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1

Coshcous turbulence and its thermalization  

SciTech Connect (OSTI)

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

2

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

3

Thermal shallow water models of geostrophic turbulence in Jovian atmospheres  

SciTech Connect (OSTI)

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

4

Turbulence  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr MayAtmosphericNuclear SecurityTensile Strain Switched Ferromagnetism in Layered NbS2TopoPortalBRDFTunable ThermalTurbines

5

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

2009-12-25T23:59:59.000Z

6

Isolation of Metals from Liquid Wastes: Reactive Scavenging in Turbulent Thermal Reactors  

SciTech Connect (OSTI)

The Overall project demonstrated that toxic metals (cesium Cs and strontium Sr) in aqueous and organic wastes can be isolated from the environment through reaction with kaolinite based sorbent substrates in high temperature reactor environments. In addition, a state-of-the art laser diagnostic tool to measure droplet characteristic in practical 'dirty' laboratory environments was developed, and was featured on the cover of a recent edition of the scientific journal ''applied Spectroscopy''. Furthermore, great strides have been made in developing a theoretical model that has the potential to allow prediction of the position and life history of every particle of waste in a high temperature, turbulent flow field, a very challenging problem involving as it does, the fundamentals of two phase turbulence and of particle drag physics.

Jost O.L. Wendt; Alan R. Kerstein; Alexander Scheeline; Arne Pearlstein; William Linak

2003-08-06T23:59:59.000Z

7

Property:Pressure Range(Psi) | Open Energy Information  

Open Energy Info (EERE)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data CenterFranconia, Virginia: EnergyPotentialUrbanUtilityScalePVCapacity Jump to: navigation, search PropertyTransfer Method Jump to:Psi) Jump

8

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 for tokamak plasma turbulence studies… (more)

Janhunen, Salomon

2013-01-01T23:59:59.000Z

9

Turbulent electron transport in edge pedestal by electron temperature gradient turbulence  

SciTech Connect (OSTI)

We present a model for turbulent electron thermal transport at the edge pedestal in high (H)-mode plasmas based on electron temperature gradient (ETG) turbulence. A quasi-linear analysis of electrostatic toroidal ETG modes shows that both turbulent electron thermal diffusivity and hyper-resistivity exhibits the Ohkawa scaling in which the radial correlation length of turbulence becomes the order of electron skin depth. Combination of the Ohkawa scales and the plasma current dependence results in a novel confinement scaling inside the pedestal region. It is also shown that ETG turbulence induces a thermoelectric pinch, which may accelerate the density pedestal formation.

Singh, R. [WCI Center for Fusion Theory, National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of) [WCI Center for Fusion Theory, National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of); Institute for Plasma Research, Bhat Gandhinagar, Gujarat 2382 428 (India); Jhang, Hogun [WCI Center for Fusion Theory, National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of)] [WCI Center for Fusion Theory, National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of); Diamond, P. H. [WCI Center for Fusion Theory, National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of) [WCI Center for Fusion Theory, National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of); CMTFO and CASS, University of California, San Diego 92093-0424, California (United States)

2013-11-15T23:59:59.000Z

10

Detection of turbulent thermal diffusion of particles in numerical simulations Nils Erland L. Haugen, Nathan Kleeorin, Igor Rogachevskii, and Axel Brandenburg  

E-Print Network [OSTI]

of applications (environmental sciences, physics of the atmosphere and meteorology, industrial turbulent flows://pof.aip.org/resource/1/PHFLE6/v24/i7 Published by the American Institute of Physics. Related Articles Light attenuation scale is large in comparison with the integral scale of the turbulence. The strength of this effect

Brandenburg, Axel

11

Turbulence and turbulent mixing in natural fluids  

E-Print Network [OSTI]

Turbulence and turbulent mixing in natural fluids begins with big bang turbulence powered by spinning combustible combinations of Planck particles and Planck antiparticles. Particle prograde accretion on a spinning pair releases 42% of the particle rest mass energy to produce more fuel for turbulent combustion. Negative viscosity and negative turbulence stresses work against gravity, creating mass-energy and space-time from the vacuum. Turbulence mixes cooling temperatures until a quark-gluon strong-force SF freeze-out. Gluon-viscosity anti-gravity ({\\Lambda}SF) exponentially inflates the fireball to preserve big bang turbulence information at scales larger than ct as the first fossil turbulence. Cosmic microwave background CMB temperature anisotropies show big bang turbulence fossils along with fossils of weak plasma turbulence triggered (10^12 s) as plasma viscous forces permit gravitational fragmentation on supercluster to galaxy mass scales (10^13 s). Turbulent morphologies and viscous-turbulent lengths a...

Gibson, Carl H

2010-01-01T23:59:59.000Z

12

Turbulent combustion  

SciTech Connect (OSTI)

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

13

TURBULENT FRBRNNING MVK130 Turbulent Combustion  

E-Print Network [OSTI]

TURBULENT F�RBR�NNING MVK130 Turbulent Combustion Poäng: 3.0 Betygskala: TH Valfri för: M4 to combustion, McGraw-Hill 1996. #12;

14

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

15

Turbulent Compressibilty of Protogalactic Gas  

E-Print Network [OSTI]

The star formation rate in galaxies should be related to the fraction of gas that can attain densities large enough for gravitational collapse. In galaxies with a turbulent interstellar medium, this fraction is controlled by the effective barotropic index $gamma = dlog P/dlog (rho)$ which measures the turbulent compressibility. When the cooling timescale is smaller than the dynamical timescale, gamma can be evaluated from the derivatives of cooling and heating functions, using the condition of thermal equilibrium. We present calculations of gamma for protogalaxies in which the metal abundance is so small that H_2 and HD cooling dominates. For a heating rate independent of temperature and proportional to the first power of density, the turbulent gas is relatively "hard", with $gamma >= 1$, at large densities, but moderately "soft", $gamma <= 0.8$, at densities below around $10^4 cm^(-3)$. At low temperatures the density probability distribution should fall ra pidly for densities larger than this value, which corresponds physically to the critical density at which collisional and radiative deexcitation rate s of HD are equal. The densities attained in turbulent protogalaxies thus depend on the relatively large deuterium abundance in our universe. We expect the same physical effect to occur in higher metallicity gas with different coolants. The case in which adiabatic (compressional) heating due to cloud collapse dominates is also discussed, and suggests a criterion for the maximum mass of Population III stars.

John Scalo; Anirban Biswas

2001-11-09T23:59:59.000Z

16

Aspects of Wave Turbulence in Preheating  

E-Print Network [OSTI]

In this work we have studied the nonlinear preheating dynamics of the $\\frac{1}{4} \\lambda \\phi^4$ inflationary model. It is well established that after a linear stage of preheating characterized by the parametric resonance, the nonlinear dynamics becomes relevant driving the system towards turbulence. Wave turbulence is the appropriated description of this phase since matter distributions are fields instead of usual fluids. Therefore, turbulence develops due to the nonlinear interations of waves, here represented by the small inhomogeneities of the inflaton field. We present relevant aspects of wave turbulence such as the Kolmogorov-Zakharov spectrum in frequency and wave number domains that indicates that there are a transfer of energy through scales. From the power spectrum of the matter energy density we were able to estimate the temperature of the thermalized system.

José A. Crespo; H. P. de Oliveira

2014-06-04T23:59:59.000Z

17

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

2010-06-05T23:59:59.000Z

18

TURBULENT FRBRNNING MVK 130 Turbulent Combustion  

E-Print Network [OSTI]

TURBULENT F�RBR�NNING MVK 130 Turbulent Combustion Antal poäng: 3.0. Valfri för: M4. Kursansvarig program med hänsyn till de modeller som används. Litteratur S.R. Turns: An introduction to combustion, Mc

19

Quantum Gravity and Turbulence  

E-Print Network [OSTI]

We apply recent advances in quantum gravity to the problem of turbulence. Adopting the AdS/CFT approach we propose a string theory of turbulence that explains the Kolmogorov scaling in 3+1 dimensions and the Kraichnan and Kolmogorov scalings in 2+1 dimensions. In the gravitational context, turbulence is intimately related to the properties of spacetime, or quantum, foam.

Vishnu Jejjala; Djordje Minic; Y. Jack Ng; Chia-Hsiung Tze

2010-05-18T23:59:59.000Z

20

Modeling Compressed Turbulence  

SciTech Connect (OSTI)

From ICE to ICF, the effect of mean compression or expansion is important for predicting the state of the turbulence. When developing combustion models, we would like to know the mix state of the reacting species. This involves density and concentration fluctuations. To date, research has focused on the effect of compression on the turbulent kinetic energy. The current work provides constraints to help development and calibration for models of species mixing effects in compressed turbulence. The Cambon, et al., re-scaling has been extended to buoyancy driven turbulence, including the fluctuating density, concentration, and temperature equations. The new scalings give us helpful constraints for developing and validating RANS turbulence models.

Israel, Daniel M. [Los Alamos National Laboratory

2012-07-13T23:59:59.000Z

Note: This page contains sample records for the topic "rangepsi 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

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

22

On Challenges for Hypersonic Turbulent Simulations  

SciTech Connect (OSTI)

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

23

Interaction of turbulent plasma flow with a hypersonic shock wave  

SciTech Connect (OSTI)

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

24

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

25

Turbulence intensity pulse propagation with self-consistent nonlinear noise  

SciTech Connect (OSTI)

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

26

Ris-R-1188(EN) Turbulence and turbulence-  

E-Print Network [OSTI]

Risø-R-1188(EN) Turbulence and turbulence- generated structural loading in wind turbine clusters to ensure sufficient structural sustainability of the wind turbines exposed to "wind farm flow turbulence intensity inside the wind farm and direct-wake turbulence intensity are being devised and a method

27

Four Lectures on Turbulent Combustion  

E-Print Network [OSTI]

Four Lectures on Turbulent Combustion N. Peters Institut f¨ur Technische Mechanik RWTH Aachen Turbulent Combustion: Introduction and Overview 1 1.1 Moment Methods in Modeling Turbulence with Combustion and Velocity Scales . . . . . . . . . . . 11 1.4 Regimes in Premixed Turbulent Combustion

Peters, Norbert

28

Turbulent transport of energetic ions  

SciTech Connect (OSTI)

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

29

PERPENDICULAR ION HEATING BY REDUCED MAGNETOHYDRODYNAMIC TURBULENCE  

SciTech Connect (OSTI)

Recent theoretical studies argue that the rate of stochastic ion heating in low-frequency Alfvén-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 Alfvén 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

30

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

31

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

32

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

SciTech Connect (OSTI)

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

33

Inertial range turbulence in kinetic plasmas  

E-Print Network [OSTI]

The transfer of turbulent energy through an inertial range from the driving scale to dissipative scales in a kinetic plasma followed by the conversion of this energy into heat is a fundamental plasma physics process. A theoretical foundation for the study of this process is constructed, but the details of the kinetic cascade are not well understood. Several important properties are identified: (a) the conservation of a generalized energy by the cascade; (b) the need for collisions to increase entropy and realize irreversible plasma heating; and (c) the key role played by the entropy cascade--a dual cascade of energy to small scales in both physical and velocity space--to convert ultimately the turbulent energy into heat. A strategy for nonlinear numerical simulations of kinetic turbulence is outlined. Initial numerical results are consistent with the operation of the entropy cascade. Inertial range turbulence arises in a broad range of space and astrophysical plasmas and may play an important role in the thermalization of fusion energy in burning plasmas.

G. G. Howes

2007-11-27T23:59:59.000Z

34

Generation of Geodesic Acoustic Modes in ITG turbulence  

SciTech Connect (OSTI)

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

35

Direct Numerical Simulations of Interfacial Turbulence at Low Froude and Weber Numbers  

E-Print Network [OSTI]

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2.1 Thermal signature of ocean surface and related subsurface dynamics 3 1.2.2 Surfactant effects on ocean surface . . . . . . . . . . . . . . . . . 5 1.2.3 Gas transfer and active thermography on turbulent buoyant con- vection... and investigation of passive scalar beneath the surfactant contaminated free surface. 6 1.2.3 Gas transfer and active thermography on turbulent buoyant convection One of the objectives of the IR thermal signature and subsurface dynamics study is to unveil...

Zhang, Qi

2014-05-22T23:59:59.000Z

36

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

37

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

38

Solar wind versus magnetosheath turbulence.  

E-Print Network [OSTI]

order statistics (Number of data points ~ 105) 22 4 !" !" = # # # $ $ b b F ! ! " ! # )()( tbtb bSolar wind versus magnetosheath turbulence. Observations of Alfven vortices. O. Alexandrova A properties of turbulence (hydrodynamics) is independent on the energy injection & dissipation energy

Demoulin, Pascal

39

Strong Imbalanced Turbulence  

E-Print Network [OSTI]

We consider stationary, forced, imbalanced, or cross-helical MHD Alfvenic turbulence where the waves traveling in one direction have higher amplitudes than the opposite waves. This paper is dedicated to so-called strong turbulence, which cannot be treated perturbatively. Our main result is that the anisotropy of the weak waves is stronger than the anisotropy of a strong waves. We propose that critical balance, which was originally conceived as a causality argument, has to be amended by what we call a propagation argument. This revised formulation of critical balance is able to handle the imbalanced case and reduces to old formulation in the balanced case. We also provide phenomenological model of energy cascading and discuss possibility of self-similar solutions in a realistic setup of driven turbulence.

A. Beresnyak; A. Lazarian

2008-07-07T23:59:59.000Z

40

Wave turbulent statistics in non-weak wave turbulence  

E-Print Network [OSTI]

In wave turbulence, it has been believed that statistical properties are well described by the weak turbulence theory, in which nonlinear interactions among wavenumbers are assumed to be small. In the weak turbulence theory, separation of linear and nonlinear time scales derived from the weak nonlinearity is also assumed. However, the separation of the time scales is often violated even in weak turbulent systems where the nonlinear interactions are actually weak. To get rid of this inconsistency, closed equations are derived without assuming the separation of the time scales in accordance with Direct-Interaction Approximation (DIA), which has been successfully applied to Navier--Stokes turbulence. The kinetic equation of the weak turbulence theory is recovered from the DIA equations if the weak nonlinearity is assumed as an additional assumption. It suggests that the DIA equations is a natural extension of the conventional kinetic equation to not-necessarily-weak wave turbulence.

Naoto Yokoyama

2011-05-08T23:59:59.000Z

Note: This page contains sample records for the topic "rangepsi 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

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

42

Turbulent Combustion Luc Vervisch  

E-Print Network [OSTI]

;19 "Perfect" combustion modes: Fuel + Oxidizer () Products Engines, gas turbines... Laboratory experiment1 Turbulent Combustion Modeling Luc Vervisch INSA de Rouen, IUF, CORIA-CNRS Quelques problèmes rencontrés en chimie numérique : Hydrologie - Combustion - Atmosphère 16 décembre, INRIA Rocquencourt #12

Kern, Michel

43

Dissipation in Turbulent Plasma due to Reconnection in Thin Current Sheets David Sundkvist,1,* Alessandro Retino`,2  

E-Print Network [OSTI]

to kinetic and thermal particle energies. In this Letter we use space plasma as a turbulence laboratory the strongly turbulent solar wind down- stream of Earth's bow shock, the so-called magnetosheath (magnetic field), and CIS (ions) experiments [17]. At 09:35 UT the spacecraft crossed the bow shock

California at Berkeley, University of

44

Turbulent Reconnection and Its Implications  

E-Print Network [OSTI]

Magnetic reconnection is a process of magnetic field topology change, which is one of the most fundamental processes in magnetized plasmas. In most astrophysical environments the Reynolds numbers are large and therefore the transition to turbulence is inevitable. This turbulence must be taken into account for any theory of magnetic reconnection, since the initially laminar configurations can transit to the turbulence state, what is demonstrated by 3D high resolution numerical simulations. We discuss ideas of how turbulence can modify reconnection with the focus on the Lazarian & Vishniac (1999) reconnection model and present numerical evidence supporting the model and demonstrate that it is closely connected to the concept of Richardson diffusion and compatible with the Lagrangian dynamics of magnetized fluids. We point out that the Generalized Ohm's Law, that accounts for turbulent motion, predicts the subdominance of the microphysical plasma effects for a realistically turbulent media. We show that on o...

Lazarian, Alex; Vishniac, Ethan T; Kowal, Grzegorz

2015-01-01T23:59:59.000Z

45

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

46

Turbulence in Atomic Hydrogen  

E-Print Network [OSTI]

Understanding the properties of interstellar turbulence is a great intellectual challenge and the urge to solve this problem is partially motivated by a necessity to explain the star formation mystery. This review deals with a recently suggested inversion technique as applied to atomic hydrogen. This technique allows to determine 3D turbulence statistics through the variations of 21 cm intensity. We claim that a radio interferometer is an ideal tool for such a study as its visibility function is directly related to the statistics of galactic HI. Next, we show how galactic rotation curve can be used to study the turbulence slice by slice and relate the statistics given in galactic coordinates and in the velocity space. The application of the technique to HI data reveals a shallow spectrum of the underlying HI density that is not compatible with a naive Kolmogorov picture. We show that the random density corresponding to the found spectrum tends to form low contrast filaments that are elongated towards the observer.

A. Lazarian

1998-04-02T23:59:59.000Z

47

Protostellar outflow-driven turbulence  

E-Print Network [OSTI]

Protostellar outflows crisscross the regions of star cluster formation, stirring turbulence and altering the evolution of the forming cluster. We model the stirring of turbulent motions by protostellar outflows, building on an observation that the scaling law of supersonic turbulence implies a momentum cascade analogous to the energy cascade in Kolmogorov turbulence. We then generalize this model to account for a diversity of outflow strengths, and for outflow collimation, both of which enhance turbulence. For a single value of its coupling coefficient the model is consistent with turbulence simulations by Li & Nakamura and, plausibly, with observations of the NGC 1333 cluster-forming region. Outflow-driven turbulence is strong enough to stall collapse in cluster-forming regions for several crossing times, relieving the mismatch between star formation and turbulent decay rates. The predicted line-width-size scaling implies radial density indices between -1 and -2 for regions supported by outflow-driven turbulence, with a tendency for steeper profiles in regions that are more massive or have higher column densities.

Christopher D. Matzner

2007-01-01T23:59:59.000Z

48

Supercomputers Capture Turbulence in the Solar Wind  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (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...

49

Advanced Computational Methods for Turbulence and Combustion...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Advanced Computational Methods for Turbulence and Combustion Advanced Computational Methods for Turbulence and Combustion Bell.png Key Challenges: Development and application of...

50

Simulation of lean premixed turbulent combustion  

E-Print Network [OSTI]

turbulent methane combustion. Proc. Combust. Inst. , 29:in premixed turbulent combustion. Proc. Combust. Inst. ,for zero Mach number combustion. Combust. Sci. Technol. ,

2008-01-01T23:59:59.000Z

51

Simple Models for Turbulent Self-Regulation in Galaxy Disks  

E-Print Network [OSTI]

We propose that turbulent heating, wave pressure and gas exchanges between different regions of disks play a dominant role in determining the preferred, quasi-equilibrium, self-similar states of gas disks on large-scales. We present simple families of analytic, thermohydrodynamic models for these global states, which include terms for turbulent pressure and Reynolds stresses. Star formation rates, phase balances, and hydrodynamic forces are all tightly coupled and balanced. The models have stratified radial flows, with the cold gas slowly flowing inward in the midplane of the disk, and with the warm/hot phases that surround the midplane flowing outward. The models suggest a number of results that are in accord with observation, as well as some novel predictions, including the following. 1) The large-scale gas density and thermal phase distributions in galaxy disks can be explained as the result of turbulent heating and spatial couplings. 2) The turbulent pressures and stresses that drive radial outflows in the warm gas also allow a reduced circular velocity there. This effect was observed by Swaters, Sancisi and van der Hulst in NGC 891, a particularly turbulent edge-on disk. The models predict that the effect should be universal in such disks. 3) They suggest that a star formation rate like the phenomenological Schmidt Law is the natural result of global thermohydrodynamical balance, and may not obtain in disks far from equilibrium. (Abridged)

Curtis Struck; Daniel C. Smith

1999-07-29T23:59:59.000Z

52

Advances in compressible turbulent mixing  

SciTech Connect (OSTI)

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

53

Observations of Edge Turbulence  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr MayAtmosphericNuclear Security Administration the ContributionsArmsSpeedingSpeedingUnder Well-ControlledObservation ofofEdge Turbulence

54

Radiosonde measurements of turbulence  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr MayAtmosphericNuclear Security Administration the1 -the Mid-Infrared at 278, 298, and 323Program2 RadiometerTurbulence detection on

55

Turbulence Effects at Small Scales  

E-Print Network [OSTI]

It is most natural to assume that mysterious Small Ionized and Neutral Structures (SINS) indiffuse ISM arise from turbulence. There are two obvious problem with such an explanation, however. First of all, it is generally believed that at the small scales turbulence should be damped. Second, turbulence with Kolmogorov spectrum cannot be the responsible for the SINS. We consider, however, effects, that provide spectral index flatter than the Kolmogorov one and allow action at very small scales. These are the shocks that arise in high Mach number turbulence and transfer of energy to small scales by instabilities in cosmic rays. Our examples indicate that the origin of SINS may be discovered through systematic studies of astrophysical turbulence.

A. Beresnyak; A. Lazarian

2006-10-26T23:59:59.000Z

56

Thermal Fluids  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Thermal Fluids The Thermal Fluids and Heat Transfer program works on thermal hydraulic reactor safety code development and experimental heat transferthermal hydraulics. The...

57

SPH compressible turbulence  

E-Print Network [OSTI]

In this paper an SPH version of the alpha turbulence model devised by Holm and his colleagues is formulated for compressible flow with a resolution that varies in space and time. The alpha model involves two velocity fields. One velocity field is obtained from the momentum equation, the other by averaging this velocity field as in the version of SPH called XSPH. The particles (fluid elements) are moved with the averaged velocity. In analogy to the continuum alpha model we obtain a particle Lagrangian from which the SPH alpha equations can be derived. The system satisfies a discrete Kelvin circulation theorem identical to that obtained with no velocity averaging. In addition, the energy, linear and angular momentum are conserved. We show that the continuum equivalent of the SPH equations are identical to the continuum alpha model, and we conjecture that they will have the same desirable features of the continuum modelincluding the reduction of energy in the high wave number modes even when the dissipation is zero. Regardless of issues concerning turbulence modelling, the SPH alpha model is a powerful extension of the XSPH algorithm which reduces disorder at short length scales and retains the constants of the motion. The SPH alpha model is simple to implement.

J. J. Monaghan

2002-04-08T23:59:59.000Z

58

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

59

Wave Decay in MHD Turbulence  

E-Print Network [OSTI]

We present a model for nonlinear decay of the weak wave in three-dimensional incompressible magnetohydrodynamic (MHD) turbulence. We show that the decay rate is different for parallel and perpendicular waves. We provide a general formula for arbitrarily directed waves and discuss particular limiting cases known in the literature. We test our predictions with direct numerical simulations of wave decay in three-dimensional MHD turbulence, and discuss the influence of turbulent damping on the development of linear instabilities in the interstellar medium and on other important astrophysical processes.

Andrey Beresnyak; Alex Lazarian

2008-05-06T23:59:59.000Z

60

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 "rangepsi 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

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

62

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

63

Preprints, 15th Symposium on Boundary Layers and Turbulence, 15-19 July, Wageningen, The Netherlands, 133-136.  

E-Print Network [OSTI]

shown that the ABL has a complicated structure involving generally quasi-persistent, thermal. These sensors were chosen to obtain observations of the thermal, kinematic and turbulent structure in the lowest beams. The wind profiler was deployed on the bow of the Oden during the entire cruise. It provided

Persson, Ola

64

Improving simulations of the upper ocean by inclusion of surface waves in the MellorYamada turbulence scheme  

E-Print Network [OSTI]

mixing. Surface waves can enhance turbulence kinetic energy and mixing of the upper ocean via wave interaction on the MellorYamada scheme and upper ocean thermal structure are examined and compared with each scheme. The behaviors of the MellorYamada scheme, as well as the simulated upper ocean thermal structure

Ezer,Tal

65

Introduction to statistical turbulence modelling. Overview, RWTH Aachen, 08./09.03.2010 Introduction to statistical turbulence modelling  

E-Print Network [OSTI]

transfer of ­ Momentum Turbulent (Reynolds) stresses ­ Heat Turbulent heat flux ­ Mass Turbulent: Fundamental equations · Averaging · Flow equations · Turbulence equations Part II: Characteristics, RWTH Aachen, 08.03.2010 Reynolds' experiment: Inject dye into pipe flow Observe filament at different

66

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

67

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

68

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

69

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

70

Effects of turbulent diffusion on the chemistry of diffuse clouds  

E-Print Network [OSTI]

Aims. We probe the effect of turbulent diffusion on the chemistry at the interface between a cold neutral medium (CNM) cloudlet and the warm neutral medium (WNM). Methods. We perform moving grid, multifluid, 1D, hydrodynamical simulations with chemistry including thermal and chemical diffusion. The diffusion coefficients are enhanced to account for turbulent diffusion. We post-process the steady-states of our simulations with a crude model of radiative transfer to compute line profiles. Results. Turbulent diffusion spreads out the transition region between the CNM and the WNM. We find that the CNM slightly expands and heats up: its CH and H$_2$ content decreases due to the lower density. The change of physical conditions and diffusive transport increase the H$^+$ content in the CNM which results in increased OH and H$_2$O. Diffusion transports some CO out of the CNM. It also brings H$_2$ into contact with the warm gas with enhanced production of CH$^+$, H$_3^+$, OH and H$_2$O at the interface. O lines are sensitive to the spread of the thermal profile in the intermediate region between the CNM and the WNM. Enhanced molecular content at the interface of the cloud broadens the molecular line profiles and helps exciting transitions of intermediate energy. The relative molecular yield are found higher for bigger clouds. Conclusions. Turbulent diffusion can be the source of additional molecular production and should be included in chemical models of the interstellar medium (ISM). It also is a good candidate for the interpretation of observational problems such as warm H$_2$, CH$^+$ formation and presence of H$_3^+$.

P. Lesaffre; M. Gerin; P. Hennebelle

2007-04-24T23:59:59.000Z

71

Turbulence and Magnetic Fields in Clouds  

E-Print Network [OSTI]

We discuss several categories of models which may explain the IMF, including the possible role of turbulence and magnetic fields.

Shantanu Basu

2004-11-15T23:59:59.000Z

72

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

73

Thermal-hydraulic analysis of cross-shaped spiral fuel in high power density BWRs  

E-Print Network [OSTI]

Preliminary analysis of the cross-shaped spiral (CSS) fuel assembly suggests great thermal-hydraulic upside. According to computational models, the increase in rod surface area, combined with an increase in coolant turbulence ...

Conboy, Thomas M

2007-01-01T23:59:59.000Z

74

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

75

Numerical Study of a Turbulent Hydraulic Jump  

E-Print Network [OSTI]

Numerical Study of a Turbulent Hydraulic Jump Qun Zhao, Shubhra Misra, Ib. A. Svendsen and James T of a Turbulent Hydraulic Jump ­ p.1/14 #12;Objective Our ultimate goal is to study the breaking waves. Numerical Study of a Turbulent Hydraulic Jump ­ p.2/14 #12;A moving bore Qiantang Bore China (Courtesy of Dr J

Zhao, Qun

76

Stability, Energetics, and Turbulent Transport in  

E-Print Network [OSTI]

fields" Department of Astrophysical Sciences Spring Colloquium Steve Cowley (UK Atomic Energy Authority of solar-wind turbulence" Chris Chen (UC Berkeley) 2:40pm "Energy spectra in MHD turbulenceStability, Energetics, and Turbulent Transport in Astrophysical, Fusion, and Solar Plasmas 8

Torquato, Salvatore

77

Turbulence transport with nonlocal interactions  

SciTech Connect (OSTI)

This preliminary report describes a variety of issues in turbulence transport analysis with particular emphasis on closure procedures that are nonlocal in wave-number and/or physical space. Anomalous behavior of the transport equations for large scale parts of the turbulence spectrum are resolved by including the physical space nonlocal interactions. Direct and reverse cascade processes in wave-number space are given a much richer potential for realistic description by the nonlocal formulations. The discussion also describes issues, many still not resolved, regarding new classes of self-similar form functions.

Linn, R.R.; Clark, T.T.; Harlow, F.H.; Turner, L.

1998-03-01T23:59:59.000Z

78

Perpendicular ion acceleration in whistler turbulence  

SciTech Connect (OSTI)

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

79

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

SciTech Connect (OSTI)

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

80

Hydrodynamical simulations of the decay of high-speed molecular turbulence. I. Dense molecular regions  

E-Print Network [OSTI]

We present the results from three dimensional hydrodynamical simulations of decaying high-speed turbulence in dense molecular clouds. We compare our results, which include a detailed cooling function, molecular hydrogen chemistry and a limited C and O chemistry, to those previously obtained for decaying isothermal turbulence. After an initial phase of shock formation, power-law decay regimes are uncovered, as in the isothermal case. We find that the turbulence decays faster than in the isothermal case because the average Mach number remains higher, due to the radiative cooling. The total thermal energy, initially raised by the introduction of turbulence, decays only a little slower than the kinetic energy. We discover that molecule reformation, as the fast turbulence decays, is several times faster than that predicted for a non-turbulent medium. This is caused by moderate speed shocks which sweep through a large fraction of the volume, compressing the gas and dust. Through reformation, the molecular density and molecular column appear as complex patterns of filaments, clumps and some diffuse structure. In contrast, the molecular fraction has a wider distribution of highly distorted clumps and copious diffuse structure, so that density and molecular density are almost identically distributed during the reformation phase. We conclude that molecules form in swept-up clumps but effectively mix throughout via subsequent expansions and compressions.

Georgi Pavlovski; Michael D. Smith; Mordecai-Mark Mac Low; Alexander Rosen

2002-08-15T23:59:59.000Z

Note: This page contains sample records for the topic "rangepsi 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

Inclusion of turbulence in solar modeling  

E-Print Network [OSTI]

The general consensus is that in order to reproduce the observed solar p-mode oscillation frequencies, turbulence should be included in solar models. However, until now there has not been any well-tested efficient method to incorporate turbulence into solar modeling. We present here two methods to include turbulence in solar modeling within the framework of the mixing length theory, using the turbulent velocity obtained from numerical simulations of the highly superadiabatic layer of the sun at three stages of its evolution. The first approach is to include the turbulent pressure alone, and the second is to include both the turbulent pressure and the turbulent kinetic energy. The latter is achieved by introducing two variables: the turbulent kinetic energy per unit mass, and the effective ratio of specific heats due to the turbulent perturbation. These are treated as additions to the standard thermodynamic coordinates (e.g. pressure and temperature). We investigate the effects of both treatments of turbulence on the structure variables, the adiabatic sound speed, the structure of the highly superadiabatic layer, and the p-mode frequencies. We find that the second method reproduces the SAL structure obtained in 3D simulations, and produces a p-mode frequency correction an order of magnitude better than the first method.

L. H. Li; F. J. Robinson; P. Demarque; S. Sofia; D. B. Guenther

2001-11-07T23:59:59.000Z

82

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

83

Transport enhancement and suppression in turbulent magnetic reconnection: A self-consistent turbulence model  

SciTech Connect (OSTI)

Through the enhancement of transport, turbulence is expected to contribute to the fast reconnection. However, the effects of turbulence are not so straightforward. In addition to the enhancement of transport, turbulence under some environment shows effects that suppress the transport. In the presence of turbulent cross helicity, such dynamic balance between the transport enhancement and suppression occurs. As this result of dynamic balance, the region of effective enhanced magnetic diffusivity is confined to a narrow region, leading to the fast reconnection. In order to confirm this idea, a self-consistent turbulence model for the magnetic reconnection is proposed. With the aid of numerical simulations where turbulence effects are incorporated in a consistent manner through the turbulence model, the dynamic balance in the turbulence magnetic reconnection is confirmed.

Yokoi, N. [Institute of Industrial Science, University of Tokyo, Tokyo (Japan)] [Institute of Industrial Science, University of Tokyo, Tokyo (Japan); Higashimori, K.; Hoshino, M. [Department of Earth and Planetary Science, University of Tokyo, Tokyo (Japan)] [Department of Earth and Planetary Science, University of Tokyo, Tokyo (Japan)

2013-12-15T23:59:59.000Z

84

Entropy Generation In The Viscous Layer Of A Turbulent Channel Flow  

SciTech Connect (OSTI)

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

85

Mimicking a turbulent signal: sequential multiaffine processes  

E-Print Network [OSTI]

An efficient method for the construction of a multiaffine process, with prescribed scaling exponents, is presented. At variance with the previous proposals, this method is sequential and therefore it is the natural candidate in numerical computations involving synthetic turbulence. The application to the realization of a realistic turbulent-like signal is discussed in detail. The method represents a first step towards the realization of a realistic spatio-temporal turbulent field.

L. Biferale; G. Boffetta; A. Celani; A. Crisanti; A. Vulpiani

1997-11-03T23:59:59.000Z

86

Two techniques for forecasting clear air turbulence  

E-Print Network [OSTI]

for the height of the 200- and )00-mb pressure surfaces associated with nonturbulent and turbulent cases . . . . . . o. . . . . o o ~ o ~ . ~ . 17 4. Empirical frequency distributions for the temperature of the 200- and 300-mb pressure surfaces associated... with nonturbulent and turbulent areas. . . . . . ~ . . . . . ~ . ~ ~ Empirical frequency distributions of the zonal wind component on the 200- and 300-mb press- ure surfaces associated with nonturbulent and turbulent areas . . . . . . . . . . . . ~ ~ 20...

Arbeiter, Randolph George

2012-06-07T23:59:59.000Z

87

Effect of Turbulence Fluctuations on Surface Heating Rate in Hypersonic Turbulent  

E-Print Network [OSTI]

Effect of Turbulence Fluctuations on Surface Heating Rate in Hypersonic Turbulent Boundary Layers) of reacting hypersonic turbulent boundary layers at conditions typical of reen- try vehicles. Surface heat in designing hypersonic vehicles is to predict aerothermo- dynamic heating. When the boundary layer

Martín, Pino

88

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

89

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

90

Effects of radiation on NO kinetics in turbulent hydrogen/air diffusion flames  

SciTech Connect (OSTI)

The authors describe a coupled radiation and NO kinetics calculation of turbulent hydrogen/air diffusion flame properties. Transport equations for mass, momentum, mixture fraction, enthalpy (sensible + chemical) including gas band radiation, and NO mass fraction are solved. NO kinetics is described by a one step thermal production mechanism. The local temperature is obtained by solving the enthalpy equation taking radiation loss from H{sub 2}O into consideration. Radiation/turbulence and chemical kinetics/turbulence interactions are treated using a clipped Gaussian probability density function (PDF) for the mixture fraction, and a delta PDF for the enthalpy. The source terms in the enthalpy and mass fraction of NO equations are treated using assumed PDF integration over the mixture fraction space. The results of the simulation are compared with existing measurements of the Emission Indices of NO (EINO) in turbulent H{sub 2}/air diffusion flames. The major conclusion of the paper is that coupled turbulence/radiation interactions should be taken into account while computing the EINO.

Sivathanu, Y.R.; Gore, J.P.; Laurendeau, N.M.

1997-07-01T23:59:59.000Z

91

Department of Chemical Engineering Thermal and Flow Engineering Laboratory  

E-Print Network [OSTI]

Aug.2013 Department of Chemical Engineering Thermal and Flow Engineering Laboratory Ron Zevenhoven.1 Fluid statics 6.2 Fluid dynamics: viscosity, laminar / turbulent flow, boundary layer 6.3 Fluid dynamics: internal flows / tube flows 6.4 Fluid dynamics: pressure drop & energy dissipation in tube systems 6.5 Flow

Zevenhoven, Ron

92

Department of Chemical Engineering Thermal and Flow Engineering Laboratory  

E-Print Network [OSTI]

August 12 Department of Chemical Engineering Thermal and Flow Engineering Laboratory Ron Zevenhoven.1 Fluid statics 6.2 Fluid dynamics: viscosity, laminar / turbulent flow, boundary layer 6.3 Fluid dynamics: internal flows / tube flows 6.4 Fluid dynamics: pressure drop & energy dissipation in tube systems 6.5 Flow

Zevenhoven, Ron

93

Stochastic superparameterization in quasigeostrophic turbulence  

SciTech Connect (OSTI)

In this article we expand and develop the authors' recent proposed methodology for efficient stochastic superparameterization algorithms for geophysical turbulence. Geophysical turbulence is characterized by significant intermittent cascades of energy from the unresolved to the resolved scales resulting in complex patterns of waves, jets, and vortices. Conventional superparameterization simulates large scale dynamics on a coarse grid in a physical domain, and couples these dynamics to high-resolution simulations on periodic domains embedded in the coarse grid. Stochastic superparameterization replaces the nonlinear, deterministic eddy equations on periodic embedded domains by quasilinear stochastic approximations on formally infinite embedded domains. The result is a seamless algorithm which never uses a small scale grid and is far cheaper than conventional SP, but with significant success in difficult test problems. Various design choices in the algorithm are investigated in detail here, including decoupling the timescale of evolution on the embedded domains from the length of the time step used on the coarse grid, and sensitivity to certain assumed properties of the eddies (e.g. the shape of the assumed eddy energy spectrum). We present four closures based on stochastic superparameterization which elucidate the properties of the underlying framework: a ‘null hypothesis’ stochastic closure that uncouples the eddies from the mean, a stochastic closure with nonlinearly coupled eddies and mean, a nonlinear deterministic closure, and a stochastic closure based on energy conservation. The different algorithms are compared and contrasted on a stringent test suite for quasigeostrophic turbulence involving two-layer dynamics on a ?-plane forced by an imposed background shear. The success of the algorithms developed here suggests that they may be fruitfully applied to more realistic situations. They are expected to be particularly useful in providing accurate and efficient stochastic parameterizations for use in ensemble-based state estimation and prediction.

Grooms, Ian, E-mail: grooms@cims.nyu.edu [Center for Atmosphere Ocean Science, Courant Institute of Mathematical Sciences, New York University, 251 Mercer St., New York, NY 10012 (United States); Majda, Andrew J., E-mail: jonjon@cims.nyu.edu [Center for Atmosphere Ocean Science, Courant Institute of Mathematical Sciences, New York University, 251 Mercer St., New York, NY 10012 (United States); Center for Prototype Climate Modelling, NYU-Abu Dhabi (United Arab Emirates)

2014-08-15T23:59:59.000Z

94

Stochastic models for turbulent reacting flows  

SciTech Connect (OSTI)

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

95

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

96

Electric field statistics in MHD turbulence  

E-Print Network [OSTI]

Electric field statistics in MHD turbulence Bernard Knaepen, Nicolas Denewet & Daniele Carati, ULB #12;Electric field statistics in MHD turbulence Outline Electric field in MHD? Particle acceleration Statistics of the electric & magnetic fields #12;Outline Electric field in MHD? Particle acceleration

Low, Robert

97

Cyclone separator having boundary layer turbulence control  

DOE Patents [OSTI]

A cyclone separator including boundary layer turbulence control that is operable to prevent undue build-up of particulate material at selected critical areas on the separator walls, by selectively varying the fluid pressure at those areas to maintain the momentum of the vortex, thereby preventing particulate material from inducing turbulence in the boundary layer of the vortical fluid flow through the separator.

Krishna, Coimbatore R. (Mt. Sinai, NY); Milau, Julius S. (Port Jefferson, NY)

1985-01-01T23:59:59.000Z

98

Fifteen Lectures on Laminar and Turbulent Combustion  

E-Print Network [OSTI]

Fifteen Lectures on Laminar and Turbulent Combustion N. Peters RWTH Aachen Ercoftac Summer School in Combustion Systems 1 Lecture 2: Calculation of Adiabatic Flame Temperatures and Chemical Equilibria 20: Laminar Diffusion Flames: Different Flow Geometries 156 Lecture 11: Turbulent Combustion: Introduction

Peters, Norbert

99

Great Plains Turbulence Environment: Its Origins, Impact, and Simulation  

SciTech Connect (OSTI)

This paper summarizes the known impacts of nocturnal turbulence on wind turbine performance and operations.

Kelley, N. D.; Jonkman, B. J.; Scott, G. N.

2006-12-01T23:59:59.000Z

100

Turbulence-chemistry interactions in reacting flows  

SciTech Connect (OSTI)

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

Note: This page contains sample records for the topic "rangepsi 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

Free Energy Cascade in Gyrokinetic Turbulence  

SciTech Connect (OSTI)

In gyrokinetic theory, the quadratic nonlinearity is known to play an important role in the dynamics by redistributing (in a conservative fashion) the free energy between the various active scales. In the present study, the free energy transfer is analyzed for the case of ion temperature gradient driven turbulence. It is shown that it shares many properties with the energy transfer in fluid turbulence. In particular, one finds a (strongly) local, forward (from large to small scales) cascade of free energy in the plane perpendicular to the background magnetic field. These findings shed light on some fundamental properties of plasma turbulence, and encourage the development of large-eddy-simulation techniques for gyrokinetics.

Banon Navarro, A.; Morel, P.; Albrecht-Marc, M.; Carati, D. [Universite Libre de Bruxelles, Faculte des Sciences, Physique Statistique et Plasmas CP 231, EURATOM Association, Campus Plaine, 1050 Brussels (Belgium); Merz, F.; Goerler, T.; Jenko, F. [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, 85748 Garching (Germany)

2011-02-04T23:59:59.000Z

102

TIDAL TURBULENCE SPECTRA FROM A COMPLIANT MOORING  

SciTech Connect (OSTI)

A compliant mooring to collect high frequency turbulence data at a tidal energy site is evaluated in a series of short demon- stration deployments. The Tidal Turbulence Mooring (TTM) improves upon recent bottom-mounted approaches by suspend- ing Acoustic Doppler Velocimeters (ADVs) at mid-water depths (which are more relevant to tidal turbines). The ADV turbulence data are superior to Acoustic Doppler Current Profiler (ADCP) data, but are subject to motion contamination when suspended on a mooring in strong currents. In this demonstration, passive stabilization is shown to be sufficient for acquiring bulk statistics of the turbulence, without motion correction. With motion cor- rection (post-processing), data quality is further improved; the relative merits of direct and spectral motion correction are dis- cussed.

Thomson, Jim; Kilcher, Levi; Richmond, Marshall C.; Talbert, Joe; deKlerk, Alex; Polagye, Brian; Guerra, Maricarmen; Cienfuegos, Rodrigo

2013-06-13T23:59:59.000Z

103

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

104

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

105

Turbulence in Astrophysical and Laboratory Plasmas  

E-Print Network [OSTI]

MIPSE, Univ of Michigan September 15, 2010 #12;Contributing Colleagues Steve Cowley (UKAEA & Imperial-principles modeling · Identification of Alfvenic solar wind turbulence · Conclusion #12;Kinetic theory when (or ) f

Shyy, Wei

106

Direct numerical simulation of turbulent reacting flows  

SciTech Connect (OSTI)

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

107

Phenomenology of turbulent dynamo growth and saturation  

E-Print Network [OSTI]

With a non local shell model of magnetohydrodynamic turbulence we investigate numerically the turbulent dynamo action for low and high magnetic Prandtl numbers ($Pm$). The results obtained in the kinematic regime and along the way to dynamo saturation are understood in terms of a phenomenological approach based on the local ($Pm\\ll 1$) or non local ($Pm\\gg 1$) nature of the energy transfers. In both cases the magnetic energy grows at small scale and saturates as an inverse `` cascade ''.

Rodion Stepanov; Franck Plunian

2007-11-08T23:59:59.000Z

108

Reaction and diffusion in turbulent combustion  

SciTech Connect (OSTI)

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

109

New perspectives on superparameterization for geophysical turbulence  

SciTech Connect (OSTI)

This is a research expository paper regarding superparameterization, a class of multi-scale numerical methods designed to cope with the intermittent multi-scale effects of inhomogeneous geophysical turbulence where energy often inverse-cascades from the unresolved scales to the large scales through the effects of waves, jets, vortices, and latent heat release from moist processes. Original as well as sparse space–time superparameterization algorithms are discussed for the important case of moist atmospheric convection including the role of multi-scale asymptotic methods in providing self-consistent constraints on superparameterization algorithms and related deterministic and stochastic multi-cloud parameterizations. Test models for the statistical numerical analysis of superparameterization algorithms are discussed both to elucidate the performance of the basic algorithms and to test their potential role in efficient multi-scale data assimilation. The very recent development of grid-free seamless stochastic superparameterization methods for geophysical turbulence appropriate for “eddy-permitting” mesoscale ocean turbulence is presented here including a general formulation and illustrative applications to two-layer quasigeostrophic turbulence, and another difficult test case involving one-dimensional models of dispersive wave turbulence. This last test case has randomly generated solitons as coherent structures which collapse and radiate wave energy back to the larger scales, resulting in strong direct and inverse turbulent energy cascades.

Majda, Andrew J. [Center for Atmosphere Ocean Science, Courant Institute of Mathematical Sciences, New York University, 251 Mercer St., New York, NY 10012 (United States); Center for Prototype Climate Modelling, NYU Abu Dhabi, Abu Dhabi (United Arab Emirates); Grooms, Ian, E-mail: grooms@cims.nyu.edu [Center for Atmosphere Ocean Science, Courant Institute of Mathematical Sciences, New York University, 251 Mercer St., New York, NY 10012 (United States)

2014-08-15T23:59:59.000Z

110

Energy Conservation and Second-Order Statistics in Stably Stratified Turbulent Boundary Layers  

E-Print Network [OSTI]

We address the dynamical and statistical description of stably stratified turbulent boundary layers with the important example of the atmospheric boundary layer with a stable temperature stratification in mind. Traditional approaches to this problem, based on the profiles of mean quantities, velocity second-order correlations, and dimensional estimates of the turbulent thermal flux run into a well known difficulty, predicting the suppression of turbulence at a small critical value of the Richardson number, in contradiction with observations. Phenomenological attempts to overcome this problem suffer from various theoretical inconsistencies. Here we present an approach taking into full account all the second-order statistics, which allows us to respect the conservation of total mechanical energy. The analysis culminates in an analytic solution of the profiles of all mean quantities and all second-order correlations removing the unphysical predictions of previous theories. We propose that the approach taken here is sufficient to describe the lower parts of the atmospheric boundary layer, as long as the Richardson number does not exceed an order of unity. For much higher Richardson numbers the physics may change qualitatively, requiring careful consideration of the potential Kelvin-Helmoholtz waves and their interaction with the vortical turbulence.

Victor S. L'vov; Itamar Procaccia; Oleksii Rudenko

2007-05-01T23:59:59.000Z

111

Effects of molecular transport on turbulence-chemistry interactions in a hydrogen-argon-air jet diffusion flame  

SciTech Connect (OSTI)

A numerical simulation of entrainment, turbulent advection, molecular import and chemical kinetics in a turbulent diffusion flame is used to investigate effects of molecular transport on turbulence-chemistry interactions. A fun finite-rate chemical mechanism is used to represent the combustion of a hydrogen-argon mixture issuing into air. Results based on incorporation of differential diffusion and variable Lewis number are compared to cases with the former effect, or both-effects, suppressed. Significant impact on radical species production and on NO emission index (based on a reduced mechanism for thermal NO) is found. A reduced mechanism for hydrogen-air combustion, omitting both effects and incorporating other simplifications, performs comparably except that its NO predictions agree well with the case of full chemistry and molecular transport, possibly due to cancellation of errors.

Menon, S.; Calhoon, W.H. Jr.; Goldin, G. [Georgia Inst. of Tech., Atlanta, GA (United States). School of Aerospace Engineering; Kerstein, A.R. [Sandia National Labs., Livermore, CA (United States)

1994-01-01T23:59:59.000Z

112

Evidence of critical balance in kinetic Alfven wave turbulence simulations  

SciTech Connect (OSTI)

A numerical simulation of kinetic plasma turbulence is performed to assess the applicability of critical balance to kinetic, dissipation scale turbulence. The analysis is performed in the frequency domain to obviate complications inherent in performing a local analysis of turbulence. A theoretical model of dissipation scale critical balance is constructed and compared to simulation results, and excellent agreement is found. This result constitutes the first evidence of critical balance in a kinetic turbulence simulation and provides evidence of an anisotropic turbulence cascade extending into the dissipation range. We also perform an Eulerian frequency analysis of the simulation data and compare it to the results of a previous study of magnetohydrodynamic turbulence simulations.

TenBarge, J. M.; Howes, G. G. [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242 (United States)

2012-05-15T23:59:59.000Z

113

Magnetic Turbulence and Thermodynamics in the Inner Region of Protoplanetary Discs  

E-Print Network [OSTI]

Using radiation magnetohydrodynamics simulations with realistic opacities and equation of state, and zero net magnetic flux, we have explored thermodynamics in the inner part of protoplanetary discs where magnetic turbulence is expected. The thermal equilibrium curve consists of the upper, lower, and middle branches. The upper (lower) branch corresponds to hot (cool) and optically very (moderately) thick discs, respectively, while the middle branch is characterized by convective energy transport near the midplane. Convection is also the major energy transport process near the low surface density end of the upper branch. There, convective motion is fast with Mach numbers reaching $\\gtrsim 0.01$, and enhances both magnetic turbulence and cooling, raising the ratio of vertically-integrated shear stress to vertically-integrated pressure by a factor of several. This convectively enhanced ratio seems a robust feature in accretion discs having an ionization transition. We have also examined causes of the S-shaped th...

Hirose, Shigenobu

2015-01-01T23:59:59.000Z

114

AQUIFER THERMAL ENERGY STORAGE  

E-Print Network [OSTI]

using aquifers for thermal energy storage. Problems outlinedmatical Modeling of Thermal Energy Storage in Aquifers,"ings of Aquifer Thermal Energy Storage Workshop, Lawrence

Tsang, C.-F.

2011-01-01T23:59:59.000Z

115

AQUIFER THERMAL ENERGY STORAGE  

E-Print Network [OSTI]

aquifers for thermal energy storage. Problems outlined aboveModeling of Thermal Energy Storage in Aquifers," Proceed-ings of Aquifer Thermal Energy Storage Workshop, Lawrence

Tsang, C.-F.

2011-01-01T23:59:59.000Z

116

AQUIFER THERMAL ENERGY STORAGE  

E-Print Network [OSTI]

using aquifers for thermal energy storage. Problems outlinedmatical Modeling of Thermal Energy Storage in Aquifers,"Proceed- ings of Aquifer Thermal Energy Storage Workshop,

Tsang, C.-F.

2011-01-01T23:59:59.000Z

117

NO concentration imaging in turbulent nonpremixed flames  

SciTech Connect (OSTI)

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

118

Anisotropic turbulent model for solar coronal heating  

E-Print Network [OSTI]

Context : We present a self-consistent model of solar coronal heating, originally developed by Heyvaert & Priest (1992), in which we include the dynamical effect of the background magnetic field along a coronal structure by using exact results from wave MHD turbulence (Galtier et al. 2000). Aims : We evaluate the heating rate and the microturbulent velocity for comparison with observations in the quiet corona, active regions and also coronal holes. Methods :The coronal structures are assumed to be in a turbulent state maintained by the slow erratic motions of the magnetic footpoints. A description for the large-scale and the unresolved small-scale dynamics are given separately. From the latter, we compute exactly (or numerically for coronal holes) turbulent viscosites that are finally used in the former to close self-consistently the system and derive the heating flux expression. Results : We show that the heating rate and the turbulent velocity compare favorably with coronal observations. Conclusions : Although the Alfven wave turbulence regime is strongly anisotropic, and could reduce a priori the heating efficiency, it provides an unexpected satisfactory model of coronal heating for both magnetic loops and open magnetic field lines.

B. Bigot; S. Galtier; H. Politano

2007-12-12T23:59:59.000Z

119

Assessment of reduced mechanisms using One Dimensional Stochastic Turbulence model  

E-Print Network [OSTI]

turbulence model for a syngas jet flame. Proceeding of FallKerstein 2002), a turbulent syngas (CO/H2/NO) jet flame wasand DNS results of the syngas jet flame was recently done

Chien, Li-Chun

2010-01-01T23:59:59.000Z

120

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

Note: This page contains sample records for the topic "rangepsi 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

Biophysical coupling between turbulence, veliger behavior, and larval supply  

E-Print Network [OSTI]

The goals of this thesis were to quantify the behavior of gastropod larvae (mud snails Ilyanassa obsoleta) in turbulence, and to investigate how that behavior affects larval supply in a turbulent coastal inlet. Gastropod ...

Fuchs, Heidi L

2005-01-01T23:59:59.000Z

122

Turbulent Flow and Transport Modeling by Long Waves and Currents  

E-Print Network [OSTI]

This dissertation presents models for turbulent flow and transport by currents and long waves in large domain. From the Navier-Stokes equations, a fully nonlinear depth-integrated equation model for weakly dispersive, turbulent and rotational flow...

Kim, Dae Hong

2010-10-12T23:59:59.000Z

123

Consider Installing Turbulators on Two- and Three-Pass Firetube...  

Broader source: Energy.gov (indexed) [DOE]

tip sheet outlines the benefits of turbulators on firetube boilers as part of optimized steam systems. STEAM TIP SHEET 25 Consider Installing Turbulators on Two- and Three-Pass...

124

PDF Calculations of Turbulent Nonpremixed Flames with Local Extinction  

E-Print Network [OSTI]

, a stochastic model of turbulence frequency, the Euclidean minimum spanning tree (EMST) mixing model, and the 16

125

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

126

Physics of Stratocumulus Top (POST): turbulent mixing across capping inversion  

E-Print Network [OSTI]

vertical water potential horizontal wind, and turbulentof potential components of horizontal wind, and buoyantwater potential temperature, horizontal wind, and turbulent

2013-01-01T23:59:59.000Z

127

Wave turbulence served up on a plate  

E-Print Network [OSTI]

Wave turbulence in a thin elastic plate is experimentally investigated. By using a Fourier transform profilometry technique, the deformation field of the plate surface is measured simultaneously in time and space. This enables us to compute the wavevector-frequency Fourier ($\\mathbf k, \\omega$) spectrum of the full space-time deformation velocity. In the 3D ($\\mathbf k, \\omega$) space, we show that the energy of the motion is concentrated on a 2D surface that represents a nonlinear dispersion relation. This nonlinear dispersion relation is close to the linear dispersion relation. This validates the usual wavenumber-frequency change of variables used in many experimental studies of wave turbulence. The deviation from the linear dispersion, which increases with the input power of the forcing, is attributed to weak non linear effects. Our technique opens the way for many new extensive quantitative comparisons between theory and experiments of wave turbulence.

Pablo Cobelli; Philippe Petitjeans; Agnes Maurel; Vincent Pagneux; Nicolas Mordant

2009-10-28T23:59:59.000Z

128

Boundary Plasma Turbulence Simulations for Tokamaks  

SciTech Connect (OSTI)

The boundary plasma turbulence code BOUT models tokamak boundary-plasma turbulence in a realistic divertor geometry using modified Braginskii equations for plasma vorticity, density (ni), electron and ion temperature (T{sub e}; T{sub i}) and parallel momenta. The BOUT code solves for the plasma fluid equations in a three dimensional (3D) toroidal segment (or a toroidal wedge), including the region somewhat inside the separatrix and extending into the scrape-off layer; the private flux region is also included. In this paper, a description is given of the sophisticated physical models, innovative numerical algorithms, and modern software design used to simulate edge-plasmas in magnetic fusion energy devices. The BOUT code's unique capabilities and functionality are exemplified via simulations of the impact of plasma density on tokamak edge turbulence and blob dynamics.

Xu, X; Umansky, M; Dudson, B; Snyder, P

2008-05-15T23:59:59.000Z

129

Turbulent round jet under gravity waves  

E-Print Network [OSTI]

) Turbulent shear stress &u'w'&/&u, & versus z/x. . . 26 3-5 Overlapped mean axial velocity &u&/&u, & versus zJx of the case of A = 0. 5 cm at six locations corresponding to figure 3-4(a) . . 28 3-6 Horizontal turbulent velocity &u' &' /&u, & versus zJx... of the case of A = 0. 5 cm with z, = 0 at. the moving jet centerline in the range of (a) x/D = 40 - 95, (b) x/D = 40 ? 57, and (c) x/D = 64 - 95 . . 30 3-7 Vertical turbulent velocity &w' & /&u, & versus z Jx of the case of A = 0. 5 cm FIGURE Page with z...

Ryu, Yong Uk

2002-01-01T23:59:59.000Z

130

Spatial and Spectral evolution of Turbulence Spectra  

SciTech Connect (OSTI)

We present a general formulation of a theory of spreading of turbulence based on nonlinear mode couplings, which is inherently linked to spectral evolution. We present a derivation from simple two-field perspective based upon a gradien diffusion hypothesis, justified by a two scale direct interaction approximation (TSDIA) for weak turbulence. The complexity and anisotropy of spatial and spectral dynamics, however, limits our analysis to examination of different classes of triad interactions. We demonstrate that radially extended eddys, are the most effective structures in promoting spreading of turbulence. Thus, spectral evolution that tends towards such eddies, facilitate spatial spreading. We also show that, in a two field model, due to their respective spectral tendencies, internal energy spreads faster than kinetic energy.

Guercan, Oe. D.; Diamond, P. H. [Center for Astrophysics and Space Sciences, La Jolla, CA 92093-0424 (United States); Department of Physics University of California at San Diego, La Jolla, CA 92093-0424 (United States); Department of Physics, University of California at San Diego, La Jolla, CA 92093-0319 (United States); Hahm, T. S. [Princeton Plasma Physics Laboratory, Princeton, NJ 08543-0451 (United States)

2006-11-30T23:59:59.000Z

131

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

132

Universal equations and constants of turbulent motion  

E-Print Network [OSTI]

This paper presents a parameter-free theory of shear-generated turbulence at asymptotically high Reynolds numbers in incompressible fluids. It is based on a two-fluids concept. Both components are materially identical and inviscid. The first component is an ensemble of quasi-rigid dipole-vortex tubes as quasi-particles in chaotic motion. The second is a superfluid performing evasive motions between the tubes. The local dipole motions follow Helmholtz' law. The vortex radii scale with the energy-containing length scale. Collisions between quasi-particles lead either to annihilation (likewise rotation, turbulent dissipation) or to scattering (counterrotation, turbulent diffusion). There are analogies with birth and death processes of population dynamics and their master equations. For free homogeneous decay the theory predicts the TKE to follow 1/t. With an adiabatic condition at the wall it predicts the logarithmic law with von Karman's constant as 1/\\sqrt{2 pi} = 0.399. Likewise rotating couples form dissipat...

Baumert, Helmut Z

2012-01-01T23:59:59.000Z

133

A signature for turbulence driven magnetic islands  

SciTech Connect (OSTI)

We investigate the properties of magnetic islands arising from tearing instabilities that are driven by an interchange turbulence. We find that such islands possess a specific signature that permits an identification of their origin. We demonstrate that the persistence of a small scale turbulence maintains a mean pressure profile, whose characteristics makes it possible to discriminate between turbulence driven islands from those arising due to an unfavourable plasma current density gradient. We also find that the island poloidal turnover time, in the steady state, is independent of the levels of the interchange and tearing energy sources. Finally, we show that a mixing length approach is adequate to make theoretical predictions concerning island flattening in the island rotation frame.

Agullo, O.; Muraglia, M.; Benkadda, S. [Aix-Marseille Université, CNRS, PIIM, UMR 7345 Marseille (France); France-Japan Magnetic Fusion Laboratory, LIA 336 CNRS, Marseille (France); Poyé, A. [Univ. Bordeaux, CNRS, CEA, CELIA (Centre Lasers Intenses et Applications), UMR 5107, F-33405 Talence (France); Yagi, M. [Plasma Theory and Simulation Gr., JAEA, Rokkasho (Japan); Garbet, X. [IRFM, CEA, St-Paul-Lez-Durance 13108 (France); Sen, A. [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India)

2014-09-15T23:59:59.000Z

134

Statistical theory of turbulent incompressible multimaterial flow  

SciTech Connect (OSTI)

Interpenetrating motion of incompressible materials is considered. ''Turbulence'' is defined as any deviation from the mean motion. Accordingly a nominally stationary fluid will exhibit turbulent fluctuations due to a single, slowly moving sphere. Mean conservation equations for interpenetrating materials in arbitrary proportions are derived using an ensemble averaging procedure, beginning with the exact equations of motion. The result is a set of conservation equations for the mean mass, momentum and fluctuational kinetic energy of each material. The equation system is at first unclosed due to integral terms involving unknown one-point and two-point probability distribution functions. In the mean momentum equation, the unclosed terms are clearly identified as representing two physical processes. One is transport of momentum by multimaterial Reynolds stresses, and the other is momentum exchange due to pressure fluctuations and viscous stress at material interfaces. Closure is approached by combining careful examination of multipoint statistical correlations with the traditional physical technique of kappa-epsilon modeling for single-material turbulence. This involves representing the multimaterial Reynolds stress for each material as a turbulent viscosity times the rate of strain based on the mean velocity of that material. The multimaterial turbulent viscosity is related to the fluctuational kinetic energy kappa, and the rate of fluctuational energy dissipation epsilon, for each material. Hence a set of kappa and epsilon equations must be solved, together with mean mass and momentum conservation equations, for each material. Both kappa and the turbulent viscosities enter into the momentum exchange force. The theory is applied to (a) calculation of the drag force on a sphere fixed in a uniform flow, (b) calculation of the settling rate in a suspension and (c) calculation of velocity profiles in the pneumatic transport of solid particles in a pipe.

Kashiwa, B.

1987-10-01T23:59:59.000Z

135

Final Report - Investigation of Intermittent Turbulence and Turbulent Structures in the Presence of Controlled Sheared Flows  

SciTech Connect (OSTI)

Final Report for grant DE-FG02-06ER54898. The dynamics and generation of intermittent plasma turbulent structures, widely known as "blobs" have been studied in the presence of sheared plasma flows in a controlled laboratory experiment.

Gilmore, Mark A. [University of New Mexico

2013-06-27T23:59:59.000Z

136

Calculation of unsteady turbulent flow around obstacles using the large eddy simulation turbulence model  

E-Print Network [OSTI]

The premise of the work presented here is to use a common analytical tool, Computational Fluid Dynamics (CFD), along with a prevalent turbulence model, Large Eddy Simulation (LES), to study the flow past rectangular cylinders. In an attempt to use...

Helton, Donald McLean

2002-01-01T23:59:59.000Z

137

A turbulence model for buoyant flows based on vorticity generation.  

SciTech Connect (OSTI)

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

138

Wave Packets and Turbulent Peter Jordan1  

E-Print Network [OSTI]

Wave Packets and Turbulent Jet Noise Peter Jordan1 and Tim Colonius2 1 D´epartement Fluides-control efforts is incomplete. Wave packets are intermittent, advecting disturbances that are correlated over review evidence of the existence, energetics, dynamics, and acous- tic efficiency of wave packets. We

Dabiri, John O.

139

Comparison of anemometers for turbulence characterization  

SciTech Connect (OSTI)

During the first phase of the US Department of Energy's turbulence characterization program, important discoveries were made about the field application of propeller-vane and cup anemometers under very turbulent conditions. First, averaged speeds measured by the propeller-vane anemometer were consistently lower than those from the cup anemometer, even though both registered virtually the same during wind-tunnel calibration testing. Second, the propeller-vane anemometers suffered from structural failures much more frequently than the cup anemometers. The difficulties associated with the use of the propeller-vane motivated us to consider the cup anemometer for turbulence measurements. At fast sample rates, the output of the cup anemometer is severely degraded by discretization error that stems from pulse counting demodulation. However, we found that a low-pass Gaussian filter could be applied to the time series of wind speed derived from the cup anemometer to yield time series and frequency spectra that compared very favorably with those obtained from the propeller-vane anemometer. This finding suggests that the cup anemometer may prove to be an inexpensive and rugged sensor appropriate for turbulence measurements for wind-energy applications.

Morris, V.R.; Barnard, J.C.; Wendell, L.L.; Tomich, S.D.

1992-10-01T23:59:59.000Z

140

AMBIPOLAR DIFFUSION HEATING IN TURBULENT SYSTEMS  

SciTech Connect (OSTI)

The temperature of the gas in molecular clouds is a key determinant of the characteristic mass of star formation. Ambipolar diffusion (AD) is considered one of the most important heating mechanisms in weakly ionized molecular clouds. In this work, we study the AD heating rate using two-fluid turbulence simulations and compare it with the overall heating rate due to turbulent dissipation. We find that for observed molecular clouds, which typically have Alfven Mach numbers of {approx}1 and AD Reynolds numbers of {approx}20, about 70% of the total turbulent dissipation is in the form of AD heating. AD has an important effect on the length scale where energy is dissipated: when AD heating is strong, most of the energy in the cascade is removed by ion-neutral drift, with a comparatively small amount of energy making it down to small scales. We derive a relation for the AD heating rate that describes the results of our simulations to within a factor of two. Turbulent dissipation, including AD heating, is generally less important than cosmic-ray heating in molecular clouds, although there is substantial scatter in both.

Li, Pak Shing [Astronomy Department, University of California, Berkeley, CA 94720 (United States); Myers, Andrew [Physics Department, University of California, Berkeley, CA 94720 (United States); McKee, Christopher F., E-mail: psli@astron.berkeley.edu, E-mail: atmyers@berkeley.edu, E-mail: cmckee@berkeley.edu [Physics Department and Astronomy Department, University of California, Berkeley, CA 94720 (United States)

2012-11-20T23:59:59.000Z

Note: This page contains sample records for the topic "rangepsi 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

Optical monitor for observing turbulent flow  

DOE Patents [OSTI]

The present invention provides an apparatus and method for non-invasively monitoring turbulent fluid flows including anisotropic flows. The present invention uses an optical technique to filter out the rays travelling in a straight line, while transmitting rays with turbulence induced fluctuations in time. The output is two dimensional, and can provide data regarding the spectral intensity distribution, or a view of the turbulence in real time. The optical monitor of the present invention comprises a laser that produces a coherent output beam that is directed through a fluid flow, which phase-modulates the beam. The beam is applied to a temporal filter that filters out the rays in the beam that are straight, while substantially transmitting the fluctuating, turbulence-induced rays. The temporal filter includes a lens and a photorefractive crystal such as BaTiO.sub.3 that is positioned in the converging section of the beam near the focal plane. An imaging system is used to observe the filtered beam. The imaging system may take a photograph, or it may include a real time camera that is connected to a computer. The present invention may be used for many purposes including research and design in aeronautics, hydrodynamics, and combustion.

Albrecht, Georg F. (Livermore, CA); Moore, Thomas R. (Rochester, NY)

1992-01-01T23:59:59.000Z

142

6, 52515268, 2006 Turbulent fluxes over  

E-Print Network [OSTI]

´exico, 04510 Mexico City, Mexico Received: 24 March 2006 ­ Accepted: 10 May 2006 ­ Published: 26 June 2006 wind speed conditions (up to 25 ms -1 ). The estimates of total momentum flux and turbulent kinetic energy can be represented very5 accurately (r2 =0.99, when data are binned every 1 ms-1 ) by empirical

Boyer, Edmond

143

Helicity within the Kolmogorov phenomenology of turbulence  

E-Print Network [OSTI]

Helicity within the Kolmogorov phenomenology of turbulence Susan Kurien Mathematical Modeling@lanl.gov In a phenomenology in which both energy and helicity exhibit net flux to the small scales it is natural in resolved numerical simulations in [4]. In a phenomenology in which both energy and helicity exhibit net

Kurien, Susan

144

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

145

Power spectra of outflow-driven turbulence  

E-Print Network [OSTI]

We investigate the power spectra of outflow-driven turbulence through high-resolution three-dimensional isothermal numerical simulations where the turbulence is driven locally in real-space by a simple spherical outflow model. The resulting turbulent flow saturates at an average Mach number of ~2.5 and is analysed through density and velocity power spectra, including an investigation of the evolution of the solenoidal and compressional components. We obtain a shallow density power spectrum with a slope of ~-1.2 attributed to the presence of a network of localised dense filamentary structures formed by strong shock interactions. The total velocity power spectrum slope is found to be ~-2.0, representative of Burgers shock dominated turbulence model. The density weighted velocity power spectrum slope is measured as ~-1.6, slightly less than the expected Kolmogorov scaling value (slope of -5/3) found in previous works. The discrepancy may be caused by the nature of our real space driving model and we suggest ther...

Moraghan, Anthony; Yoon, Suk-Jin

2015-01-01T23:59:59.000Z

146

Electron acceleration and turbulence in solar  

E-Print Network [OSTI]

, 2005 Free magnetic energy ~2 1032 ergs #12;"Standard" model of a solar flare/CME Solar corona T ~ 106 K Electron energies >10 MeV Proton energies >100 MeV Large solar flare releases about 1032 ergs (about halfElectron acceleration and turbulence in solar flares Eduard Kontar School of Physics and Astronomy

University College London

147

Universal constants and equations of turbulent motion  

E-Print Network [OSTI]

In the spirit of Prandtl [1926], for turbulence at high Reynolds number we present an analogy with the kinetic theory of gases, with dipoles made of Thorpe's [1977] quasi-solid vortex tubes as frictionless, incompressible but deformable quasi-particles. Their movements are governed by Helmholtz' elementary vortex rules applied locally. A contact interaction or 'collision' leads either to random scatter of a trajectory or to the formation of two likewise rotating, fundamentally unstable whirls forming a dissipative patch slowly rotating around its center of mass which is almost at rest. This approach predicts von Karman's constant as 1/sqrt(2 pi) = 0.399 and the spatio-temporal dynamics of energy-containing time and length scales controlling turbulent mixing Baumert [2009]. A link to turbulence spectra was missing so far. In the present paper it is shown that the above image of random vortex-dipole movements is compatible with Kolmogorov's turbulence spectra if dissipative patches, beginning as two likewise ro...

Baumert, Helmut Z

2011-01-01T23:59:59.000Z

148

Colloidal particle deposition in turbulent flow  

SciTech Connect (OSTI)

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

149

Combustion-turbulence interaction in the turbulent boundary layer over a hot surface  

SciTech Connect (OSTI)

The turbulence-combustion interaction in a reacting turbulent boundary layer over a heated flat plate was studied. Ethylene/air mixture with equivalence ratio of 0.35 was used. The free stream velocity was 10.5 m/s and the wall temperature was 1250/sup 0/K. Combustion structures visualization was provided by high-speed schlieren photographs. Fluid density statistics were deduced from Rayleigh scattering intensity measurements. A single-component laser Doppler velocimetry system was used to obtain mean and root-mean-square velocity distributions, the Reynolds stress, the streamwise and the cross-stream turbulent kinetic energy diffusion, and the production of turbulent kinetic energy by Reynolds stress. The combustion process was dominated by large-scale turbulent structures of the boundary layer. Combustion causes expansion of the boundary layer. No overall self-similarity is observed in either the velocity or the density profiles. Velocity fluctuations were increased in part of the boundary layer and the Reynolds stress was reduced. The turbulent kinetic energy diffusion pattern was changed significantly and a modification of the boundary layer assumption will be needed when dealing with this problem analytically. 11 figures, 1 table.

Ng, T.T.; Cheng, R.K.; Robben, F.; Talbot, L.

1982-01-01T23:59:59.000Z

150

A Dynamical Model of Plasma Turbulence in the Solar Wind  

E-Print Network [OSTI]

A dynamical approach, rather than the usual statistical approach, is taken to explore the physical mechanisms underlying the nonlinear transfer of energy, the damping of the turbulent fluctuations, and the development of coherent structures in kinetic plasma turbulence. It is argued that the linear and nonlinear dynamics of Alfven waves are responsible, at a very fundamental level, for some of the key qualitative features of plasma turbulence that distinguish it from hydrodynamic turbulence, including the anisotropic cascade of energy and the development of current sheets at small scales. The first dynamical model of kinetic turbulence in the weakly collisional solar wind plasma that combines self-consistently the physics of Alfven waves with the development of small-scale current sheets is presented and its physical implications are discussed. This model leads to a simplified perspective on the nature of turbulence in a weakly collisional plasma: the nonlinear interactions responsible for the turbulent casca...

Howes, G G

2015-01-01T23:59:59.000Z

151

THE INTERPLAY OF TURBULENCE AND MAGNETIC FIELDS IN STAR-FORMING REGIONS: SIMULATIONS AND OBSERVATIONS  

SciTech Connect (OSTI)

We analyze a suite of thin-sheet magnetohydrodynamical simulations based on the formulation of Basu, Ciolek, Dapp, and Wurster. These simulations allow us to examine the observational consequences to a star-forming region of varying the input level of turbulence (between thermal and a Mach number of 4) and the initial magnetic field strength corresponding to a range of mass to flux ratios between subcritical ({mu}{sub 0} = 0.5) and supercritical ({mu}{sub 0} = 10). The input turbulence is allowed to decay over the duration of the simulation. We compare the measured observable quantities with those found from surveying the Perseus molecular cloud. We find that only the most turbulent of simulations (high Mach number and weak magnetic field) have sufficient large-scale velocity dispersion (at {approx}1 pc) to match that observed across extinction regions in Perseus. Generally, the simulated core ({approx}0.02 pc) and line-of-sight velocity dispersions provide a decent match to observations. The motion between the simulated core and its local environment, however, is far too large in simulations with high large-scale velocity dispersion.

Kirk, Helen; Johnstone, Doug [Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 1A1 (Canada); Basu, Shantanu [Department of Physics and Astronomy, University of Western Ontario, 1151 Richmond Street, London, ON, N6A 3K7 (Canada)], E-mail: hkirk@uvastro.phys.uvic.ca

2009-07-10T23:59:59.000Z

152

Thermal conductivity of thermal-battery insulations  

SciTech Connect (OSTI)

The thermal conductivities of a variety of insulating materials used in thermal batteries were measured in atmospheres of argon and helium using several techniques. (Helium was used to simulate the hydrogen atmosphere that results when a Li(Si)/FeS{sub 2} thermal battery ages.) The guarded-hot-plate method was used with the Min-K insulation because of its extremely low thermal conductivity. For comparison purposes, the thermal conductivity of the Min-K insulating board was also measured using the hot-probe method. The thermal-comparator method was used for the rigid Fiberfrax board and Fiberfrax paper. The thermal conductivity of the paper was measured under several levels of compression to simulate the conditions of the insulating wrap used on the stack in a thermal battery. The results of preliminary thermal-characterization tests with several silica aerogel materials are also presented.

Guidotti, R.A.; Moss, M.

1995-08-01T23:59:59.000Z

153

High Temperature Thermal Array for Next Generation Solar Thermal...  

Broader source: Energy.gov (indexed) [DOE]

High Temperature Thermal Array for Next Generation Solar Thermal Power Production High Temperature Thermal Array for Next Generation Solar Thermal Power Production This...

154

Seasonal thermal energy storage  

SciTech Connect (OSTI)

This report describes the following: (1) the US Department of Energy Seasonal Thermal Energy Storage Program, (2) aquifer thermal energy storage technology, (3) alternative STES technology, (4) foreign studies in seasonal thermal energy storage, and (5) economic assessment.

Allen, R.D.; Kannberg, L.D.; Raymond, J.R.

1984-05-01T23:59:59.000Z

155

Refined Critical Balance in Strong Alfvénic Turbulence  

E-Print Network [OSTI]

We present numerical evidence that in strong Alfv\\'enic turbulence, the critical balance principle---equality of the nonlinear decorrelation and linear propagation times---is scale invariant, in the sense that the probability distribution of the ratio of these times is independent of scale. This result only holds if the local alignment of the Elsasser fields is taken into account in calculating the nonlinear time. At any given scale, the degree of alignment is found to increase with fluctuation amplitude, supporting the idea that the cause of alignment is mutual dynamical shearing of Elsasser fields. The scale-invariance of critical balance (while all other quantities of interest are strongly intermittent, i.e., have scale-dependent distributions) suggests that it is the most robust of the scaling principles used to describe Alfv\\'enic turbulence.

A. Mallet; A. A. Schekochihin; B. D. G. Chandran

2014-06-21T23:59:59.000Z

156

Generalized Batchelor functions of isotropic turbulence  

E-Print Network [OSTI]

We generalize Batchelor's parameterization of the autocorrelation functions of isotropic turbulence in a form involving a product expansion with multiple small scales. The richer small scale structure acquired this way, compared to the usual Batchelor function, is necessary so that the associated energy spectrum approximate well actual spectra in the universal equilibrium range. We propose that the generalized function provides an approximation of arbitrary accuracy for actual spectra of isotropic turbulence over the universal equilibrium range. The degree of accuracy depends on the number of higher moments which are determinable and it is reflected in the number of small scales involved. The energy spectrum of the generalized function is derived, and for the case of two small scales is compared with data from high-resolution direct numerical simulations. We show that the compensated spectra (which illustrate the bottleneck effect) and dissipation spectra are encapsulated excellently, in accordance with our p...

Gravanis, Elias

2015-01-01T23:59:59.000Z

157

Thermal unobtainiums? The perfect thermal conductor and  

E-Print Network [OSTI]

contribute to thermal resistance · Isotopically pure diamond has highest thermal conductivity of any material materials: disordered layered crystals Conclude with some thoughts on promising, high-risk, research even in a computer model. #12;Thermal resistance is created by Umklapp scattering (U

Braun, Paul

158

NONIDEAL MAGNETOHYDRODYNAMIC TURBULENT DECAY IN MOLECULAR CLOUDS  

SciTech Connect (OSTI)

It is well known that nonideal magnetohydrodynamic (MHD) effects are important in the dynamics of molecular clouds: both ambipolar diffusion and possibly the Hall effect have been identified as significant. We present the results of a suite of simulations with a resolution of 512{sup 3} of turbulent decay in molecular clouds, incorporating a simplified form of both ambipolar diffusion and the Hall effect simultaneously. The initial velocity field in the turbulence is varied from being super-Alfvenic and hypersonic, through to trans-Alfvenic but still supersonic. We find that ambipolar diffusion increases the rate of decay of the turbulence increasing the decay from t {sup -1.25} to t {sup -1.4}. The Hall effect has virtually no impact in this regard. The power spectra of density, velocity, and the magnetic field are all affected by the nonideal terms, being steepened significantly when compared with ideal MHD turbulence with exponents. The density power-spectra components change from {approx}1.4 to {approx}2.1 for the ideal and nonideal simulations respectively, and power spectra of the other variables all show similar modifications when nonideal effects are considered. Again, the dominant source of these changes is ambipolar diffusion rather than the Hall effect. There is also a decoupling between the velocity field and the magnetic field at short length scales. The Hall effect leads to enhanced magnetic reconnection, and hence less power, at short length scales. The dependence of the velocity dispersion on the characteristic length scale is studied and found not to be power law in nature.

Downes, T. P. [School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland); O'Sullivan, S. [National Centre for Plasma Science and Technology, Dublin City University, Glasnevin, Dublin 9 (Ireland)], E-mail: turlough.downes@dcu.ie

2009-08-20T23:59:59.000Z

159

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

160

Universal constants and equations of turbulent motion  

E-Print Network [OSTI]

In the spirit of Prandtl's conjecture of 1926, for turbulence at high Reynolds number we present an analogy with the kinetic theory of gases, with dipoles made of quasi-rigid and 'dressed' vortex tubes as frictionless, incompressible but deformable quasi-particles. Their movements are governed by Helmholtz' elementary vortex rules applied locally. A contact interaction or 'collision' leads either to random scatter of a trajectory or to the formation of two likewise rotating, fundamentally unstable whirls forming a dissipative patch slowly rotating around its center of mass which is almost at rest. This approach predicts von Karman's constant as 1/sqrt(2 pi) = 0.399 and the spatio-temporal dynamics of energy-containing time and length scales controlling turbulent mixing [Baumert 2009]. A link to turbulence spectra was missing so far. In the present paper it is shown that the above image of random vortex-dipole movements is compatible with Kolmogorov's turbulence spectra if dissipative patches, beginning as two likewise rotating eddies, evolve locally into a space-filling bearing in the sense of Herrmann [1990], i.e. into an "Apollonian gear". Its parts and pieces are incompressible and flexibly deformable vortex tubes which are frictionless, excepting the dissipative scale of size zero. For steady and locally homogeneous conditions our approach predicts the dimensionless pre-factor in the 3D Eulerian wavenumber spectrum as [(4 pi)^2/3]/3 = 1.8, and in the Lagrangian frequency spectrum as 2. Our derivations rest on geometry, methods from many-particle physics, and on elementary conservation laws.

Helmut Z. Baumert

2011-07-25T23:59:59.000Z

Note: This page contains sample records for the topic "rangepsi 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

Free energy balance in gyrokinetic turbulence  

SciTech Connect (OSTI)

Free energy plays an important role in gyrokinetic theory, since it is known to be a nonlinear invariant. Its evolution equations are derived and analyzed for the case of ion temperature gradient driven turbulence, using the formalism adopted in the Gene code. In particular, the ion temperature gradient drive, the collisional dissipation as well as entropy/electrostatic energy transfer channels represented by linear curvature and parallel terms are analyzed in detail.

Banon Navarro, A.; Morel, P.; Albrecht-Marc, M.; Carati, D. [Statistical and Plasma Physics Laboratory, Universite Libre de Bruxelles (Belgium); Merz, F.; Goerler, T.; Jenko, F. [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany)

2011-09-15T23:59:59.000Z

162

On specification of initial conditions in turbulence models  

SciTech Connect (OSTI)

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

163

Two-fluid description of wave-particle interactions in strong Buneman turbulence  

SciTech Connect (OSTI)

To understand the nature of anomalous resistivity in magnetic reconnection, we investigate turbulence-induced momentum transport and energy dissipation while a plasma is unstable to the Buneman instability in force-free current sheets. Using 3D particle-in-cell simulations, we find that the macroscopic effects generated by wave-particle interactions in Buneman instability can be approximately described by a set of electron fluid equations. We show that both energy dissipation and momentum transport along electric current in the current layer are locally quasi-static, but globally dynamic and irreversible. Turbulent drag dissipates both the streaming energy of the current sheet and the associated magnetic energy. The net loss of streaming energy is converted into the electron component heat conduction parallel to the magnetic field and increases the electron Boltzmann entropy. The growth of self-sustained Buneman waves satisfies a Bernoulli-like equation that relates the turbulence-induced convective momentum transport and thermal momentum transport. Electron trapping and de-trapping drive local momentum transports, while phase mixing converts convective momentum into thermal momentum. The drag acts like a micro-macro link in the anomalous heating processes. The decrease of magnetic field maintains an inductive electric field that re-accelerates electrons, but most of the magnetic energy is dissipated and converted into the component heat of electrons perpendicular to the magnetic field. This heating process is decoupled from the heating of Buneman instability in the current sheets. Ion heating is weak but ions play an important role in assisting energy exchanges between waves and electrons. Cold ion fluid equations together with our electron fluid equations form a complete set of equations that describes the occurrence, growth, saturation and decay of the Buneman instability.

Che, H. [NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States)

2014-06-15T23:59:59.000Z

164

Rayleigh/Raman/LIF measurements in a turbulent lean premixed combustor  

SciTech Connect (OSTI)

Much of the industrial electrical generation capability being added worldwide is gas-turbine engine based and is fueled by natural gas. These gas-turbine engines use lean premixed (LP) combustion to meet the strict NO{sub x} emission standards, while maintaining acceptable levels of CO. In conventional, diffusion flame gas turbine combustors, large amount of NO{sub x} forms in the hot stoichiometric zones via the Zeldovich (thermal) mechanism. Hence, lean premixed combustors are rapidly becoming the norm, since they are specifically designed to avoid these hot stoichiometric zones and the associated thermal NO{sub x}. However, considerable research and development are still required to reduce the NO{sub x} levels (25-40 ppmvd adjusted to 15% O{sub 2} with the current technology), to the projected goal of under 10 ppmvd by the turn of the century. Achieving this objective would require extensive experiments in LP natural gas (or CH{sub 4}) flames for understanding the combustion phenomena underlying the formation of the exhaust pollutants. Although LP combustion is an effective way to control NO{sub x}, the downside is that it increases the CO emissions. The formation and destruction of the pollutants (NO{sub x} and CO) are strongly affected by the fluid mechanics, the finite-rate chemistry, and their (turbulence-chemistry) interactions. Hence, a thorough understanding of these interactions is vital for controlling and reducing the pollutant emissions. The present research is contributing to this goal by providing a detailed nonintrusive laser based data set with good spatial and temporal resolutions of the pollutants (NO and CO) along with the major species, temperature, and OH. The measurements reported in this work, along with the existing velocity data on a turbulent LP combustor burning CH{sub 4}, would provide insight into the turbulence-chemistry interactions and their effect on pollutant formation.

Nandula, S.P.; Pitz, R.W. [Vanderbilt Univ., Nashville, TN (United States). Dept. of Mechanical Engineering; Barlow, R.S.; Fiechtner, G.J. [Sandia National Labs., Albuquerque, NM (United States)

1995-12-31T23:59:59.000Z

165

Thermal Control & System Integration  

Broader source: Energy.gov [DOE]

The thermal control and system integration activity focuses on issues such as the integration of motor and power control technologies and the development of advanced thermal control technologies....

166

Forecasting Turbulent Modes with Nonparametric Diffusion Models  

E-Print Network [OSTI]

This paper presents a nonparametric diffusion modeling approach for forecasting partially observed noisy turbulent modes. The proposed forecast model uses a basis of smooth functions (constructed with the diffusion maps algorithm) to represent probability densities, so that the forecast model becomes a linear map in this basis. We estimate this linear map by exploiting a previously established rigorous connection between the discrete time shift map and the semi-group solution associated to the backward Kolmogorov equation. In order to smooth the noisy data, we apply diffusion maps to a delay embedding of the noisy data, which also helps to account for the interactions between the observed and unobserved modes. We show that this delay embedding biases the geometry of the data in a way which extracts the most predictable component of the dynamics. The resulting model approximates the semigroup solutions of the generator of the underlying dynamics in the limit of large data and in the observation noise limit. We will show numerical examples on a wide-range of well-studied turbulent modes, including the Fourier modes of the energy conserving Truncated Burgers-Hopf (TBH) model, the Lorenz-96 model in weakly chaotic to fully turbulent regimes, and the barotropic modes of a quasi-geostrophic model with baroclinic instabilities. In these examples, forecasting skills of the nonparametric diffusion model are compared to a wide-range of stochastic parametric modeling approaches, which account for the nonlinear interactions between the observed and unobserved modes with white and colored noises.

Tyrus Berry; John Harlim

2015-01-27T23:59:59.000Z

167

Phenomenology of Wall Bounded Newtonian Turbulence  

E-Print Network [OSTI]

We construct a simple analytic model for wall-bounded turbulence, containing only four adjustable parameters. Two of these parameters characterize the viscous dissipation of the components of the Reynolds stress-tensor and other two parameters characterize their nonlinear relaxation. The model offers an analytic description of the profiles of the mean velocity and the correlation functions of velocity fluctuations in the entire boundary region, from the viscous sub-layer, through the buffer layer and further into the log-layer. As a first approximation, we employ the traditional return-to-isotropy hypothesis, which yields a very simple distribution of the turbulent kinetic energy between the velocity components in the log-layer: the streamwise component contains a half of the total energy whereas the wall-normal and the cross-stream components contain a quarter each. In addition, the model predicts a very simple relation between the von-K\\'arm\\'an slope $\\kappa $ and the turbulent velocity in the log-law region $v^+$ (in wall units): $v^+=6 \\kappa$. These predictions are in excellent agreement with DNS data and with recent laboratory experiments.

Victor S. L'vov; Anna Pomyalov; Itamar Procaccia; Sergej S. Zilitinkevich

2005-06-28T23:59:59.000Z

168

Universal equations and constants of turbulent motion  

E-Print Network [OSTI]

This paper presents a parameter-free theory of shear-generated turbulence at asymptotically high Reynolds numbers in incompressible fluids. It is based on a two-fluids concept. Both components are materially identical and inviscid. The first component is an ensemble of quasi-rigid dipole-vortex tubes as quasi-particles in chaotic motion. The second is a superfluid performing evasive motions between the tubes. The local dipole motions follow Helmholtz' law. The vortex radii scale with the energy-containing length scale. Collisions between quasi-particles lead either to annihilation (likewise rotation, turbulent dissipation) or to scattering (counterrotation, turbulent diffusion). There are analogies with birth and death processes of population dynamics and their master equations. For free homogeneous decay the theory predicts the TKE to follow 1/t. With an adiabatic condition at the wall it predicts the logarithmic law with von Karman's constant as 1/\\sqrt{2 pi} = 0.399. Likewise rotating couples form dissipative patches almost at rest ($\\rightarrow$ intermittency) wherein the spectrum evolves like an "Apollonian gear" as discussed first by Herrmann, 1990. On this basis the prefactor of the 3D-wavenumber spectrum is predicted as (1/3)(4 pi)^{2/3}=1.8; in the Lagrangian frequency spectrum it is simply 2. The results are situated well within the scatter range of observational, experimental and DNS results.

Helmut Z. Baumert

2012-03-22T23:59:59.000Z

169

Continuous representation for shell models of turbulence  

E-Print Network [OSTI]

In this work we construct and analyze continuous hydrodynamic models in one space dimension, which are induced by shell models of turbulence. After Fourier transformation, such continuous models split into an infinite number of uncoupled subsystems, which are all identical to the same shell model. The two shell models, which allow such a construction, are considered: the dyadic (Desnyansky--Novikov) model with the intershell ratio $\\lambda = 2^{3/2}$ and the Sabra model of turbulence with $\\lambda = \\sqrt{2+\\sqrt{5}} \\approx 2.058$. The continuous models allow understanding various properties of shell model solutions and provide their interpretation in physical space. We show that the asymptotic solutions of the dyadic model with Kolmogorov scaling correspond to the shocks (discontinuities) for the induced continuous solutions in physical space, and the finite-time blowup together with its viscous regularization follow the scenario similar to the Burgers equation. For the Sabra model, we provide the physical space representation for blowup solutions and intermittent turbulent dynamics.

Alexei A. Mailybaev

2014-09-16T23:59:59.000Z

170

Fusion Rules in Turbulent Systems with Flux Equilibrium  

E-Print Network [OSTI]

Fusion rules in turbulence specify the analytic structure of many-point correlation functions of the turbulent field when a group of coordinates coalesce. We show that the existence of flux equilibrium in fully developed turbulent systems combined with a direct cascade induces universal fusion rules. In certain examples these fusion rules suffice to compute the multiscaling exponents exactly, and in other examples they give rise to an infinite number of scaling relations that constrain enormously the structure of the allowed theory.

Victor L'vov; Itamar Procaccia

1995-07-27T23:59:59.000Z

171

Massively Parallel Spectral Element Large Eddy Simulation of a Turbulent Channel Using Wall Models  

E-Print Network [OSTI]

Wall-bounded turbulent flows are prevalent in engineering and industrial applications. Walls greatly affect turbulent characteristics in many ways including production and propagation of turbulent stresses. While computational fluid dynamics can...

Rabau, Joshua I

2013-05-01T23:59:59.000Z

172

Advanced Turbulence Measurements and Signal Processing for Hydropower Flow Characterization  

E-Print Network [OSTI]

Advanced Turbulence Measurements and Signal Processing for Hydropower Flow Characterization and flow characterization within full scale conventional hydropower systems, at marine and hydrokinetic

173

Hot Particle and Turbulent Transport Effects on Resistive Instabilities  

SciTech Connect (OSTI)

This research project included two main thrusts; energetic particle effects on resistive MHD modes in tokamaks, and turbulence interactions with tearing modes in simplified geometry.

Brennan, Dylan P.

2012-10-16T23:59:59.000Z

174

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

175

Scientists use plasma shaping to control turbulence in stellarators...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

to control turbulence in stellarators By John Greenwald By John Greenwald October 21, 2014 Tweet Widget Google Plus One Share on Facebook Magnetic field strength in a...

176

aperiodic magnetic turbulence: Topics by E-print Network  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

star formation and the interstellar medium. The density, pressure, and temperature distribution in a turbulent interstellar medium is described in comparison to a medium dominated...

177

alfven wave turbulence: Topics by E-print Network  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

from 1 Solar Radius to 1 AU: an Analytical Treatment CERN Preprints Summary: We study the propagation, reflection, and turbulent dissipation of Alfven waves in coronal holes and...

178

E-Print Network 3.0 - anisotropic magnetohydrodynamic turbulence...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Physics 57 Michigan Institute for Plasma Sci- Summary: of turbulent fluc- tuations in the solar wind. While magnetohydrodynamics remains the appro- priate theory... Michigan...

179

Thermalization and condensation in an incoherently pumped passive optical cavity  

SciTech Connect (OSTI)

We study theoretically and numerically the condensation and the thermalization of classical optical waves in an incoherently pumped passive Kerr cavity. We show that the dynamics of the cavity exhibits a turbulent behavior that can be described by the wave turbulence theory. A mean-field kinetic equation is derived, which reveals that, in its high finesse regime, the cavity behaves essentially as a conservative Hamiltonian system. In particular, the intracavity turbulent field is shown to relax adiabatically toward a thermodynamic equilibrium state of energy equipartition. As a consequence of this effect of wave thermalization, the incoherent optical field undergoes a process of condensation, characterized by the spontaneous emergence of a plane wave from the incoherently pumped cavity. The condensation process is an equilibrium phase transition that occurs below a critical value of the (kinetic) energy of the incoherent pump. In spite of the dissipative nature of the cavity dynamics, the condensate fraction of the high-finesse cavity field is found in quantitative agreement with the theory inherited from the purely conservative (Hamiltonian) nonlinear Schroedinger equation.

Michel, C.; Picozzi, A. [Laboratoire Interdisciplinaire Carnot de Bourgogne, CNRS, Universite de Bourgogne, F-21078 Dijon (France); Haelterman, M. [Service OPERA, Universite Libre de Bruxelles, B-1050 Brussels (Belgium); Suret, P.; Randoux, S. [Laboratoire de Physique des Lasers, Atomes et Molecules, CNRS, Universite de Lille, F-59655 Villeneuve d'Ascq (France); Kaiser, R. [Institut Non Lineaire de Nice, CNRS, Universite de Nice Sophia-Antipolis, F-06560 Valbonne (France)

2011-09-15T23:59:59.000Z

180

Anomalous Viscosity, Resistivity, and Thermal Diffusivity of the Solar Wind Plasma  

E-Print Network [OSTI]

In this paper we have estimated typical anomalous viscosity, resistivity, and thermal difffusivity of the solar wind plasma. Since the solar wind is collsionless plasma, we have assumed that the dissipation in the solar wind occurs at proton gyro radius through wave-particle interactions. Using this dissipation length-scale and the dissipation rates calculated using MHD turbulence phenomenology [Verma et al., 1995a], we estimate the viscosity and proton thermal diffusivity. The resistivity and electron’s thermal diffusivity have also been estimated. We find that all our transport quantities are several orders of magnitude higher than those calculated earlier using classical transport theories of Braginskii. In this paper we have also estimated the eddy turbulent viscosity. 1 1

Mahendra K. Verma

2008-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "rangepsi 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

Anomalous Viscosity, Resistivity, and Thermal Diffusivity of the Solar Wind Plasma  

E-Print Network [OSTI]

In this paper we have estimated typical anomalous viscosity, resistivity, and thermal difffusivity of the solar wind plasma. Since the solar wind is collsionless plasma, we have assumed that the dissipation in the solar wind occurs at proton gyro radius through wave-particle interactions. Using this dissipation length-scale and the dissipation rates calculated using MHD turbulence phenomenology [{\\it Verma et al.}, 1995a], we estimate the viscosity and proton thermal diffusivity. The resistivity and electron's thermal diffusivity have also been estimated. We find that all our transport quantities are several orders of magnitude higher than those calculated earlier using classical transport theories of {\\it Braginskii}. In this paper we have also estimated the eddy turbulent viscosity.

Mahendra K. Verma

1995-09-05T23:59:59.000Z

182

E-Print Network 3.0 - astrophysical turbulent plasma Sample Search...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Turbulence in Molecular Clouds SciDAC 2009 - Astrophysics - San... Kolmogorov's phenomenology to supersonic regime? Turbulence in ... Source: Kritsuk, Alexei - Center for...

183

E-Print Network 3.0 - atmospheric turbulence structures Sample...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Elperin, Tov - Department of Mechanical Engineering, Ben-Gurion University Collection: Engineering 12 Turbulence and turbulent mixing in natural fluids This article has been...

184

E-Print Network 3.0 - atmospheric turbulence Sample Search Results  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Summary: by dissipation of the turbulent energy and tur- bulent eddies will transport heat to different atmospheric re... ., MST radar studies of wind and turbulence in the...

185

Thermal Management of Solar Cells  

E-Print Network [OSTI]

a better thermal conductance and when ceramic particles areor ceramic fillers that enhances thermal conductivity. Solid

Saadah, Mohammed Ahmed

2013-01-01T23:59:59.000Z

186

Adaptive LES Methodology for Turbulent Flow Simulations  

SciTech Connect (OSTI)

Although turbulent flows are common in the world around us, a solution to the fundamental equations that govern turbulence still eludes the scientific community. Turbulence has often been called one of the last unsolved problem in classical physics, yet it is clear that the need to accurately predict the effect of turbulent flows impacts virtually every field of science and engineering. As an example, a critical step in making modern computational tools useful in designing aircraft is to be able to accurately predict the lift, drag, and other aerodynamic characteristics in numerical simulations in a reasonable amount of time. Simulations that take months to years to complete are much less useful to the design cycle. Much work has been done toward this goal (Lee-Rausch et al. 2003, Jameson 2003) and as cost effective accurate tools for simulating turbulent flows evolve, we will all benefit from new scientific and engineering breakthroughs. The problem of simulating high Reynolds number (Re) turbulent flows of engineering and scientific interest would have been solved with the advent of Direct Numerical Simulation (DNS) techniques if unlimited computing power, memory, and time could be applied to each particular problem. Yet, given the current and near future computational resources that exist and a reasonable limit on the amount of time an engineer or scientist can wait for a result, the DNS technique will not be useful for more than 'unit' problems for the foreseeable future (Moin & Kim 1997, Jimenez & Moin 1991). The high computational cost for the DNS of three dimensional turbulent flows results from the fact that they have eddies of significant energy in a range of scales from the characteristic length scale of the flow all the way down to the Kolmogorov length scale. The actual cost of doing a three dimensional DNS scales as Re{sup 9/4} due to the large disparity in scales that need to be fully resolved. State-of-the-art DNS calculations of isotropic turbulence have recently been completed at the Japanese Earth Simulator (Yokokawa et al. 2002, Kaneda et al. 2003) using a resolution of 40963 (approximately 10{sup 11}) grid points with a Taylor-scale Reynolds number of 1217 (Re {approx} 10{sup 6}). Impressive as these calculations are, performed on one of the world's fastest super computers, more brute computational power would be needed to simulate the flow over the fuselage of a commercial aircraft at cruising speed. Such a calculation would require on the order of 10{sup 16} grid points and would have a Reynolds number in the range of 108. Such a calculation would take several thousand years to simulate one minute of flight time on today's fastest super computers (Moin & Kim 1997). Even using state-of-the-art zonal approaches, which allow DNS calculations that resolve the necessary range of scales within predefined 'zones' in the flow domain, this calculation would take far too long for the result to be of engineering interest when it is finally obtained. Since computing power, memory, and time are all scarce resources, the problem of simulating turbulent flows has become one of how to abstract or simplify the complexity of the physics represented in the full Navier-Stokes (NS) equations in such a way that the 'important' physics of the problem is captured at a lower cost. To do this, a portion of the modes of the turbulent flow field needs to be approximated by a low order model that is cheaper than the full NS calculation. This model can then be used along with a numerical simulation of the 'important' modes of the problem that cannot be well represented by the model. The decision of what part of the physics to model and what kind of model to use has to be based on what physical properties are considered 'important' for the problem. It should be noted that 'nothing is free', so any use of a low order model will by definition lose some information about the original flow.

Oleg V. Vasilyev

2008-06-12T23:59:59.000Z

187

Sub-Alfvenic Non-Ideal MHD Turbulence Simulations with Ambipolar Diffusion: I. Turbulence Statistics  

SciTech Connect (OSTI)

Most numerical investigations on the role of magnetic fields in turbulent molecular clouds (MCs) are based on ideal magneto-hydrodynamics (MHD). However, MCs are weakly ionized, so that the time scale required for the magnetic field to diffuse through the neutral component of the plasma by ambipolar diffusion (AD) can be comparable to the dynamical time scale. We have performed a series of 256{sup 3} and 512{sup 3} simulations on supersonic but sub-Alfvenic turbulent systems with AD using the Heavy-Ion Approximation developed in Li et al. (2006). Our calculations are based on the assumption that the number of ions is conserved, but we show that these results approximately apply to the case of time-dependent ionization in molecular clouds as well. Convergence studies allow us to determine the optimal value of the ionization mass fraction when using the heavy-ion approximation for low Mach number, sub-Alfvenic turbulent systems. We find that ambipolar diffusion steepens the velocity and magnetic power spectra compared to the ideal MHD case. Changes in the density PDF, total magnetic energy, and ionization fraction are determined as a function of the AD Reynolds number. The power spectra for the neutral gas properties of a strongly magnetized medium with a low AD Reynolds number are similar to those for a weakly magnetized medium; in particular, the power spectrum of the neutral velocity is close to that for Burgers turbulence.

Klein, R I; Li, P S; McKee, C F; Fisher, R

2008-04-10T23:59:59.000Z

188

Section 10: Turbulence and reactive flows 1 Section 10: Turbulence and reactive flows  

E-Print Network [OSTI]

premixed combustion is recently a theme of interest in gas turbines and other industrial applications flames #12;2 Section 10: Turbulence and reactive flows for gas turbine application. In: International Gas combustion LES in- cluding thickened flame model A. Hosseinzadeh, A. Sadiki, J. Janicka (TU Darmstadt) Lean

Kohlenbach, Ulrich

189

Turbulence-Chemistry Interaction in Lean Premixed Hydrogen Combustion  

E-Print Network [OSTI]

alternatives to traditional petroleum and natural gas fuels. Burning under lean condi- tions reduces of conditions expected from gas turbine combustors. At these higher turbulence in- tensities, hydrogen flamesTurbulence-Chemistry Interaction in Lean Premixed Hydrogen Combustion A. J. Aspden1,2 , M. S. Day2

Bell, John B.

190

Fluctuations of energy flux in wave turbulence Eric Falcon,1  

E-Print Network [OSTI]

Fluctuations of energy flux in wave turbulence ´Eric Falcon,1 S´ebastien Auma^itre,2 Claudio Falc gravity and capillary wave turbulence in a statistically stationary regime displays fluctuations much interactions transfer kinetic energy toward small scales where viscous dissipation takes place

Falcon, Eric

191

Characterizing Ocean Turbulence from Argo, Acoustic Doppler, and Simulation Data  

E-Print Network [OSTI]

. TurbSim models statistics at the height of a turbine hub (5m) well, but do not model coherent eventsCharacterizing Ocean Turbulence from Argo, Acoustic Doppler, and Simulation Data Katherine Mc Ocean Turbulence from Argo, Acoustic Doppler, and Simulation Data written by Katherine McCaffrey has

Fox-Kemper, Baylor

192

Lagrangian tetrad dynamics and the phenomenology of turbulence Michael Chertkov  

E-Print Network [OSTI]

Lagrangian tetrad dynamics and the phenomenology of turbulence Michael Chertkov Department Jersey 07974 Received 23 September 1998; accepted 21 April 1999 A new phenomenological model of turbulent in the right direction one must rely on phenomenology. One reason for pursuing the modeling approach

Chertkov, Mikhael

193

The Turbulent Alfvenic Aurora C. C. Chaston,1  

E-Print Network [OSTI]

The Turbulent Alfve´nic Aurora C. C. Chaston,1 C. Salem,1 J. W. Bonnell,1 C. W. Carlson,1 R. E) It is demonstrated from observations that the Alfve´nic aurora may be powered by a turbulent cascade transverse acceleration of electrons from near-Earth space to form the aurora. We find that regions of Alfve´n wave

California at Berkeley, University of

194

Fractal dimension and turbulence in Giant HII Regions  

E-Print Network [OSTI]

We have measured the fractal dimensions of the Giant HII Regions Hubble X and Hubble V in NGC6822 using images obtained with the Hubble's Wide Field Planetary Camera 2 (WFPC2). These measures are associated with the turbulence observed in these regions, which is quantified through the velocity dispersion of emission lines in the visible. Our results suggest low turbulence behaviour.

Caicedo-Ortiz, H E; López-Bonilla, J; Castañeda, H O

2015-01-01T23:59:59.000Z

195

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" IRMA Strasbourg, 23.Jan.2008 #12;Introduction DNS of Primary Breakup in Diesel Injection Phase Transition Modeling Turbulence Modeling Summary Outline 1 Introduction 2 DNS of Primary Breakup in Diesel

Helluy, Philippe

196

ANISOTROPY LENGTHENS THE DECAY TIME OF TURBULENCE IN MOLECULAR CLOUDS  

SciTech Connect (OSTI)

The decay of isothermal turbulence with velocity anisotropy is investigated using computational simulations and synthetic observations. We decompose the turbulence into isotropic and anisotropic components with total velocity dispersions {sigma}{sub iso} and {sigma}{sub ani}, respectively. We find that the decay rate of the turbulence depends on the crossing time of the isotropic component only. A cloud of size L with significant anisotropy in its turbulence has a dissipation time, t{sub diss} = L/(2{sigma}{sub iso}). This translates into turbulent energy decay rates on the cloud scale that can be much lower for anisotropic turbulence than for isotropic turbulence. To help future observations determine whether observed molecular clouds have the level of anisotropy required to maintain the observed level of turbulence over their lifetimes, we performed a principal component analysis on our simulated clouds. Even with projection effects washing out the anisotropic signal, there is a measurable difference in the axis-constrained principal component analysis performed in directions parallel and perpendicular to the direction of maximum velocity dispersion. When this relative difference, {psi}, is 0.1, there is enough anisotropy for the dissipation time to triple the expected isotropic value. We provide a fit for converting {psi} into an estimate for the dissipation time, t{sub diss}.

Hansen, Charles E.; McKee, Christopher F.; Klein, Richard I. [Astronomy Department, University of California, Berkeley, CA 94720 (United States)

2011-09-01T23:59:59.000Z

197

Supersonic turbulent boundary layers with periodic mechanical non-equilibrium  

E-Print Network [OSTI]

. It was documented that proper roughness selection coupled with a sufficiently strong favorable pressure gradient produced regions of �negative� production in the transport of turbulent stress. This led to localized areas of significant turbulence stress...

Ekoto, Isaac Wesley

2007-04-25T23:59:59.000Z

198

Heat release response of acoustically forced turbulent premixed flamesrole  

E-Print Network [OSTI]

Heat release response of acoustically forced turbulent premixed flames­role of kinematic surface to coherent forcing and turbulent fluctuations are coupled even at linear order in coherent forcing amplitude, ea, due to flame propagation (kinematic restoration). This coupling effectively causes

Lieuwen, Timothy C.

199

In-Flight Measurements of Freestream Atmospheric Turbulence Intensities  

E-Print Network [OSTI]

difference in turbulence intensity. It has been determined through this work that the levels of freestream turbulence range from 0.023% - 0.047% with an average of 0.035%. These levels were reached through the use of temporal correlations to remove electronic...

Fanning, Joshua 1987-

2012-11-05T23:59:59.000Z

200

Modeling of combustion noise spectrum from turbulent premixed flames  

E-Print Network [OSTI]

Modeling of combustion noise spectrum from turbulent premixed flames Y. Liu, A. P. Dowling, T. D, Nantes, France 2321 #12;Turbulent combustion processes generate sound radiation due to temporal changes, this temporal correlation and its role in the modeling of combustion noise spectrum are studied by analyzing

Paris-Sud XI, Université de

Note: This page contains sample records for the topic "rangepsi 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

AIAA980057 RELATING TURBULENCE TO WIND TURBINE BLADE LOADS  

E-Print Network [OSTI]

AIAA­98­0057 RELATING TURBULENCE TO WIND TURBINE BLADE LOADS: PARAMETRIC STUDY WITH MULTIPLE that is most useful in estimating fatigue loads on wind turbine blades. The histograms of rainflow counted turbulence measures---can be used to estimate fatigue loads on wind turbine blades. We first de­ scribe

Sweetman, Bert

202

RESEARCH ARTICLE Development and characterization of a variable turbulence  

E-Print Network [OSTI]

(7):1037­1048, 2009), where variable blockage ratio slots are located upstream of a contoured nozzle. Vortical A Nozzle exit area E Power spectral density ReD Geometric Reynolds number Rel Turbulent Reynolds number SLRESEARCH ARTICLE Development and characterization of a variable turbulence generation system A

Lieuwen, Timothy C.

203

Center for Turbulence Research Annual Research Briefs 2001  

E-Print Network [OSTI]

Center for Turbulence Research Annual Research Briefs 2001 3 Large-eddy simulation of gas turbine, and solver capable of performing large-eddy simulation in geometries as complex as the combustor of a gas-turbine' grids encountered in complex geometries such as the Pratt & Whitney combustor. · Turbulent validations

Apte, Sourabh V.

204

Taming turbulence in magnetized plasmas: from fusion energy to  

E-Print Network [OSTI]

occurs (fusion of particle beams will not work...) Thermonuclear fusion in a confined plasma (T~10 keTaming turbulence in magnetized plasmas: from fusion energy to black hole accretion disks Troy?: In fusion plasmas turbulent leakage of heat and particles is a key issue. Sheared flow can suppress

205

Stretching of polymers in a turbulent environment  

E-Print Network [OSTI]

The interaction of polymers with small-scale velocity gradients can trigger a coil-stretch transition in the polymers. We analyze this transition within a direct numerical simulation of shear turbulence with an Oldroyd-B model for the polymer. In the coiled state the lengths of polymers are distributed algebraically with an exponent alpha=2 gamma-1/De, where gamma is a characteristic stretching rate of the flow and De the Deborah number. In the stretched state we demonstrate that the length distribution of the polymers is limited by the feedback to the flow.

Bruno Eckhardt; Jochen Kronjaeger; Joerg Schumacher

2002-01-20T23:59:59.000Z

206

Supercomputers Capture Turbulence in the Solar Wind  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr May JunDatastreamsmmcrcalgovInstrumentsrucLas ConchasPassiveSubmittedStatus TomAbout »Lab (NewportSuccess Stories T ECapture Turbulence in

207

Fusion Rules and Conditional Statistics in Turbulent Advection  

E-Print Network [OSTI]

Fusion rules in turbulence address the asymptotic properties of many-point correlation functions when some of the coordinates are very close to each other. Here we put to experimental test some non-trivial consequences of the fusion rules for scalar correlations in turbulence. To this aim we examine passive turbulent advection as well as convective turbulence. Adding one assumption to the fusion rules one obtains a prediction for universal conditional statistics of gradient fields. We examine the conditional average of the scalar dissipation field $\\left$ for $R$ in the inertial range, and find that it is linear in $T(\\B.r+\\B.R)-T(\\B.r)$ with a fully determined proportionality constant. The implications of these findings for the general scaling theory of scalar turbulence are discussed.

Emily S. C. Ching; Victor S. L'vov; Itamar Procaccia

1996-07-02T23:59:59.000Z

208

The energetic coupling of scales in gyrokinetic plasma turbulence  

SciTech Connect (OSTI)

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 für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany); Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Max-Planck/Princeton Center for Plasma Physics (Germany); Navarro, Alejandro Bañón, E-mail: alejandro.banon.navarro@ipp.mpg.de [Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Jenko, Frank, E-mail: frank.jenko@ipp.mpg.de [Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Max-Planck/Princeton Center for Plasma Physics (Germany)

2014-07-15T23:59:59.000Z

209

MHD Turbulence: Properties of Alfven, Slow and Fast Modes  

E-Print Network [OSTI]

We summarise basic properties of MHD turbulence. First, MHD turbulence is not so messy as it is believed. In fact, the notion of strong non-linear coupling of compressible and incompressible motions along MHD cascade is not tenable. Alfven, slow and fast modes of MHD turbulence follow their own cascades and exhibit degrees of anisotropy consistent with theoretical expectations. Second, the fast decay of turbulence is not related to the compressibility of fluid. Rates of decay of compressible and incompressible motions are very similar. Third, the properties of Alfven and slow modes are similar to their counterparts in the incompressible MHD. The properties of fast modes are similar to accoustic turbulence, which does require more studies. Fourth, the density at low Mach numbers and logarithm of density at higher Mach numbers exhibit Kolmogorov-type spectrum.

A. Lazarian; A. Beresnyak

2005-05-29T23:59:59.000Z

210

Reconnection events in two-dimensional Hall magnetohydrodynamic turbulence  

SciTech Connect (OSTI)

The statistical study of magnetic reconnection events in two-dimensional turbulence has been performed by comparing numerical simulations of magnetohydrodynamics (MHD) and Hall magnetohydrodynamics (HMHD). The analysis reveals that the Hall term plays an important role in turbulence, in which magnetic islands simultaneously reconnect in a complex way. In particular, an increase of the Hall parameter, the ratio of ion skin depth to system size, broadens the distribution of reconnection rates relative to the MHD case. Moreover, in HMHD the local geometry of the reconnection region changes, manifesting bifurcated current sheets and quadrupolar magnetic field structures in analogy to laminar studies, leading locally to faster reconnection processes in this case of reconnection embedded in turbulence. This study supports the idea that the global rate of energy dissipation is controlled by the large scale turbulence, but suggests that the distribution of the reconnection rates within the turbulent system is sensitive to the microphysics at the reconnection sites.

Donato, S.; Servidio, S.; Carbone, V. [Dipartimento di Fisica, Universita della Calabria, I-87036 Cosenza (Italy); Dmitruk, P. [Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Instituto de Fisica de Buenos Aires, CONICET, Buenos Aires (Argentina); Shay, M. A.; Matthaeus, W. H. [Bartol Research Institute and Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States); Cassak, P. A. [Department of Physics, West Virginia University, Morgantown, West Virginia 26506 (United States)

2012-09-15T23:59:59.000Z

211

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

212

Internal wave energy radiated from a turbulent mixed layer  

SciTech Connect (OSTI)

We examine mixed-layer deepening and the generation of internal waves in stratified fluid resulting from turbulence that develops in response to an applied surface stress. In laboratory experiments the stress is applied over the breadth of a finite-length tank by a moving roughened conveyor belt. The turbulence in the shear layer is characterized using particle image velocimetry to measure the kinetic energy density. The internal waves are measured using synthetic schlieren to determine their amplitudes, frequencies, and energy density. We also perform fully nonlinear numerical simulations restricted to two dimensions but in a horizontally periodic domain. These clearly demonstrate that internal waves are generated by transient eddies at the integral length scale of turbulence and which translate with the background shear along the base of the mixed layer. In both experiments and simulations we find that the energy density of the generated waves is 1%–3% of the turbulent kinetic energy density of the turbulent layer.

Munroe, James R., E-mail: jmunroe@mun.ca [Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St. John's, Newfoundland A1B 3X7 (Canada); Sutherland, Bruce R., E-mail: bsuther@ualberta.ca [Departments of Physics and Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2R3 (Canada)

2014-09-15T23:59:59.000Z

213

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

214

Ignition of hydrogen/air mixing layer in turbulent flows  

SciTech Connect (OSTI)

Autoignition of a scalar hydrogen/air mixing layer in homogeneous turbulence is studied using direct numerical simulation. An initial counterflow of unmixed nitrogen-diluted hydrogen and heated air is perturbed by two-dimensional homogeneous turbulence. The temperature of the heated air stream is chosen to be 1,100 K which is substantially higher than the crossover temperature at which the rates of the chain branching and termination reactions become equal. Three different turbulence intensities are tested in order to assess the effect of the characteristic flow time on the ignition delay. For each condition, a simulation without heat release is also performed. The ignition delay determined with and without heat release is shown to be almost identical up to the point of ignition for all of the turbulence intensities tested, and the predicted ignition delays agree well within a consistent error band. It is also observed that the ignition kernel always occurs where hydrogen is focused, and the peak concentration of HO{sub 2} is aligned well with the scalar dissipation rate. The dependence of the ignition delay on turbulence intensity is found to be nonmonotonic. For weak to moderate turbulence the ignition is facilitated by turbulence via enhanced mixing, while for stronger turbulence, whose timescale is substantially smaller than the ignition delay, the ignition is retarded due to excessive scalar dissipation, and hence diffusive loss, at the ignition location. However, for the wide range of initial turbulence fields studied, the variation in ignition delay due to the corresponding variation in turbulence intensity appears to be quite small.

Im, H.G.; Chen, J.H. [Sandia National Labs., Livermore, CA (United States). Combustion Research Facility; Law, C.K. [Princeton Univ., NJ (United States). Dept. of Mechanical and Aerospace Engineering

1998-03-01T23:59:59.000Z

215

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

216

HEATS: Thermal Energy Storage  

SciTech Connect (OSTI)

HEATS Project: The 15 projects that make up ARPA-E’s HEATS program, short for “High Energy Advanced Thermal Storage,” seek to develop revolutionary, cost-effective ways to store thermal energy. HEATS focuses on 3 specific areas: 1) developing high-temperature solar thermal energy storage capable of cost-effectively delivering electricity around the clock and thermal energy storage for nuclear power plants capable of cost-effectively meeting peak demand, 2) creating synthetic fuel efficiently from sunlight by converting sunlight into heat, and 3) using thermal energy storage to improve the driving range of electric vehicles (EVs) and also enable thermal management of internal combustion engine vehicles.

None

2012-01-01T23:59:59.000Z

217

Caviton dynamics in strong Langmuir turbulence  

SciTech Connect (OSTI)

Recent studies based on long time computer simulations of Langmuir turbulence as described by Zakharov's model will be reviewed. These show that for strong to moderate ion sound samping the turbulent energy is dominantly in nonlinear ''caviton'' excitations which are localized in space and time. A local caviton model will be presented which accounts for the nucleation-collapse-burnout cycles of individual cavitons as well as their space-time correlations. This model is in detailed agreement with many features of the electron density fluctuation spectra in the ionosphere modified by powerful hf waves as measured by incoherent scatter radar. Recently such observations have verified a prediction of the theory that ''free'' Langmuir waves are emitted in the caviton collapse process. These observations and theoretical considerations also strongly imply that cavitons in the heated ionosphere, under certain conditions, evolve to states in which they are ordered in space and time. The sensitivity of the high frequency Langmuir field dynamics to the low frequency ion density fluctuations and the related caviton nucleation process will be discussed. 40 refs., 19 figs.

DuBois, D.; Rose, H.A.; Russell, D.

1989-01-01T23:59:59.000Z

218

Dynamics of cavitons in strong Langmuir turbulence  

SciTech Connect (OSTI)

Recent studies of Langmuir turbulence as described by Zakharov's model will be reviewed. For parameters of interest in laser-plasma experiments and for ionospheric hf heating experiments a significant fraction of the turbulent energy is in nonlinear caviton'' excitations which are localized in space and time. A local caviton model will be presented which accounts for the nucleation-collapse-burnout cycles of individual cavitons as well as their space-time correlations. This model is in detailed agreement with many features of the electron density fluctuation spectra in the ionosphere modified by powerful hf waves as measured by incoherent scatter radar. Recently such observations have verified a prediction of the theory that free'' Langmuir waves are emitted in the caviton collapse process. Observations and theoretical considerations also imply that when the pump frequency is slightly lower than the ambient electron plasma frequency cavitons may evolve to states in which they are ordered in space and time. The sensitivity of the high frequency Langmuir field dynamics to the low frequency ion density fluctuations and the related caviton nucleation process will be discussed. 42 refs., 12 figs.

DuBois, D.F.; Rose, H.A.; Russell, D.

1990-01-01T23:59:59.000Z

219

Flame front geometry in premixed turbulent flames  

SciTech Connect (OSTI)

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

220

Anomalous scalings in differential models of turbulence  

E-Print Network [OSTI]

Differential models for hydrodynamic, passive-scalar and wave turbulence given by nonlinear first- and second-order evolution equations for the energy spectrum in the $k$-space were analysed. Both types of models predict formation an anomalous transient power-law spectra. The second-order models were analysed in terms of self-similar solutions of the second kind, and a phenomenological formula for the anomalous spectrum exponent was constructed using numerics for a broad range of parameters covering all known physical examples. The first-order models were examined analytically, including finding an analytical prediction for the anomalous exponent of the transient spectrum and description of formation of the Kolmogorov-type spectrum as a reflection wave from the dissipative scale back into the inertial range. The latter behaviour was linked to pre-shock/shock singularities similar to the ones arising in the Burgers equation. Existence of the transient anomalous scaling and the reflection-wave scenario are argued to be a robust feature common to the finite-capacity turbulence systems. The anomalous exponent is independent of the initial conditions but varies for for different models of the same physical system.

Simon Thalabard; Sergey Nazarenko; Sebastien Galtier; Medvedev Sergey

2015-02-24T23:59:59.000Z

Note: This page contains sample records for the topic "rangepsi 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

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

222

Scrape-off layer tokamak plasma turbulence  

SciTech Connect (OSTI)

Two-dimensional (2D) interchange turbulence in the scrape-off layer of tokamak plasmas and their subsequent contribution to anomalous plasma transport has been studied in recent years using electron continuity, current balance, and electron energy equations. In this paper, numerically it is demonstrated that the inclusion of ion energy equation in the simulation changes the nature of plasma turbulence. Finite ion temperature reduces floating potential by about 15% compared with the cold ion temperature approximation and also reduces the radial electric field. Rotation of plasma blobs at an angular velocity about 1.5 Multiplication-Sign 10{sup 5} rad/s has been observed. It is found that blob rotation keeps plasma blob charge separation at an angular position with respect to the vertical direction that gives a generation of radial electric field. Plasma blobs with high electron temperature gradients can align the charge separation almost in the radial direction. Influence of high ion temperature and its gradient has been presented.

Bisai, N.; Singh, R.; Kaw, P. K. [Institute for Plasma Research, Bhat, Gandhinagar, Gujarat 382428 (India)

2012-05-15T23:59:59.000Z

223

Non-thermal Plasma Chemistry Non-thermal Thermal  

E-Print Network [OSTI]

-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;Leuchtstoffröhre Plasma-Bildschirm Energiesparlampe #12;electrical engineering light sources textile industry

Greifswald, Ernst-Moritz-Arndt-Universität

224

Study of Emission TurbulenceRadiation Interaction in Hypersonic Boundary Layers  

E-Print Network [OSTI]

Study of Emission Turbulence­Radiation Interaction in Hypersonic Boundary Layers L. Duan and M. P of emission turbulence­radiation interaction in hypersonic turbulent boundary layers, representative interaction between turbulence and emission at the hypersonic environment under investigation. An explanation

Martín, Pino

225

On Measuring the Terms of the Turbulent Kinetic Energy Budget from an AUV LOUIS GOODMAN  

E-Print Network [OSTI]

of production of turbulent kinetic energy (TKE). Heat flux is obtained by correlating the vertical velocityOn Measuring the Terms of the Turbulent Kinetic Energy Budget from an AUV LOUIS GOODMAN School of the steady-state, homogeneous turbulent kinetic energy budgets are obtained from mea- surements of turbulence

Goodman, Louis

226

Thermal contact resistance  

E-Print Network [OSTI]

This work deals with phenomena of thermal resistance for metallic surfaces in contact. The main concern of the work is to develop reliable and practical methods for prediction of the thermal contact resistance for various ...

Mikic, B. B.

1966-01-01T23:59:59.000Z

227

Thermal Processes | Department of Energy  

Broader source: Energy.gov (indexed) [DOE]

Hydrogen Production Current Technology Thermal Processes Thermal Processes Some thermal processes use the energy in various resources, such as natural gas, coal, or biomass,...

228

COLLISIONLESS DAMPING AT ELECTRON SCALES IN SOLAR WIND TURBULENCE  

SciTech Connect (OSTI)

The dissipation of turbulence in the weakly collisional solar wind plasma is governed by unknown kinetic mechanisms. Two candidates have been suggested to play an important role in the dissipation, collisionless damping via wave-particle interactions and dissipation in small-scale current sheets. High resolution spacecraft measurements of the turbulent magnetic energy spectrum provide important constraints on the dissipation mechanism. The limitations of popular fluid and hybrid numerical schemes for simulation of the dissipation of solar wind turbulence are discussed, and instead a three-dimensional kinetic approach is recommended. We present a three-dimensional nonlinear gyrokinetic simulation of solar wind turbulence at electron scales that quantitatively reproduces the exponential form of the turbulent magnetic energy spectrum measured in the solar wind. A weakened cascade model that accounts for nonlocal interactions and collisionless Landau damping also quantitatively agrees with the observed exponential form. These results establish that a turbulent cascade of kinetic Alfven waves that is terminated by collisionless Landau damping is sufficient to explain the observed magnetic energy spectrum in the dissipation range of solar wind turbulence.

TenBarge, J. M.; Howes, G. G. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States); Dorland, W., E-mail: jason-tenbarge@uiowa.edu [Department of Physics, University of Maryland, College Park, MA 20742-3511 (United States)

2013-09-10T23:59:59.000Z

229

Multiwavelength Thermal Emission  

E-Print Network [OSTI]

Multiwavelength Astronomy NASA #12;Thermal Emission #12;Thermal Emission Non-thermal p-p collisions Optical IR Radio/ Microwave sources of emission massive stars, WHIM, Ly many dust, cool objects-ray ~GeV Gamma-ray ~TeV sources of emission AGN, clusters, SNR, binaries, stars AGN (obscured), shocks

California at Santa Cruz, University of

230

Thermal Performance Benchmarking (Presentation)  

SciTech Connect (OSTI)

This project will benchmark the thermal characteristics of automotive power electronics and electric motor thermal management systems. Recent vehicle systems will be benchmarked to establish baseline metrics, evaluate advantages and disadvantages of different thermal management systems, and identify areas of improvement to advance the state-of-the-art.

Moreno, G.

2014-11-01T23:59:59.000Z

231

Thermal neutron detection system  

DOE Patents [OSTI]

According to the present invention, a system for measuring a thermal neutron emission from a neutron source, has a reflector/moderator proximate the neutron source that reflects and moderates neutrons from the neutron source. The reflector/moderator further directs thermal neutrons toward an unmoderated thermal neutron detector.

Peurrung, Anthony J. (Richland, WA); Stromswold, David C. (West Richland, WA)

2000-01-01T23:59:59.000Z

232

Edge Turbulence Velocity Changes with Lithium Coating on NSTX  

SciTech Connect (OSTI)

Lithium coating improves energy confinement and eliminates edge localized modes in NSTX, but the mechanism of this improvement is not yet well understood. We used the gas-puff-imaging (GPI) diagnostic on NSTX to measure the changes in edge turbulence which occurred during a scan with variable lithium wall coating, in order to help understand the reason for the confinement improvement with lithium. There was a small increase in the edge turbulence poloidal velocity and a decrease in the poloidal velocity fluctuation level with increased lithium. The possible effect of varying edge neutral density on turbulence damping was evaluated for these cases in NSTX. __________________________________________________

Cao, A.; Zweben, S. J.; Stotler, D. P.; Bell, M.; Diallo, A.; Kaye, S. M.; LeBlanc, B.

2012-08-10T23:59:59.000Z

233

Compressive turbulent cascade and heating in the solar wind  

SciTech Connect (OSTI)

A turbulent energy cascade has been recently identified in high-latitude solar wind data samples by using a Yaglom-like relation. However, analogous scaling law, suitably modified to take into account compressible fluctuations, has been observed in a much more extended fraction of the same data set recorded by the Ulysses spacecraft. Thus, it seems that large scale density fluctuations, despite their low amplitude, play a major role in the basic scaling properties of turbulence. The compressive turbulent cascade, moreover, seems to be able to supply the energy needed to account for the local heating of the non-adiabatic solar wind.

Marino, R. [Dipartimento di Fisica, Universita della Calabria, Ponte Bucci 31C, I-87036 Rende (Italy); University of Nice Sophia Antipolis, CNRS, Observatoire de la Cote d'Azur, B.P. 4229, 06304 Nice Cedex 4 (France); Sorriso-Valvo, L. [Liquid Crystal Laboratory, INFM/CNR, Ponte Bucci 33B, I-87036 Rende (Italy); Carbone, V. [Dipartimento di Fisica, Universita della Calabria, Ponte Bucci 31C, I-87036 Rende (Italy); Noullez, A. [University of Nice Sophia Antipolis, CNRS, Observatoire de la Cote d'Azur, B.P. 4229, 06304 Nice Cedex 4 (France); Bruno, R. [INAF-Istituto Fisica Spazio Interplanetario, Rome (Italy)

2010-03-25T23:59:59.000Z

234

An h-adaptive finite element method for turbulent heat transfer  

SciTech Connect (OSTI)

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

235

Nonextensive statistical dynamics applied to wall turbulence  

E-Print Network [OSTI]

We apply a formalism of nonextensive statistical mechanics to experimental wall turbulence data, for the first time to our knowledge. Wind tunnel data for velocity differences a streamwise distance $r$ apart are compared to the prediction from theory as developed by Beck. The simplest theory, in which all free parameters are removed, is found to reproduce statistics for the wall-normal velocity component remarkably well, even for $r$ well beyond the corresponding integral scale, while the corresponding description of the streamwise velocity fluctuations is reasonable at separations below the integral scale. A least-squares 2-parameter fit is performed, and the dependence of the optimum parameter values on wall separation and $r$ is analysed. Both parameters are found to be approximately independent of wall-separation in the logarithmic sub-layer.

Simen Å Ellingsen; Per-Åge Krogstad

2014-02-10T23:59:59.000Z

236

Nonlinear parallel momentum transport in strong turbulence  

E-Print Network [OSTI]

Most existing theoretical studies of momentum transport focus on calculating the Reynolds stress based on quasilinear theory, without considering the \\emph{nonlinear} momentum flux-$$. However, a recent experiment on TORPEX found that the nonlinear toroidal momentum flux induced by blobs makes a significant contribution as compared to the Reynolds stress [Labit et al., Phys. Plasmas {\\bf 18}, 032308 (2011)]. In this work, the nonlinear parallel momentum flux in strong turbulence is calculated by using three dimensional Hasegawa-Mima equation. It is shown that nonlinear diffusivity is smaller than quasilinear diffusivity from Reynolds stress. However, the leading order nonlinear residual stress can be comparable to the quasilinear residual stress, and so could be important to intrinsic rotation in tokamak edge plasmas. A key difference from the quasilinear residual stress is that parallel fluctuation spectrum asymmetry is not required for nonlinear residual stress.

Wang, Lu; Diamond, P H

2015-01-01T23:59:59.000Z

237

Quantitative imaging of turbulent and reacting flows  

SciTech Connect (OSTI)

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

238

Similarity solutions and applications to turbulent upward flame spread on noncharring materials  

SciTech Connect (OSTI)

The primary achievement in this work has been the discovery that turbulent upward flame spread on noncharring materials (for pyrolysis lengths less than 1.8m) can be directly predicted by using measurable flammability parameters. These parameters are: a characteristic length scale which is proportional to a turbulent combustion and mixing related length scale parameter ({dot q}{double_prime}{sub net}({Delta}H{sub c}/{Delta}H{sub v})){sup 2}, a pyrolysis or ignition time {tau}{sub p}, and a parameter which determines the transient pyrolysis history of a non-charring material: {lambda} = L/c{Delta}T{sub p} = ratio of the latent heat to the sensible heat of the pyrolysis temperature of the material. In the length scale parameter, {dot q}{double_prime}{sub net} is the total net heat flux from the flames to the wall (i.e., total heat flux minus reradiation losses), {Delta}H{sub c} is the heat of combustion and {Delta}H{sub v} is an effective heat of gasification for the material. The pyrolysis or ignition time depends (for thermally thick conditions) on the material thermal inertia, the pyrolysis temperature, and the total heat flux from the flames to the wall, {dot q}{double_prime}{sub fw}. The present discovery was made possible by using both a numerical simulation, developed earlier, and exact similarity solutions, which are developed in this work. The predictions of the analysis have been validated by comparison with upward flame spread experiments on PMMA.

Delichatsios, M.A.; Delichatsios, M.; Chen, Y. [Factory Mutual Research Corporation, Norwood, MA (United States)] [Factory Mutual Research Corporation, Norwood, MA (United States); Hasemi, Y. [Ministry of Construction, Tsukuba (Japan). Building Research Inst.] [Ministry of Construction, Tsukuba (Japan). Building Research Inst.

1995-08-01T23:59:59.000Z

239

Discreteness and resolution effects in rapidly rotating turbulence  

E-Print Network [OSTI]

Rotating turbulence is characterized by the nondimensional Rossby number Ro, which is a measure of the strength of the Coriolis term relative to that of the nonlinear term. For rapid rotation (Ro?0), nonlinear interactions ...

Bourouiba, Lydia

240

Magnetohydrodynamic lattice Boltzmann simulations of turbulence and rectangular jet flow  

E-Print Network [OSTI]

relaxation time (SRT) parameter for the Maxwell’s 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

Note: This page contains sample records for the topic "rangepsi 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

Cross-Scale Effects in Solar-Wind Turbulence  

SciTech Connect (OSTI)

The understanding of the small-scale termination of the turbulent energy cascade in collisionless plasmas is nowadays one of the outstanding problems in space physics. In the absence of collisional viscosity, the dynamics at small scales is presumably kinetic in nature; the identification of the physical mechanism which replaces energy dissipation and establishes the link between macroscopic and microscopic scales would open a new scenario in the study of turbulent heating in space plasmas. We present a numerical analysis of kinetic effects along the turbulent energy cascade in solar-wind plasmas which provides an effective unified interpretation of a wide set of spacecraft observations and shows that, simultaneously with an increase in the ion perpendicular temperature, strong bursts of electrostatic activity in the form of ion-acoustic turbulence are produced together with accelerated beams in the ion distribution function.

Valentini, F.; Veltri, P. [Dipartimento di Fisica and CNISM, Universita della Calabria, 87036 Rende (Serbia and Montenegro) (Italy); Califano, F. [Dipartimento di Fisica and CNISM, Universita di Pisa, 56127 Pisa (Italy); Mangeney, A. [Observatoire de Paris-Meudon, 92195 Meudon Cedex (France)

2008-07-11T23:59:59.000Z

242

Atmospheric Lagrangian coherent structures considering unresolved turbulence and forecast uncertainty  

E-Print Network [OSTI]

Atmospheric Lagrangian coherent structures considering unresolved turbulence and forecast structures Stochastic trajectory Stochastic FTLE field Ensemble forecasting Uncertainty analysis a b s t r of the forecast FTLE fields is analyzed using ensemble forecasting. Unavoidable errors of the forecast velocity

Ross, Shane

243

Experimental Signatures of Critically Balanced Turbulence in MAST  

E-Print Network [OSTI]

Beam emission spectroscopy (BES) measurements of ion-scale density fluctuations in the MAST tokamak are used to show that the turbulence correlation time, the drift time associated with ion temperature or density gradients, ...

Ghim, Y.-c.

244

Test particle study of ion transport in drift type turbulence  

SciTech Connect (OSTI)

Ion transport regimes in drift type turbulence are determined in the frame of a realistic model for the turbulence spectrum based on numerical simulations. The model includes the drift of the potential with the effective diamagnetic velocity, turbulence anisotropy, and dominant waves. The effects of the zonal flow modes are also analyzed. A semi-analytical method that is able to describe trajectory stochastic trapping or eddying is used for obtaining the transport coefficients as function of the parameters of the turbulence. Analytical approximations of the transport coefficients are derived from the results. They show the transition from Bohm to gyro-Bohm scaling as plasma size increases in very good agreement with the numerical simulations.

Vlad, M.; Spineanu, F. [National Institute of Laser, Plasma and Radiation Physics, Association EURATOM-MEdC, Atomistilor 409, 077125 Magurele, Bucharest (Romania)] [National Institute of Laser, Plasma and Radiation Physics, Association EURATOM-MEdC, Atomistilor 409, 077125 Magurele, Bucharest (Romania)

2013-12-15T23:59:59.000Z

245

Behavior of buoyant moist plumes in turbulent atmospheres  

E-Print Network [OSTI]

A widely applicable computational model of buoyant moist plumes in turbulent atmospheres has been constructed. To achieve this a one dimensional Planetary Boundary Layer (P.B.L.) model has been developed to account for ...

Hamza, Redouane

1981-01-01T23:59:59.000Z

246

Turbulent drag reduction by constant near-wall forcing  

E-Print Network [OSTI]

Injection of high molecular weight polymer solutions or gas in the near-wall region of a liquid boundary layer can result in turbulent drag reduction of more than ...

JIN XU, SUCHUAN DONG, MARTIN R. MAXEY and GEORGE E. KARNIADAKIS

2007-06-07T23:59:59.000Z

247

Water Vapor Turbulence Statistics in the Convective Boundary...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

This study presented the first long-term data set of variance and skewness turbulent statistic profiles in the CBL, spanning a range of seasons and environmental conditions. These...

248

Pdf modeling of turbulent nonpremixed methane jet flames  

SciTech Connect (OSTI)

An expanded model of turbulent nonpremixed combustion is presented. In the model, the scalar mixing and reactions are described by a probability density function (pdf) submodel capable of handling five scalars, while the turbulent velocity field is described by a second-order moment closure. Two plausible chemical reaction models are considered: a five-scalar, four-step, reduced reaction mechanism, and a four-scalar constrained equilibrium model. Detailed comparisons of model predictions with laser Raman experimental dat provide a valuable evaluation of the model's ability in predicting nonequilibrium chemistry in turbulent nonpremixed flames. Overall, the model fails to predict greater departure from chemical equilibrium as mixing rates are increased. Interestingly, this failure is not due to the chemical model, both of which perform satisfactorily. Instead, the failure to predict greater departure from chemical equilibrium is a subtle artifact of the current Monte Carlo simulation of turbulent mixing and chemical reaction.

Chen, J.Y.; Kollmann, W.; Dibble, R.W. (Sandia National Labs., Livermore, CA (USA). Combustion Research Faclity)

1989-01-01T23:59:59.000Z

249

A numerical investigation of collisionality and turbulent transport  

E-Print Network [OSTI]

An investigation of collisionality's role in turbulent transport in magnetized plasma using the GS2 gyrokinetic simulation software is presented. The investigation consists of three parts, conducted by way of numerical ...

Lindsey, Martin L., S.B. Massachusetts Institute of Technology

2014-01-01T23:59:59.000Z

250

System Identification and Active Control of a Turbulent Boundary Layer  

E-Print Network [OSTI]

An experimental investigation is made into the active control of the near-wall region of a turbulent boundary layer using a linear control scheme. System identification in the boundary layer provides optimal transfer ...

Rathnasingham, Ruben

251

NUMERICAL MODELING OF TURBULENT FLOW IN A COMBUSTION TUNNEL  

E-Print Network [OSTI]

1VJcDona·ld, H. (1979) Combustion r 1 iodeJ·ing in Two and1979) Practical Turbulent-Combustion Interaction Models forInternation on Combustors. Combustion The 17th Symposium

Ghoniem, A.F.

2013-01-01T23:59:59.000Z

252

Turbulent Transport in Tokamak Plasmas with Rotational Shear  

SciTech Connect (OSTI)

Nonlinear gyrokinetic simulations are conducted to investigate turbulent transport in tokamak plasmas with rotational shear. At sufficiently large flow shears, linear instabilities are suppressed, but transiently growing modes drive subcritical turbulence whose amplitude increases with flow shear. This leads to a local minimum in the heat flux, indicating an optimal ExB shear value for plasma confinement. Local maxima in the momentum fluxes are observed, implying the possibility of bifurcations in the ExB shear. The critical temperature gradient for the onset of turbulence increases with flow shear at low flow shears; at higher flow shears, the dependence of heat flux on temperature gradient becomes less stiff. The turbulent Prandtl number is found to be largely independent of temperature and flow gradients, with a value close to unity.

Barnes, M.; Highcock, E. G. [Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3NP (United Kingdom); Euratom/CCFE Fusion Association, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Parra, F. I.; Schekochihin, A. A. [Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3NP (United Kingdom); Cowley, S. C.; Roach, C. M. [Euratom/CCFE Fusion Association, Culham Science Centre, Abingdon OX14 3DB (United Kingdom)

2011-04-29T23:59:59.000Z

253

Lattice Boltzmann equation simulations of turbulence, mixing, and combustion  

E-Print Network [OSTI]

We explore the capability of lattice Boltzmann equation (LBE) method for complex fluid flows involving turbulence, mixing, and reaction. In the first study, LBE schemes for binary scalar mixing and multi-component reacting flow with reactions...

Yu, Huidan

2006-04-12T23:59:59.000Z

254

Understanding and predicting soot generation in turbulent non-premixed jet flames.  

SciTech Connect (OSTI)

This report documents the results of a project funded by DoD's Strategic Environmental Research and Development Program (SERDP) on the science behind development of predictive models for soot emission from gas turbine engines. Measurements of soot formation were performed in laminar flat premixed flames and turbulent non-premixed jet flames at 1 atm pressure and in turbulent liquid spray flames under representative conditions for takeoff in a gas turbine engine. The laminar flames and open jet flames used both ethylene and a prevaporized JP-8 surrogate fuel composed of n-dodecane and m-xylene. The pressurized turbulent jet flame measurements used the JP-8 surrogate fuel and compared its combustion and sooting characteristics to a world-average JP-8 fuel sample. The pressurized jet flame measurements demonstrated that the surrogate was representative of JP-8, with a somewhat higher tendency to soot formation. The premixed flame measurements revealed that flame temperature has a strong impact on the rate of soot nucleation and particle coagulation, but little sensitivity in the overall trends was found with different fuels. An extensive array of non-intrusive optical and laser-based measurements was performed in turbulent non-premixed jet flames established on specially designed piloted burners. Soot concentration data was collected throughout the flames, together with instantaneous images showing the relationship between soot and the OH radical and soot and PAH. A detailed chemical kinetic mechanism for ethylene combustion, including fuel-rich chemistry and benzene formation steps, was compiled, validated, and reduced. The reduced ethylene mechanism was incorporated into a high-fidelity LES code, together with a moment-based soot model and models for thermal radiation, to evaluate the ability of the chemistry and soot models to predict soot formation in the jet diffusion flame. The LES results highlight the importance of including an optically-thick radiation model to accurately predict gas temperatures and thus soot formation rates. When including such a radiation model, the LES model predicts mean soot concentrations within 30% in the ethylene jet flame.

Wang, Hai (University of Southern California, Los Angeles, CA); Kook, Sanghoon; Doom, Jeffrey; Oefelein, Joseph Charles; Zhang, Jiayao; Shaddix, Christopher R.; Schefer, Robert W.; Pickett, Lyle M.

2010-10-01T23:59:59.000Z

255

Statistics of turbulence via polarimetry: alignment of grains and atoms  

E-Print Network [OSTI]

Most astrophysical fluids are turbulent and magnetized. Fluctuations of polarization provide a promising way to study astrophysical magnetic turbulence. We discuss polarization that arises from grains and atoms aligned in respect to magnetic field, describe the processes of alignment, explain when the alignment reflects the direction of magnetic field. We show that temporal fluctuations of interplanetary magnetic field can be studied using aligned sodium atoms.

A. Lazarian; Huirong Yan

2005-05-29T23:59:59.000Z

256

Angular multiscale statistics of Lagrangian trajectories in turbulence  

E-Print Network [OSTI]

The angle between subsequent particle displacement increments is evaluated as a function of the timelag in isotropic turbulence. It is shown that the evolution of this angle contains two well-defined power-laws, reflecting the multi-scale dynamics of high-Reynolds number turbulence. The proba-bility density function of the directional change is shown to be self-similar and well approximated by an analytically derived model assuming Gaussianity and independence of the velocity and the Lagrangian acceleration.

Bos, Wouter; Schneider, Kai

2015-01-01T23:59:59.000Z

257

Turbulent transport across shear layers in magnetically confined plasmas  

SciTech Connect (OSTI)

Shear layers modify the turbulence in diverse ways and do not only suppress it. A spatial-temporal investigation of gyrofluid simulations in comparison with experiments allows to identify further details of the transport process across shear layers. Blobs in and outside a shear layer merge, thereby exchange particles and heat and subsequently break up. Via this mechanism particles and heat are transported radially across shear layers. Turbulence spreading is the immanent mechanism behind this process.

Nold, B.; Ramisch, M. [Institut für Grenzflächenverfahrenstechnik und Plasmatechnologie, Universität Stuttgart, D-70569 Stuttgart (Germany); Manz, P.; Birkenmeier, G. [Physik-Department E28, Technische Universität München, James-Franck-Str.1, D-85748 Garching (Germany); Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Ribeiro, T. T.; Müller, H. W.; Scott, B. D. [Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Fuchert, G. [IJL, Université de Lorraine, CNRS (UMR 7198), BP 40239 Vandoeuvre-lès-Nancy (France); Stroth, U. [Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Physik-Department E28, Technische Universität München, James-Franck-Str.1, D-85748 Garching (Germany)

2014-10-15T23:59:59.000Z

258

Coastal Microstructure: From Active Overturn to Fossil Turbulence  

E-Print Network [OSTI]

.................................................................................... 33 Figure 10. Front view of the sensor package installed on MSS profiler including two shear probes, micro-temperature, micro-conductivity, accurate- temperature, accurate-conductivity, acceleration, turbidity, and depth sensors... frequently used in oceanography. A very important characteristic of turbulence is that it produces highly persistent, irreversible effects in a variety of hydro-physical fields. Linear waves come and go without leaving any trace, but turbulence...

Leung, Pak Tao

2012-02-14T23:59:59.000Z

259

Adaptive Mesh Refinement for Supersonic Molecular Cloud Turbulence  

E-Print Network [OSTI]

We performed a series of three-dimensional numerical simulations of supersonic homogeneous Euler turbulence with adaptive mesh refinement (AMR) and effective grid resolution up to 1024^3 zones. Our experiments describe non-magnetized driven supersonic turbulent flows with an isothermal equation of state. Mesh refinement on shocks and shear is implemented to cover dynamically important structures with the highest resolution subgrids and calibrated to match the turbulence statistics obtained from the equivalent uniform grid simulations. We found that at a level of resolution slightly below 512^3, when a sufficient integral/dissipation scale separation is first achieved, the fraction of the box volume covered by the AMR subgrids first becomes smaller than unity. At the higher AMR levels subgrids start covering smaller and smaller fractions of the whole volume, which scale with the Reynolds number as Re^{-1/4}. We demonstrate the consistency of this scaling with a hypothesis that the most dynamically important structures in intermittent supersonic turbulence are strong shocks with a fractal dimension of two. We show that turbulence statistics derived from AMR simulations and simulations performed on uniform grids agree surprisingly well, even though only a fraction of the volume is covered by AMR subgrids. Based on these results, we discuss the signature of dissipative structures in the statistical properties of supersonic turbulence and their role in overall flow dynamics.

Alexei G. Kritsuk; Michael L. Norman; Paolo Padoan

2005-06-02T23:59:59.000Z

260

Effect of turbulent heat transfer on continuous ingot solidification  

SciTech Connect (OSTI)

For many continuous ingot casting processes, turbulent heat transfer in the molten pool plays a critical role which, along with buoyancy and surface tension, is responsible for the quality of the end products. Based on a modified low Reynolds number K-[epsilon] two-equation closure, accounting for the phase change and mushy zone formation, the effect of turbulent heat transfer on the solidification characteristics during titanium alloy ingot casting in an electron beam melting process is investigated. The overall heat transfer rate is enhanced by turbulent transport via two sources, one through the correlated velocity and temperature fluctuations present for both single- and multi-phase flows, and the other through the correlated velocity and release of latent heat fluctuations which are unique to the flows with phase change. The roles played by both mechanisms are identified and assessed. The present turbulence model predicts that although the mushy zone defined by the mean temperature field is generally of substantial thickness as a result of the convection effect, the actual instantaneous zone thickness varies substantially due to turbulence effect. This finding is in contrast to the traditionally held viewpoint, based on the conduction analysis, of a generally thin mushy zone. The impact of turbulent heat transfer on local dendrite formation and remelting is illustrated and the issues involved in model development highlighted.

Shyy, W.; Chen, M.H. (Univ. of Florida, Gainesville, FL (United States). Dept. of Aerospace Engineering); Pang, Y.; Wei, D.Y. (GE Aircraft Engines, Engineering Materials Technology Labs., Lynn, MA (United States)); Hunter, G.B. (GE Aircraft Engines, Engineering Materials Technology Labs., Cincinnati, OH (United States))

1993-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "rangepsi 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

GYROKINETIC PARTICLE SIMULATION OF TURBULENT TRANSPORT IN BURNING PLASMAS  

SciTech Connect (OSTI)

The SciDAC project at the IFS advanced the state of high performance computing for turbulent structures and turbulent transport. The team project with Prof Zhihong Lin [PI] at Univ California Irvine produced new understanding of the turbulent electron transport. The simulations were performed at the Texas Advanced Computer Center TACC and the NERSC facility by Wendell Horton, Lee Leonard and the IFS Graduate Students working in that group. The research included a Validation of the electron turbulent transport code using the data from a steady state university experiment at the University of Columbia in which detailed probe measurements of the turbulence in steady state were used for wide range of temperature gradients to compare with the simulation data. These results were published in a joint paper with Texas graduate student Dr. Xiangrong Fu using the work in his PhD dissertation. X.R. Fu, W. Horton, Y. Xiao, Z. Lin, A.K. Sen and V. Sokolov, “Validation of electron Temperature gradient turbulence in the Columbia Linear Machine, Phys. Plasmas 19, 032303 (2012).

Horton, Claude Wendell

2014-06-10T23:59:59.000Z

262

The evaluation of a turbulent loads characterization system  

SciTech Connect (OSTI)

In this paper we discuss an on-line turbulent load characterization system that has been designed to acquire loading spectra from turbines of the same design operating in several different environments and from different turbine designs operating in the same environment. This System simultaneously measures the rainflow-counted alternating and mean loading spectra and the hub-height turbulent mean shearing stress and atmospheric stability associated with the turbulent inflow. We discuss the theory behind the measurement configuration and the results of proof-of-concept testing recently performed at the National Wind Technology Center (NWTC) using a Bergey EXCEL-S 10-kW wind turbine. The on-line approach to characterizing the load spectra and the inflow turbulent scaling parameter produces results that are consistent with other measurements. The on-line approximation of the turbulent shear stress or friction velocity u* also is considered adequate. The system can be used to characterize turbulence loads during turbine deployment in a wide variety of environments. Using the WISPER protocol, we found that a wide-range, variable-speed turbine will accumulate a larger number of stress cycles in the low-cycle, high-amplitude (LCHA) region when compared with a constant speed rotor under similar inflow conditions.

Kelley, N.D.; McKenna, H.E. [National Renewable Energy Lab., Golden, CO (United States)

1996-01-01T23:59:59.000Z

263

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

264

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 (OSTI)

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

265

Thermal comfort during surgery  

E-Print Network [OSTI]

THERMAL COMFORT DURING SURGERY A Thesis by DAVID HAROLD MANNING Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE December 1978 Major Subject: Industrial... Engineering THERMAL COMFORT DURING SURGERY A Thesis by DAVID HAROLD MANNING Approved as to style and content by: airman of C it ee Head of Department Member Me er December 1978 ABSTRACT Thermal Comfort During Surgery (December 1978) David Harold...

Manning, David Harold

1978-01-01T23:59:59.000Z

266

Thermal Infrared Remote Sensing  

E-Print Network [OSTI]

Thermal Infrared Remote Sensing Thermal Infrared Remote Sensing #12;0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4 and x-ray Ultraviolet Infrared Microwave and radio waves Wavelength in meters (m) Electromagnetic.77 700 red limit 30k0.041 2.48 green500 near-infrared far infrared ultraviolet Thermal Infrare refers

267

Isolation of Metals from Liquid Wastes: Reactive Scavenging in Turbulent Thermal Reactors  

SciTech Connect (OSTI)

Sorption of cesium and strontium on kaolinite powders was investigated as a means to minimize the emissions of these metals during certain high temperature processes currently being developed to isolate and dispose of radiological and mixed wastes. In this work, non-radioactive aqueous cesium acetate or strontium acetate was atomized down the center of a natural gas flame supported on a variable-swirl burner in a refractory-lined laboratory-scale combustion facility. Kaolinite powder was injected at a post-flame location in the combustor. Cesium readily vaporizes in the high temperature regions of the combustor, but was reactively scavenged onto dispersed kaolinite. Global sorption mechanisms of cesium vapor on kaolinite were quantified, and are related to those available in the literature for sodium and lead. Both metal adsorption and substrate deactivation steps are important, and so there is an optimum temperature, between 1400 and 1500 K, at which maximum sorption occurs. The presence of chlorine inhibits cesium sorption. In contrast to cesium, and in the absence of chlorine, strontium was only partially vaporized and was, therefore, only partially scavengeable. The strontium data did not allow quantification of global kinetic mechanisms of interaction, although equilibrium arguments provided insight into the effects of chlorine on strontium sorption. These results have implications for the use of sorbents to control cesium and strontium emissions during high temperature waste processing including incineration and vitrification.

William Linak

2004-12-16T23:59:59.000Z

268

Variable pressure thermal insulating jacket  

DOE Patents [OSTI]

A device for controlled insulation of a thermal device is disclosed. The device includes a thermal jacket with a closed volume able to be evacuated to form an insulating jacket around the thermal source. A getter material is in communication with the closed volume of the thermal jacket. The getter material can absorb and desorb a control gas to control gas pressure in the volume of the thermal jacket to control thermal conductivity in the thermal jacket. 10 figs.

Nelson, P.A.; Malecha, R.F.; Chilenskas, A.A.

1994-09-20T23:59:59.000Z

269

NANO REVIEW Open Access Thermal conductivity and thermal boundary  

E-Print Network [OSTI]

NANO REVIEW Open Access Thermal conductivity and thermal boundary resistance of nanostructures and the thermal transport prop- erties is a key point to design materials with preferred thermal properties with the heat dissipation on them. The influence of the interfacial roughness on the thermal conductivity

Boyer, Edmond

270

Anomalous scalings in differential models of turbulence  

E-Print Network [OSTI]

Differential models for hydrodynamic, passive-scalar and wave turbulence given by nonlinear first- and second-order evolution equations for the energy spectrum in the $k$-space were analysed. Both types of models predict formation an anomalous transient power-law spectra. The second-order models were analysed in terms of self-similar solutions of the second kind, and a phenomenological formula for the anomalous spectrum exponent was constructed using numerics for a broad range of parameters covering all known physical examples. The first-order models were examined analytically, including finding an analytical prediction for the anomalous exponent of the transient spectrum and description of formation of the Kolmogorov-type spectrum as a reflection wave from the dissipative scale back into the inertial range. The latter behaviour was linked to pre-shock/shock singularities similar to the ones arising in the Burgers equation. Existence of the transient anomalous scaling and the reflection-wave scenario are argu...

Thalabard, Simon; Galtier, Sebastien; Sergey, Medvedev

2015-01-01T23:59:59.000Z

271

Residual Energy Spectrum of Solar Wind Turbulence  

E-Print Network [OSTI]

It has long been known that the energy in velocity and magnetic field fluctuations in the solar wind is not in equipartition. In this paper, we present an analysis of 5 years of Wind data at 1 AU to investigate the reason for this. The residual energy (difference between energy in velocity and magnetic field fluctuations) was calculated using both the standard magnetohydrodynamic (MHD) normalization for the magnetic field and a kinetic version, which includes temperature anisotropies and drifts between particle species. It was found that with the kinetic normalization, the fluctuations are closer to equipartition, with a mean normalized residual energy of sigma_r = -0.19 and mean Alfven ratio of r_A = 0.71. The spectrum of residual energy, in the kinetic normalization, was found to be steeper than both the velocity and magnetic field spectra, consistent with some recent MHD turbulence predictions and numerical simulations, having a spectral index close to -1.9. The local properties of residual energy and cros...

Chen, C H K; Salem, C S; Maruca, B A

2013-01-01T23:59:59.000Z

272

Primordial magnetic field amplification from turbulent reheating  

SciTech Connect (OSTI)

We analyze the possibility of primordial magnetic field amplification by a stochastic large scale kinematic dynamo during reheating. We consider a charged scalar field minimally coupled to gravity. During inflation this field is assumed to be in its vacuum state. At the transition to reheating the state of the field changes to a many particle/anti-particle state. We characterize that state as a fluid flow of zero mean velocity but with a stochastic velocity field. We compute the scale-dependent Reynolds number Re(k), and the characteristic times for decay of turbulence, t{sub d} and pair annihilation t{sub a}, finding t{sub a} << t{sub d}. We calculate the rms value of the kinetic helicity of the flow over a scale L and show that it does not vanish. We use this result to estimate the amplification factor of a seed field from the stochastic kinematic dynamo equations. Although this effect is weak, it shows that the evolution of the cosmic magnetic field from reheating to galaxy formation may well be more complex than as dictated by simple flux freezing.

Calzetta, Esteban [Departamento de Física, FCEyN-UBA and IFIBA-CONICET, Cdad. Universitaria, Buenos Aires (Argentina); Kandus, Alejandra, E-mail: calzetta@df.uba.ar, E-mail: kandus@uesc.br [LATO - DCET - UESC. Rodovia Ilhéus-Itabuna, km 16 s/n, CEP: 45662-900, Salobrinho, Ilhéus-BA (Brazil)

2010-08-01T23:59:59.000Z

273

Thermal protection apparatus  

DOE Patents [OSTI]

The disclosure is directed to an apparatus for thermally protecting sensitive components in tools used in a geothermal borehole. The apparatus comprises a Dewar within a housing. The Dewar contains heat pipes such as brass heat pipes for thermally conducting heat from heat sensitive components such as electronics to a heat sink such as ice.

Bennett, G.A.; Elder, M.G.; Kemme, J.E.

1984-03-20T23:59:59.000Z

274

Mechanical Engineering & Thermal Group  

E-Print Network [OSTI]

Mechanical Engineering & Thermal Group The Mechanical Engineering (ME) & Thermal Group at LASP has, and ground- based mechanical systems. Instrument Design Building on decades of design experience that has evolved with the complexity of instrument design demands, LASP mechanical engineers develop advanced

Mojzsis, Stephen J.

275

Thermal protection apparatus  

DOE Patents [OSTI]

An apparatus which thermally protects sensitive components in tools used in a geothermal borehole. The apparatus comprises a Dewar within a housing. The Dewar contains heat pipes such as brass heat pipes for thermally conducting heat from heat sensitive components to a heat sink such as ice.

Bennett, Gloria A. (Los Alamos, NM); Elder, Michael G. (Los Alamos, NM); Kemme, Joseph E. (Albuquerque, NM)

1985-01-01T23:59:59.000Z

276

Solar thermal aircraft  

DOE Patents [OSTI]

A solar thermal powered aircraft powered by heat energy from the sun. A heat engine, such as a Stirling engine, is carried by the aircraft body for producing power for a propulsion mechanism, such as a propeller. The heat engine has a thermal battery in thermal contact with it so that heat is supplied from the thermal battery. A solar concentrator, such as reflective parabolic trough, is movably connected to an optically transparent section of the aircraft body for receiving and concentrating solar energy from within the aircraft. Concentrated solar energy is collected by a heat collection and transport conduit, and heat transported to the thermal battery. A solar tracker includes a heliostat for determining optimal alignment with the sun, and a drive motor actuating the solar concentrator into optimal alignment with the sun based on a determination by the heliostat.

Bennett, Charles L. (Livermore, CA)

2007-09-18T23:59:59.000Z

277

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

278

Thermal Recovery Methods  

SciTech Connect (OSTI)

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

279

Thermal treatment wall  

DOE Patents [OSTI]

A thermal treatment wall emplaced to perform in-situ destruction of contaminants in groundwater. Thermal destruction of specific contaminants occurs by hydrous pyrolysis/oxidation at temperatures achievable by existing thermal remediation techniques (electrical heating or steam injection) in the presence of oxygen or soil mineral oxidants, such as MnO.sub.2. The thermal treatment wall can be installed in a variety of configurations depending on the specific objectives, and can be used for groundwater cleanup, wherein in-situ destruction of contaminants is carried out rather than extracting contaminated fluids to the surface, where they are to be cleaned. In addition, the thermal treatment wall can be used for both plume interdiction and near-wellhead in-situ groundwater treatment. Thus, this technique can be utilized for a variety of groundwater contamination problems.

Aines, Roger D. (Livermore, CA); Newmark, Robin L. (Livermore, CA); Knauss, Kevin G. (Livermore, CA)

2000-01-01T23:59:59.000Z

280

Microsecond switchable thermal antenna  

SciTech Connect (OSTI)

We propose a thermal antenna that can be actively switched on and off at the microsecond scale by means of a phase transition of a metal-insulator material, the vanadium dioxide (VO{sub 2}). This thermal source is made of a periodically patterned tunable VO{sub 2} nanolayer, which support a surface phonon-polariton in the infrared range in their crystalline phase. Using electrodes properly registered with respect to the pattern, the VO{sub 2} phase transition can be locally triggered by ohmic heating so that the surface phonon-polariton can be diffracted by the induced grating, producing a highly directional thermal emission. Conversely, when heating less, the VO{sub 2} layers cool down below the transition temperature, the surface phonon-polariton cannot be diffracted anymore so that thermal emission is inhibited. This switchable antenna could find broad applications in the domain of active thermal coatings or in those of infrared spectroscopy and sensing.

Ben-Abdallah, Philippe, E-mail: pba@institutoptique.fr; Benisty, Henri; Besbes, Mondher [Laboratoire Charles Fabry, UMR 8501, Institut d'Optique, CNRS, Université Paris-Sud 11, 2, Avenue Augustin Fresnel, 91127 Palaiseau Cedex (France)

2014-07-21T23:59:59.000Z

Note: This page contains sample records for the topic "rangepsi 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

GRAVITATIONALLY UNSTABLE FLAMES: RAYLEIGH-TAYLOR STRETCHING VERSUS TURBULENT WRINKLING  

SciTech Connect (OSTI)

In this paper, we provide support for the Rayleigh-Taylor-(RT)-based subgrid model used in full-star simulations of deflagrations in Type Ia supernovae explosions. We use the results of a parameter study of two-dimensional direct numerical simulations of an RT unstable model flame to distinguish between the two main types of subgrid models (RT or turbulence dominated) in the flamelet regime. First, we give scalings for the turbulent flame speed, the Reynolds number, the viscous scale, and the size of the burning region as the non-dimensional gravity (G) is varied. The flame speed is well predicted by an RT-based flame speed model. Next, the above scalings are used to calculate the Karlovitz number (Ka) and to discuss appropriate combustion regimes. No transition to thin reaction zones is seen at Ka = 1, although such a transition is expected by turbulence-dominated subgrid models. Finally, we confirm a basic physical premise of the RT subgrid model, namely, that the flame is fractal, and thus self-similar. By modeling the turbulent flame speed, we demonstrate that it is affected more by large-scale RT stretching than by small-scale turbulent wrinkling. In this way, the RT instability controls the flame directly from the large scales. Overall, these results support the RT subgrid model.

Hicks, E. P. [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and the Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208 (United States); Rosner, R., E-mail: eph2001@columbia.edu [Computation Institute, University of Chicago, 5735 S. Ellis Ave., Chicago, IL 60637 (United States)

2013-07-10T23:59:59.000Z

282

A spray-suppression model for turbulent combustion  

SciTech Connect (OSTI)

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

283

Chemical Enrichment RGS cluster sample (CHEERS): Constraints on turbulence  

E-Print Network [OSTI]

Feedback from AGN, galactic mergers, and sloshing are thought to give rise to turbulence, which may prevent cooling in clusters. We aim to measure the turbulence in clusters of galaxies and compare the measurements to some of their structural and evolutionary properties. It is possible to measure the turbulence of the hot gas in clusters by estimating the velocity widths of their X-ray emission lines. The RGS Spectrometers aboard XMM-Newton are currently the only instruments provided with sufficient effective area and spectral resolution in this energy domain. We benefited from excellent 1.6Ms new data provided by the CHEERS project. The new observations improve the quality of the archival data and allow us to place constraints for some clusters, which were not accessible in previous work. One-half of the sample shows upper limits on turbulence less than 500km/s. For several sources, our data are consistent with relatively strong turbulence with upper limits on the velocity widths that are larger than 1000km/...

Pinto, Ciro; Werner, Norbert; de Plaa, Jelle; Fabian, Andrew C; Zhang, Yu-Ying; Kaastra, Jelle S; Finoguenov, Alexis; Ahoranta, Jussi

2015-01-01T23:59:59.000Z

284

Measurement of turbulent wind velocities using a rotating boom apparatus  

SciTech Connect (OSTI)

The present report covers both the development of a rotating-boom facility and the evaluation of the spectral energy of the turbulence measured relative to the rotating boom. The rotating boom is composed of a helicopter blade driven through a pulley speed reducer by a variable speed motor. The boom is mounted on a semiportable tower that can be raised to provide various ratios of hub height to rotor diameter. The boom can be mounted to rotate in either the vertical or horizontal plane. Probes that measure the three components of turbulence can be mounted at any location along the radius of the boom. Special hot-film sensors measured two components of the turbulence at a point directly in front of the rotating blade. By using the probe rotated 90/sup 0/ about its axis, the third turbulent velocity component was measured. Evaluation of the spectral energy distributions for the three components of velocity indicates a large concentration of energy at the rotational frequency. At frequencies slightly below the rotational frequency, the spectral energy is greatly reduced over that measured for the nonrotating case measurements. Peaks in the energy at frequencies that are multiples of the rotation frequency were also observed. We conclude that the rotating boom apparatus is suitable and ready to be used in experiments for developing and testing sensors for rotational measurement of wind velocity from wind turbine rotors. It also can be used to accurately measure turbulent wind for testing theories of rotationally sampled wind velocity.

Sandborn, V.A.; Connell, J.R.

1984-04-01T23:59:59.000Z

285

Localized dynamic subgrid closure for simulation of magnetohydrodynamic turbulence  

SciTech Connect (OSTI)

A local dynamic kinetic energy model (LDKM) for large-eddy simulation (LES) of magnetohydrodynamic (MHD) turbulence is proposed. The proposed MHD turbulence model evaluates all model coefficients locally and dynamically without any ad hoc averaging. This model also does not assume low magnetic Reynolds numbers. The turbulent residual-helicity effect ({alpha}-effect) appearing in the magnetic induction equation is successfully modeled. For validation, high-Re decaying isotropic decay turbulence with and without a mean magnetic field are studied using LES. The effect of rotation is also studied. For the case without rotation, it is observed that the energy spectrum follows a k{sup -5/3} law. For the case with rotation, it is shown that two mechanisms, phase scrambling due to frame rotation and Joule dissipation, are competing, and two distinct regimes with respect to rotation rate are observed. There is a critical rotation rate at which the energy decays most in MHD turbulence. It is also shown that this MHD-LDKM model is applicable to wide variety of high/low magnetic Reynolds number applications.

Miki, Kenji; Menon, Suresh [Georgia Institute of Technology, School of Aerospace Engineering, Atlanta, Georgia 30332-0150 (United States)

2008-07-15T23:59:59.000Z

286

E-Print Network 3.0 - atmospheric turbulence utilizing Sample...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

of atmospheric particles; Cloud turbulence... but for the dissipation rate of turbulence energy s800 cm2 sy3 . 12;( )M. Pinsky et al.rAtmospheric Research 49 1998 99... , and...

287

Studies of Turbulence in Shallow Sediment Laden Flow With Superimposed Rainfall  

E-Print Network [OSTI]

turbulent medium, a partial differential equation was developed as a mathematical model which describes the change in sediment concentration with time and space for two dimensional open channel flow with isotropic turbulence. The input parameters...

Barfield, B. J.

288

High-Temperature Thermal Array for Next Generation Solar Thermal...  

Broader source: Energy.gov (indexed) [DOE]

Thermal Array for Next Generation Solar Thermal Power Production Award Number: DE-EE00025828 Report Date: March 15, 2013 PI: Stephen Obrey * Technical approach is focused on...

289

The absence of inactive regions in turbulent flow: Evidence from light scattering experiments  

E-Print Network [OSTI]

prediction3) for large q,4 hasled to modelswhich imply that the turbulence consists of "active" regions

Pak, Hyuk Kyu

290

Forecasting clear-air turbulence within sub-layers of the stratosphere by discriminant function analysis  

E-Print Network [OSTI]

. ANALYSIS OF DATA 21 a. Stratification . . . . . . . . . . . . . . . . . . 21 b. Determination of variables used . . . . . . . . . . 22 c. Determination of linear discriminant functions . . . 24 d. Determination of non-linear discriminant functions . 26... result of this procedure, the 46 xB-70 aircraft flights yielded 94 turbulent and 78 non-turbulent segments, while the 23 YF-12A flights yielded 18 turbulent and 22 non-turbulent segments. h. N~t* 1 ' 1 Since most of the data obtained from...

Clark, Terry Lee

1974-01-01T23:59:59.000Z

291

Instability, mixing, and transition to turbulence in a laser-driven counterflowing shear experiment  

SciTech Connect (OSTI)

In a turbulence experiment conducted at the Omega Laser Facility [Boehly et al., Opt. Commun. 133, 495 (1997)

Doss, F. W.; Loomis, E. N.; Welser-Sherrill, L.; Fincke, J. R.; Flippo, K. A. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Keiter, P. A. [Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, Michigan 48109 (United States)

2013-01-15T23:59:59.000Z

292

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

293

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

294

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

295

Turbulent patterns in wall-bounded flows: a Turing instability?  

E-Print Network [OSTI]

In their way to/from turbulence, plane wall-bounded flows display an interesting transitional regime where laminar and turbulent oblique bands alternate, the origin of which is still mysterious. In line with Barkley's recent work about the pipe flow transition involving reaction-diffusion concepts, we consider plane Couette flow in the same perspective and transform Waleffe's classical four-variable model of self-sustaining process into a reaction-diffusion model. We show that, upon fulfillment of a condition on the relative diffusivities of its variables, the featureless turbulent regime becomes unstable against patterning as the result of a Turing instability. A reduced two-variable model helps us to delineate the appropriate region of parameter space. An {\\it intrinsic} status is therefore given to the pattern's wavelength for the first time. Virtues and limitations of the model are discussed, calling for a microscopic support of the phenomenological approach.

Manneville, Paul

2012-01-01T23:59:59.000Z

296

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.

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

2014-01-01T23:59:59.000Z

297

Temporal Intermittency of Energy Dissipation in Magnetohydrodynamic Turbulence  

E-Print Network [OSTI]

Energy dissipation in magnetohydrodynamic (MHD) turbulence is known to be highly intermittent in space, being concentrated in sheet-like coherent structures. Much less is known about intermittency in time, another fundamental aspect of turbulence which has great importance for observations of solar flares and other space/astrophysical phenomena. In this Letter, we investigate the temporal intermittency of energy dissipation in numerical simulations of MHD turbulence. We consider four-dimensional spatiotemporal structures, "flare events", responsible for a large fraction of the energy dissipation. We find that although the flare events are often highly complex, they exhibit robust power-law distributions and scaling relations. We find that the probability distribution of dissipated energy has a power law index close to -1.75, similar to observations of solar flares, indicating that intense dissipative events dominate the heating of the system. We also discuss the temporal asymmetry of flare events as a signatu...

Zhdankin, Vladimir; Boldyrev, Stanislav

2015-01-01T23:59:59.000Z

298

Can Protostellar Jets Drive Supersonic Turbulence in Molecular Clouds?  

E-Print Network [OSTI]

Jets and outflows from young stellar objects are proposed candidates to drive supersonic turbulence in molecular clouds. Here, we present the results from multi-dimensional jet simulations where we investigate in detail the energy and momentum deposition from jets into their surrounding environment and quantify the character of the excited turbulence with velocity probability density functions. Our study include jet--clump interaction, transient jets, and magnetised jets. We find that collimated supersonic jets do not excite supersonic motions far from the vicinity of the jet. Supersonic fluctuations are damped quickly and do not spread into the parent cloud. Instead subsonic, non-compressional modes occupy most of the excited volume. This is a generic feature which can not be fully circumvented by overdense jets or magnetic fields. Nevertheless, jets are able to leave strong imprints in their cloud structure and can disrupt dense clumps. Our results question the ability of collimated jets to sustain supersonic turbulence in molecular clouds.

Robi Banerjee; Ralf S. Klessen; Christian Fendt

2007-06-25T23:59:59.000Z

299

Radiation induces turbulence in particle-laden fluids  

SciTech Connect (OSTI)

When a transparent fluid laden with solid particles is subject to radiative heating, non-uniformities in particle distribution result in local fluid temperature fluctuations. Under the influence of gravity, buoyancy induces vortical fluid motion which can lead to strong preferential concentration, enhancing the local heating and more non-uniformities in particle distribution. By employing direct numerical simulations this study shows that the described feedback loop can create and sustain turbulence. The velocity and length scale of the resulting turbulence is not known a priori, and is set by balance between viscous forces and buoyancy effects. When the particle response time is comparable to a viscous time scale, introduced in our analysis, the system exhibits intense fluctuations of turbulent kinetic energy and strong preferential concentration of particles.

Zamansky, Rémi [Centre for Turbulence Research, Stanford University, Stanford, California 94305-3035 (United States); Coletti, Filippo [Mechanical Engineering, Stanford University, California 94305-3035 (United States); Massot, Marc [Centre for Turbulence Research, Stanford University, Stanford, California 94305-3035 (United States); Ecole Centrale Paris, Laboratoire EM2C - UPR CNRS 288 et Fédération de Mathématiques - FR CNRS 3487, Grande Voie des Vignes, 92295 Chatenay-Malabry Cedex (France); Mani, Ali [Centre for Turbulence Research, Stanford University, Stanford, California 94305-3035 (United States); Mechanical Engineering, Stanford University, California 94305-3035 (United States)

2014-07-15T23:59:59.000Z

300

Turbulent Nonpremixed Flames (TNF): Experimental Data Archives and Computational Submodels  

DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]

In the 1990s an international collaboration formed around a series of workshops that became known collectively as the International Workshop on Measurement and Computation of Turbulent Non-Premixed Flames (TNF). An online library, hosted by Sandia National Laboratory (California) was established that provides data sets and submodels or "mechanisms" for the study of turbulence-chemistry interactions in turbulent nonpremixed and partially premixed combustion. Data are organized by flame types: simple jet flames, piloted jet flames, bluff body flames, and swirl flames. These data sets provide a means for collaborative comparisons of both measured and simulated/modeled research results and also assist scientists in determining priorities for further research. More than 20 data sets or databases are available from this website, along with various downloadable files of chemical mechanisms. The website also provides an extensive bibliography and the proceedings of the workshops themselves from 1996 through 2012. Information continues to be added to this collection.

Note: This page contains sample records for the topic "rangepsi 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

Residual energy in magnetohydrodynamic turbulence and in the solar wind  

E-Print Network [OSTI]

Recent observations indicate that kinetic and magnetic energies are not in equipartition in the solar wind turbulence. Rather, magnetic fluctuations are more energetic and have somewhat steeper energy spectrum compared to the velocity fluctuations. This leads to the presence of the so-called residual energy E_r=E_v-E_b in the inertial interval of turbulence. This puzzling effect is addressed in the present paper in the framework of weak turbulence theory. Using a simple model of weakly colliding Alfv\\'en waves, we demonstrate that the kinetic-magnetic equipartition indeed gets broken as a result of nonlinear interaction of Alfv\\'en waves. We establish that magnetic energy is indeed generated more efficiently as a result of these interactions, which proposes an explanation for the solar wind observations.

Stanislav Boldyrev; Jean Carlos Perez; Vladimir Zhdankin

2011-08-30T23:59:59.000Z

302

Multilayer thermal barrier coating systems  

DOE Patents [OSTI]

The present invention generally describes multilayer thermal barrier coating systems and methods of making the multilayer thermal barrier coating systems. The thermal barrier coating systems comprise a first ceramic layer, a second ceramic layer, a thermally grown oxide layer, a metallic bond coating layer and a substrate. The thermal barrier coating systems have improved high temperature thermal and chemical stability for use in gas turbine applications.

Vance, Steven J. (Orlando, FL); Goedjen, John G. (Oviedo, FL); Sabol, Stephen M. (Orlando, FL); Sloan, Kelly M. (Longwood, FL)

2000-01-01T23:59:59.000Z

303

Solar Thermal Conversion  

SciTech Connect (OSTI)

The thermal conversion process of solar energy is based on well-known phenomena of heat transfer (Kreith 1976). In all thermal conversion processes, solar radiation is absorbed at the surface of a receiver, which contains or is in contact with flow passages through which a working fluid passes. As the receiver heats up, heat is transferred to the working fluid which may be air, water, oil, or a molten salt. The upper temperature that can be achieved in solar thermal conversion depends on the insolation, the degree to which the sunlight is concentrated, and the measures taken to reduce heat losses from the working fluid.

Kreith, F.; Meyer, R. T.

1982-11-01T23:59:59.000Z

304

Short wavelength ion temperature gradient turbulence  

SciTech Connect (OSTI)

The ion temperature gradient (ITG) mode in the high wavenumber regime (k{sub y}{rho}{sub s}>1), referred to as short wavelength ion temperature gradient mode (SWITG) is studied using the nonlinear gyrokinetic electromagnetic code GENE. It is shown that, although the SWITG mode may be linearly more unstable than the standard long wavelength (k{sub y}{rho}{sub s}<1) ITG mode, nonlinearly its contribution to the total thermal ion heat transport is found to be low. We interpret this as resulting from an increased zonal flow shearing effect on the SWITG mode suppression.

Chowdhury, J.; Ganesh, R. [Institute for Plasma Research, Bhat, Gandhinagar (India); Brunner, S.; Lapillonne, X.; Villard, L. [CRPP, Association EURATOM-Confederation Suisse, EPFL, 1015 Lausanne (Switzerland); Jenko, F. [Max-Planck-Institut fuer Plasmaphysik Boltzmannstr. 2, D-85748 Garching (Germany)

2012-10-15T23:59:59.000Z

305

Wave Turbulence in Superfluid 4 Energy Cascades, Rogue Waves & Kinetic Phenomena  

E-Print Network [OSTI]

Outline Wave Turbulence in Superfluid 4 He: Energy Cascades, Rogue Waves & Kinetic Phenomena Conference, Chernogolovka, 3 August 2009 McClintock Efimov Ganshin Kolmakov Mezhov-Deglin Wave Turbulence in Superfluid 4 He #12;Outline Outline 1 Introduction Motivation 2 Modelling wave turbulence Need for models

Fominov, Yakov

306

Predictive Inner-Outer Model for Turbulent Boundary Layers Applied to Hypersonic DNS Data  

E-Print Network [OSTI]

Predictive Inner-Outer Model for Turbulent Boundary Layers Applied to Hypersonic DNS Data Clara numerical simulation (DNS) data of supersonic and hypersonic turbulent boundaries with Mach 3 and Mach 7, and Martin12­14 on DNS of hypersonic turbulent boundary layers demonstrates the existence of large scale

Martín, Pino

307

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

308

Small-scale magnetic buoyancy and magnetic pumping effects in a turbulent convection  

E-Print Network [OSTI]

We determine the nonlinear drift velocities of the mean magnetic field and nonlinear turbulent magnetic diffusion in a turbulent convection. We show that the nonlinear drift velocities are caused by the three kinds of the inhomogeneities, i.e., inhomogeneous turbulence; the nonuniform fluid density and the nonuniform turbulent heat flux. The inhomogeneous turbulence results in the well-known turbulent diamagnetic and paramagnetic velocities. The nonlinear drift velocities of the mean magnetic field cause the small-scale magnetic buoyancy and magnetic pumping effects in the turbulent convection. These phenomena are different from the large-scale magnetic buoyancy and magnetic pumping effects which are due to the effect of the mean magnetic field on the large-scale density stratified fluid flow. The small-scale magnetic buoyancy and magnetic pumping can be stronger than these large-scale effects when the mean magnetic field is smaller than the equipartition field. We discuss the small-scale magnetic buoyancy and magnetic pumping effects in the context of the solar and stellar turbulent convection. We demonstrate also that the nonlinear turbulent magnetic diffusion in the turbulent convection is anisotropic even for a weak mean magnetic field. In particular, it is enhanced in the radial direction. The magnetic fluctuations due to the small-scale dynamo increase the turbulent magnetic diffusion of the toroidal component of the mean magnetic field, while they do not affect the turbulent magnetic diffusion of the poloidal field.

I. Rogachevskii; N. Kleeorin

2006-05-18T23:59:59.000Z

309

ANALYTIC STUDY OF SHELL MODELS OF TURBULENCE PETER CONSTANTIN, BORIS LEVANT, AND EDRISS S. TITI  

E-Print Network [OSTI]

Abstract. In this paper we study analytically the viscous sabra shell model of energy turbulent cascade. We of the energy-cascade mechanism in turbulence can be found in [2]. The sabra shell model of turbulence describes". The equations of motion of the sabra shell model of turbu- lence have the following form dun dt = i(akn+1un+2u n

Constantin, Peter

310

Phys. Plasmas 2 (8), August 1995, 3017 Wavelet bicoherence: A new turbulence analysis tool  

E-Print Network [OSTI]

1 Phys. Plasmas 2 (8), August 1995, 3017 Wavelet bicoherence: A new turbulence analysis tool B, Madrid, Spain Abstract A recently introduced tool for the analysis of turbulence, wavelet bicoherence [B and usefulness of a new analysis tool for chaos and turbulence that was recently introduced [1]. First, we

Martín-Solís, José Ramón

311

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

312

Error Rate Performance of Coded Free-Space Optical Links over Gamma-Gamma Turbulence Channels  

E-Print Network [OSTI]

Error Rate Performance of Coded Free-Space Optical Links over Gamma-Gamma Turbulence Channels Murat be used over free-space optical (FSO) links to mitigate turbulence-induced fading. In this paper, we channels, considering the recently introduced gamma-gamma turbulence model. We derive a pairwise error

Li, Tiffany Jing

313

Small scale turbulence and instabilities observed simultaneously by radiosondes and the MU radar.  

E-Print Network [OSTI]

Small scale turbulence and instabilities observed simultaneously by radiosondes and the MU radar. R-French field campaign devoted to study small-scale turbulence and instabilities in the lower atmosphere for retrieving small-scale turbulence parameters from ST radars. However, the dominant sources

314

Thermal insulations using vacuum panels  

DOE Patents [OSTI]

Thermal insulation vacuum panels are formed of an inner core of compressed low thermal conductivity powders enclosed by a ceramic/glass envelope evaluated to a low pressure.

Glicksman, Leon R. (Lynnfield, MA); Burke, Melissa S. (Pittsburgh, PA)

1991-07-16T23:59:59.000Z

315

Fusion Rules in Navier-Stokes Turbulence: First Experimental Tests  

E-Print Network [OSTI]

We present the first experimental tests of the recently derived fusion rules for Navier-Stokes (N-S) turbulence. The fusion rules address the asymptotic properties of many-point correlation functions as some of the coordinates coalesce, and form an important ingredient of the nonperturbative statistical theory of turbulence. Here we test the fusion rules when the spatial separations lie within the inertial range, and find good agreement between experiment and theory. An unexpected result is a simple linear law for the Laplacian of the velocity fluctuation conditioned on velocity increments across large separations.

Adrienne L. Fairhall; Brindesh Dhruva; Victor S. L'vov; Itamar Procaccia; Katepalli R. Sreenivasan

1997-01-16T23:59:59.000Z

316

A Tree Swaying in a Turbulent Wind: A Scaling Analysis  

E-Print Network [OSTI]

A tentative scaling theory is presented of a tree swaying in a turbulent wind. It is argued that the turbulence of the air within the crown is in the inertial regime. An eddy causes a dynamic bending response of the branches according to a time criterion. The resulting expression for the penetration depth of the wind yields an exponent which appears to be consistent with that pertaining to the morphology of the tree branches. An energy criterion shows that the dynamics of the branches is basically passive. The possibility of hydrodynamic screening by the leaves is discussed.

Theo Odijk

2014-07-10T23:59:59.000Z

317

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 Rémy Dominique Gérard

2012-11-13T23:59:59.000Z

318

Electron geodesic acoustic modes in electron temperature gradient mode turbulence  

SciTech Connect (OSTI)

In this work, the first demonstration of an electron branch of the geodesic acoustic mode (el-GAM) driven by electron temperature gradient (ETG) modes is presented. The work is based on a fluid description of the ETG mode retaining non-adiabatic ions and the dispersion relation for el-GAMs driven nonlinearly by ETG modes is derived. A new saturation mechanism for ETG turbulence through the interaction with el-GAMs is found, resulting in a significantly enhanced ETG turbulence saturation level compared to the mixing length estimate.

Anderson, Johan; Nordman, Hans [Department of Earth and Space Sciences, Chalmers University of Technology, SE-412 96 Goeteborg (Sweden); Singh, Raghvendra; Kaw, Predhiman [Institute for Plasma Research, Bhat, Gandhinagar, Gujarat 382428 (India)

2012-08-15T23:59:59.000Z

319

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

320

A turbulent transport network model in MULTIFLUX coupled with TOUGH2  

SciTech Connect (OSTI)

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

Note: This page contains sample records for the topic "rangepsi 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

Manipulation of Thermal Phonons  

E-Print Network [OSTI]

to manipulate the behavior of phonons is crucial for both energy applications and the cooling of integrated circuits. A novel class of artificially periodic structured materials — phononic crystals — might make manipulation of thermal phonons possible. In many...

Hsu, Chung-Hao

2013-03-28T23:59:59.000Z

322

Thermally Polymerized Rylene Nanoparticles  

E-Print Network [OSTI]

Rylene dyes functionalized with varying numbers of phenyl trifluorovinyl ether (TFVE) moieties were subjected to a thermal emulsion polymerization to yield shape-persistent, water-soluble chromophore nanoparticles. Perylene ...

Andrew, Trisha Lionel

323

Thermal Insulation Systems  

E-Print Network [OSTI]

Thermal insulation systems are receiving a high degree of attention in view of increasing energy cost. Industrial, commercial and residential energy users are all well aware of energy cost increases and great emphasis is being directed to energy...

Stanley, T. F.

1982-01-01T23:59:59.000Z

324

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

325

Contact thermal lithography  

E-Print Network [OSTI]

Contact thermal lithography is a method for fabricating microscale patterns using heat transfer. In contrast to photolithography, where the minimum achievable feature size is proportional to the wavelength of light used ...

Schmidt, Aaron Jerome, 1979-

2004-01-01T23:59:59.000Z

326

Photovoltaic-thermal collectors  

DOE Patents [OSTI]

A photovoltaic-thermal solar cell including a semiconductor body having antireflective top and bottom surfaces and coated on each said surface with a patterned electrode covering less than 10% of the surface area. A thermal-absorbing surface is spaced apart from the bottom surface of the semiconductor and a heat-exchange fluid is passed between the bottom surface and the heat-absorbing surface.

Cox, III, Charles H. (Carlisle, MA)

1984-04-24T23:59:59.000Z

327

Dynamic modelling for thermal micro-actuators using thermal networks  

E-Print Network [OSTI]

Dynamic modelling for thermal micro-actuators using thermal networks Beatriz L´opez-Wallea,1 and analytical calculations. Key words: Micro-actuators, Thermal modelling, Electrical analogy, Thermal network 1 and MicroMechatronic Systems Department (AS2M), 24 rue Alain Savary, 25000 Besan¸con, France Abstract

Paris-Sud XI, Université de

328

Notes 08. Turbulence flow in thin film bearings : Characteristics and Modeling  

E-Print Network [OSTI]

NOTES 8. TURBULENCE IN THIN FILM FLOWS. Dr. Luis San Andr?s ? 2009 1 Notes 8. Turbulence in Thin Film Flows Notes 8 detail the characteristics of turbulent flows and provide insight into the flow instabilities that precede transition from a... for averaging of turbulent flow velocities [s] NOTES 8. TURBULENCE IN THIN FILM FLOWS. Dr. Luis San Andr?s ? 2009 2 Ta 2 Re C R ?? ?? ?? . Taylor number ?? 1, 2, 3 i i u ? Components of velocity field [m/s] = ? ? ii uu?? ?? 1, 2, 3 , ii i uu...

San Andres, Luis

2009-01-01T23:59:59.000Z

329

MAGNETIC FIELD STRUCTURES AND TURBULENT COMPONENTS IN THE STAR-FORMING MOLECULAR CLOUDS OMC-2 AND OMC-3  

SciTech Connect (OSTI)

The SCUBA polarized 850 {mu}m thermal emission data of the OMC-2 region in Orion A are added to and homogeneously reduced with data already available in the OMC-3 region. The data set shows that OMC-2 is a region generally less polarized than OMC-3. Where coincident, most of the 850 {mu}m polarization pattern is similar to that measured in 350 {mu}m polarization data. Only 850 {mu}m polarimetry data have been obtained in and around MMS7, FIR1 and FIR2, and in the region south of FIR6. A realignment of the polarization vectors with the filament can be seen near FIR1 in the region south of OMC-3. An analysis shows that the energy injected by CO outflows and H{sub 2} jets associated with OMC-2 and OMC-3 does not appear to alter the polarization patterns at a scale of the 14'' resolution beam. A second-order structure function analysis of the polarization position angles shows that OMC-2 is a more turbulent region than OMC-3. OMC-3 appears to be a clear case of a magnetically dominated region with respect to the turbulence. However, for OMC-2 it is not clear that this is the case. A more in-depth analysis of five regions displayed along OMC-2/3 indicates a decrease of the mean polarization degree and an increase of the turbulent angular dispersion from north to south. A statistical analysis suggests the presence of two depolarization regimes in our maps: one regime including the effects of the cores, the other one excluding it.

Poidevin, Frederick [Universidade de Sao Paulo, Instituto de Astronomia, Geofisica e CIencas Atmosfericas, Rua do Matao 1226, Butanta, Sao Paulo, SP 05508-900 (Brazil); Bastien, Pierre [Departement de Physique and Observatoire du Mont-Megantic, Universite de Montreal, C.P. 6128, Succ. Centre-ville, Montreal, Quebec H3C 3J7 (Canada); Matthews, Brenda C., E-mail: Poidevin@astro.iag.usp.b, E-mail: Bastien@astro.umontreal.c, E-mail: brenda.matthews@nrc-cnrc.gc.c [Herzberg Institute of Astrophysics, National Research Council of Canada, Victoria, BC (Canada)

2010-06-20T23:59:59.000Z

330

ECRH microwave beam broadening in the edge turbulent plasma  

SciTech Connect (OSTI)

The influence of turbulent plasma density fluctuations on angular and spatial beam width is treated analytically in the framework of WKB based eikonal method. Reasonable agreement of analytical and numerical treatment results is demonstrated within the domain of quasi-optical approximation validity. Significant broadening of microwave beams is predicted for future ECRH experiments at ITER.

Sysoeva, E. V.; Gusakov, E. Z.; Popov, A. Yu. [Ioffe Institute, St. Petersburg, Russia and RL PAT SPbSPU, St. Petersburg (Russian Federation); Silva, F. da [Institute of Plasmas and Nuclear Fusion, IST, Lisbon (Portugal); Heuraux, S. [IJL UMR-7198 CNRS-Université de Lorraine, BP70239, 54506 Vandoeuvre Cedex (France)

2014-02-12T23:59:59.000Z

331

Fun With Plasma Turbulence, From Fusion Energy to Black Holes  

E-Print Network [OSTI]

) & in astrophysics · Summarize status of fusion energy research · Cross-validation: statistical techniques useful Energy is Essentially Unchanged since 1980 Cumulative Funding 0 5000 10000 15000 20000 25000 30000 35000Fun With Plasma Turbulence, From Fusion Energy to Black Holes Greg Hammett Miller Visiting Research

Hammett, Greg

332

Stochastic modeling of lift and drag dynamics under turbulent conditions  

E-Print Network [OSTI]

measurement. The model is being developed with the aim to integrate it into a general wind energy converter dynamics, drag dynamics. 1 Introduction Wind energy converters (WECs) are permanently exposed to turbulent.peinke@forwind.de in every second, which imposes different risks. The dynamical nature of the wind has a significant impact

Peinke, Joachim

333

Center for Turbulence Research Proceedings of the Summer Program 2012  

E-Print Network [OSTI]

turbulence within the separation bubble and more accurate (earlier) reattach- ment. The new model yields of the separation bubble from DNS of Marquillie et al. (2008); (x - xsep)/(xreattach - xsep) = 8% (solid), 46% (dash), 83% (dash-dot), 121% (dash-dot-dot). A rapid increase in near-wall dissipation is seen in the rear

Wang, Wei

334

Status of Research on Fusion Energy and Plasma Turbulence  

E-Print Network [OSTI]

Status of Research on Fusion Energy and Plasma Turbulence Candy, Waltz (General Atomics) Greg Project · A DOE, Office of Fusion Energy Sciences, SciDAC (Scientific Discovery Through Advanced Computing_annual.html #12;#12;#12;Progress in Fusion Energy Outpaced Computers J.B. Lister #12;Progress in Fusion

Hammett, Greg

335

EFFECTS OF VEGETATION ON TURBULENCE, SEDIMENT TRANSPORT AND STREAM MORPHOLOGY  

SciTech Connect (OSTI)

Vegetation, from an individual stem to multiple stems in various configurations, profoundly alters turbulent flows. These alterations influence sediment transport and stream morphology, but depend on complex interactions and relationships between flow, plants and sediment properties. This is illustrated for three case studies that represent a variety of macrophyte patterns and scales in the environment: flows through simulated uniformly distributed plant stems, emergent and submerged; flows with alternating simulated stem patches; and flow around an isolated stem in a flood plain. The emergent case demonstrates that when density is sparse the mean velocity and turbulence intensities vary horizontally around the stems, which would promote a heterogeneous bedform morphology. However, it is still unclear how density, submergence ratio, and flow Reynolds number, in combination, influence interference effects, vortex shedding and dissipation, and velocity, pressure and lift fluctuations that affect sediment entrainment. The submerged case demonstrates significant reduction of the mean velocity, turbulence intensities, and turbulent shear near the bed compared to an unobstructed flow and supports numerous observations that vegetation promotes deposition or stabilizes bed sediments. The case of alternating emergent vegetation patches illustrates how vegetation adjusts the bed promoting scour in open water and deposition within the patches. The isolated stem case illustrates the variety of coherent structures generated, their complex interaction, and their role in specific sediment transport phenomena observed. Additional research is required, however, to quantify thresholds and relationships for flow-vegetation-sediment interactions so that aquatic macrophyte plantings can be used more effectively in water resource management.

Neary, Vincent S [ORNL

2012-01-01T23:59:59.000Z

336

Refined similarity hypotheses in shell models of turbulence  

E-Print Network [OSTI]

A major challenge in turbulence research is to understand from first principles the origin of anomalous scaling of the velocity fluctuations in high-Reynolds-number turbulent flows. One important idea was proposed by Kolmogorov [J. Fluid Mech. {\\bf 13}, 82 (1962)], which attributes the anomaly to the variations of the locally averaged energy dissipation rate. Kraichnan later pointed out [J. Fluid Mech. {\\bf 62}, 305 (1973)] that the locally averaged energy dissipation rate is not an inertial-range quantity and a proper inertial-range quantity would be the local energy transfer rate. As a result, Kraichnan's idea attributes the anomaly to the variations of the local energy transfer rate. These ideas, generally known as refined similarity hypotheses, can also be extended to study the anomalous scaling of fluctuations of an active scalar, like the temperature in turbulent convection. In this paper, we examine the validity of these refined similarity hypotheses and their extensions to an active scalar in shell models of turbulence. We find that Kraichnan's refined similarity hypothesis and its extension are valid.

Emily S. C. Ching; H. Guo; T. S. Lo

2008-04-16T23:59:59.000Z

337

Center for Turbulence Research Annual Research Briefs 2012  

E-Print Network [OSTI]

Center for Turbulence Research Annual Research Briefs 2012 153 Bifurcation analysis of scramjet unstart By I. Jang, J. W. Nichols AND P. Moin 1. Motivation and objectives Scramjet unstart occurs when of unstart is an important limiting factor on the performance of scramjet engines. In the Predictive Science

Wang, Wei

338

Center for Turbulence Research Annual Research Briefs 2012  

E-Print Network [OSTI]

a model for uncertainty quantification (UQ) of high-speed turbulent combustion in a scramjet engine/boundary layer interaction, a phenomenon important to scramjet combustors. In addition to aleatory uncertainties from simulation of a full scramjet engine to an investigation of crackling supersonic jets to solar

Wang, Wei

339

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

340

Modeling Turbulent Hydraulic Fracture Near a Free Surface  

E-Print Network [OSTI]

Modeling Turbulent Hydraulic Fracture Near a Free Surface Victor C. Tsai Seismological Laboratory consider a hydraulic fracture problem in which the crack grows parallel to a free surface, subject to fully components. wall Wall shear stress. ^· Non-dimensionalized ·. 1 Introduction Hydraulic fracture has been

Note: This page contains sample records for the topic "rangepsi 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

Modeling Turbulent Hydraulic Fracture Near a Free Surface  

E-Print Network [OSTI]

Modeling Turbulent Hydraulic Fracture Near a Free Surface Victor C. Tsai Seismological Laboratory consider a hydraulic fracture problem in which the crack grows parallel to a free surface, subject to fully components. ^· Non-dimensionalized ·. 1 Introduction Hydraulic fracture has been studied for many years

342

Passive Tomography of Turbulence Strength Marina Alterman1  

E-Print Network [OSTI]

expensive. Turbulence significantly affects the efficiency of wind turbine #12;2 M. Alterman, Y. Y), wind, and atmospheric stability. This is measured using special Doppler lidars [9, 31], which are very. Schechner, M. Vo and S. G. Narasimhan farms [31], hence optimizing turbines and farms involves measuring TS

Sheikh, Yaser Ajmal

343

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.

344

LES of a Hydrogen-Enriched Lean Turbulent Premixed Flame  

E-Print Network [OSTI]

LES of a Hydrogen-Enriched Lean Turbulent Premixed Flame Francisco E. Hern´andez-P´erez , Clinton the observed behaviour is examined. Hydrogen-hydrocarbon fuel blends appear to be a promising option to synergistically pave the way toward pure hydrogen-based combustion systems while alleviating green-house gas

Groth, Clinton P. T.

345

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.

346

Aeroelastic Analysis of Bridges: Effects of Turbulence and Aerodynamic Nonlinearities  

E-Print Network [OSTI]

Aeroelastic Analysis of Bridges: Effects of Turbulence and Aerodynamic Nonlinearities Xinzhong Chen for capturing the emerging concerns in bridge aerodynamics introduced by aerodynamic nonlinearities/or with aerodynamic characteristics sensitive to the effective angle of incidence. This paper presents a nonlinear

Kareem, Ahsan

347

Numerical Aerodynamic Optimization Incorporating Laminar-Turbulent Transition Prediction  

E-Print Network [OSTI]

Numerical Aerodynamic Optimization Incorporating Laminar-Turbulent Transition Prediction J. Driver-dimensional Newton­Krylov aerodynamic shape optimization algorithm is applied to several optimization problems a striking demonstration of the capability of the Newton­ Krylov aerodynamic optimization algorithm to design

Zingg, David W.

348

NACA0015 Measurements in LM Wind Tunnel and Turbulence  

E-Print Network [OSTI]

NACA0015 Measurements in LM Wind Tunnel and Turbulence Generated Noise Franck Bertagnolio Risø, Denmark November 2008 #12;Author: Franck Bertagnolio Title: NACA0015 Measurements in LM Wind Tunnel on its surface and measured in the wind tunnel at LM Glasfiber at various inflow speeds, angles of attack

349

Transition in Localized Pipe Flow Turbulence Fernando Mellibovsky,1  

E-Print Network [OSTI]

Transition in Localized Pipe Flow Turbulence Fernando Mellibovsky,1 Alvaro Meseguer,1 Tobias M (Received 24 March 2009; published 31 July 2009) Direct numerical simulation of transitional pipe flow, during the second stage, spreads out to fill the pipe. DOI: 10.1103/PhysRevLett.103.054502 PACS numbers

Meseguer, Alvaro

350

Gravity surface wave turbulence in a laboratory flume  

E-Print Network [OSTI]

We present experimental results for water wave turbulence excited by piston-like programmed wavemakers in a water flume with horisontal dimensions 6x12x1.5 meters. Our main finding is that for a wide range of excitation amplitudes the energy spectrum has a power-law scaling, $E_\\omega \\sim \\omega^{-\

Petr Denissenko; Sergei Lukaschuk; Sergey Nazarenko

2006-11-08T23:59:59.000Z

351

Direct numerical simulation of turbulent Taylor–Couette flow  

E-Print Network [OSTI]

the flow is characterized by the radius ratio, ? = R1/R2, where R1 and R2 are the radii ... vortices at the critical onset Taylor number Tc (defined as the Taylor number at which ... Beyond 5 × 105Tc these turbulent vortices became fragmented and lost .... employ a stiffly stable velocity-correction-type scheme with a third-order ...

2007-08-23T23:59:59.000Z

352

Magnetic energy production by turbulence in binary neutron star mergers  

E-Print Network [OSTI]

The simultaneous detection of electromagnetic and gravitational wave emission from merging neutron star binaries would aid greatly in their discovery and interpretation. By studying turbulent amplification of magnetic fields in local high-resolution simulations of neutron star merger conditions, we demonstrate that magnetar-level (~10^16) G fields are present throughout the merger duration. We find that the small-scale turbulent dynamo converts 60% of the randomized kinetic energy into magnetic fields on a merger time scale. Since turbulent magnetic energy dissipates through reconnection events which accelerate relativistic electrons, turbulence may facilitate the conversion of orbital kinetic energy into radiation. If 10^-4 of the ~ 10^53 erg of orbital kinetic available gets processed through reconnection, and creates radiation in the 15-150 keV band, then the fluence at 200 Mpc would be 10^-7 erg/cm^2, potentially rendering most merging neutron stars in the advanced LIGO and Virgo detection volumes detecta...

Zrake, Jonathan

2013-01-01T23:59:59.000Z

353

Velocity centroids as tracers of the turbulent velocity statistics  

E-Print Network [OSTI]

We use the results of magnetohydrodynamic (MHD) simulations to emulate spectroscopic observations and use maps of centroids to study their statistics. In order to assess under which circumstances the scaling properties of the velocity field can be retrieved from velocity centroids, we compare two point statistics (structure functions and power-spectra) of velocity centroids with those of the underlying velocity field and analytic predictions presented in a previous paper (Lazarian & Esquivel 2003). We tested a criterion for recovering velocity spectral index from velocity centroids derived in our previous work, and propose an approximation of the early criterion using only the variances of ``unnormalized'' velocity centroids and column density maps. It was found that both criteria are necessary, however not sufficient to determine if the centroids recover velocity statistics. Both criteria are well fulfilled for subsonic turbulence. We find that for supersonic turbulence with sonic Mach numbers > 2.5 centroids fail to trace the spectral index of velocity. Asymptotically, however, we claim that recovery of velocity statistics is always possible provided that the density spectrum is steep and the observed inertial range is sufficiently extended. In addition, we show that velocity centroids are useful for anisotropy studies and determining the direction of magnetic field, even if the turbulence is highly supersonic, but only if it is sub-Alfvenic. This provides a tool for mapping the magnetic field direction, and testing whether the turbulence is sub-Alfvenic or super-Alfvenic.

A. Esquivel; A. Lazarian

2005-05-28T23:59:59.000Z

354

Discrete wave turbulence of rotational capillary water waves  

E-Print Network [OSTI]

We study the discrete wave turbulent regime of capillary water waves with constant non-zero vorticity. The explicit Hamiltonian formulation and the corresponding coupling coefficient are obtained. We also present the construction and investigation of resonance clustering. Some physical implications of the obtained results are discussed.

Adrian Constantin; Elena Kartashova; Erik Wahlén

2010-05-12T23:59:59.000Z

355

LES Simulations of Turbulent Combustion in a Type Ia Supernovae  

E-Print Network [OSTI]

to be thermonuclear explosions of white dwarfs. SNIa are important sources of energy and chemical elements deposited of the burning are all determined by the speed of thermonuclear burning [27]. The problem of turbulent combustion. The mechanism and the speed of thermonuclear burning in SNIa remain an unsolved theoretical problem. A recent

New York at Stoney Brook, State University of

356

Turbulent heating of the corona and solar wind: the heliospheric  

E-Print Network [OSTI]

resembles magnetic lines of force Eclipse observations show the `solar corona' Thomson-scattered white light ­ photospheric light scattered from dust, solar spectrum remains ­ `zodiacal light' E corona ­ emission linesTurbulent heating of the corona and solar wind: the heliospheric dark energy problem Stuart D. Bale

357

Notes 09. Fluid inertia and turbulence in fluid film bearings  

E-Print Network [OSTI]

. Luis San Andr?s ? 2009 14 References: Constantinescu, V.N., 1962, ?Analysis of Bearings Operating in the Turbulent Flow Regime,? ASME Journal of Lubrication Technology, Vol. 82, pp. 139-151. Hashimoto, H., S. Wada, M. Sumitomo, 1989, ?The Effects...

San Andres, Luis

2009-01-01T23:59:59.000Z

358

Anisotropic MHD Turbulence in the Interstellar Medium and Solar Wind  

E-Print Network [OSTI]

in k-space Energy cascade rate: (k) k E(k) { Energy spectrum: = constant E(k)dk = total energy = 5;Globally isotropic 2D energy spectrum (logarithmic contours) +0 #12;Current sheet formation intense current. Bhattacharjee, K. Germaschewski S. Galtier #12;Outline · Introduction · Global anisotropy: weak MHD turbulence

Ng, Chung-Sang

359

Anisotropic MHD Turbulence C. S. Ng and A. Bhattacharjee  

E-Print Network [OSTI]

cascade rate:!(k) " k# E(k)$ { Energy spectrum: = constant E(k)! dk = total energy ! " = 5/2, # = 3], power spectra for the total kinetic energy (a) and for the total magnetic energy (b) The best fit · 2D MHD turbulence simulations -- globally isotropic with local anisotropy · Conclusion · Global

Ng, Chung-Sang

360

1 A Grid based distributed simulation of Plasma Turbulence  

E-Print Network [OSTI]

1 A Grid based distributed simulation of Plasma Turbulence Beniamino Di Martino and Salvatore- cati, Rome, Italy Grid technology is widespreading, but most grid-enabled applications just exploit of Grid platforms. In this paper the porting on a Globus equipped platform of a hierarchically distributed

Vlad, Gregorio

Note: This page contains sample records for the topic "rangepsi 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

Wind Energy Applications of Unified and Dynamic Turbulence Models  

E-Print Network [OSTI]

Wind Energy Applications of Unified and Dynamic Turbulence Models Stefan Heinz and Harish Gopalan applicable as a low cost alternative. 1 Introduction There is a growing interest in using wind energy suggests the possibility of providing 20% of the electricity in the U.S. by wind energy in 2030

Heinz, Stefan

362

ATMOSPHERIC TURBULENCE MODELING AND IMPLICATIONS FOR WIND ENERGY  

E-Print Network [OSTI]

turbines off too early in high winds, or may risk severe damage to the rotors and blades by operating under Introduction Wind turbines sit at the very bottom of the at- mospheric boundary layer, where winds are highly turbulent, shear events are intermittent, and land- atmosphere interactions may be strong. Turbine hub

Chow, Fotini Katopodes

363

Global Turbulence Simulations of CYCLONE Base Case and MAST Plasmas  

SciTech Connect (OSTI)

The non-local effects of turbulence can affect the transport especially in devices when the ration of ion gyroradius to plasma size ({rho}{sub i}*) is large. We show how the local linear and nonlinear ITG flux-tube results are modified when the simulations are done with finite {rho}{sub i}* in a global code.

Saarelma, S.; Akers, R.; Reshko, M.; Roach, C. M.; Romanelli, M.; Thyagaraja, A. [EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxfordshire OX143DB (United Kingdom); Peeters, A. [Centre for Fusion, Space and Astrophysics, Warwick University, Coventry CV4 7AL (United Kingdom); Bottino, A. [MPI fuer Plasmaphysik, EURATOM Association, D-85748 Garching (Germany); Jolliet, S. [Centre de Recherches en Physique des Plasmas, Association EURATOM-Confederation Suisse, EPFL, 1015 Lausanne (Switzerland)

2008-11-01T23:59:59.000Z

364

Center for Turbulence Research Annual Research Briefs 2008  

E-Print Network [OSTI]

simulation of a 20 sector of a Pratt & Whitney gas turbine engine, encompassing the fan, low- and high-pressure compressors, combustor, high- and low-pressure turbines, and the exit nozzle as illustrated in Fig. 1 of turbulent combustion in a gas turbine engine combustor By D. You, F. Ham AND P. Moin 1. Motivation

Prinz, Friedrich B.

365

Probing plasma turbulence by modulating the electron temperature gradient  

E-Print Network [OSTI]

The local value of a/L[subscript Te], a turbulence drive term, was modulated with electron cyclotron heating in L-mode discharges on DIII-D [ J. L. Luxon, Nucl. Fusion 42, 614 (2002) ] and the density and electron temperature ...

DeBoo, J. C.

366

Uncovering the Lagrangian Skeleton of Turbulence Manikandan Mathur,1  

E-Print Network [OSTI]

April 2007) We present a technique that uncovers the Lagrangian building blocks of turbulence, and apply, strain, and energy have all been suggested as defining quantities [1,2]. However, different definitions through sources and sinks in the bottom of the tank, thus producing near the bottom of the tank

Texas at Austin. University of

367

Center for Turbulence Research Annual Research Briefs 2008  

E-Print Network [OSTI]

combustion engines and gas-turbine aircraft engines. Therefore, the ability to perform accurate numerical relevant to combustion modeling for future research. 2. Mathematical model 2.1. Governing equations The gas, or collision and coalescence with other droplets. The resulting vapor in the gas phase undergoes turbulent

Prinz, Friedrich B.

368

Center for Turbulence Research Proceedings of the Summer Program 2012  

E-Print Network [OSTI]

, such as shear-layers, piloted, bluff-body and swirl-stabilized jet diffu- sion flames and gas-turbine combustorsCenter for Turbulence Research Proceedings of the Summer Program 2012 397 Budget analysis and model. Kolla AND J. H. Chen An a priori analysis of the flamelet-model is conducted to systematically assess

Wang, Wei

369

Modelling and Measurements of Power Losses and Turbulence  

E-Print Network [OSTI]

at Middelgrunden Offshore Wind Farm R. J. Barthelmie*, , S. T. Frandsen and M. N. Nielsen, Wind Energy Department and turbulence increase due to wind turbine wake interac- tions in large offshore wind farms is crucial interactions in large offshore wind farms is crucial to optimizing wind farm design. Power losses due

Pryor, Sara C.

370

Implicit large eddy simulations of anisotropic weakly compressible turbulence with application to core-collapse supernovae  

E-Print Network [OSTI]

(Abridged) In the implicit large eddy simulation (ILES) paradigm, the dissipative nature of high-resolution shock-capturing schemes is exploited to provide an implicit model of turbulence. Recent 3D simulations suggest that turbulence might play a crucial role in core-collapse supernova explosions, however the fidelity with which turbulence is simulated in these studies is unclear. Especially considering that the accuracy of ILES for the regime of interest in CCSN, weakly compressible and strongly anisotropic, has not been systematically assessed before. In this paper we assess the accuracy of ILES using numerical methods most commonly employed in computational astrophysics by means of a number of local simulations of driven, weakly compressible, anisotropic turbulence. We report a detailed analysis of the way in which the turbulent cascade is influenced by the numerics. Our results suggest that anisotropy and compressibility in CCSN turbulence have little effect on the turbulent kinetic energy spectrum and a...

Radice, David; Ott, Christian D

2015-01-01T23:59:59.000Z

371

Energy spectra of finite temperature superfluid helium-4 turbulence  

SciTech Connect (OSTI)

A mesoscopic model of finite temperature superfluid helium-4 based on coupled Langevin-Navier-Stokes dynamics is proposed. Drawing upon scaling arguments and available numerical results, a numerical method for designing well resolved, mesoscopic calculations of finite temperature superfluid turbulence is developed. The application of model and numerical method to the problem of fully developed turbulence decay in helium II, indicates that the spectral structure of normal-fluid and superfluid turbulence is significantly more complex than that of turbulence in simple-fluids. Analysis based on a forced flow of helium-4 at 1.3 K, where viscous dissipation in the normal-fluid is compensated by the Lundgren force, indicate three scaling regimes in the normal-fluid, that include the inertial, low wavenumber, Kolmogorov k{sup ?5/3} regime, a sub-turbulence, low Reynolds number, fluctuating k{sup ?2.2} regime, and an intermediate, viscous k{sup ?6} range that connects the two. The k{sup ?2.2} regime is due to normal-fluid forcing by superfluid vortices at high wavenumbers. There are also three scaling regimes in the superfluid, that include a k{sup ?3} range that corresponds to the growth of superfluid vortex instabilities due to mutual-friction action, and an adjacent, low wavenumber, k{sup ?5/3} regime that emerges during the termination of this growth, as superfluid vortices agglomerate between intense normal-fluid vorticity regions, and weakly polarized bundles are formed. There is also evidence of a high wavenumber k{sup ?1} range that corresponds to the probing of individual-vortex velocity fields. The Kelvin waves cascade (the main dynamical effect in zero temperature superfluids) appears to be damped at the intervortex space scale.

Kivotides, Demosthenes [Department of Aeronautics, Imperial College London, London SW7 2AZ (United Kingdom)

2014-10-15T23:59:59.000Z

372

Article for thermal energy storage  

DOE Patents [OSTI]

A thermal energy storage composition is provided which is in the form of a gel. The composition includes a phase change material and silica particles, where the phase change material may comprise a linear alkyl hydrocarbon, water/urea, or water. The thermal energy storage composition has a high thermal conductivity, high thermal energy storage, and may be used in a variety of applications such as in thermal shipping containers and gel packs.

Salyer, Ival O. (Dayton, OH)

2000-06-27T23:59:59.000Z

373

Measurements of Electron Thermal Transport due to Electron Temperature Gradient Modes in a Basic Experiment  

SciTech Connect (OSTI)

Production and identification of electron temperature gradient modes have already been reported [X. Wei, V. Sokolov, and A. K. Sen, Phys. Plasmas 17, 042108 (2010)]. Now a measurement of electron thermal conductivity via a unique high frequency triple probe yielded a value of {chi}{sub perpendiculare} ranging between 2 and 10 m{sup 2}/s, which is of the order of a several gyrobohm diffusion coefficient. This experimental result appears to agree with a value of nonlocal thermal conductivity obtained from a rough theoretical estimation and not inconsistent with gyrokinetic simulation results for tokamaks. The first experimental scaling of the thermal conductivity versus the amplitude of the electron temperature gradient fluctuation is also obtained. It is approximately linear, indicating a strong turbulence signature.

Sokolov, V.; Sen, A. K. [Plasma Research Laboratory, Columbia University, New York, New York 10027 (United States)

2011-10-07T23:59:59.000Z

374

THERMAL NEUTRON BACKSCATTER IMAGING.  

SciTech Connect (OSTI)

Objects of various shapes, with some appreciable hydrogen content, were exposed to fast neutrons from a pulsed D-T generator, resulting in a partially-moderated spectrum of backscattered neutrons. The thermal component of the backscatter was used to form images of the objects by means of a coded aperture thermal neutron imaging system. Timing signals from the neutron generator were used to gate the detection system so as to record only events consistent with thermal neutrons traveling the distance between the target and the detector. It was shown that this time-of-flight method provided a significant improvement in image contrast compared to counting all events detected by the position-sensitive {sup 3}He proportional chamber used in the imager. The technique may have application in the detection and shape-determination of land mines, particularly non-metallic types.

VANIER,P.; FORMAN,L.; HUNTER,S.; HARRIS,E.; SMITH,G.

2004-10-16T23:59:59.000Z

375

Thermal insulated glazing unit  

SciTech Connect (OSTI)

An improved insulated glazing unit is provided which can attain about R5 to about R10 thermal performance at the center of the glass while having dimensions about the same as those of a conventional double glazed insulated glazing unit. An outer glazing and inner glazing are sealed to a spacer to form a gas impermeable space. One or more rigid, non-structural glazings are attached to the inside of the spacer to divide the space between the inner and outer glazings to provide insulating gaps between glazings of from about 0.20 inches to about 0.40 inches. One or more glazing surfaces facing each thermal gap are coated with a low emissivity coating. Finally, the thermal gaps are filled with a low conductance gas such as krypton gas.

Selkowitz, Stephen E. (Piedmont, CA); Arasteh, Dariush K. (Oakland, CA); Hartmann, John L. (Seattle, WA)

1991-01-01T23:59:59.000Z

376

Thermal insulated glazing unit  

SciTech Connect (OSTI)

An improved insulated glazing unit is provided which can attain about R5 to about R10 thermal performance at the center of the glass while having dimensions about the same as those of a conventional double glazed insulated glazing unit. An outer glazing and inner glazing are sealed to a spacer to form a gas impermeable space. One or more rigid, non-structural glazings are attached to the inside of the spacer to divide the space between the inner and outer glazings to provide insulating gaps between glazings of from about 0.20 inches to about 0.40 inches. One or more glazing surfaces facing each thermal gap are coated with a low emissivity coating. Finally, the thermal gaps are filled with a low conductance gas such as krypton gas. 2 figs.

Selkowitz, S.E.; Arasteh, D.K.; Hartmann, J.L.

1988-04-05T23:59:59.000Z

377

Thermal trim for luminaire  

DOE Patents [OSTI]

A luminaire with a thermal pathway to reduce the junction temperature of the luminaire's light source, and methods for so doing, are disclosed. The luminaire includes a can, a light engine, and a trim, that define a substantially continuous thermal pathway from the light engine to a surrounding environment. The can defines a can cavity and includes a can end region. The light engine is within the can cavity and includes a light source and a heat sink, including a heat sink end region, coupled thereto. The trim is at least partially disposed within the can cavity and includes a first trim end region coupled to the heat sink end region and a second trim end region coupled to the can end region. Thermal interface material may be located between: the heat sink and the trim, the trim and the can, and/or the heat sink and the light source.

Bazydola, Sarah; Ghiu, Camil-Daniel; Harrison, Robert; Jeswani, Anil

2013-11-19T23:59:59.000Z

378

Thermal test options  

SciTech Connect (OSTI)

Shipping containers for radioactive materials must be qualified to meet a thermal accident environment specified in regulations, such at Title 10, Code of Federal Regulations, Part 71. Aimed primarily at the shipping container design, this report discusses the thermal testing options available for meeting the regulatory requirements, and states the advantages and disadvantages of each approach. The principal options considered are testing with radiant heat, furnaces, and open pool fires. The report also identifies some of the facilities available and current contacts. Finally, the report makes some recommendations on the appropriate use of these different testing methods.

Koski, J.A.; Keltner, N.R.; Sobolik, K.B.

1993-02-01T23:59:59.000Z

379

Thermal ignition combustion system  

DOE Patents [OSTI]

The thermal ignition combustion system comprises means for providing walls defining an ignition chamber, the walls being made of a material having a thermal conductivity greater than 20 W/m C and a specific heat greater than 480 J/kg C with the ignition chamber being in constant communication with the main combustion chamber, means for maintaining the temperature of the walls above a threshold temperature capable of causing ignition of a fuel, and means for conducting fuel to the ignition chamber. 8 figs.

Kamo, R.; Kakwani, R.M.; Valdmanis, E.; Woods, M.E.

1988-04-19T23:59:59.000Z

380

Scattering Solar Thermal Concentrators  

Broader source: Energy.gov [DOE]

"This fact sheet describes a scattering solar thermal concentrators project awarded under the DOE's 2012 SunShot Concentrating Solar Power R&D award program. The team, led by the Pennsylvania State University, is working to demonstrate a new, scattering-based approach to concentrating sunlight that aims to improve the overall performance and reliability of the collector field. The research team aims to show that scattering solar thermal collectors are capable of achieving optical performance equal to state-of-the-art parabolic trough systems, but with the added benefits of immunity to wind-load tracking error, more efficient land use, and utilization of stationary receivers."

Note: This page contains sample records for the topic "rangepsi 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

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

SciTech Connect (OSTI)

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

382

Formation of Turbulent Cones in Accretion Disk Outflows and Application to Broad Line Regions of Active Galactic Nuclei  

E-Print Network [OSTI]

We consider the stability of an accretion disk wind to cloud formation when subject to a central radiation force. For a vertical launch velocity profile that is Keplerian or flatter and the presence of a significant radiation pressure, the wind flow streamlines cross in a conical layer. We argue that such regions are highly unstable, and are natural sites for supersonic turbulence and, consequently, density compressions. We suggest that combined with thermal instability these will all conspire to produce clouds. Such clouds can exist in dynamical equilibrium, constantly dissipating and reforming. As long as there is an inner truncation radius to the wind, our model emerges with a biconical structure similar to that inferred by Elvis (2000) for the broad line region (BLR) of active galactic nuclei (AGN). Our results may also apply to other disk-wind systems.

A. Y. Poludnenko; E. G. Blackman; A. Frank

2002-01-24T23:59:59.000Z

383

Systems analysis of thermal storage  

SciTech Connect (OSTI)

During FY 1981, analyses were conducted on thermal storage concepts for solar thermal applications. These studies include estimates of both the obtainable costs of thermal storage concepts and their worth to a user (i.e., value). Based on obtainable costs and performance, an in-depth study evaluated thermal storage concepts for water/steam, organic fluid, and gas/Brayton solar thermal receivers. Promising and nonpromising concepts were identified. A study to evaluate thermal storage concepts for a liquid metal receiver was initiated. The value of thermal storage in a solar thermal industrial process heat application was analyzed. Several advanced concepts are being studied, including ground-mounted thermal storage for parabolic dishes with Stirling engines.

Copeland, R.J.

1981-08-01T23:59:59.000Z

384

The Local Variational Multiscale Method for Turbulence Simulation.  

SciTech Connect (OSTI)

Accurate and efficient turbulence simulation in complex geometries is a formidable chal-lenge. Traditional methods are often limited by low accuracy and/or restrictions to simplegeometries. We explore the merger of Discontinuous Galerkin (DG) spatial discretizationswith Variational Multi-Scale (VMS) modeling, termed Local VMS (LVMS), to overcomethese limitations. DG spatial discretizations support arbitrarily high-order accuracy on un-structured grids amenable for complex geometries. Furthermore, high-order, hierarchicalrepresentation within DG provides a natural framework fora prioriscale separation crucialfor VMS implementation. We show that the combined benefits of DG and VMS within theLVMS method leads to promising new approach to LES for use in complex geometries.The efficacy of LVMS for turbulence simulation is assessed by application to fully-developed turbulent channelflow. First, a detailed spatial resolution study is undertakento record the effects of the DG discretization on turbulence statistics. Here, the localhp[?]refinement capabilites of DG are exploited to obtain reliable low-order statistics effi-ciently. Likewise, resolution guidelines for simulating wall-bounded turbulence using DGare established. We also explore the influence of enforcing Dirichlet boundary conditionsindirectly through numericalfluxes in DG which allows the solution to jump (slip) at thechannel walls. These jumps are effective in simulating the influence of the wall commen-surate with the local resolution and this feature of DG is effective in mitigating near-wallresolution requirements. In particular, we show that by locally modifying the numericalviscousflux used at the wall, we are able to regulate the near-wall slip through a penaltythat leads to improved shear-stress predictions. This work, demonstrates the potential ofthe numerical viscousflux to act as a numerically consistent wall-model and this successwarrents future research.As in any high-order numerical method some mechanism is required to control aliasingeffects due to nonlinear interactions and to ensure nonlinear stability of the method. Inthis context, we evaluate the merits of two approaches to de-aliasing -- spectralfilteringand polynomial dealiasing. While both approaches are successful, polynomial-dealiasingis found to be better suited for use in large-eddy simulation. Finally, results using LVMSare reported and show good agreement with reference direct numerical simulation therebydemonstrating the effectiveness of LVMS for wall-bounded turbulence. This success pavesthe way for future applications of LVMS to more complex turbulentflows.3

Collis, Samuel Scott; Ramakrishnan, Srinivas

2005-05-01T23:59:59.000Z

385

Thermal Reactor Safety  

SciTech Connect (OSTI)

Information is presented concerning fire risk and protection; transient thermal-hydraulic analysis and experiments; class 9 accidents and containment; diagnostics and in-service inspection; risk and cost comparison of alternative electric energy sources; fuel behavior and experiments on core cooling in LOCAs; reactor event reporting analysis; equipment qualification; post facts analysis of the TMI-2 accident; and computational methods.

Not Available

1980-06-01T23:59:59.000Z

386

Thermal management of nanoelectronics  

E-Print Network [OSTI]

-state thermoelectric on- spot cooling, requiring efficient thermoelectric materials that can be integrated with the IC are further complicated by the fact that the material's ability to conduct heat deteriorates when at the packaging level but also at the nanoscale materials and device levels. THERMAL CHALLENGES AT NANOSCALE One

387

Thermal Infrared Remote Sensing  

E-Print Network [OSTI]

to us, like reflective ("nearreflective ("near--" infrared (0.7" infrared (0.7 -- 3.03.0 µµm)m) andand near-infrared far infrared ultraviolet Thermal Infrared refers to region o EM spectrum from ~3 - 14 µm.landscape. IMPORTANT: NEARIMPORTANT: NEAR--INFRARED is short enough wavelength toINFRARED is short enough wavelength

388

Low thermal conductivity skutterudites  

SciTech Connect (OSTI)

Recent experimental results on semiconductors with the skutterudite crystal structure show that these materials possess attractive transport properties and have a good potential for achieving ZT values substantially larger than for state-of-the-art thermoelectric materials. Both n-type and p-type conductivity samples have been obtained, using several preparation techniques. Associated with a low hole effective mass, very high carrier mobilities, low electrical resistivities and moderate Seebeck coefficients are obtained in p-type skutterudites. For a comparable doping level, the carrier mobilities of n-type samples are about an order of magnitude lower than the values achieved on p-type samples. However, the much larger electron effective masses and Seebeck coefficients on p-type samples. However, the much larger electron effective masses and Seebeck coefficients make n-type skutterudite promising candidates as well. Unfortunately, the thermal conductivities of the binary skutterudites compounds are too large, particularly at low temperatures, to be useful for thermoelectric applications. Several approaches to the reduction of the lattice thermal conductivity in skutterudites are being pursued: heavy doping, formation of solid solutions and alloys, study of novel ternary and filled skutterudite compounds. All those approaches have already resulted in skutterudite compositions with substantially lower thermal conductivity values in these materials. Recently, superior thermoelectric properties in the moderate to high temperature range were achieved for compositions combining alloying and filling of the skutterudite structure. Experimental results and mechanisms responsible for low thermal conductivity in skutterudites are discussed.

Fleurial, J.P.; Caillat, T.; Borshchevsky, A.

1997-07-01T23:59:59.000Z

389

Thermal barrier coating  

DOE Patents [OSTI]

A thermal barrier coating for hot gas path components of a combustion turbine based on a zirconia-scandia system. A layer of zirconium scandate having the hexagonal Zr.sub.3 Sc.sub.4 O.sub.12 structure is formed directly on a superalloy substrate or on a bond coat formed on the substrate.

Bowker, Jeffrey Charles (Gibsonia, PA); Sabol, Stephen M. (Orlando, FL); Goedjen, John G. (Oviedo, FL)

2001-01-01T23:59:59.000Z

390

High-Temperature Thermal Array for Next Generation Solar Thermal...  

Broader source: Energy.gov (indexed) [DOE]

3 Q1 High-Temperature Thermal Array for Next Generation Solar Thermal Power Production - FY13 Q1 This document summarizes the progress of this Los Alamos National Laboratory...

391

Preliminary requirements for thermal storage subsystems in solar thermal applications  

SciTech Connect (OSTI)

Methodologies for the analysis of value and comparing thermal storage concepts are presented. Value is a measure of worth and is determined by the cost of conventional fuel systems. Value data for thermal storage in large solar thermal electric power applications are presented. Thermal storage concepts must be compared when all are performing the same mission. A method for doing that analysis, called the ranking index, is derived. Necessary data to use the methodology are included.

Copeland, R.J.

1980-04-01T23:59:59.000Z

392

Development of one-equation transition/turbulence models  

SciTech Connect (OSTI)

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

393

Ionization front-driven turbulence in the clumpy interstellar medium  

E-Print Network [OSTI]

We present 3D radiation-gasdynamical simulations of an ionization front running into a dense clump. In our setup, a B0 star irradiates an overdensity which is at a distance of 10 pc and modelled as a supercritical 100 M_sol Bonnor-Ebert sphere. The radiation from the star heats up the gas and creates a shock front that expands into the interstellar medium. The shock compresses the clump material while the ionizing radiation heats it up. The outcome of this "cloud-crushing" process is a fully turbulent gas in the wake of the clump. In the end, the clump entirely dissolves. We propose that this mechanism is very efficient in creating short-living supersonic turbulence in the vicinity of massive stars.

Thomas Peters; Robi Banerjee; Ralf S. Klessen

2008-08-20T23:59:59.000Z

394

Turbulence transition and the edge of chaos in pipe flow  

E-Print Network [OSTI]

The linear stability of pipe flow implies that only perturbations of sufficient strength will trigger the transition to turbulence. In order to determine this threshold in perturbation amplitude we study the \\emph{edge of chaos} which separates perturbations that decay towards the laminar profile and perturbations that trigger turbulence. Using the lifetime as an indicator and methods developed in (Skufca et al, Phys. Rev. Lett. {\\bf 96}, 174101 (2006)) we show that superimposed on an overall $1/\\Re$-scaling predicted and studied previously there are small, non-monotonic variations reflecting folds in the edge of chaos. By tracing the motion in the edge we find that it is formed by the stable manifold of a unique flow field that is dominated by a pair of downstream vortices, asymmetrically placed towards the wall. The flow field that generates the edge of chaos shows intrinsic chaotic dynamics.

Tobias M Schneider; Bruno Eckhardt; James A Yorke

2007-03-30T23:59:59.000Z

395

Shock-induced turbulent flow in baffle systems  

SciTech Connect (OSTI)

Experiments are described on shock propagation through 2-D aligned and staggered baffle systems. Flow visualization was provided by shadow and schlieren photography, recorded by the Cranz-Schardin camera. Also single-frame, infinite-fringe, color interferograms were used. Intuition suggests that this is a rather simple 2-D shock diffraction problem. However, flow visualization reveals that the flow rapidly evolved into a complex 3-D turbulent mixing problem. Mushroom-shaped mixing regions blocked the flow into the next baffle orifice. Thus energy was transferred from the directed kinetic energy (induced by the shock) to rotational energy of turbulent mixing, and then dissipated by molecular effects. These processes dramatically dissipate the strength of the shock wave. The experiments provide an excellent test case that could be used to assess the accuracy of computer code calculations of such problems.

Kuhl, A.L. [Lawrence Livermore National Lab., CA (United States); Reichenbach, H. [Fraunhofer-Institut fuer Kurzzeitdynamik - Ernst-Mach-Institut (EMI), Freiburg im Breisgau (Germany)

1993-07-01T23:59:59.000Z

396

Multiphase turbulent interstellar medium: some recent results from radio astronomy  

E-Print Network [OSTI]

The radio frequency 1.4 GHz transition of the atomic hydrogen is one of the important tracers of the diffuse neutral interstellar medium. Radio astronomical observations of this transition, using either a single dish telescope or an array interferometer, reveal different properties of the interstellar medium. Such observations are particularly useful to study the multiphase nature and turbulence in the interstellar gas. Observations with multiple radio telescopes have recently been used to study these two closely related aspects in greater detail. Using various observational techniques, the density and the velocity fluctuations in the Galactic interstellar medium was found to have a Kolmogorov-like power law power spectra. The observed power law scaling of the turbulent velocity dispersion with the length scale can be used to derive the true temperature distribution of the medium. Observations from a large ongoing atomic hydrogen absorption line survey have also been used to study the distribution of gas at d...

Roy, Nirupam

2015-01-01T23:59:59.000Z

397

Gyrotactic trapping in laminar and turbulent Kolmogorov flow  

E-Print Network [OSTI]

Phytoplankton patchiness, namely the heterogeneous distribution of microalgae over multiple spatial scales, dramatically impacts marine ecology. A spectacular example of such heterogeneity occurs in thin phytoplankton layers (TPLs), where large numbers of photosynthetic microorganisms are found within a small depth interval. Some species of motile phytoplankton can form TPLs by gyrotactic trapping due to the interplay of their particular swimming style (directed motion biased against gravity) and the transport by a flow with shear along the direction of gravity. Here we consider gyrotactic swimmers in numerical simulations of the Kolmogorov shear flow, both in laminar and turbulent regimes. In the laminar case, we show that the swimmer motion is integrable and the formation of TPLs can be fully characterized by means of dynamical systems tools. We then study the effects of rotational Brownian motion or turbulent fluctuations (appearing when the Reynolds number is large enough) on TPLs. In both cases we show that TPLs become transient, and we characterize their persistence.

Francesco Santamaria; Filippo De Lillo; Massimo Cencini; Guido Boffetta

2014-10-07T23:59:59.000Z

398

Coherent structures in ion temperature gradient turbulence-zonal flow  

SciTech Connect (OSTI)

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); Gürcan, Ö. 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

399

Beyond the Betz Theory - Blockage, Wake Mixing and Turbulence  

E-Print Network [OSTI]

Recent analytical models concerning the limiting efficiency of marine hydrokinetic (MHK) devices are reviewed with an emphasis on the significance of blockages (of local as well as global flow passages) and wake mixing. Also discussed is the efficiency of power generation from fully developed turbulent open channel flows. These issues are primarily concerned with the design/optimization of tidal turbine arrays; however, some of them are relevant to wind turbines as well.

Nishino, Takafumi

2013-01-01T23:59:59.000Z

400

Intermittency and turbulence in a magnetically confined fusion plasma  

E-Print Network [OSTI]

We investigate the intermittency of magnetic turbulence as measured in Reversed Field Pinch plasmas. We show that the Probability Distribution Functions of magnetic field differences are not scale invariant, that is the wings of these functions are more important at the smallest scales, a classical signature of intermittency. We show that scaling laws appear also in a region very close to the external wall of the confinement device, and we present evidences that the observed intermittency increases moving towards the wall.

V. Carbone; L. Sorriso-Valvo; E. Martines; V. Antoni; P. Veltri

2001-01-30T23:59:59.000Z

Note: This page contains sample records for the topic "rangepsi 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

Energy dissipation statistics in a shell model of turbulence  

E-Print Network [OSTI]

The Reynolds number dependence of the statistics of energy dissipation is investigated in a shell model of fully developed turbulence. The results are in agreement with a model which accounts for fluctuations of the dissipative scale with the intensity of energy dissipation. It is shown that the assumption of a fixed dissipative scale leads to a different scaling with Reynolds which is not compatible with numerical results.

G. Boffetta; A. Celani; D. Roagna

1999-09-30T23:59:59.000Z

402

Advances in three-dimensional turbulence measurement capability  

SciTech Connect (OSTI)

Requirements for three-dimensional turbulence velocity measurements for wind turbine purposes have recently led to advances in anemometer accuracy and resolution, particularly for situations when the angle of the wind relative to the anemometer axis is large. New precision calibration data for a complete three-dimensional UVW propeller anemometer are presented. Repeatability of calibration data and comparison with previous calibrations are shown. Special attention is given to the calibration of the crosswind components, V and W. 4 refs., 9 figs.

Connell, J.R.; Morris, V.R.

1988-11-01T23:59:59.000Z

403

Simulations of Turbulent Flows with Strong Shocks and Density Variations  

SciTech Connect (OSTI)

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

404

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

405

Noise correction of turbulent spectra obtained from Acoustic Doppler Velocimeters  

SciTech Connect (OSTI)

Accurately estimated auto-spectral density functions are essential for characterization of turbulent flows, and they also have applications in computational fluid dynamics modeling, site and inflow characterization for hydrokinetic turbines, and inflow turbulence generation. The Acoustic Doppler Velocimeter (ADV) provides single-point temporally resolved data, that are used to characterize turbulent flows in rivers, seas, and oceans. However, ADV data are susceptible to contamination from various sources, including instrument noise, which is the intrinsic limit to the accuracy of acoustic velocity measurements. Due to the presence of instrument noise, the spectra obtained are altered at high frequencies. The focus of this study is to develop a robust and effective method for accurately estimating auto-spectral density functions from ADV data by reducing or removing the spectral contribution derived from instrument noise. For this purpose, the “Noise Auto-Correlation” (NAC) approach was developed, which exploits the correlation properties of instrument noise to identify and remove its contribution from spectra. The spectra estimated using the NAC approach exhibit increased fidelity and a slope of -5/3 in the inertial range, which is typically observed for turbulent flows. Finally, this study also compares the effectiveness of low-pass Gaussian filters in removing instrument noise with that of the NAC approach. For the data used in this study, both the NAC and Gaussian filter approaches are observed to be capable of removing instrument noise at higher frequencies from the spectra. However, the NAC results are closer to the expected frequency power of -5/3 in the inertial sub-range.

Durgesh, Vibhav; Thomson, Jim; Richmond, Marshall C.; Polagye, Brian

2014-03-02T23:59:59.000Z

406

Examination of steam generator turbulence by large eddy simulation  

E-Print Network [OSTI]

techniques (Biringen, ei ah 1981; Yakhot et al. 1986). Clark et ah (1979) quantified the various subgrid scale (SGS) terms in LES by comparing their results to a direct simulation. Schumann (1975) used an integral conservation equation combined with an SGS... in the past . The most important interactions are: fluidelastic instability, vortex shedding, turbulent buffeting, and acoustic resonance. Fluidelastic instability results from a coupled fluid-tube force interaction. The instability is also thought...

Bagwell, Ted Glyn

1989-01-01T23:59:59.000Z

407

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

SciTech Connect (OSTI)

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

408

AQUIFER THERMAL ENERGY STORAGE-A SURVEY  

E-Print Network [OSTI]

High temperature underground thermal energy storage, inProceedings, Thermal Energy Storage in Aquifers Workshop:underground thermal energy storage, in ATES newsletter:

Tsang, Chin Fu

2012-01-01T23:59:59.000Z

409

THERMAL ENERGY STORAGE IN AQUIFERS WORKSHOP  

E-Print Network [OSTI]

Survey of Thermal Energy Storage in Aquifers Coupled withconcept of thermal energy storage in aquifers was suggestedLow Temperature Thermal Energy Storage Program of Oak Ridge

Authors, Various

2011-01-01T23:59:59.000Z

410

Ocean Thermal Extractable Energy Visualization: Final Technical...  

Office of Environmental Management (EM)

Ocean Thermal Extractable Energy Visualization: Final Technical Report Ocean Thermal Extractable Energy Visualization: Final Technical Report Report about the Ocean Thermal...

411

OCEAN THERMAL ENERGY CONVERSION PROGRAMMATIC ENVIRONMENTAL ASSESSMENT  

E-Print Network [OSTI]

M.D. (editor) Ocean Thermal Energy Conversion (OTEC) Draftin Ocean Thermal Energy Conversion (OTEC) technology haveThe Ocean Thermal Energy Conversion (OTEC) 2rogrammatic

Sands, M.Dale

2013-01-01T23:59:59.000Z

412

AQUIFER THERMAL ENERGY STORAGE-A SURVEY  

E-Print Network [OSTI]

1978, High temperature underground thermal energy storage,in Proceedings, Thermal Energy Storage in Aquifers Workshop:High temperature underground thermal energy storage, in ATES

Tsang, Chin Fu

2012-01-01T23:59:59.000Z

413

Gyrokinetic Particle Simulation of Compressible Electromagnetic Turbulence in High-? Plasmas  

SciTech Connect (OSTI)

Supported by this award, the PI and his research group at the University of California, Irvine (UCI) have carried out computational and theoretical studies of instability, turbulence, and transport in laboratory and space plasmas. Several massively parallel, gyrokinetic particle simulation codes have been developed to study electromagnetic turbulence in space and laboratory plasmas. In space plasma projects, the simulation codes have been successfully applied to study the spectral cascade and plasma heating in kinetic Alfven wave turbulence, the linear and nonlinear properties of compressible modes including mirror instability and drift compressional mode, and the stability of the current sheet instabilities with finite guide field in the context of collisionless magnetic reconnection. The research results have been published in 25 journal papers and presented at many national and international conferences. Reprints of publications, source codes, and other research-related information are also available to general public on the PI’s webpage (http://phoenix.ps.uci.edu/zlin/). Two PhD theses in space plasma physics are highlighted in this report.

Lin, Zhihong

2014-03-13T23:59:59.000Z

414

Communication with spatially modulated Light through turbulent Air across Vienna  

E-Print Network [OSTI]

The transverse spatial modes of light offer a large state-space with interesting physical properties. For exploiting it in future long-distance experiments, spatial modes will have to be transmitted over turbulent free-space links. Numerous recent lab-scale experiments have found significant degradation in the mode quality after transmission through simulated turbulence and consecutive coherent detection. Here we experimentally analyze the transmission of one prominent class of spatial modes, the orbital-angular momentum (OAM) modes, through 3 km of strong turbulence over the city of Vienna. Instead of performing a coherent phase-dependent measurement, we employ an incoherent detection scheme which relies on the unambiguous intensity patterns of the different spatial modes. We use a pattern recognition algorithm (an artificial neural network) to identify the characteristic mode pattern displayed on a screen at the receiver. We were able to distinguish between 16 different OAM mode superpositions with only ~1.7% error, and use them to encode and transmit small grey-scale images. Moreover, we found that the relative phase of the superposition modes is not affected by the atmosphere, establishing the feasibility for performing long-distance quantum experiments with the OAM of photons. Our detection method works for other classes of spatial modes with unambiguous intensity patterns as well, and can further be improved by modern techniques of pattern recognition.

Mario Krenn; Robert Fickler; Matthias Fink; Johannes Handsteiner; Mehul Malik; Thomas Scheidl; Rupert Ursin; Anton Zeilinger

2014-11-12T23:59:59.000Z

415

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

416

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

417

An observational study of turbulence in the SPBL  

SciTech Connect (OSTI)

Turbulence in the stable planetary boundary layer (SPBL) is complicated by intermittency, gravity waves, long time scales and meso-scale forcing. Surface features and topography are also important. This study examines turbulence near the top of the SPBL with data taken from a network of 61 m towers. The focus is on the role of moderately complex terrain on turbulent intermittency and spatial variation. The Savannah River Site is {approx}150 km from the Atlantic Ocean and is characterized by rolling forested hills and an average elevation of {approx}80 m ASL. Typical variations in elevation are 50 m (peak to valley) with a horizontal scale of several km. The most important topographic feature is the Savannah River flood plain, which borders the SRS to the southwest. This flood plain is 3-7 km wide with an average elevation of 40 m ASL. Nine 60 meter towers are located on the SRS, generally at higher elevations (81 - 109 m ASL), except for the D tower which is in the Savannah River flood plain (elevation 43 m ASL). The Cl tower differs from the other 8 towers because it collects data at 2, 18, and 36 m as well as 61 m. The TV tower, located 8 km northwest of the SRS, is instrumented at 8 levels from the surface to 300 m.

Kurzeja, R.

1997-09-01T23:59:59.000Z

418

Transient vortex events in the initial value problem for turbulence  

E-Print Network [OSTI]

A vorticity surge event that could be a paradigm for a wide class of bursting events in turbulence is studied to examine how the energy cascade is established and how this event could serve as a new test of LES turbulence models. This vorticity surge event is tied to the formation of the energy cascade in a direct numerical simulation by the traditional signatures of a turbulent energy cascade such as spectra approaching -5/3 and strongly Beltramized vortex tubes. A coherent mechanism is suggested by the nearly simultaneous development of a maximum of the peak vorticity $\\|\\omega\\|_\\infty$, growth of the dissipation, the appearance of a helically aligned local vortex configuration and strong, transient oscillations in the helicity wavenumber spectrum. This coherence is also examined for two LES models, a traditional purely dissipative eddy viscosity model and a modern method (LANS$-\\alpha$) that respects the nonlinear transport properties of fluids. Both LES models properly represent the spectral energy and energy dissipation associated with this vorticity surge event. However, only the model that preserves nonlinear fluid transport properties reproduces the helical properties, including Beltrami-like vortex tubes.

Darryl D. Holm; Robert M. Kerr

2001-10-19T23:59:59.000Z

419

Liquid metal thermal electric converter  

DOE Patents [OSTI]

A liquid metal thermal electric converter which converts heat energy to electrical energy. The design of the liquid metal thermal electric converter incorporates a unique configuration which directs the metal fluid pressure to the outside of the tube which results in the structural loads in the tube to be compressive. A liquid metal thermal electric converter refluxing boiler with series connection of tubes and a multiple cell liquid metal thermal electric converter are also provided.

Abbin, Joseph P. (Albuquerque, NM); Andraka, Charles E. (Albuquerque, NM); Lukens, Laurance L. (Albuquerque, NM); Moreno, James B. (Albuquerque, NM)

1989-01-01T23:59:59.000Z

420

Low Conductivity Thermal Barrier Coatings  

E-Print Network [OSTI]

Low Conductivity Thermal Barrier Coatings A Dissertation Presented to The Faculty of the School conductivity of the coatings. The minimum thermal conductivity occurs at a low rotation rate and is 0.8 W intrinsic thermal conductivity, good phase stability and greater resistance to sintering and CMAS attack

Wadley, Haydn

Note: This page contains sample records for the topic "rangepsi 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

A New Proof on Net Upscale Energy Cascade in 2D and QG Turbulence  

E-Print Network [OSTI]

A general proof that more energy flows upscale than downscale in two-dimensional (2D) turbulence and barotropic quasi-geostrophic (QG) turbulence is given. A proof is also given that in Surface QG turbulence, the reverse is true. Though some of these results are known in restricted cases, the proofs given here are pedagogically simpler, require fewer assumptions and apply to both forced and unforced cases.

Eleftherios Gkioulekas; Ka Kit Tung

2006-09-30T23:59:59.000Z

422

Overview of the TurbSim Stochastic Inflow Turbulence Simulator: Version 1.10  

SciTech Connect (OSTI)

The Turbsim stochastic inflow turbulence code was developed to provide a numerical simulation of a full-field flow that contains coherent turbulence structures that reflect the proper spatiotemporal turbulent velocity field relationships seen in instabilities associated with nocturnal boundary layer flows. This report provides the user with an overview of how the TurbSim code has been developed and some of the theory behind that development.

Kelley, N. D.; Jonkman, B. J.

2006-09-01T23:59:59.000Z

423

Thermal Stabilization Blend Plan  

SciTech Connect (OSTI)

This Blend Plan documents the feed material items that are stored in 2736-2 vaults, the 2736-ZB 638 cage, the 192C vault, and the 225 vault that will be processed through the thermal stabilization furnaces. The purpose of thermal stabilization is to heat the material to 1000 degrees Celsius to drive off all water and leave the plutonium and/or uranium as oxides. The stabilized material will be sampled to determine the Loss On Ignition (LOI) or percent water. The stabilized material must meet water content or LOI of less than 0.5% to be acceptable for storage under DOE-STD-3013-99 specifications. Out of specification material will be recycled through the furnaces until the water or LOI limits are met.

RISENMAY, H.R.

2000-05-02T23:59:59.000Z

424

Thermal synthesis apparatus  

DOE Patents [OSTI]

An apparatus for thermal conversion of one or more reactants to desired end products includes an insulated reactor chamber having a high temperature heater such as a plasma torch at its inlet end and, optionally, a restrictive convergent-divergent nozzle at its outlet end. In a thermal conversion method, reactants are injected upstream from the reactor chamber and thoroughly mixed with the plasma stream before entering the reactor chamber. The reactor chamber has a reaction zone that is maintained at a substantially uniform temperature. The resulting heated gaseous stream is then rapidly cooled by passage through the nozzle, which "freezes" the desired end product(s) in the heated equilibrium reaction stage, or is discharged through an outlet pipe without the convergent-divergent nozzle. The desired end products are then separated from the gaseous stream.

Fincke, James R. (Idaho Falls, ID) [Idaho Falls, ID; Detering, Brent A. (Idaho Falls, ID) [Idaho Falls, ID

2009-08-18T23:59:59.000Z

425

Thermal reactor safety  

SciTech Connect (OSTI)

Information is presented concerning new trends in licensing; seismic considerations and system structural behavior; TMI-2 risk assessment and thermal hydraulics; statistical assessment of potential accidents and verification of computational methods; issues with respect to improved safety; human factors in nuclear power plant operation; diagnostics and activities in support of recovery; LOCA transient analysis; unresolved safety issues and other safety considerations; and fission product transport.

Not Available

1980-06-01T23:59:59.000Z

426

Cermet fuel thermal conductivity  

E-Print Network [OSTI]

CERMET FUEL THERMAL CONDUCTIVITY A Thesis by JOHN MARK ALVIS, JR. Submitted to the Graduate College of Texas A&. M University in partial fulfilment of the requirements for the degree of MASTER OF SCIENCE August 1988 Major Subject: Nuclear... particles of low conductivity dispersed in a metal matrix of high conductivity. A computer code was developed in order to compute the conductivity of cermet fuels as predicted by existing models and an additional model derived in this work...

Alvis, John Mark

1988-01-01T23:59:59.000Z

427

Thermally actuated thermionic switch  

DOE Patents [OSTI]

A thermally actuated thermionic switch which responds to an increase of temperature by changing from a high impedance to a low impedance at a predictable temperature set point. The switch has a bistable operation mode switching only on temperature increases. The thermionic material may be a metal which is liquid at the desired operation temperature and held in matrix in a graphite block reservoir, and which changes state (ionizes, for example) so as to be electrically conductive at a desired temperature.

Barrus, D.M.; Shires, C.D.

1982-09-30T23:59:59.000Z

428

Methods of forming thermal management systems and thermal management methods  

DOE Patents [OSTI]

A thermal management system for a vehicle includes a heat exchanger having a thermal energy storage material provided therein, a first coolant loop thermally coupled to an electrochemical storage device located within the first coolant loop and to the heat exchanger, and a second coolant loop thermally coupled to the heat exchanger. The first and second coolant loops are configured to carry distinct thermal energy transfer media. The thermal management system also includes an interface configured to facilitate transfer of heat generated by an internal combustion engine to the heat exchanger via the second coolant loop in order to selectively deliver the heat to the electrochemical storage device. Thermal management methods are also provided.

Gering, Kevin L.; Haefner, Daryl R.

2012-06-05T23:59:59.000Z

429

Multiscale thermal transport.  

SciTech Connect (OSTI)

A concurrent computational and experimental investigation of thermal transport is performed with the goal of improving understanding of, and predictive capability for, thermal transport in microdevices. The computational component involves Monte Carlo simulation of phonon transport. In these simulations, all acoustic modes are included and their properties are drawn from a realistic dispersion relation. Phonon-phonon and phonon-boundary scattering events are treated independently. A new set of phonon-phonon scattering coefficients are proposed that reflect the elimination of assumptions present in earlier analytical work from the simulation. The experimental component involves steady-state measurement of thermal conductivity on silicon films as thin as 340nm at a range of temperatures. Agreement between the experiment and simulation on single-crystal silicon thin films is excellent, Agreement for polycrystalline films is promising, but significant work remains to be done before predictions can be made confidently. Knowledge gained from these efforts was used to construct improved semiclassical models with the goal of representing microscale effects in existing macroscale codes in a computationally efficient manner.

Graham, Samuel Jr. (; .); Wong, C. C.; Piekos, Edward Stanley

2004-02-01T23:59:59.000Z

430

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

SciTech Connect (OSTI)

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

431

E-Print Network 3.0 - advanced turbulence models Sample Search...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

K. Sudo, M. Sumida... Models -- Mesh Inlet Outlet 12;V&V of Turbulence Models -- Wall Static Pressure (1) Spalart... ... Source: McDonald, Kirk - Department of Physics,...

432

Turbulence Spectra from Spectral Lines: Tests of the Velocity Channel Analysis and Velocity Coordinate Spectrum Techniques  

E-Print Network [OSTI]

Turbulence is a key element of the dynamics of astrophysical fluids, including those of interstellar medium, clusters of galaxies and circumstellar regions. Turbulent motions induce Doppler shifts of observable emission and absorption lines and this motivates studies of turbulence using precision spectroscopy. We provide high resolution numerical testing of the two promising techniques, namely, Velocity Channel Analysis and Velocity Coordinate Spectrum. We obtain an expression for the shot noise that the discretization of the numerical data entails and successfully test it. We show that numerical resolution required for recovering the underlying turbulent spectrum from observations depend on the spectral index of velocity fluctuations. Thus the low resolution testing may be misleading.

A. Chepurnov; A. Lazarian

2007-01-31T23:59:59.000Z

433

E-Print Network 3.0 - atmospheric optical turbulence Sample Search...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

in magnetized plasmas Summary: EURATOM -- Ris National Laboratory Optics and Plasma Research Department, OPL-128 DK-4000 Roskilde... scale turbulent fluctuations is of great...

434

E-Print Network 3.0 - air pollution turbulence Sample Search...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Search Powered by Explorit Topic List Advanced Search Sample search results for: air pollution turbulence Page: << < 1 2 3 4 5 > >> 1 Air Pollution Physics and Chemistry...

435

Dispersed Phase of Non-Isothermal Particles in Rotating Turbulent Flows  

E-Print Network [OSTI]

We suggest certain effects, caused by interaction between rotation and gravitation with turbulence structure, for the cooling/heating of dispersed phase of non-isothermal particles in rotating turbulent fluid flows. These effects are obtained through the derivation of kinetic or probability density function based macroscopic equations for the particles. In doing so, for one-way temperature coupling, we also show that homogeneous, isotropic non-isothermal fluid turbulence does not influence the mean temperature (though it influences mean velocity) of the dispersed phase of particles settling due to gravitational force in the isotropic turbulence.

Pandya, R V R

2015-01-01T23:59:59.000Z

436

A Topological Framework for the Interactive Exploration of Large Scale Turbulent Combustion  

E-Print Network [OSTI]

comparison of terascale combustion simulation data. Mathe-premixed hydrogen ?ames. Combustion and Flame, [7] J. L.of Large Scale Turbulent Combustion Peer-Timo Bremer 1 ,

Bremer, Peer-Timo

2010-01-01T23:59:59.000Z

437

Consider Installing Turbulators on Two- and Three-Pass Firetube Boilers  

SciTech Connect (OSTI)

This revised ITP tip sheet on installing turbulators on firetube boilers provides how-to advice for improving the system using low-cost, proven practices and technologies.

Not Available

2006-01-01T23:59:59.000Z

438

Macroscopic implications from phase space dynamics of tokamak turbulence : relaxation, transport, and flow generation  

E-Print Network [OSTI]

Turbulent plasma and flow generation . . . . . . . . . . .of Intrinsic Rotation Generation in Tokamaks . . 2.12.2.2 Flow generation and stationary state . . . . . 2.3

Kosuga, Yusuke

2012-01-01T23:59:59.000Z

439

Oscillations of a Turbulent Jet Incident Upon an Edge  

SciTech Connect (OSTI)

For the case of a jet originating from a fully turbulent channel flow and impinging upon a sharp edge, the possible onset and nature of coherent oscillations has remained unexplored. In this investigation, high-image-density particle image velocimetry and surface pressure measurements are employed to determine the instantaneous, whole-field characteristics of the turbulent jet-edge interaction in relation to the loading of the edge. It is demonstrated that even in absence of acoustic resonant or fluid-elastic effects, highly coherent, self-sustained oscillations rapidly emerge above the turbulent background. Two clearly identifiable modes of instability are evident. These modes involve large-scale vortices that are phase-locked to the gross undulations of the jet and its interaction with the edge, and small-scale vortices, which are not phase-locked. Time-resolved imaging of instantaneous vorticity and velocity reveals the form, orientation, and strength of the large-scale concentrations of vorticity approaching the edge in relation to rapid agglomeration of small-scale vorticity concentrations. Such vorticity field-edge interactions exhibit rich complexity, relative to the simplified pattern of vortex-edge interaction traditionally employed for the quasi-laminar edgetone. Furthermore, these interactions yield highly nonlinear surface pressure signatures. The origin of this nonlinearity, involving coexistence of multiple frequency components, is interpreted in terms of large- and small-scale vortices embedded in distributed vorticity layers at the edge. Eruption of the surface boundary layer on the edge due to passage of the large-scale vortex does not occur; rather apparent secondary vorticity concentrations are simply due to distension of the oppositely-signed vorticity layer at the tip of the edge. The ensemble-averaged turbulent statistics of the jet quickly take on an identity that is distinct from the statistics of the turbulent boundary layer in the channel. Large increases in Reynolds stress occur due to onset of the small-scale concentrations of vorticity immediately downstream of separation; substantial increases at locations further downstream arise from development of the large-scale vorticity concentrations.

J.C. Lin; D. Rockwell

2000-09-19T23:59:59.000Z

440

THE COLLAPSE OF TURBULENT CORES AND RECONNECTION DIFFUSION  

SciTech Connect (OSTI)

In order for a molecular cloud clump to form stars, some transport of magnetic flux is required from the denser internal regions to the outer regions; otherwise, this can prevent the gravitational collapse. Fast magnetic reconnection, which takes place in the presence of turbulence, can induce a process of reconnection diffusion that has been elaborated on in earlier theoretical works. We have named this process turbulent reconnection diffusion, or simply RD. This paper continues our numerical study of this process and its implications. In particular, we extend our studies of RD in cylindrical clouds and consider more realistic clouds with spherical gravitational potentials (from embedded stars); we also account for the effects of the gas self-gravity. We demonstrate that, within our setup reconnection, diffusion is efficient. We have also identified the conditions under which RD becomes strong enough to make an initially subcritical cloud clump supercritical and induce its collapse. Our results indicate that the formation of a supercritical core is regulated by a complex interplay between gravity, self-gravity, the magnetic field strength, and nearly transonic and trans-Alfvénic turbulence; therefore, it is very sensitive to the initial conditions of the system. In particular, self-gravity helps RD and, as a result, the magnetic field decoupling from the collapsing gas becomes more efficient compared with the case of an external gravitational field. Our simulations confirm that RD can transport magnetic flux from the core of collapsing clumps to the envelope, but only a few of them become nearly critical or supercritical sub-Alfvénic cores, which is consistent with the observations. Furthermore, we have found that the supercritical cores built up in our simulations develop a predominantly helical magnetic field geometry that is also consistent with recent observations. Finally, we have also evaluated the effective values of the turbulent RD coefficient in our simulations and found that they are much larger than the numerical diffusion coefficient, especially for initially trans-Alfvénic clouds, thus ensuring that the detected magnetic flux removal is due to the action of turbulent RD rather than numerical diffusivity.

Leão, M. R. M.; De Gouveia Dal Pino, E. M.; Santos-Lima, R. [Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, R. do Matão, 1226, São Paulo, SP 05508-090 (Brazil); Lazarian, A., E-mail: mleao@ime.unicamp.br, E-mail: dalpino@astro.iag.usp.br, E-mail: rlima@astro.iag.usp.br, E-mail: alazarian@facstaff.wisc.edu [Department of Astronomy, University of Wisconsin, Madison, WI 53706 (United States)

2013-11-01T23:59:59.000Z

Note: This page contains sample records for the topic "rangepsi 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

Thermal control structure and garment  

DOE Patents [OSTI]

A flexible thermally conductive structure. The structure generally includes a plurality of thermally conductive yarns, at least some of which are at least partially disposed adjacent to an elastomeric material. Typically, at least a portion of the plurality of thermally conductive yarns is configured as a sheet. The yarns may be constructed from graphite, metal, or similar materials. The elastomeric material may be formed from urethane or silicone foam that is at least partially collapsed, or from a similar material. A thermal management garment is provided, the garment incorporating a flexible thermally conductive structure.

Klett, James W. (Knoxville, TN); Cameron, Christopher Stan (Sanford, NC)

2012-03-13T23:59:59.000Z

442

THERMAL PERFORMANCE OF MANAGED WINDOW SYSTEMS  

E-Print Network [OSTI]

on Thermal Performance of the Exterior Envelopes ofof thermal loads resulting from the building envelope areThermal Test Facility, LhL-9653, prepared for the ASHRAE/DOE Conference-on"t:heThermal Performance the Exterior Envelope

Selkowitz, S. E.

2011-01-01T23:59:59.000Z

443

Thermal management systems and methods  

DOE Patents [OSTI]

A thermal management system for a vehicle includes a heat exchanger having a thermal energy storage material provided therein, a first coolant loop thermally coupled to an electrochemical storage device located within the first coolant loop and to the heat exchanger, and a second coolant loop thermally coupled to the heat exchanger. The first and second coolant loops are configured to carry distinct thermal energy transfer media. The thermal management system also includes an interface configured to facilitate transfer of heat generated by an internal combustion engine to the heat exchanger via the second coolant loop in order to selectively deliver the heat to the electrochemical storage device. Thermal management methods are also provided.

Gering, Kevin L.; Haefner, Daryl R.

2006-12-12T23:59:59.000Z

444

Thermal and non-thermal energies in solar flares  

E-Print Network [OSTI]

The energy of the thermal flare plasma and the kinetic energy of the non-thermal electrons in 14 hard X-ray peaks from 9 medium-sized solar flares have been determined from RHESSI observations. The emissions have been carefully separated in the spectrum. The turnover or cutoff in the low-energy distribution of electrons has been studied by simulation and fitting, yielding a reliable lower limit to the non-thermal energy. It remains the largest contribution to the error budget. Other effects, such as albedo, non-uniform target ionization, hot target, and cross-sections on the spectrum have been studied. The errors of the thermal energy are about equally as large. They are due to the estimate of the flare volume, the assumption of the filling factor, and energy losses. Within a flare, the non-thermal/thermal ratio increases with accumulation time, as expected from loss of thermal energy due to radiative cooling or heat conduction. Our analysis suggests that the thermal and non-thermal energies are of the same magnitude. This surprising result may be interpreted by an efficient conversion of non-thermal energy to hot flare plasma.

Pascal Saint-Hilaire; Arnold O. Benz

2005-03-03T23:59:59.000Z

445

Integrated Vehicle Thermal Management Systems (VTMS) Analysis...  

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

Integrated Vehicle Thermal Management Power Electronic Thermal System Performance and Integration Characterization and Development of Advanced Heat Transfer Technologies...

446

Ultratough, Thermally Stable Polycrystalline Diamond/Silicon...  

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

Ultratough, Thermally Stable Polycrystalline DiamondSilicon Carbide Nanocomposites for Drill Bits Ultratough, Thermally Stable Polycrystalline DiamondSilicon Carbide...

447

Report on workshop on thermal property measurements  

SciTech Connect (OSTI)

Results of thermogravimetric analysis of basalt is discussed. Heat capacity, thermal conductivity and thermal expansion are specifically addressed. (CBS)

Robertson, E.C.

1987-01-01T23:59:59.000Z

448

Turbulence Investigation and Reproduction for Assisting Downstream Migrating Juvenile Salmonids, Part II of II; Effects of Induced Turbulence on Behavior of Juvenile Salmon, 2001-2005 Final Report.  

SciTech Connect (OSTI)

Passage through dams is a major source of mortality of anadromous juvenile salmonids because some populations must negotiate up to eight dams in Columbia and Snake rivers. Dams cause direct mortality when fish pass through turbines, but dams may also cause indirect mortality by altering migration conditions in rivers. Forebays immediately upstream of dams have decreased the water velocity of rivers and may contribute substantially to the total migration delay of juvenile salmonids. Recently, Coutant (2001a) suggested that in addition to low water velocities, lack of natural turbulence may contribute to migration delay by causing fish to lose directional cues. Coutant (2001a) further hypothesized that restoring turbulence in dam forebays may reduce migration delay by providing directional cues that allow fish to find passage routes more quickly (Coutant 2001a). Although field experiments have yielded proof of the concept of using induced turbulence to guide fish to safe passage routes, little is known about mechanisms actually causing behavioral changes. To test hypotheses about how turbulence influences movement and behavior of migrating juvenile salmonids, we conducted two types of controlled experiments at Cowlitz Falls Dam, Washington. A common measure of migration delay is the elapsed time between arrival at, and passage through, a dam. Therefore, for the first set of experiments, we tested the effect of induced turbulence on the elapsed time needed for fish to traverse through a raceway and pass over a weir at its downstream end (time trial experiment). If turbulence helps guide fish to passage routes, then fish should pass through the raceway quicker in the presence of appropriately scaled and directed turbulent cues. Second, little is known about how the physical properties of water movement provide directional cues to migrating juvenile salmonids. To examine the feasibility of guiding fish with turbulence, we tested whether directed turbulence could guide fish into one of two channels in the raceway, and subsequently cause them to pass disproportionately over the weir where turbulent cues were aimed (guidance experiment). Last, we measured and mapped water velocity and turbulence during the experiments to understand water movement patterns and the spatial distribution of turbulence in the raceways.

Perry, Russell W.; Farley, M. Jared; Hansen, Gabriel S. (US Geological Survey, Western Fisheries Research Center, Columbia River Research Laboratory, Cook, WA)

2005-07-01T23:59:59.000Z

449

Thermal indicator for wells  

DOE Patents [OSTI]

Minute durable plate-like thermal indicators are employed for precision measuring static and dynamic temperatures of well drilling fluids. The indicators are small enough and sufficiently durable to be circulated in the well with drilling fluids during the drilling operation. The indicators include a heat resistant indicating layer, a coacting meltable solid component and a retainer body which serves to unitize each indicator and which may carry permanent indicator identifying indicia. The indicators are recovered from the drilling fluid at ground level by known techniques.

Gaven, Jr., Joseph V. (Oakton, VA); Bak, Chan S. (Newbury Park, CA)

1983-01-01T23:59:59.000Z

450

Thermally switchable dielectrics  

DOE Patents [OSTI]

Precursor polymers to conjugated polymers, such as poly(phenylene vinylene), poly(poly(thiophene vinylene), poly(aniline vinylene), and poly(pyrrole vinylene), can be used as thermally switchable capacitor dielectrics that fail at a specific temperature due to the non-conjugated precursor polymer irreversibly switching from an insulator to the conjugated polymer, which serves as a bleed resistor. The precursor polymer is a good dielectric until it reaches a specific temperature determined by the stability of the leaving groups. Conjugation of the polymer backbone at high temperature effectively disables the capacitor, providing a `built-in` safety mechanism for electronic devices.

Dirk, Shawn M.; Johnson, Ross S.

2013-04-30T23:59:59.000Z

451

Thermal network reduction  

SciTech Connect (OSTI)

A method is presented for reducing the number of elements required in a thermal network representation of a building. The method is based on matching the actual building response at two frequencies, the diurnal response and 3-day response. The procedure provides a straightforward methodology for combining all the various materials inside a discrete building zone into a few nodes while retaining a high degree of accuracy in the dynamic response. An example is given showing a comparison between a large network and the reduced network.

Balcomb, J.D.

1983-06-01T23:59:59.000Z

452

Thermal network reduction  

SciTech Connect (OSTI)

A method is presented for reducing the number of elements required in a thermal network representation of a building. The method is based on matching the actual building response at two frequencies, the diurnal response and 3-day response. The procedure provides a straightforward methodology for combining all the various materials inside a discrete building zone into a few nodes while retaining a high degree of accuracy in the dynamic response. An example is given showing a comparison between a large network and the reduced network.

Balcomb, J.D.

1983-01-01T23:59:59.000Z

453

Radiation-turbulence interactions in pulverized-coal flames. Quarterly report No. III, March 15, 1994--June 15, 1994  

SciTech Connect (OSTI)

The work concerns the development of computer codes for the simulation of radiation turbulence interactions in coal flames. Experimental studies in tandem with the turbulence calculations are based on optical observation of scattered light from coal particles under combustion conditions.

Menguec, M.P.; McDonough, J.M.

1994-09-01T23:59:59.000Z

454

Condensation and thermalization of classsical optical waves in a waveguide  

SciTech Connect (OSTI)

We consider the long-term evolution of a random nonlinear wave that propagates in a multimode optical waveguide. The optical wave exhibits a thermalization process characterized by an irreversible evolution toward an equilibrium state. The tails of the equilibrium distribution satisfy the property of energy equipartition among the modes of the waveguide. As a consequence of this thermalization, the optical field undergoes a process of classical wave condensation, which is characterized by a macroscopic occupation of the fundamental mode of the waveguide. Considering the nonlinear Schroedinger equation with a confining potential, we formulate a wave turbulence description of the random wave into the basis of the eigenmodes of the waveguide. The condensate amplitude is calculated analytically as a function of the wave energy, and it is found in quantitative agreement with the numerical simulations. The analysis reveals that the waveguide configuration introduces an effective physical frequency cutoff, which regularizes the ultraviolet catastrophe inherent to the ensemble of classical nonlinear waves. The numerical simulations have been performed in the framework of a readily accessible nonlinear fiber optics experiment.

Aschieri, P.; Doya, V. [Laboratoire de Physique de la Matiere Condensee, CNRS, University of Nice Sophia-Antipolis, F-06108 Nice (France); Garnier, J. [Laboratoire de Probabilites et Modeles Aleatoires, University of Paris VII, F-75251 Paris (France); Michel, C.; Picozzi, A. [Laboratoire Interdisciplinaire Carnot de Bourgogne, CNRS, University of Burgundy, F-21078 Dijon (France)

2011-03-15T23:59:59.000Z

455

High Temperature Thermal Array for Next Generation Solar Thermal...  

Broader source: Energy.gov (indexed) [DOE]

A 10% increase in shaft work is directly attributable to modified thermal heat capacity Engineering HTF Specific heat yields modified power output. 27 127 227 327 427 527...

456

Electric Vehicle Battery Thermal Issues and Thermal Management Techniques (Presentation)  

SciTech Connect (OSTI)

This presentation examines the issues concerning thermal management in electric drive vehicles and management techniques for improving the life of a Li-ion battery in an EDV.

Rugh, J. P.; Pesaran, A.; Smith, K.

2013-07-01T23:59:59.000Z

457

Clustering instability of the spatial distribution of inertial particles in turbulent flows Tov Elperin* and Nathan Kleeorin  

E-Print Network [OSTI]

, cyclone dust separation, abrasive water-jet cutting and in turbulent com- bustion see, e.g., Refs. 1

Elperin, Tov

458

Gyrokinetic Particle Simulation of Turbulent Transport in Burning Plasmas  

SciTech Connect (OSTI)

The three-year project GPS-TTBP resulted in over 152 publications and 135 presentations. This summary focuses on the scientific progress made by the project team. A major focus of the project was on the physics intrinsic rotation in tokamaks. Progress included the first ever flux driven study of net intrinsic spin-up, mediated by boundary effects (in collaboration with CPES), detailed studies of the microphysics origins of the Rice scaling, comparative studies of symmetry breaking mechanisms, a pioneering study of intrinsic torque driven by trapped electron modes, and studies of intrinsic rotation generation as a thermodynamic engine. Validation studies were performed with C-Mod, DIII-D and CSDX. This work resulted in very successful completion of the FY2010 Theory Milestone Activity for OFES, and several prominent papers of the 2008 and 2010 IAEA Conferences. A second major focus was on the relation between zonal flow formation and transport non-locality. This culminated in the discovery of the ExB staircase - a conceptually new phenomenon. This also makes useful interdisciplinary contact with the physics of the PV staircase, well-known in oceans and atmospheres. A third topic where progress was made was in the simulation and theory of turbulence spreading. This work, now well cited, is important for understanding the dynamics of non-locality in turbulent transport. Progress was made in studies of conjectured non-diffusive transport in trapped electron turbulence. Pioneering studies of ITB formation, coupling to intrinsic rotation and hysteresis were completed. These results may be especially significant for future ITER operation. All told, the physics per dollar performance of this project was quite good. The intense focus was beneficial and SciDAC resources were essential to its success.

Diamond, P.H.; Lin, Z.; Wang, W.; Horton, W.; Klasky, S.; Decyk, V.; Ma, K.-L.; Chames, J.; Adams, M.

2011-09-21T23:59:59.000Z

459

Role of the basin boundary conditions in gravity wave turbulence  

E-Print Network [OSTI]

Gravity wave turbulence is studied experimentally in a large wave basin where irregular waves are generated unidirectionally. The role of the basin boundary conditions (absorbing or reflecting) and of the forcing properties are investigated. To that purpose, an absorbing sloping beach opposite to the wavemaker can be replaced by a reflecting vertical wall. We observe that the wave field properties depend strongly on these boundary conditions. Quasi-one dimensional field of nonlinear waves propagate before to be damped by the beach whereas a more multidirectional wave field is observed with the wall. In both cases, the wave spectrum scales as a frequency-power law with an exponent that increases continuously with the forcing amplitude up to a value close to -4, which is the value predicted by the weak turbulence theory. The physical mechanisms involved are probably different according to the boundary condition used, but cannot be easily discriminated with only temporal measurements. We have also studied freely decaying gravity wave turbulence in the closed basin. No self-similar decay of the spectrum is observed, whereas its Fourier modes decay first as a time power law due to nonlinear mechanisms, and then exponentially due to linear viscous damping. We estimate the linear, nonlinear and dissipative time scales to test the time scale separation that highlights the important role of a large scale Fourier mode. By estimation of the mean energy flux from the initial decay of wave energy, the Kolmogorov-Zakharov constant is evaluated and found to be compatible with a recent theoretical value.

Luc Deike; Benjamin Miquel; Pablo Gutiérrez-Matus; Timothée Jamin; Benoit Semin; Sébastien Aumaitre; Michael Berhanu; Eric Falcon; Félicien BONNEFOY

2014-12-16T23:59:59.000Z

460

Gasdynamic Model of Turbulent Combustion in TNT Explosions  

SciTech Connect (OSTI)

A model is proposed to simulate turbulent combustion in confined TNT explosions. It is based on: (i) the multi-component gasdynamic conservation laws, (ii) a fast-chemistry model for TNT-air combustion, (iii) a thermodynamic model for frozen reactants and equilibrium products, (iv) a high-order Godunov scheme providing a non-diffusive solution of the governing equations, and (v) an ILES approach whereby adaptive mesh refinement is used to capture the energy bearing scales of the turbulence on the grid. Three-dimensional numerical simulations of explosion fields from 1.5-g PETN/TNT charges were performed. Explosions in six different chambers were studied: three calorimeters (volumes of 6.6-l, 21.2-l and 40.5-l with L/D = 1), and three tunnels (L/D = 3.8, 4.65 and 12.5 with volumes of 6.3-l) - to investigate the influence of chamber volume and geometry on the combustion process. Predicted pressures histories were quite similar to measured pressure histories for all cases studied. Experimentally, mass fraction of products, Y{sub p}{sup exp}, reached a peak value of 88% at an excess air ratio of twice stoichiometric, and then decayed with increasing air dilution; mass fractions Y{sub p}{sup calc} computed from the numerical simulations followed similar trends. Based on this agreement, we conclude that the dominant effect that controls the rate of TNT combustion with air is the turbulent mixing rate; the ILES approach along with the fast-chemistry model used here adequately captures this effect.

Kuhl, A L; Bell, J B; Beckner, V E

2010-01-08T23:59:59.000Z

Note: This page contains sample records for the topic "rangepsi 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

Solar thermal power system  

DOE Patents [OSTI]

A solar thermal power generator includes an inclined elongated boiler tube positioned in the focus of a solar concentrator for generating steam from water. The boiler tube is connected at one end to receive water from a pressure vessel as well as connected at an opposite end to return steam back to the vessel in a fluidic circuit arrangement that stores energy in the form of heated water in the pressure vessel. An expander, condenser, and reservoir are also connected in series to respectively produce work using the steam passed either directly (above a water line in the vessel) or indirectly (below a water line in the vessel) through the pressure vessel, condense the expanded steam, and collect the condensed water. The reservoir also supplies the collected water back to the pressure vessel at the end of a diurnal cycle when the vessel is sufficiently depressurized, so that the system is reset to repeat the cycle the following day. The circuital arrangement of the boiler tube and the pressure vessel operates to dampen flow instabilities in the boiler tube, damp out the effects of solar transients, and provide thermal energy storage which enables time shifting of power generation to better align with the higher demand for energy during peak energy usage periods.

Bennett, Charles L.

2010-06-15T23:59:59.000Z

462

Gravity Wave Turbulence in Wave Tanks: Space and Time Statistics Sergei Lukaschuk,1,* Sergey Nazarenko,2  

E-Print Network [OSTI]

Gravity Wave Turbulence in Wave Tanks: Space and Time Statistics Sergei Lukaschuk,1,* Sergey the first simultaneous space-time measurements for gravity wave turbulence in a large laboratory flume. We found that the slopes of k and ! wave spectra depend on wave intensity. This cannot be explained by any

Nazarenko, Sergey

463

Turbulent Character of Wind Energy Patrick Milan, Matthias Wachter, and Joachim Peinke  

E-Print Network [OSTI]

and more wind turbines become integrated into our electric grids, a proper understanding stress the need for a profound understanding of the physics of turbulence and its impact on wind energyTurbulent Character of Wind Energy Patrick Milan, Matthias Wa¨chter, and Joachim Peinke ForWind

Peinke, Joachim

464

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

465

MHD turbulence in Saturn's magnetosheath downstream of a quasi parallel bow shock  

E-Print Network [OSTI]

1 MHD turbulence in Saturn's magnetosheath downstream of a quasi parallel bow shock M. B. Bavassano of the MHD turbulence downstream of a quasi parallel shock is investigated using plasma and magnetic eld data. The characteristics of the waves observed in that region are compared with those of the waves present: (i) downstream

Richardson, John

466

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

467

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

468

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

469

PREDICTION OF THE PROTON-TO-TOTAL TURBULENT HEATING IN THE SOLAR WIND  

SciTech Connect (OSTI)

This paper employs a recent turbulent heating prescription to predict the ratio of proton-to-total heating due to the kinetic dissipation of Alfvenic turbulence as a function of heliocentric distance. Comparing to a recent empirical estimate for this turbulent heating ratio in the high-speed solar wind, the prediction shows good agreement with the empirical estimate for R {approx}> 0.8 AU, but predicts less ion heating than the empirical estimate at smaller heliocentric radii. At these smaller radii, the turbulent heating prescription, calculated in the gyrokinetic limit, fails because the turbulent cascade is predicted to reach the proton cyclotron frequency before Landau damping terminates the cascade. These findings suggest that the turbulent cascade can reach the proton cyclotron frequency at R {approx}< 0.8 AU, leading to a higher level of proton heating than predicted by the turbulent heating prescription in the gyrokinetic limit. At larger heliocentric radii, R {approx}> 0.8 AU, this turbulent heating prescription contains all of the necessary physical mechanisms needed to reproduce the empirically estimated proton-to-total heating ratio.

Howes, G. G. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States)

2011-09-01T23:59:59.000Z

470

Electron and proton heating by solar wind turbulence B. Breech,1  

E-Print Network [OSTI]

Electron and proton heating by solar wind turbulence B. Breech,1 W. H. Matthaeus,2 S. R. Cranmer,3. Oughton (2009), Electron and proton heating by solar wind turbulence, J. Geophys. Res., 114, A09103, doi profile, requiring some process(es) to provide additional heat sources. One possible, and successful

Oughton, Sean

471

On the Study of Uncertainty in Inflow Turbulence Model Parameters in Wind Turbine Applications  

E-Print Network [OSTI]

On the Study of Uncertainty in Inflow Turbulence Model Parameters in Wind Turbine Applications Korn, Austin, TX 78712 In stochastic simulation of inflow turbulence random fields for wind turbine applica models can be in turn highly variable. Turbine load and performance variability could as well result

Manuel, Lance

472

On the use of proper orthogonal decomposition to describe inflow turbulence and wind turbine loads  

E-Print Network [OSTI]

On the use of proper orthogonal decomposition to describe inflow turbulence and wind turbine loads, USA Keywords: Proper Orthogonal Decomposition, inflow turbulence, wind turbine ABSTRACT: We discuss experienced by a wind turbine. A methodology is proposed that employs low- dimensional POD models

Manuel, Lance

473

Characterization of the effect of Froude number on surface waves and heat transfer in inclined turbulent  

E-Print Network [OSTI]

describes wave/heat transfer phenomena in inclined turbulent open surface water flows. The experiments wereCharacterization of the effect of Froude number on surface waves and heat transfer in inclined Abstract Interfacial heat transport in open channel turbulent flows is strongly dependent on surface waves

Abdou, Mohamed

474

Turbulent Oxygen Flames in Type Ia Supernovae A. J. Aspden1  

E-Print Network [OSTI]

Turbulent Oxygen Flames in Type Ia Supernovae A. J. Aspden1 , J. B. Bell1 , and S. E. Woosley2 oxygen flames. The two aims of the paper are to examine the response of the inductive oxygen flame to intense levels of turbulence, and to explore the possibility of transition to detonation in the oxygen

475

Modeling the Motion of a Hot, Turbulent Gas Nick Foster and Dimitris Metaxas  

E-Print Network [OSTI]

Modeling the Motion of a Hot, Turbulent Gas Nick Foster and Dimitris Metaxas Center for Human model gas motion due to fans and heat convection. The method combines specialized forms of the equations: Animation, Convection, Gaseous Phenomena, Gas Simulations, Physics-Based Modeling, Steam, Smoke, Turbulent

Frey, Pascal

476

The Effects of Turbulence on the Aerodynamics of Oscillating Fred L. Haan, Jr a  

E-Print Network [OSTI]

The Effects of Turbulence on the Aerodynamics of Oscillating Prisms Fred L. Haan, Jr a , Ahsan ABSTRACT: This experimental study, focusing on the effects of turbulence on long-span bridge aerodynamics and the spanwise correlation of the overall aerodynamic lift and moment. This exami- nation was conducted

Kareem, Ahsan

477

A Topological Framework for the Interactive Exploration of Large Scale Turbulent Combustion  

E-Print Network [OSTI]

A Topological Framework for the Interactive Exploration of Large Scale Turbulent Combustion Peer a new topological framework for the analysis of large scale, time-varying, turbulent combustion consumption thresh- olds for an entire time-dependent combustion simulation. By computing augmented merge

Knowles, David William

478

Fine Structure of the Solar Wind Turbulence Inferred from Simultaneous Radio Occultation Observations at  

E-Print Network [OSTI]

Fine Structure of the Solar Wind Turbulence Inferred from Simultaneous Radio Occultation Observations at Widely-Spaced Ground Stations M.K. Bird , P. Janardhan , A.I. Efimov, L.N. Samoznaev, V extended for up to four hours, thereby allowing studies of solar wind turbulence dynamics at spatial scales

Padmanabhan, Janardhan

479

High-performance Computation and Visualization of Plasma Turbulence on Graphics Processors  

E-Print Network [OSTI]

1 High-performance Computation and Visualization of Plasma Turbulence on Graphics Processors George thermonuclear fusion devices. Turbulence in plasma can lead to energy losses and various catastrophic events be mapped efficiently to modern graphics processors, dramatically reducing cost while increasing both

Varshney, Amitabh

480

Acceleration statistics of solid particles in turbulent channel flow R. Zamansky, I. Vinkovic, and M. Gorokhovski  

E-Print Network [OSTI]

) suggesting that when particle inertia increases, particle acceler- ation variance decreases due to bothAcceleration statistics of solid particles in turbulent channel flow R. Zamansky, I. Vinkovic in near-wall turbulence Phys. Fluids 24, 035110 (2012) Smoothed particle hydrodynamics simulations

Boyer, Edmond

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481

Scalar dissipation rate based flamelet modelling of turbulent premixed flames  

E-Print Network [OSTI]

). . . . . . . . . . . . . . 94 6.10 Comparison of turbulent flame speed expressions to the experimen- tal database of Abdel-Gayed et al. (1987) for two values of flame stretch parameter, K: (i) K = 0.053 and (ii) K = 0.15. . . . . . . 95 x LIST OF FIGURES 7.1 The regime diagram... space variable for c xix Chapter 1 Introduction Combustion is a phenomenon that occurs all around us: a burning candle, a do- mestic boiler, an aircraft engine etc., to name a few instances. Since the dawn of the industrial age, energy derived from...

Kolla, Hemanth

2010-03-16T23:59:59.000Z

482

Planar Richtmyer-Meshkov instabilities and transition to turbulence  

SciTech Connect (OSTI)

Extensive recent work has demonstrated that predictive under-resolved simulations of the velocity fields in turbulent flows are possible without resorting to explicit subgrid models. When using a class of physics-capturing high-resolution finite-volume numerical algorithms. This strategy is denoted implicit large eddy simulation (ILES, MILES). The performance of ILES in the substantially more difficult problem of under-resolved material mixing driven by under-resolved velocity fields and initial conditions (ICs) is a focus of the present work. Progress is presented in analyzing the effects of IC combined spectral content and thickness parametrizations. In the large eddy simulation (LES). the large energy containing structures are resolved, the smaller, presumably more isotropic, structures are filtered out, and effects of subgrid scales (SGS) are modeled. ILES effectively addresses the seemingly insurmountable issues posed to LES by under-resolution. by relying on the use of SGS modeling and filtering provided implicitly by a class of physics capturing numerics; extensive verification and validation in areas of engineering. geophysics. and astrophysics has been reported. In many areas of interest such as. inertial confinement fusion. understanding the collapse of the outer cores of supernovas. and supersonic combustion engines, vorticity is introduced at material interfaces by the impulsive loading of shock waves. and turbulence is generated via Richtmyer-Meshkov instabilities (RMI). Given that ILES is based on locally-adaptive, non-oscillatory. finite-volume methods it is naturally suited to emulate shock physics. The unique combination of shock and turbulence emulation capabilities supports direct use of ILES as an effective simulation anzatz for RMI. Here, we further test this approach using a particular strategy based on a nominally-inviscid, Schmidt number {approx} 1, simulation model that uses the LANL RAGE code to investigate planar RMI. Issues of initial material interface characterization and modeling difficulties, and effects of IC resolved spectral content on transitional and late-time turbulent mixing were examined in our previous work. The focus here is to carry out a systematic analysis of effects of combined IC spectral content and thickness.

Grinstein, Fernando F [Los Alamos National Laboratory; Gowardhan, Akshay [Los Alamos National Laboratory; Ristorcelli, Ray [Los Alamos National Laboratory

2011-01-21T23:59:59.000Z

483

Forecasting stratospheric clear-air turbulence by discriminant analysis  

E-Print Network [OSTI]

by Discriminant Analysis. (December lg73) Robert Earl Cox, A. B. , Dartmouth College Directed by: Dr. Jam s R. Scoggins The appllca'bili. ty of the statis! ical method of discriminart sna1ysis Lo the prediction of clear-air turbulence over the western Unixed... OF THE LITFRATURE b. Current related research 3. TUPJIVLENCE AND ITS PREDICTION a. Mathematical formulation b. The case for statistical prediction 12 4. ANALYTICAL METHODS 16 a. Data b. Discriminant analysis c. Selection of variables 22 5. RESULTS a...

Cox, Robert Earl

1973-01-01T23:59:59.000Z

484

Applications of large eddy simulation methods to gyrokinetic turbulence  

SciTech Connect (OSTI)

The large eddy simulation (LES) approach—solving numerically the large scales of a turbulent system and accounting for the small-scale influence through a model—is applied to nonlinear gyrokinetic systems that are driven by a number of different microinstabilities. Comparisons between modeled, lower resolution, and higher resolution simulations are performed for an experimental measurable quantity, the electron density fluctuation spectrum. Moreover, the validation and applicability of LES is demonstrated through a series of diagnostics based on the free energetics of the system.

Bañón Navarro, A., E-mail: alejandro.banon.navarro@ipp.mpg.de; Happel, T. [Max-Planck-Institut für Plasmaphysik, EURATOM Association, D-85748 Garching (Germany)] [Max-Planck-Institut für Plasmaphysik, EURATOM Association, D-85748 Garching (Germany); Teaca, B. [Applied Mathematics Research Centre, Coventry University, Coventry CV1 5FB (United Kingdom) [Applied Mathematics Research Centre, Coventry University, Coventry CV1 5FB (United Kingdom); Max-Planck für Sonnensystemforschung, Max-Planck-Str. 2, D-37191 Katlenburg-Lindau (Germany); Max-Planck/Princeton Center for Plasma Physics (Germany); Jenko, F. [Max-Planck-Institut für Plasmaphysik, EURATOM Association, D-85748 Garching (Germany) [Max-Planck-Institut für Plasmaphysik, EURATOM Association, D-85748 Garching (Germany); Max-Planck/Princeton Center for Plasma Physics (Germany); Hammett, G. W. [Max-Planck/Princeton Center for Plasma Physics, Princeton Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, New Jersey 08543 (United States)] [Max-Planck/Princeton Center for Plasma Physics, Princeton Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, New Jersey 08543 (United States); Collaboration: ASDEX Upgrade Team

2014-03-15T23:59:59.000Z

485

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

486

Energy transfers in shell models for MHD turbulence  

E-Print Network [OSTI]

A systematic procedure to derive shell models for MHD turbulence is proposed. It takes into account the conservation of ideal quadratic invariants such as the total energy, the cross-helicity and the magnetic helicity as well as the conservation of the magnetic energy by the advection term in the induction equation. This approach also leads to simple expressions for the energy exchanges as well as to unambiguous definitions for the energy fluxes. When applied to the existing shell models with nonlinear interactions limited to the nearest neighbour shells, this procedure reproduces well known models but suggests a reinterpretation of the energy fluxes.

T. Lessinnes; M. K. Verma; D. Carati

2008-07-31T23:59:59.000Z

487

Cloud-Scale Vertical Velocity and Turbulent Dissipation Rate Retrievals  

SciTech Connect (OSTI)

Time-height fields of retrieved in-cloud vertical wind velocity and turbulent dissipation rate, both retrieved primarily from vertically-pointing, Ka-band cloud radar measurements. Files are available for manually-selected, stratiform, mixed-phase cloud cases observed at the North Slope of Alaska (NSA) site during periods covering the Mixed-Phase Arctic Cloud Experiment (MPACE, late September through early November 2004) and the Indirect and Semi-Direct Aerosol Campaign (ISDAC, April-early May 2008). These time periods will be expanded in a future submission.

Shupe, Matthew

2013-05-22T23:59:59.000Z

488

Cloud-Scale Vertical Velocity and Turbulent Dissipation Rate Retrievals  

DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]

Time-height fields of retrieved in-cloud vertical wind velocity and turbulent dissipation rate, both retrieved primarily from vertically-pointing, Ka-band cloud radar measurements. Files are available for manually-selected, stratiform, mixed-phase cloud cases observed at the North Slope of Alaska (NSA) site during periods covering the Mixed-Phase Arctic Cloud Experiment (MPACE, late September through early November 2004) and the Indirect and Semi-Direct Aerosol Campaign (ISDAC, April-early May 2008). These time periods will be expanded in a future submission.

Shupe, Matthew

489

Systems analysis of thermal storage  

SciTech Connect (OSTI)

During FY80 analyses were conducted on thermal storage concepts for solar thermal applications. These studies include both estimates of the obtainable costs of thermal storage concepts and their worth to a user (i.e., value). Based on obtainable costs and performance, promising thermal storage concepts are being identified. A preliminary screening was completed in FY80 and a more in-depth study was initiated. Value studies are being conducted to establish cost goals. A ranking of storage concepts based on value in solar thermal electric plants was conducted for both diurnal and long duration applications. Ground mounted thermal storage concepts for a parabolic dish/Stirling systtem are also being evaluated.

Copeland, R. J.

1980-08-01T23:59:59.000Z

490

Critical Behavior in the Relaminarization of Localized Turbulence in Pipe Flow Ashley P. Willis* and Rich R. Kerswell  

E-Print Network [OSTI]

Critical Behavior in the Relaminarization of Localized Turbulence in Pipe Flow Ashley P. Willis of localized turbulence in a pipe are examined by direct numerical simulation. As in recent experimental data, of which initial disturbances at a given Re trigger sustained turbulence in a pipe, is really two separate

Willis, Ashley

491

EXPERIMENTAL STUDY OF TURBULENT SUPERCRITICAL OPEN CHANNEL WATER FLOW AS APPLIED TO THE CLiFF CONCEPT  

E-Print Network [OSTI]

is to investigate the hydrodynamic and heat transfer phenomena in the near-surface region of a turbulent open-turbulence interaction are the most important processes that determine the heat transfer rate in CLiFF flows. The current, low conductivity fluid, turbulence, surface waves, heat transfer ________________ Corresponding

California at Los Angeles, University of

492

Experimental study of turbulent supercritical open channel water flow as applied to the CLiFF concept  

E-Print Network [OSTI]

; Liquid wall; Low conductivity fluid; Turbulence; Surface waves; Heat transfer 1. Introduction In fusion not experience strong MHD forces and to a large extent remain turbulent, but their heat transfer capabilitiesExperimental study of turbulent supercritical open channel water flow as applied to the CLi

Abdou, Mohamed

493

Numerical Simulation of Premixed Turbulent Methane Combustion John B. Bell, Marcus S. Day and Joseph F. Grcar  

E-Print Network [OSTI]

LBNL-49331 Numerical Simulation of Premixed Turbulent Methane Combustion John B. Bell, Marcus S of Premixed Turbulent Methane Combustion Abstract In this paper we study the behavior of a premixed turbulent an adaptive time-dependent low Mach number combustion algorithm based on a second-order projection formulation

494

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

495

Microviscometric studies on thermal diffusion  

E-Print Network [OSTI]

HICROVISCKStTRIC STUDIES THERMAL DIFFUSION A Thesis Eddie Reyfls Submitted to the Grsducte School of the Agricultursl sfld Mechanical College of Texas in partisl fulfillment of the requireeeflts far the degree of MASTER OF SCIENCE August... microliter samples to 1'/ reproduceability, This equipment is used to observe the thermal diffusion effects of polystyrene in toluene solutions in c 01uslus-Dickel thermal diffusion column. An inversion in the values of concentration and molecular veight...

Reyna, Eddie

2012-06-07T23:59:59.000Z

496

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

SciTech Connect (OSTI)

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

497

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

SciTech Connect (OSTI)

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

498

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

SciTech Connect (OSTI)

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

499

Controlling the level of the ideal invariant fluxes for MHD turbulence using TURBO spectral solver  

E-Print Network [OSTI]

The ideal invariants present in the formalism of magnetohydrodynamics (MHD), i.e. global quantities that are conserved in the absence of sources and dissipative effects, play an important role in various theoretical and numerical studies of MHD turbulence. The fluxes of these ideal invariants represent separate channels that transfer the information across different scales in a turbulent system. Once a statistically stationary state of turbulence is reached, the amount of any ideal invariant quantity introduced in the system by a forcing mechanism equals the amount of the same quantity removed by the dissipative effects from the system. For highly developed turbulence, these two mechanisms act predominantly at different scales that are largely separated. Since the ideal invariant quantities cascade between scales, a constant flux is generated with great implication on the state of the system. Numerically, controlling the ideal invariant fluxes levels for a turbulent MHD system is important for the analysis of...

Teaca, B; Knaepen, B; Carati, D

2011-01-01T23:59:59.000Z

500

Kinetic Energy Decay Rates of Supersonic and Super-Alfvenic Turbulence in Star-Forming Clouds  

E-Print Network [OSTI]

We present numerical studies of compressible, decaying turbulence, with and without magnetic fields, with initial rms Alfven and Mach numbers ranging up to five, and apply the results to the question of the support of star-forming interstellar clouds of molecular gas. We find that, in 1D, magnetized turbulence actually decays faster than unmagnetized turbulence. In all the regimes that we have studied 3D turbulence-super-Alfvenic, supersonic, sub-Alfvenic, and subsonic-the kinetic energy decays as (t-t0)^(-x), with 0.85 < x < 1.2. We compared results from two entirely different algorithms in the unmagnetized case, and have performed extensive resolution studies in all cases, reaching resolutions of 256^3 zones or 350,000 particles. We conclude that the observed long lifetimes and supersonic motions in molecular clouds must be due to external driving, as undriven turbulence decays far too fast to explain the observations.

Mordecai-Mark Mac Low; Ralf S. Klessen; Andreas Burkert; Michael D. Smith

1997-12-01T23:59:59.000Z