing the turbulent flow fields layers is important in advancing supersonic and hypersonic flight technology. In a high-speed boundary

Martín, Pino

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


421

Assessment of high-resolution methods for numerical simulations of compressible turbulence with shock waves  

SciTech Connect

Flows in which shock waves and turbulence are present and interact dynamically occur in a wide range of applications, including inertial confinement fusion, supernovae explosion, and scramjet propulsion. Accurate simulations of such problems are challenging because of the contradictory requirements of numerical methods used to simulate turbulence, which must minimize any numerical dissipation that would otherwise overwhelm the small scales, and shock-capturing schemes, which introduce numerical dissipation to stabilize the solution. The objective of the present work is to evaluate the performance of several numerical methods capable of simultaneously handling turbulence and shock waves. A comprehensive range of high-resolution methods (WENO, hybrid WENO/central difference, artificial diffusivity, adaptive characteristic-based filter, and shock fitting) and suite of test cases (Taylor-Green vortex, Shu-Osher problem, shock-vorticity/entropy wave interaction, Noh problem, compressible isotropic turbulence) relevant to problems with shocks and turbulence are considered. The results indicate that the WENO methods provide sharp shock profiles, but overwhelm the physical dissipation. The hybrid method is minimally dissipative and leads to sharp shocks and well-resolved broadband turbulence, but relies on an appropriate shock sensor. Artificial diffusivity methods in which the artificial bulk viscosity is based on the magnitude of the strain-rate tensor resolve vortical structures well but damp dilatational modes in compressible turbulence; dilatation-based artificial bulk viscosity methods significantly improve this behavior. For well-defined shocks, the shock fitting approach yields good results.

Johnsen, Eric [Center for Turbulence Research, Stanford University, Stanford, CA 94305 (United States)], E-mail: johnsen@stanford.edu; Larsson, Johan [Center for Turbulence Research, Stanford University, Stanford, CA 94305 (United States)], E-mail: jola@stanford.edu; Bhagatwala, Ankit V. [Department of Aeronautics and Astronautics, Stanford University, Stanford, CA 94305 (United States); Cabot, William H. [Lawrence Livermore National Laboratory, Livermore, CA 94551 (United States); Moin, Parviz [Center for Turbulence Research, Stanford University, Stanford, CA 94305 (United States); Olson, Britton J. [Department of Aeronautics and Astronautics, Stanford University, Stanford, CA 94305 (United States); Rawat, Pradeep S. [Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, CA 90095 (United States); Shankar, Santhosh K. [Department of Aeronautics and Astronautics, Stanford University, Stanford, CA 94305 (United States); Sjoegreen, Bjoern [Lawrence Livermore National Laboratory, Livermore, CA 94551 (United States); Yee, H.C. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Zhong Xiaolin [Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, CA 90095 (United States); Lele, Sanjiva K. [Department of Aeronautics and Astronautics, Stanford University, Stanford, CA 94305 (United States)

2010-02-20T23:59:59.000Z

422

Center for Turbulence Research Proceedings of the Summer Program 2008  

E-Print Network (OSTI)

-equilibrium excitation of vibrational degrees of freedom. High temperatures make it necessary to consider chemical to increased ablation and, as a worst-case-scenario, to the failure of the underlying TPS (thermal protection (i.e., mounts). The flow conditions are high Mach number and hot flow since this is not attainable

Prinz, Friedrich B.

423

Theory of free surface flow over rough seeping beds  

Science Journals Connector (OSTI)

...horizontal bed is assumed to be rough consisting of sediment...the other hand, in the rough flow regime (Re *70...the introduction, the set of equations (3.2...turbulent flow over a rough planar sand bed. The...The flow conditions were set in such a way that sediment...

2007-01-01T23:59:59.000Z

424

Omega?to?the?one?third term in dispersion relation for acoustic pulse propagation through turbulence  

Science Journals Connector (OSTI)

The authors earlier formulation of pulse propagation through turbulence required a somewhat ad hoc separation of the effects of large scale and small scale turbulence with the selection of a cut?off turbulentwave number k c that separates the two regimes. A neater?cleaner formulation proceeds with the premise that the frequency dispersion of pulses is caused by that part of the turbulence spectrum which lies in the inertial range originally predicted by Kolmogoroff. The acoustic propagating waves dispersion relation has the acoustic wave number being of the form k=(?/c)+F(?) where c is a spatially averaged sound speed and where for mechanical turbulence the extra term F(?) must depend on only the angular frequency ? the sound speedc and the turbulent energy dissipation ? per unit fluid mass and per unit time. If the turbulence is weak then the quantity F(?) has to be of second order in the portions of the turbulent fluid velocity in the intertial range so following Kolmogoroffs reasoning it must vary with ? as ?2/3. Simple dimensional analysis then reveals that F(?) is K?2/3 c ?7/3?1/3 the latter factor being as announced in the title of this abstract and K being a universal dimensionless complex constant. A similar result holds for thermal turbulence. The analysis showing that the separating?out of the effects of turbulence in the inertial regime is in fact possible yields K=?0.37e i?/3. The dispersion is typically small but has an accumulative effect that leads to a sizable pulse distortion over large propagation distances. [Work supported by NASA Langley Research Center.

Allan D. Pierce

1995-01-01T23:59:59.000Z

425

The computation of three-dimensional systems with various turbulence model variations  

SciTech Connect

The standard {kappa}-{epsilon} equations and other turbulence corrections are evaluated and reported with respect to their applicability in three-dimensional flows. The turbulence models are formulated on the assumption that an isotropic eddy viscosity and the modified Boussinesq hypothesis adequately describe the stress distributions, and that the source of predictive error is a consequence of the modeled terms in the {kappa}-{epsilon} equations. Turbulence model corrections are incorporated to investigate their impact on these errors. Predictions from various turbulence models are compared with experimental data from an isothermal 3-D configuration. The data comparisons delineate the relative advantages and disadvantages of various modifications. The {kappa}-{epsilon} model performs competitively with other model corrections and in some instances is judged to be superior than the modified treatments. However, given the additional computational time and the marginal superiority of the investigated models, it is recommended that present 3-D computational code calculations retain the standard {kappa}-{epsilon} model.

Hassan, M.A. [Cairo Univ., Giza (Egypt). Mechanical Power Engineering Dept.

1996-12-31T23:59:59.000Z

426

Atmospheric and Wake Turbulence Impacts on Wind Turbine Fatigue Loading: Preprint  

SciTech Connect

Large-eddy simulations of atmospheric boundary layers under various stability and surface roughness conditions are performed to investigate the turbulence impact on wind turbines. In particular, the aeroelastic responses of the turbines are studied to characterize the fatigue loading of the turbulence present in the boundary layer and in the wake of the turbines. Two utility-scale 5 MW turbines that are separated by seven rotor diameters are placed in a 3 km by 3 km by 1 km domain. They are subjected to atmospheric turbulent boundary layer flow and data is collected on the structural response of the turbine components. The surface roughness was found to increase the fatigue loads while the atmospheric instability had a small influence. Furthermore, the downstream turbines yielded higher fatigue loads indicating that the turbulent wakes generated from the upstream turbines have significant impact.

Lee, S.; Churchfield, M.; Moriarty, P.; Jonkman, J.; Michalakes, J.

2011-12-01T23:59:59.000Z

427

Accepted, Nuclear Fusion, 1999 Turbulent Transport and Turbulence in Radiative I-Mode Plasmas in  

E-Print Network (OSTI)

Accepted, Nuclear Fusion, 1999 Turbulent Transport and Turbulence in Radiative I-Mode Plasmas of Physics University of Alberta Edmonton, Alberta Canada, T6G 2J1 1/4/00 17:25 PM #12;Accepted, Nuclear Fusion, 1999 1 Abstract First measurements of turbulence levels and turbulence-induced transport

California at San Diego, University of

428

Assessment of TurbulenceChemistry Interaction in Hypersonic Turbulent Boundary Layers  

E-Print Network (OSTI)

Assessment of Turbulence­Chemistry Interaction in Hypersonic Turbulent Boundary Layers L. Duan of the turbulence­chemistry interaction are performed in hypersonic turbulent boundary layers using direct numerical simulation flowfields under typical hypersonic conditions representative of blunt-body and slender- body

Martín, Pino

429

Selected problems in turbulence theory and modeling  

E-Print Network (OSTI)

Three different topics of turbulence research that cover modeling, theory and model computation categories are selected and studied in depth. In the first topic, "velocity gradient dynamics in turbulence" (modeling), the Lagrangian linear diffusion...

Jeong, Eun-Hwan

2004-09-30T23:59:59.000Z

430

Effects of Atmospheric Turbulence on Ballistic Testing  

Science Journals Connector (OSTI)

The effects of atmospheric turbulence on munition target scatter are determined from numerical simulations of ballistic trajectories through many realizations of realistic simulated turbulent wind fields. A technique is evaluated for correcting ...

Rod Frehlich; Robert Sharman; Charles Clough; Michael Padovani; Kelly Fling; Ward Boughers; W. Scott Walton

2008-05-01T23:59:59.000Z

431

A semi-analytic model of the turbulent multi-phase interstellar medium  

Science Journals Connector (OSTI)

......the specific thermal energy of the cold phase, has...cooling and heating (Audit Hennebelle 2010; Seifried...2011). To preserve energy conservation in our model...4.2 Exchange of energy between the phases In...turbulence (e.g. Audit Hennebelle 2010; Seifried......

H. Braun; W. Schmidt

2012-04-11T23:59:59.000Z

432

Saturation levels of heat-flux- and fast-electron-driven ion-acoustic-wave turbulence  

Science Journals Connector (OSTI)

Saturation levels of ion-acoustic-wave turbulence driven by a heat-flux and a suprathermal electron current have been calculated on the basis of perturbed-orbit theory. The levels are found to be lower than those commonly estimated from simple trapping arguments and too low to explain the thermal-flux inhibition observed in many laser-plasma experiments.

H. C. Barr and T. J. M. Boyd

1981-10-01T23:59:59.000Z

433

Thermal desorption for passive dosimeter  

E-Print Network (OSTI)

~ ~ ~ \\ ~ ~ ~ ~ Flare Tubes for Thermal Desorber . . . . . ~. . . . . . ~ ~ . 27 4. 5 ~ Thermal Desorber Manufactured by Century System Sample Flow from Thermal Desorber to Gas Chromatograph 29 6. Direct Injection Port for Therma1 Desorber . . . . . $2... the gas badges and. providing additional guidance in conducting the study. DEDICATZOil This thesis is cedicated to my parents and my wife, Unice, for their support during the last t', o years AHSTHACT ACKI;ODL DG~~. 'ITS D' DICATICI'. LIST OF TABL...

Liu, Wen-Chen

1981-01-01T23:59:59.000Z

434

Stimulated Neutrino Transformation Through Turbulence  

E-Print Network (OSTI)

We derive an analytical solution for the flavor evolution of a neutrino through a turbulent density profile which is found to accurately predict the amplitude and transition wavelength of numerical solutions on a case-by-case basis. The evolution is seen to strongly depend upon those Fourier modes in the turbulence which are approximately the same as the splitting between neutrino eigenvalues. Transitions are strongly enhanced by those Fourier modes in the turbulence which are approximately the same as the splitting between neutrino eigenvalues. We also find a suppression of transitions due to the long wavelength modes when the ratio of their amplitude and the wavenumber is of order, or greater than, the first root of the Bessel function $J_0$.

Kelly M. Patton; James P. Kneller; Gail C. McLaughlin

2014-04-15T23:59:59.000Z

435

Comment on Heat transfer and fluid flow in microchannels and nanochannels at high Knudsen number using thermal lattice-Boltzmann method  

Science Journals Connector (OSTI)

In this Comment we reveal the falsehood of the claim that the lattice Bhatnagar-Gross-Krook (BGK) model is capable of modeling shear-driven, pressure-driven, and mixed shear-pressure-driven rarified [sic] flows and heat transfer up to Kn=1 in the transitional regime made in a recent paper [Ghazanfarian and Abbassi, Phys. Rev. E 82, 026307 (2010)]. In particular, we demonstrate that the so-called Knudsen effects described are merely numerical artifacts of the lattice BGK model and they are unphysical. Specifically, we show that the erroneous results for the pressure-driven flow in a microchannel imply the false and unphysical condition that 6?Kn

Li-Shi Luo

2011-10-25T23:59:59.000Z

436

Comparative study of two- and three-dimensional modeling on arc discharge phenomena inside a thermal plasma torch with hollow electrodes  

SciTech Connect

A comparative study between two- and three-dimensional (2D and 3D) modeling is carried out on arc discharge phenomena inside a thermal plasma torch with hollow electrodes, in order to evaluate the effects of arc root configuration characterized by either 2D annular or 3D highly localized attachment on the electrode surface. For this purpose, a more precise 3D transient model has been developed by taking account of 3D arc current distribution and arc root rotation. The 3D simulation results apparently reveal that the 3D arc root attachment brings about the inherent 3D and turbulence nature of plasma fields inside the torch. It is also found that the constricted arc column near the vortex chamber plays an important role in heating and acceleration of injected arc gases by concentrating arc currents on the axis of the hollow electrodes. The inherent 3D nature of arc discharge is well preserved inside the cathode region, while these 3D features slowly diminish behind the vortex chamber where the turbulent flow begins to be developed in the anode region. Based on the present simulation results, it is noted that the mixing effects of the strong turbulent flow on the heat and mass transfer are mainly responsible for the gradual relaxation of the 3D structures of plasma fields into the 2D axisymmetric ones that eventually appear in the anode region near the torch exit. From a detailed comparison of the 3D results with the 2D ones, the arc root configuration seems to have a significant effect on the heat transfer to the electrode surfaces interacting with the turbulent plasma flow. That is, in the 2D simulation based on an axisymmetric stationary model, the turbulence phenomena are fairly underestimated and the amount of heat transferred to the cold anode wall is calculated to be smaller than that obtained in the 3D simulation. For the validation of the numerical simulations, calculated plasma temperatures and axial velocities are compared with experimentally measured ones, and the 3D simulation turns out to be more accurate than the 2D simulation as a result of a relatively precise description of the turbulent phenomena inside the torch using a more realistic model of arc root attachment. Finally, it is suggested that the 3D transient formulation is indeed required for describing the real arc discharge phenomena inside the torch, while the 2D stationary approach is sometimes useful for getting practical information about the time-averaged plasma characteristics outside the torch because of its simplicity and rapidness in computation.

Kim, Keun Su; Park, Jin Myung; Choi, Sooseok; Kim, Jongin; Hong, Sang Hee [Department of Nuclear Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of)

2008-02-15T23:59:59.000Z

437

Flows and Non-thermal Velocities in Solar Active Regions Observed with the Extreme-ultraviolet Imaging Spectrometer on Hinode: A Tracer of Active Region Sources of Heliospheric Magnetic Fields?  

E-Print Network (OSTI)

From Doppler velocity maps of active regions constructed from spectra obtained by the Extreme-ultraviolet Imaging Spectrometer (EIS) on the Hinode spacecraft we observe large areas of outflow (20-50 km/s) that can persist for at least a day. These outflows occur in areas of active regions that are faint in coronal spectral lines formed at typical quiet Sun and active region temperatures. The outflows are positively correlated with non-thermal velocities in coronal plasmas. The bulk mass motions and non-thermal velocities are derived from spectral line centroids and line widths, mostly from a strong line of Fe XII at 195.12 Angstroms. The electron temperature of the outflow regions estimated from an Fe XIII to Fe XII line intensity ratio is about 1.2-1.4 MK. The electron density of the outflow regions derived from a density sensitive intensity ratio of Fe XII lines is rather low for an active region. Most regions average around 7E10+8 cm(-3), but there are variations on pixel spatial scales of about a factor of 4. We discuss results in detail for two active regions observed by EIS. Images of active regions in line intensity, line width, and line centroid are obtained by rastering the regions. We also discuss data from the active regions obtained from other orbiting spacecraft that support the conclusions obtained from analysis of the EIS spectra. The locations of the flows in the active regions with respect to the longitudinal photospheric magnetic fields suggest that these regions might be tracers of long loops and/or open magnetic fields that extend into the heliosphere, and thus the flows could possibly contribute significantly to the solar wind.

G. A. Doschek; H. P. Warren; J. T. Mariska; K. Muglach; J. L. Culhane; H. Hara; T Watanabe

2008-07-17T23:59:59.000Z

438

General single phase wellbore flow model  

SciTech Connect

A general wellbore flow model, which incorporates not only frictional, accelerational and gravitational pressure drops, but also the pressure drop caused by inflow, is presented in this report. The new wellbore model is readily applicable to any wellbore perforation patterns and well completions, and can be easily incorporated in reservoir simulators or analytical reservoir inflow models. Three dimensionless numbers, the accelerational to frictional pressure gradient ratio R{sub af}, the gravitational to frictional pressure gradient ratio R{sub gf}, and the inflow-directional to accelerational pressure gradient ratio R{sub da}, have been introduced to quantitatively describe the relative importance of different pressure gradient components. For fluid flow in a production well, it is expected that there may exist up to three different regions of the wellbore: the laminar flow region, the partially-developed turbulent flow region, and the fully-developed turbulent flow region. The laminar flow region is located near the well toe, the partially-turbulent flow region lies in the middle of the wellbore, while the fully-developed turbulent flow region is at the downstream end or the heel of the wellbore. Length of each region depends on fluid properties, wellbore geometry and flow rate. As the distance from the well toe increases, flow rate in the wellbore increases and the ratios R{sub af} and R{sub da} decrease. Consequently accelerational and inflow-directional pressure drops have the greatest impact in the toe region of the wellbore. Near the well heel the local wellbore flow rate becomes large and close to the total well production rate, here R{sub af} and R{sub da} are small, therefore, both the accelerational and inflow-directional pressure drops can be neglected.

Ouyang, Liang-Biao; Arbabi, S.; Aziz, K.

1997-02-05T23:59:59.000Z

439

Flow Test | Open Energy Information  

Open Energy Info (EERE)

Flow Test Flow Test Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Exploration Technique: Flow Test Details Activities (38) Areas (33) Regions (1) NEPA(3) Exploration Technique Information Exploration Group: Downhole Techniques Exploration Sub Group: Well Testing Techniques Parent Exploration Technique: Well Testing Techniques Information Provided by Technique Lithology: Stratigraphic/Structural: Hydrological: Flow tests provide information on permeability, recharge rates, reservoir pressures, fluid chemistry, and scaling. Thermal: Flow tests can measure temperature variations with time to estimate characteristics about the heat source. Dictionary.png Flow Test: Flow tests are typically conducted shortly after a well has been drilled to test its productivity. The well is opened and fluids are released, the

440

Turbulent resuspension of small nondeformable particles  

SciTech Connect

An energy-balance resuspension model is modified and applied to the resuspension of a monolayer of nondeformable spherical particles. The particle-surface adhesive force is calculated from a microscopic model based on the Lennard-Jones intermolecular potential. Pairwise additivity of intermolecular interactions is assumed and elastic flattening of the particles is neglected. From the resulting particle-surface interaction potential the natural frequency of vibration of a particle on a surface and the depth of the potential well are calculated. The particle resuspension rate is calculated using the results of a previously developed energy-balance model, where the influence of fluid flow on the bound particle motion is recognized. The effect of surface roughness is included by introducing an effective particle radius that results in log-normally distributed adhesive forces. The predictions of the model are compared with experimental results for the resuspension of Al{sub 2}O{sub 3} particles from stainless steel surfaces. Particle resuspension due to turbulent fluid flow is important in the interaction of the atmosphere with various surfaces and in numerous industrial processes. For example, in the nuclear industry, fission-product aerosols released during a postulated severe accident in a Light Water Reactor may deposit and resuspend repeatedly in the vessel circuit and containment.

Lazaridis, M.; Drossinos, Y. [European Commission, Ispra (Italy). Joint Research Centre] [European Commission, Ispra (Italy). Joint Research Centre; Georgopoulos, P.G. [Rutgers-the State Univ., Piscataway, NJ (United States). Environmental and Occupational Health Sciences Inst.] [Rutgers-the State Univ., Piscataway, NJ (United States). Environmental and Occupational Health Sciences Inst.; [Univ. of Medicine and Dentistry of New Jersey, Piscataway, NJ (United States)

1998-08-01T23:59:59.000Z

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


441

Perpendicular ion acceleration in whistler turbulence  

SciTech Connect

Whistler turbulence is an important contributor to solar wind turbulence dissipation. This turbulence contains obliquely propagating whistler waves at electron scales, and these waves have electrostatic components perpendicular to the mean magnetic field. In this paper, a full kinetic, two-dimensional particle-in-cell simulation shows that whistler turbulence can accelerate ions in the direction perpendicular to the mean magnetic field. When the ions pass through wave-particle resonances region in the phase space during their cyclotron motion, the ions are effectively accelerated in the perpendicular direction. The simulation results suggest that whistler turbulence contributes to the perpendicular heating of ions observed in the solar wind.

Saito, S. [Graduate School of Science, Nagoya University, Furocho, Chikusa, Nagoya 464-8601 (Japan)] [Graduate School of Science, Nagoya University, Furocho, Chikusa, Nagoya 464-8601 (Japan); Nariyuki, Y. [Faculty of Human Development, University of Toyama, 3190, Toyama 930-8555 (Japan)] [Faculty of Human Development, University of Toyama, 3190, Toyama 930-8555 (Japan)

2014-04-15T23:59:59.000Z

442

Simulation of swirling coal combustion using a full two-fluid model and an AUSM turbulence-chemistry model?  

Science Journals Connector (OSTI)

A full two-fluid model of reacting gas-particle flows with an algebraic unified second-order moment turbulence-chemistry model for the turbulent reaction rate of NO formation are used to simulate swirling coal combustion. The sub-models are the k?kp two-phase turbulence model, the EBUArrhenius volatile and CO combustion model, the six-flux radiation model, coal devolatilization model and char combustion model. The prediction results are in good agreement with the experimental results taken from references.

L.X. Zhou; Y. Zhang; J. Zhang

2003-01-01T23:59:59.000Z

443

Wave turbulence in quantum fluids  

Science Journals Connector (OSTI)

...range, as shown by the inset bifurcation diagram. Fig. 2. Second sound turbulence...metastable state. (Inset) Bifurcation diagram showing regions of stability (unshaded) and...159 . 9 Ryutova M Tarbell T ( 2003 ) MHD shocks and the origin of the solar transition...

German V. Kolmakov; Peter Vaughan Elsmere McClintock; Sergey V. Nazarenko

2014-01-01T23:59:59.000Z

444

RETRAN-02: a program for transient thermal-hydraulic analysis of complex fluid flow systems. Volume 1. Theory and numerics (Revision 2). [PWR; BWR  

SciTech Connect

RETRAN-02 represents a significant achievement in the development of a versatile and reliable computer program for use in best-estimate transient thermal-hydraulic analysis of LWR systems. The RETRAN-02 computer program is an extension of the RETRAN-01 program designed to provide analysis capabilities for: (1) BWR and PWR transients; (2) small-break loss-of-coolant accidents; (3) balance of plant modeling; and (4) anticipated transients without scram, while maintaining the analysis capabilities of the predecessor code. This report (the first of a four-volume computer code manual) describes the theory and numerical algorithms of the RETRAN-02 code. The three companion volumes describe the programming aspects, the programming details, and the verification and qualification performed with RETRAN.

McFadden, J.H.; Narum, R.E.; Peterson, C.E.; Noble, C.; Farman, R.F.; McClure, J.A.; Paulsen, M.P.; Richert, K.D.; Hughes, E.D.; Gose, G.C.

1984-11-01T23:59:59.000Z

445

Numerical study on the turbulence structures in closely spaced rod bundle subchannels  

SciTech Connect

Fully developed turbulent flow through simulated rod bundle subchannels formed by a rod-trapezoidal duct was numerically studied. With a simple coordinate system transformation from an orthogonal cylindrical system to a nonorthogonal curvilinear system, the highly irregular flow passage of a rod-trapezoidal duct was converted to that of a regular rectangle. An empirical anisotropic eddy viscosity distribution based on existing experimental data was used in conjunction with the algebraic stress model to address the influence of coherent large-scale cross-gap eddy motion, whose existence in closely spaced rod bundle subchannels has bene substantiated by extensive hot-wire measurements. Results of the calculation are compared with experimental data, with emphasis on secondary flow and turbulence kinetic energy. The credibility of this numerical scheme was establishment through a series of numerical tests on simple geometry flows.

Wu, X. (Univ. of Manitoba, Winnipeg (Canada). Dept. of Mechanical Engineering)

1994-06-01T23:59:59.000Z

446

A Scalable Turbulent Mixing Aerosol Reactor for Oxide-Coated Silicon Nanoparticles  

E-Print Network (OSTI)

of Technology, 391 South Holliston Avenue, Pasadena, California 91125 A new, turbulent flow aerosol reactor. These composite nanoparticles were synthesized under clean conditions, deposited on 200 mm diameter silicon wafers aerosol technology is routinely integrated into microelectronics processing. Foremost is reluctance

Atwater, Harry

447

Properties of vortices in the self-similar turbulent jet A. Agrawal, A.K. Prasad  

E-Print Network (OSTI)

to the fundamental importance of their flow physics. Consequently, their time-averaged velocity profiles, spread rate turbulent axisymmetric jet. The velocity fields were high-pass filtered to expose the vortical structures, the strongest eddies in the high-pass fil- tered field occur near the jet axis. The average circulation

Prasad, Ajay K.

448

Characterization of the effect of Froude number on surface waves and heat transfer in inclined turbulent  

E-Print Network (OSTI)

Characterization of the effect of Froude number on surface waves and heat transfer in inclined describes wave/heat transfer phenomena in inclined turbulent open surface water flows. The experiments were. These changes lead to a heat transfer improvement, enough to double the heat transfer coefficient

Abdou, Mohamed

449

Direct Numerical Simulation of a Hypersonic Turbulent Boundary Layer on a Large Domain  

E-Print Network (OSTI)

Direct Numerical Simulation of a Hypersonic Turbulent Boundary Layer on a Large Domain Stephan Priebe , M. Pino Mart´in The direct numerical simulation (DNS) of a spatially-developing hypersonic There are few studies of hypersonic flows at Mach number greater than 5 and few involve the measurement of mean

Martín, Pino

450

Measurements and analysis of turbulent consumption speeds of H2/CO mixtures Prabhakar Venkateswaran a,  

E-Print Network (OSTI)

Available online 9 February 2011 Keywords: Syngas Hydrogen Global consumption speeds Turbulent flame speed since they are the primary constitu- ents of syngas fuels. Data are reported at mean flow velocities than SL,0. ? 2011 The Combustion Institute. Published by Elsevier Inc. All rights reserved. 1

Lieuwen, Timothy C.

451

Using cavitation to measure statistics of low-pressure events in large-Reynolds-number turbulence  

E-Print Network (OSTI)

a high-speed video system. A fast photo detector is used to measure the scaling of the cavitation fluc- tuations by measuring the light scattered from cavitating bubbles in a small region of the flowUsing cavitation to measure statistics of low-pressure events in large-Reynolds-number turbulence A

La Porta, Arthur

452

Noise in non?premixed turbulent syngas flames  

Science Journals Connector (OSTI)

A turbulent syngas flame may generate acoustic noise of high acoustic intensity in a combustion chamber. This may lead to the failure of construction components in a gas turbine engine in periods of the order of 1100 hours. The research as described in the literature has almost exclusively been performed on the generation of noise in premixed methane or propane flames. Syngas fuel is a mixture of hydrogen and carbon monoxide and the burners used are of the non?premixed type. In this research the effect of turbulence and syngas composition on noise generation is investigated. A laboratory is set up to test syngas flames of a thermal power of 50 kW in a cylindrical air?cooled combustion chamber. Experiments are performed at several fuel compositions and burner inlet conditions. The flame sound intensity is measured in the combustion chamber equipped with acoustic dampers. The paper discusses the measured sound spectra. A model is derived for the generation of sound in a turbulent non?premixed flame. In this model it is shown that the sound generation is related to the dependence of density on mixture fraction in a flame with fast chemistry. A fluctuation in mixture fraction will lead to sound generation.

Sikke A. Klein; Jim B. W. Kok

1998-01-01T23:59:59.000Z

453

TURBULENCE IN THE INTERGALACTIC MEDIUM: SOLENOIDAL AND DILATATIONAL MOTIONS AND THE IMPACT OF NUMERICAL VISCOSITY  

SciTech Connect

We use a suite of cosmological hydrodynamical simulations, run by two fixed grid codes, to investigate the properties of solenoidal and dilatational motions of the intergalactic medium (IGM) and the impact of numerical viscosity on turbulence in an ?CDM universe. The codes differ only in the spatial difference discretization. We find that (1) The vortical motion grows rapidly since z = 2 and reaches ?10 km s{sup 1}-90 km s{sup 1} at z = 0. Meanwhile, the small-scale compressive ratio r{sub CS} drops from 0.84 to 0.47, indicating comparable vortical and compressive motions at z = 0. (2) Power spectra of the solenoidal velocity possess two regimes, ?k {sup 0.89} and ?k {sup 2.02}, while the total and dilatational velocity follow the scaling k {sup 1.88} and k {sup 2.20}, respectively, in the turbulent range. The IGM turbulence may contain two distinct phases, the supersonic and post-supersonic phases. (3) The non-thermal pressure support, measured by the vortical kinetic energy, is comparable with the thermal pressure for ?{sub b} ? 10-100, or T < 10{sup 5.5} K at z = 0.0. The deviation of the baryon fraction from the cosmic mean shows a preliminary positive correlation with the turbulence pressure support. (4) A relatively higher numerical viscosity would dissipate both the compressive and vortical motions of the IGM into thermal energy more effectively, resulting in less developed vorticity, remarkably shortened inertial range, and leading to a non-negligible uncertainty in the thermal history of gas accretion. Shocks in regions outside of clusters are significantly suppressed by numerical viscosity since z = 2, which may directly cause the different levels of turbulence between the two codes.

Zhu, Weishan; Gu, Qiusheng [School of Astronomy and Space Science, Nanjing University, Nanjing, 210092 (China); Feng, Long-long [Purple Mountain Observatory, Nanjing, 210008 (China); Xia, Yinhua [School of Mathematical Sciences, University of Science and Technology of China, Hefei, Anhui 230026 (China); Shu, Chi-Wang [Division of Applied Mathematics, Brown University, Providence, RI 02912 (United States); Fang, Li-Zhi [Department of Physics, University of Arizona, Tucson, AZ 85721 (United States)

2013-11-01T23:59:59.000Z

454

The conservative cascade of kinetic energy in compressible turbulence  

E-Print Network (OSTI)

The physical nature of compressible turbulence is of fundamental importance in a variety of astrophysical settings. We present the first direct evidence that mean kinetic energy cascades conservatively beyond a transitional "conversion" scale-range despite not being an invariant of the compressible flow dynamics. We use high-resolution three-dimensional simulations of compressible hydrodynamic turbulence on $512^3$ and $1024^3$ grids. We probe regimes of forced steady-state isothermal flows and of unforced decaying ideal gas flows. The key quantity we measure is pressure dilatation cospectrum, $E^{PD}(k)$, where we provide the first numerical evidence that it decays at a rate faster than $k^{-1}$ as a function of wavenumber. This is sufficient to imply that mean pressure dilatation acts primarily at large-scales and that kinetic and internal energy budgets statistically decouple beyond a transitional scale-range. Our results suggest that an extension of Kolmogorov's inertial-range theory to compressible turbu...

Aluie, Hussein; Li, Hui

2011-01-01T23:59:59.000Z

455

Turbulent equipartitions in two dimensional drift convection  

SciTech Connect

Unlike the thermodynamic equipartition of energy in conservative systems, turbulent equipartitions (TEP) describe strongly non-equilibrium systems such as turbulent plasmas. In turbulent systems, energy is no longer a good invariant, but one can utilize the conservation of other quantities, such as adiabatic invariants, frozen-in magnetic flux, entropy, or combination thereof, in order to derive new, turbulent quasi-equilibria. These TEP equilibria assume various forms, but in general they sustain spatially inhomogeneous distributions of the usual thermodynamic quantities such as density or temperature. This mechanism explains the effects of particle and energy pinch in tokamaks. The analysis of the relaxed states caused by turbulent mixing is based on the existence of Lagrangian invariants (quantities constant along fluid-particle or other orbits). A turbulent equipartition corresponds to the spatially uniform distribution of relevant Lagrangian invariants. The existence of such turbulent equilibria is demonstrated in the simple model of two dimensional electrostatically turbulent plasma in an inhomogeneous magnetic field. The turbulence is prescribed, and the turbulent transport is assumed to be much stronger than the classical collisional transport. The simplicity of the model makes it possible to derive the equations describing the relaxation to the TEP state in several limits.

Isichenko, M.B.; Yankov, V.V. [Univ. of California, Santa Barbara, CA (United States). Inst. for Theoretical Physics

1995-07-25T23:59:59.000Z

456

RETRAN-02: A program for transient thermal-hydraulic analysis of complex fluid flow systems: Volume 1, Theory and numerics (Revision 4)  

SciTech Connect

RETRAN-02 represents a significant achievement in the development of a versatile and reliable computer program for use in best-estimate transient thermal-hydraulic analysis of light water reactor systems. The RETRAN-02 computer program is an extension of the RETRAN-01 program designed to provide analysis capabilities for (1) BWR and PWR transients, (2) small break loss of coolant accidents, (3) balance of plant modeling, and (4) anticipated transients without scram, while maintaining the analysis capabilities of the predecessor code. The RETRAN-02 computer code is constructed in a semimodular and dynamic dimensioned form where additions to the code can be easily carried out as new and improved models are developed. The NRC, at the request of a group of utilities, had Argonne National Laboratory perform a technical review of RETRAN-01 MOD003 and RETRAN-02 MOD002. This review was completed in May 1983, and the NRC issued a Safety Evaluation Report on RETRAN in September 1984. Revision 4 of the RETRAN-02 computer code manuals describes the MOD005 version of the code. This report (the first of a four-volume computer code manual) describes the theory and numerical algorithms of the RETRAN-02 code. The three companion volumes describe the programming details, the user input requirements and sample problem input and output files, and the verification and qualification performed with RETRAN. 186 refs., 75 figs., 30 tabs.

McFadden, J.H.; Narum, R.E.; Peterson, C.E.; Noble, C.; Farman, R.F.; McClure, J.A.; Paulsen, M.P.; Richert, K.D.; Hughes, E.D.; Gose, G.C.

1988-11-01T23:59:59.000Z

457

Evaluation of a CFD-model for simulation of simplified flow conditioners  

SciTech Connect

Perforated plate flow conditioners are used to generate a fully developed turbulent flow profile upstream of an orifice meter. It is very time-consuming to measure the effect of a flow conditioner for different upstream flow profiles. Therefore a project is initiated to evaluate the performance of a computational fluid computer code for this purpose. If the code correctly predicts the flow characteristics downstream of more complex flow conditioners. In this study a k-{var_epsilon} CFD-model was used to predict the flow downstream of obstruction plates having one large or nine small holes. Both mean velocity, turbulent kinetic energy, k, and the dissipation rate of turbulent kinetic energy, {var_epsilon}, were calculated and compared against measured data. The results indicate that it is possible to predict the mean velocity well and that the accuracy of the predicted k and {var_epsilon} depends on the complexity of the flow.

Erdal, A. [Statoil/K-LAB, Haugesund (Norway); Torbergsen, L.E.; Rimestad, S.; Krogstad, P.A. [Norwegian Inst. of Technology, Trondheim (Norway)

1995-12-31T23:59:59.000Z

458

On the Degeneration of Turbulence at High Reynolds Numbers  

E-Print Network (OSTI)

Turbulent fluctuations in a fluid wind down at a certain rate once stirring has stopped. The role of the most basic parameter in fluid mechanics, the Reynolds number, in setting this decay rate is not generally known. This paper concerns the high-Reynolds-number limit of the process. In a wind-tunnel experiment that reached higher Reynolds numbers than ever before and covered more than two decades in the Reynolds number ($10^4 speed of the flow, $M$ the forcing scale, and $\

Sinhuber, Michael; Bewley, Gregory P

2014-01-01T23:59:59.000Z

459

Wind reversals in turbulent Rayleigh-Benard convection  

E-Print Network (OSTI)

The phenomenon of irregular cessation and subsequent reversal of the large-scale circulation in turbulent Rayleigh-B\\'enard convection is theoretically analysed. The force and thermal balance on a single plume detached from the thermal boundary layer yields a set of coupled nonlinear equations, whose dynamics is related to the Lorenz equations. For Prandtl and Rayleigh numbers in the range $10^{-2} \\leq \\Pr \\leq 10^{3}$ and $10^{7} \\leq \\Ra \\leq 10^{12}$, the model has the following features: (i) chaotic reversals may be exhibited at Ra $\\geq 10^{7}$; (ii) the Reynolds number based on the root mean square velocity scales as $\\Re_{rms} \\sim \\Ra^{[0.41 ... 0.47]}$ (depending on Pr), and as $\\Re_{rms} \\sim \\Pr^{-[0.66 ... 0.76]}$ (depending on Ra); and (iii) the mean reversal frequency follows an effective scaling law $\\omega / (\

Francisco Fontenele Araujo; S. Grossmann; D. Lohse

2005-08-29T23:59:59.000Z

460

Profiles of heating in turbulent coronal magnetic loops  

E-Print Network (OSTI)

Context: The location of coronal heating in magnetic loops has been the subject of a long-lasting controversy: does it occur mostly at the loop footpoints, at the top, is it random, or is the average profile uniform? Aims: We try to address this question in model loops with MHD turbulence and a profile of density and/or magnetic field along the loop. Methods: We use the ShellAtm MHD turbulent heating model described in Buchlin & Velli (2006), with a static mass density stratification obtained by the HydRad model (Bradshaw & Mason 2003). This assumes the absence of any flow or heat conduction subsequent to the dynamic heating. Results: The average profile of heating is quasi-uniform, unless there is an expansion of the flux tube (non-uniform axial magnetic field) or the variation of the kinetic and magnetic diffusion coefficients with temperature is taken into account: in the first case the heating is enhanced at footpoints, whereas in the second case it is enhanced where the dominant diffusion coefficient is enhanced. Conclusions: These simulations shed light on the consequences on heating profiles of the complex interactions between physical effects involved in a non-uniform turbulent coronal loop.

E. Buchlin; P. J. Cargill; S. J. Bradshaw; M. Velli

2007-02-28T23:59:59.000Z

Note: This page contains sample records for the topic "flow thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


461

Mean- Field Approximation and a Small Parameter in Turbulence Theory  

E-Print Network (OSTI)

Numerical and physical experiments on two-dimensional (2d) turbulence show that the differences of transverse components of velocity field are well described by a gaussian statistics and Kolmogorov scaling exponents. In this case the dissipation fluctuations are irrelevant in the limit of small viscosity. In general, one can assume existence of critical space-dimensionality $d=d_{c}$, at which the energy flux and all odd-order moments of velocity difference change sign and the dissipation fluctuations become dynamically unimportant. At $d', leading to the observed gaussian statistics and Kolmogorov scaling of transverse velocity differences. It is shown that in the vicinity of $d=d_{c}$ the ratio of the relaxation and translation characteristic times decreases to zero, thus giving rise to a small parameter of the theory. The expressions for pressure and dissipation contributions to the exact equation for the generating function of transverse velocity differences are derived in the vicinity of $d=d_{c}$. The resulting equation describes experimental data on two-dimensional turbulence and demonstrate onset of intermittency as $d-d_{c}>0$ and $r/L\\to 0$ in three-dimensional flows in close agreement with experimental data. In addition, some new exact relations between correlation functions of velocity differences are derived. It is also predicted that the single-point pdf of transverse velocity difference in developing as well as in the large-scale stabilized two-dimensional turbulence is a gaussian.

Victor Yakhot

2000-01-13T23:59:59.000Z

462

Condensation of cloud microdroplets in homogeneous isotropic turbulence  

E-Print Network (OSTI)

The growth by condensation of small water droplets in a three-dimensional homogeneous isotropic turbulent flow is considered. Within a simple model of advection and condensation, the dynamics and growth of millions of droplets are integrated. A droplet-size spectra broadening is obtained and it is shown to increase with the Reynolds number of turbulence, by means of two series of direct numerical simulations at increasing resolution. This is a key point towards a proper evaluation of the effects of turbulence for condensation in warm clouds, where the Reynolds numbers typically achieve huge values. The obtained droplet-size spectra broadening as a function of the Reynolds number is shown to be consistent with dimensional arguments. A generalization of this expectation to Reynolds numbers not accessible by DNS is proposed, yielding upper and lower bounds to the actual size-spectra broadening. A further DNS matching the large scales of the system suggests consistency of the picture drawn, while additional effort is needed to evaluate the impact of this effect for condensation in more realistic cloud conditions.

Alessandra S. Lanotte; Agnese Seminara; Federico Toschi

2008-07-15T23:59:59.000Z

463