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1

Turbulent thermal diffusion of aerosols in geophysics and laboratory experiments  

E-Print Network (OSTI)

We discuss a new phenomenon of turbulent thermal diffusion associated with turbulent transport of aerosols in the atmosphere and in laboratory experiments. The essence of this phenomenon is the appearance of a nondiffusive mean flux of particles in the direction of the mean heat flux, which results in the formation of large-scale inhomogeneities in the spatial distribution of aerosols that accumulate in regions of minimum mean temperature of the surrounding fluid. This effect of turbulent thermal diffusion was detected experimentally. In experiments turbulence was generated by two oscillating grids in two directions of the imposed vertical mean temperature gradient. We used Particle Image Velocimetry to determine the turbulent velocity field, and an Image Processing Technique based on an analysis of the intensity of Mie scattering to determine the spatial distribution of aerosols. Analysis of the intensity of laser light Mie scattering by aerosols showed that aerosols accumulate in the vicinity of the minimum mean temperature due to the effect of turbulent thermal diffusion. Geophysical applications of the obtained results are discussed.

A. Eidelman; T. Elperin; N. Kleeorin; A. Krein; I. Rogachevskii; J. Buchholz; G. Gruenefeld

2004-11-11T23:59:59.000Z

2

Thermal Instability and Magnetic Pressure in the Turbulent Interstellar Medium  

E-Print Network (OSTI)

We review recent results on the nonlinear development of thermal instability (TI) in the context of the turbulent atomic interstellar medium (ISM). First, we discuss the growth of entropy perturbations in isolation, as a function of the ratio \\eta of the cooling time to the dynamical crossing time. For \\eta~ 0.3) and occurs at scales with \\eta>1. We then consider the behavior of magnetic pressure in turbulent regimes. We propose that the reported lack of correlation between the magnetic pressure and the density is a consequence of the different scaling of the magnetic pressure with density for the slow and fast modes of nonlinear MHD waves. This implies that magnetic ``pressure'' is not a suitable candidate for supplementing thermal pressure in the presence of TI, and that polytropic descriptions of it are probably not adequate in the fully turbulent regime. Finally, we consider TI in a turbulent ISM-like medium. We find that the flow does not exhibit sharp phase transitions, as would be expected in classical...

Vázquez-Semadeni, E; Passot, T; Sánchez-Salcedo, F J; Vazquez-Semadeni, Enrique; Gazol, Adriana; Passot, Thierry; Sanchez-Salcedo, Javier

2003-01-01T23:59:59.000Z

3

Progress in Simulating Turbulent Electron Thermal Transport in NSTX  

SciTech Connect

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

Guttenfelder, Walter

2013-07-17T23:59:59.000Z

4

Thermal conduction and particle transport in strong MHD turbulence, with application to galaxy-cluster plasmas  

E-Print Network (OSTI)

We investigate field-line separation in strong MHD turbulence analytically and with direct numerical simulations. We find that in the static-magnetic-field approximation the thermal conductivity in galaxy clusters is reduced by a factor of about 5-10 relative to the Spitzer thermal conductivity of a non-magnetized plasma. We also estimate how the thermal conductivity would be affected by efficient turbulent resistivity.

Benjamin D. G. Chandran; Jason L. Maron

2003-03-11T23:59:59.000Z

5

Regulation of thermal conductivity in hot galaxy clusters by MHD turbulence  

E-Print Network (OSTI)

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

Steven A. Balbus; Christopher S. Reynolds

2008-06-05T23:59:59.000Z

6

A Large-Eddy Simulation Study of Thermal Effects on Turbulence Coherent Structures in and above a Building Array  

Science Conference Proceedings (OSTI)

Thermal effects on turbulent flow in and above a cubical building array are numerically investigated using the parallelized large-eddy simulation model (PALM). Two cases (no heating and bottom heating) are simulated and are compared with each ...

Seung-Bu Park; Jong-Jin Baik

2013-06-01T23:59:59.000Z

7

A Large-Eddy Simulation Study of Thermal Effects on Turbulent Flow and Dispersion in and above a Street Canyon  

Science Conference Proceedings (OSTI)

Thermal effects on turbulent flow and dispersion in and above an idealized street canyon with a street aspect ratio of 1 are numerically investigated using the parallelized large-eddy simulation model (“PALM”). Each of upwind building wall, street ...

Seung-Bu Park; Jong-Jin Baik; Siegfried Raasch; Marcus Oliver Letzel

2012-05-01T23:59:59.000Z

8

Origin of the Temperature Oscillation in Turbulent Thermal Convection  

E-Print Network (OSTI)

We report an experimental study of the three-dimensional spatial structure of the low frequency temperature oscillations in a cylindrical Rayleigh-B\\'{e}nard convection cell. It is found that thermal plumes are not emitted periodically, but randomly and continuously, from the top and bottom plates. We further found that the oscillation of the temperature field does not originate from the boundary layers, but rather is a result of the horizontal motion of the hot ascending and cold descending fluids being modulated by the twisting and sloshing motion of the bulk flow field.

Xi, Heng-Dong; Zhou, Quan; Chan, Tak-Shing; Xia, Ke-Qing

2008-01-01T23:59:59.000Z

9

Turbulence  

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

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

10

Thermal-Instability-Driven Turbulent Mixing in Galactic Disks: I. Effective Mixing of Metals  

E-Print Network (OSTI)

Observations show that radial metallicity gradients in disk galaxies are relatively shallow, if not flat, especially at large galactocentric distances and for galaxies in the high-redshift universe. Given that star formation and metal production are centrally concentrated, this requires a mechanism to redistribute metals. However, the nature of this mechanism is poorly understood, let alone quantified. To address this problem, we conduct magnetohydrodynamical simulations of a local shearing sheet of a thin, thermally unstable, gaseous disk driven by a background stellar spiral potential, including metals modeled as passive scalar fields. Contrary to what a simple \\alpha\\ prescription for the gas disk would suggest, we find that turbulence driven by thermal instability is very efficient at mixing metals, regardless of the presence or absence of stellar spiral potentials or magnetic fields. The timescale for homogenizing randomly distributed metals is comparable to or less than the local orbital time in the dis...

Yang, Chao-Chin

2012-01-01T23:59:59.000Z

11

MAGNETOROTATIONAL TURBULENCE IN STRATIFIED SHEARING BOXES WITH PERFECT GAS EQUATION OF STATE AND FINITE THERMAL DIFFUSIVITY  

SciTech Connect

We present a numerical study of turbulence and dynamo action in stratified shearing boxes with zero mean magnetic flux. We assume that the fluid obeys the perfect gas law and has finite (constant) thermal diffusivity. The calculations begin from an isothermal state spanning three scale heights above and below the mid-plane. After a long transient the layers settle to a stationary state in which thermal losses out of the boundaries are balanced by dissipative heating. We identify two regimes. The first is a conductive regime in which the heat is transported mostly by conduction and the density decreases with height. In the limit of large thermal diffusivity this regime resembles the more familiar isothermal case. The second is the convective regime, observed at smaller values of the thermal diffusivity, in which the layer becomes unstable to overturning motions, the heat is carried mostly by advection, and the density becomes nearly constant throughout the layer. In this latter constant-density regime we observe evidence for large-scale dynamo action leading to a substantial increase in transport efficiency relative to the conductive case.

Bodo, G.; Rossi, P. [INAF, Osservatorio Astronomico di Torino, Strada Osservatorio 20, I-10025 Pino Torinese (Italy); Cattaneo, F. [The Computation Institute, University of Chicago, 5735 S. Ellis Avenue, Chicago, IL 60637 (United States); Mignone, A. [Dipartimento di Fisica Generale, Univesita di Torino, via Pietro Giuria 1, I-10125 Torino (Italy)

2012-12-20T23:59:59.000Z

12

Property:Available Sensors | Open Energy Information  

Open Energy Info (EERE)

Sensors Sensors Jump to: navigation, search Property Name Available Sensors Property Type Text Pages using the property "Available Sensors" Showing 25 pages using this property. (previous 25) (next 25) 1 1.5-ft Wave Flume Facility + Flow, Pressure Range(psi), Turbulence, ... 10-ft Wave Flume Facility + Flow, Pressure Range(psi), Turbulence, ... 11-ft Wave Flume Facility + Flow, Pressure Range(psi), Turbulence, ... 2 2-ft Flume Facility + Flow, Pressure Range(psi), Turbulence, ... 3 3-ft Wave Flume Facility + Flow, Pressure Range(psi), Turbulence, ... 5 5-ft Wave Flume Facility + Flow, Pressure Range(psi), Turbulence, ... 6 6-ft Wave Flume Facility + Flow, Pressure Range(psi), Turbulence, ... A Alden Large Flume + Pressure Range(psi), Velocity, Displacement, ...

13

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

E-Print Network (OSTI)

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

A. Bershadskii

2009-08-27T23:59:59.000Z

14

Algebraic Turbulent Heat Flux Model for Prediction of Thermal Stratification in Piping Systems  

Science Conference Proceedings (OSTI)

Technical Paper / Special Issue on the 14th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-14) / Thermal Hydraulics

M. Pellegrini; H. Endo; E. Merzari; H. Ninokata

15

Near-Surface Turbulence and Thermal Structure in a Wind-Driven Sea  

Science Conference Proceedings (OSTI)

Ocean surface turbulence at high sea states is evaluated using heat as a naturally occurring passive tracer. A freely drifting instrument with a mechanically driven temperature profiler, fixed depth thermistors, and conductivity cells was used to ...

Johannes R. Gemmrich; David M. Farmer

1999-03-01T23:59:59.000Z

16

Numerical Simulation of a Buoyant Thermal Using the k-? Turbulence Model  

Science Conference Proceedings (OSTI)

Possibilities for describing turbulent mixing processes through the use of the two-equation k-? model modified to take into account the effects of streamline curvature and buoyancy are discussed. It is shown that one of the k-? model constants ...

Y. A. Dovgalyuk; M. A. Zatevakhin; E. N. Stankova

1994-09-01T23:59:59.000Z

17

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

Science Conference Proceedings (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

18

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

SciTech Connect

A Generic Technology for treatment of DOE Metal-Bearing Liquid Waste The DOE metal-bearing liquid waste inventory is large and diverse, both with respect to the metals (heavy metals, transuranics, radionuclides) themselves, and the nature of the other species (annions, organics, etc.) present. Separation and concentration of metals is of interest from the standpoint of reducing the volume of waste that will require special treatment or isolation, as well as, potentially, from the standpoint of returning some materials to commerce by recycling. The variety of metal-bearing liquid waste in the DOE complex is so great that it is unlikely that any one process (or class of processes) will be suitable for all material. However, processes capable of dealing with a wide variety of wastes will have major advantages in terms of process development, capital, and operating costs, as well as in environmental and safety permitting. Moreover, to the extent that a process operates well with a variety of metal-bearing liquid feedwastes, its performance is likely to be relatively robust with respect to the inevitable composition variations in each waste feed. One such class of processes involves high-temperature treatment of atomized liquid waste to promote reactive capture of volatile metallic species on collectible particulate substrates injected downstream of a flame zone. Compared to low-temperature processes that remove metals from the original liquid phase by extraction, precipitation, ion exchange, etc., some of the attractive features of high-temperature reactive scavenging are: The organic constituents of some metal-bearing liquid wastes (in particular, some low-level mixed wastes) must be treated thermally in order to meet the requirements of the Resource Conservation and Recovery Act (RCRA) and Toxic Substances Control Act (TSCA), and the laws of various states. No species need be added to an already complex liquid system. This is especially important in light of the fact that DOE has already experienced problems with organic complexants added to precipitate radionuclides. For example, the Defense Nuclear Facilities Safety Board has expressed, in a formal Recommendation to the Secretary of Energy, its concern about the evolution of benzene vapor in concentrations greater then the lower flammability limit from tanks to which sodium tetraphenylborate has been added to precipitate 137Cs in the ''In-Tank Precipitation'' (ITP) process at the Savannah River Site. Other species added to the waste in the ITP process are sodium titanate (to adsorb 90Sr and Pu), and oxalic acid. Avoiding addition of organics to radioactive waste has the additional advantage that is likely to significantly reduce the rate of radiolytic and radiolytically-induced hydrogen generation (c.f. Meisel et al., [1993]), in which it is shown that removal of organics reduces the rate of hydrogen generation in simulated waste from Hanford tank 241-SY-101 by over 70%. Organic species already present are destroyed with very high efficiency. This attribute is especially attractive with respect to high-level tank waste at the Hanford Site, in which large amounts of citrate, glyoxylate, EDTA (ethylenediaminetetraacetic acid), and HEDTA [N-(2- hydroxyethyl)-ethylenediaminetriacetic acid] were added to precipitate radionuclides. These organic species are important in the thermal and radiolytic generation of methane, hydrogen, and nitrous oxide, flammable mixtures of which are episodically vented from 25 tanks on Hanford's Flammable Gas Watch List [Hopkins, 1994]. The same basic approach can be used to treat a broad range of liquid wastes, in each case concentrating the metals (regardless of liquid-phase oxidation state or association with chelators or absorbents) using a collectible sorbent, and destroying any organic species present. In common with the Army's approach (see section 2.2) to the thermal destruction of a 10 range of chemical warfare agents (GB, VX, and two blister agents), this may drastically simplify process and plant design and

Wendt, Jost O.L.

2001-09-30T23:59:59.000Z

19

Turbulence Structure of the Convective Boundary Layer. Part II. Phonenix 78 Aircraft Observations of Thermals and Their Environment  

Science Conference Proceedings (OSTI)

A conditional sampling technique based upon the mixed layer spectra of vertical velocity and temperature is developed. This technique is used to analyze the turbulence data obtained by aircraft during the Phoenix 78 convective boundary layer ...

George S. Young

1988-02-01T23:59:59.000Z

20

Turbulence Structure of the Convective Boundary Layer. Part III: The Vertical Velocity Budgets of Thermals and Their Environment  

Science Conference Proceedings (OSTI)

The dynamics of thermal updrafts and compensating environmental downdrafts in the convective boundary layer are examined using observations from the Phoenix 78 field experiment. Separate vertical velocity budgets are presented for thermal ...

George S. Young

1988-07-01T23:59:59.000Z

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.


21

Transilient Turbulence Theory. Part II: Turbulent Adjustment  

Science Conference Proceedings (OSTI)

Turbulent adjustment is a scheme where dynamic instabilities in the flow are eliminated by turbulence. It is a form of first-order turbulence closure that is applicable to numerical forecast models of the atmosphere. The responsive form of ...

Roland B. Stull; Takehiko Hasegawa

1984-12-01T23:59:59.000Z

22

A Numerical Study of Turbulent Processes in the Marine Upper Layers  

Science Conference Proceedings (OSTI)

A second-order turbulence closure model, similar to Mellor and Yamada's (1974) level-3 model, is implemented. This is used to investigate the role of the different turbulent processes and the resulting dynamical and thermal structures, for ...

Patrice Klein; Michel Coantic

1981-06-01T23:59:59.000Z

23

On the theory of turbulent flame velocity  

E-Print Network (OSTI)

The renormalization ideas of self-similar dynamics of a strongly turbulent flame front are applied to the case of a flame with realistically large thermal expansion of the burning matter. In that case a flame front is corrugated both by external turbulence and the intrinsic flame instability. The analytical formulas for the velocity of flame propagation are obtained. It is demonstrated that the flame instability is of principal importance when the integral turbulent length scale is much larger than the cut off wavelength of the instability. The developed theory is used to analyse recent experiments on turbulent flames propagating in tubes. It is demonstrated that most of the flame velocity increase measured experimentally is provided by the large scale effects like the flame instability, and not by the small-scale external turbulence.

Vitaly Bychkov; Vyacheslav Akkerman; Arkady Petchenko

2012-10-19T23:59:59.000Z

24

Interstellar MHD Turbulence and Star Formation  

E-Print Network (OSTI)

This chapter reviews the nature of turbulence in the Galactic interstellar medium (ISM) and its connections to the star formation (SF) process. The ISM is turbulent, magnetized, self-gravitating, and is subject to heating and cooling processes that control its thermodynamic behavior. The turbulence in the warm and hot ionized components of the ISM appears to be trans- or subsonic, and thus to behave nearly incompressibly. However, the neutral warm and cold components are highly compressible, as a consequence of both thermal instability in the atomic gas and of moderately-to-strongly supersonic motions in the roughly isothermal cold atomic and molecular components. Within this context, we discuss: i) the production and statistical distribution of turbulent density fluctuations in both isothermal and polytropic media; ii) the nature of the clumps produced by thermal instability, noting that, contrary to classical ideas, they in general accrete mass from their environment; iii) the density-magnetic field correla...

Vazquez-Semadeni, Enrique

2012-01-01T23:59:59.000Z

25

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;

26

Physical Processes of Interstellar Turbulence  

E-Print Network (OSTI)

I discuss the role of self-gravity and radiative heating and cooling in shaping the nature of the turbulence in the interstellar medium (ISM) of our galaxy. The heating and cooling cause it to be highly compressible, and, in some regimes of density and temperature, to become thermally unstable, tending to spontaneously segregate into warm/diffuse and cold/dense phases. On the other hand, turbulence is an inherently mixing process, tending to replenish the density and temperature ranges that would be forbidden under thermal processes alone. The turbulence in the ionized ISM appears to be transonic (i.e, with Mach numbers $\\Ms \\sim 1$), and thus to behave essentially incompressibly. However, in the neutral medium, thermal instability causes the sound speed of the gas to fluctuate by up to factors of $\\sim 30$, and thus the flow can be highly supersonic with respect to the dense/cold gas, although numerical simulations suggest that this behavior corresponds more to the ensemble of cold clumps than to the clumps'...

Vazquez-Semadeni, Enrique

2012-01-01T23:59:59.000Z

27

Physical Processes of Interstellar Turbulence  

E-Print Network (OSTI)

I discuss the role of self-gravity and radiative heating and cooling in shaping the nature of the turbulence in the interstellar medium (ISM) of our galaxy. The heating and cooling cause it to be highly compressible, and, in some regimes of density and temperature, to become thermally unstable, tending to spontaneously segregate into warm/diffuse and cold/dense phases. On the other hand, turbulence is an inherently mixing process, tending to replenish the density and temperature ranges that would be forbidden under thermal processes alone. The turbulence in the ionized ISM appears to be transonic (i.e, with Mach numbers $\\Ms \\sim 1$), and thus to behave essentially incompressibly. However, in the neutral medium, thermal instability causes the sound speed of the gas to fluctuate by up to factors of $\\sim 30$, and thus the flow can be highly supersonic with respect to the dense/cold gas, although numerical simulations suggest that this behavior corresponds more to the ensemble of cold clumps than to the clumps' internal velocity dispersion. Finally, coherent large-scale compressions in the warm neutral medium (induced by, say, the passage of spiral arms or by supernova shock waves) can produce large, dense molecular clouds that are subject to their own self-gravity, and begin to contract gravitationally. Because they are populated by nonlinear density fluctuations, whose local free-fall times are significantly smaller than that of the whole cloud, the fluctuations terminate their collapse earlier, giving rise to a regime of hierarchical gravitational fragmentation, with small-scale collapses occurring within larger-scale ones. Thus, the "turbulence" in molecular clouds may be dominated by a gravitationally contracting component at all scales.

Enrique Vazquez-Semadeni

2012-02-20T23:59:59.000Z

28

Turbulent flow in graphene  

E-Print Network (OSTI)

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

Kumar S. Gupta; Siddhartha Sen

2009-11-03T23:59:59.000Z

29

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

30

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

31

Heat release effects on decaying homogeneous compressible turbulence  

E-Print Network (OSTI)

High Mach-number compressible flows with heat release are inherently more complicated than incompressible flows due to, among other reasons, the activation of the thermal energy mode. Such flow fields can experience significant fluctuations in density, temperature, viscosity, conductivity and specific heat, which affect velocity and pressure fluctuations. Furthermore, the flow field cannot be assumed to be dilatation-free in high Mach numbers and even in low Mach-number flows involving combustion, or in boundary layers on heated walls. The main issue in these high-speed and highly-compressible flows is the effect of thermal gradients and fluctuations on turbulence. The thermal field has various routes through which it affects flow structures of compressible turbulence. First, it has direct influence through pressure, which affects turbulence via pressure-strain correlation. The indirect effects of thermal fields on compressible turbulence are through the changes in flow properties. The high temperature gradients alter the transport coefficient and compressibility of the flow. The objective of this work is to answer the following questions: How do temperature fluctuations change the compressible flow structure and energetics? How does compressibility in the flow affect the non-linear pressure redistribution process? What is the main effect of spatial transport-coefficient variation? We perform direct numerical simulations (DNS) to answer the above questions. The investigations are categorized into four parts: 1) Turbulent energy cascade and kinetic-internal energy interactions under the influence of temperature fluctuations; 2) Return-to-isotropy of anisotropic turbulence under the influence of large temperature fluctuations; 3) The effect of turbulent Mach number and dilatation level on small-scale (velocity-gradient) dynamics; 4) The effect of variable transport-coefficients (viscosity and diffusivity) on cascade and dissipation processes of turbulence. The findings lead to a better understanding of temperature fluctuation effects on non-linear processes in compressible turbulence. This improved understanding is expected to provide direction for improving second-order closure models of compressible turbulence.

Lee, Kurn Chul

2008-05-01T23:59:59.000Z

32

Modeling Compressed Turbulence  

Science Conference Proceedings (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

33

MHD Turbulence Revisited  

E-Print Network (OSTI)

Kraichnan (1965) proposed that MHD turbulence occurs as a result of collisions between oppositely directed Alfvén wave packets. Recent work has generated some controversy over the nature of non linear couplings between colliding Alfvén waves. We find that the resolution to much of the confusion lies in the existence of a new type of turbulence, intermediate turbulence, in which the cascade of energy in the inertial range exhibits properties intermediate between those of weak and strong turbulent cascades. Some properties of intermediate MHD turbulence are: (i) in common with weak turbulent cascades, wave packets belonging to the inertial range are long lived; (ii) however, components of the strain tensor are so large that, similar to the situation in strong turbulence, perturbation theory is not applicable; (iii) the breakdown of perturbation theory results from the divergence of neighboring field lines due to wave packets whose perturbations in velocity and magnetic fields are localized, but whose perturba...

Goldreich, P

1996-01-01T23:59:59.000Z

34

Diffusion Processes in Turbulent Magnetic Fields  

E-Print Network (OSTI)

We study of the effect of turbulence on diffusion processes within magnetized medium. While we exemplify our treatment with heat transfer processes, our results are quite general and are applicable to different processes, e.g. diffusion of heavy elements. Our treatment is also applicable to describing the diffusion of cosmic rays arising from magnetic field wandering. In particular, we find that when the energy injection velocity is smaller than the Alfven speed the heat transfer is partially suppressed, while in the opposite regime the effects of turbulence depend on the intensity of driving. In fact, the scale $l_A$ at which the turbulent velocity is equal the Alfven velocity is a new important parameter. When the electron mean free path $\\lambda$ is larger than $l_A$, the stronger the the turbulence, the lower thermal conductivity by electrons is. The turbulent motions, however, induces their own advective transport, that can provide effective diffusivity. For clusters of galaxies, we find that the turbulence is the most important agent for heat transfer. We also show that the domain of applicability of the subdiffusion concept is rather limited.

Alex Lazarian

2007-07-04T23:59:59.000Z

35

Diffusion Processes in Turbulent Magnetic Fields  

E-Print Network (OSTI)

We study of the effect of turbulence on diffusion processes within magnetized medium. While we exemplify our treatment with heat transfer processes, our results are quite general and are applicable to different processes, e.g. diffusion of heavy elements. Our treatment is also applicable to describing the diffusion of cosmic rays arising from magnetic field wandering. In particular, we find that when the energy injection velocity is smaller than the Alfven speed the heat transfer is partially suppressed, while in the opposite regime the effects of turbulence depend on the intensity of driving. In fact, the scale $l_A$ at which the turbulent velocity is equal the Alfven velocity is a new important parameter. When the electron mean free path $\\lambda$ is larger than $l_A$, the stronger the the turbulence, the lower thermal conductivity by electrons is. The turbulent motions, however, induces their own advective transport, that can provide effective diffusivity. For clusters of galaxies, we find that the turbule...

Lazarian, Alex

2007-01-01T23:59:59.000Z

36

Spectral Wave–Turbulence Decomposition  

Science Conference Proceedings (OSTI)

A new method of wave–turbulence decomposition is introduced, for which the only instrument required is one high-frequency pointwise velocity sensor. This is a spectral method that assumes equilibrium turbulence and no wave–turbulence interaction. ...

Jeremy D. Bricker; Stephen G. Monismith

2007-08-01T23:59:59.000Z

37

Radiosonde measurements of turbulence  

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

at Cranwell, Lincolnshire, W. H. Pick and G. A. Bull, 1926. 3 Talk structure * Geomagnetic sensors to measure orientation * Orientation variability as a turbulence measure *...

38

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

SciTech Connect

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

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

2011-07-15T23:59:59.000Z

39

Fossil turbulence and fossil turbulence waves can be dangerous  

E-Print Network (OSTI)

Turbulence is defined as an eddy-like state of fluid motion where the inertial-vortex forces of the eddies are larger than any other forces that tend to damp the eddies out. By this definition, turbulence always cascades from small scales where vorticity is created to larger scales where turbulence fossilizes. Fossil turbulence is any perturbation in a hydrophysical field produced by turbulence that persists after the fluid is no longer turbulent at the scale of the perturbation. Fossil turbulence patterns and fossil turbulence waves preserve and propagate energy and information about previous turbulence. Ignorance of fossil turbulence properties can be dangerous. Examples include the Osama bin Laden helicopter crash and the Air France 447 Airbus crash, both unfairly blamed on the pilots. Observations support the proposed definitions, and suggest even direct numerical simulations of turbulence require caution.

Carl H Gibson

2012-11-25T23:59:59.000Z

40

Scaling Relations for Turbulence in Multiphase Interstellar Medium  

E-Print Network (OSTI)

We simulate the dynamics of phase transition in radiatively cooling interstellar gas in three dimensions with a high order hydrodynamic method. We have previously shown (Kritsuk & Norman 2002a) in simulations with non-equilibrium initial conditions that thermal instability induces supersonic turbulence as a by-product of the phase transition which leads to formation of multiphase medium. We rely on a generalization of the She & Leveque (1994) model to study velocity scaling relations in this decaying turbulence and compare those with analogous results for compressible isothermal turbulence. Since radiative cooling promotes nonlinear instabilities in highly supersonic flows, turbulence in our simulations tends to be more intermittent than in the isothermal case. Hausdorff dimension of the most singular dissipative structures, D, can be as high as 2.3, while in supersonic isothermal turbulence D is limited by a more primitive nature of dissipation (shocks): D<=2. We also show that single-phase veloci...

Kritsuk, A G; Kritsuk, Alexei G.; Norman, Michael L.

2004-01-01T23:59:59.000Z

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.


41

Enhancement and suppression of heat transfer by MHD turbulence  

E-Print Network (OSTI)

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

A. Lazarian

2006-08-02T23:59:59.000Z

42

On Challenges for Hypersonic Turbulent Simulations  

SciTech Connect

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

Yee, H C; Sjogreen, B

2009-01-14T23:59:59.000Z

43

Chemical turbulence equivalent to Nikolavskii turbulence  

E-Print Network (OSTI)

We find evidence that a certain class of reaction-diffusion systems can exhibit chemical turbulence equivalent to Nikolaevskii turbulence. The distinctive characteristic of this type of turbulence is that it results from the interaction of weakly stable long-wavelength modes and unstable short-wavelength modes. We indirectly study this class of reaction-diffusion systems by considering an extended complex Ginzburg-Landau (CGL) equation that was previously derived from this class of reaction-diffusion systems. First, we show numerically that the power spectrum of this CGL equation in a particular regime is qualitatively quite similar to that of the Nikolaevskii equation. Then, we demonstrate that the Nikolaevskii equation can in fact be obtained from this CGL equation through a phase reduction procedure applied in the neighborhood of a codimension-two Turing--Benjamin-Feir point.

Dan Tanaka

2004-03-09T23:59:59.000Z

44

TURBULENT CONVECTION MODEL IN THE OVERSHOOTING REGION. II. THEORETICAL ANALYSIS  

SciTech Connect

Turbulent convection models (TCMs) are thought to be good tools to deal with the convective overshooting in the stellar interior. However, they are too complex to be applied to calculations of stellar structure and evolution. In order to understand the physical processes of the convective overshooting and to simplify the application of TCMs, a semi-analytic solution is necessary. We obtain the approximate solution and asymptotic solution of the TCM in the overshooting region, and find some important properties of the convective overshooting. (1) The overshooting region can be partitioned into three parts: a thin region just outside the convective boundary with high efficiency of turbulent heat transfer, a power-law dissipation region of turbulent kinetic energy in the middle, and a thermal dissipation area with rapidly decreasing turbulent kinetic energy. The decaying indices of the turbulent correlations k, u{sub r}'T'-bar, and T'T'-bar are only determined by the parameters of the TCM, and there is an equilibrium value of the anisotropic degree {omega}. (2) The overshooting length of the turbulent heat flux u{sub r}'T'-bar is about 1H{sub k} (H{sub k} = |dr/dln k|). (3) The value of the turbulent kinetic energy at the convective boundary k{sub C} can be estimated by a method called the maximum of diffusion. Turbulent correlations in the overshooting region can be estimated by using k{sub C} and exponentially decreasing functions with the decaying indices.

Zhang, Q. S.; Li, Y., E-mail: zqs@ynao.ac.cn, E-mail: ly@ynao.ac.cn [National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, P.O. Box 110, Kunming 650011 (China)

2012-05-01T23:59:59.000Z

45

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

46

The first turbulent combustion  

E-Print Network (OSTI)

The first turbulent combustion arises in a hot big bang cosmological model Gibson (2004) where nonlinear exothermic turbulence permitted by quantum mechanics, general relativity, multidimensional superstring theory, and fluid mechanics cascades from Planck to strong force freeze out scales with gravity balancing turbulent inertial-vortex forces. Interactions between Planck scale spinning and non-spinning black holes produce high Reynolds number turbulence and temperature mixing with huge Reynolds stresses driving the rapid inflation of space. Kolmogorovian turbulent temperature patterns are fossilized as strong-force exponential inflation stretches them beyond the scale of causal connection ct where c is light speed and t is time. Fossil temperature turbulence patterns seed nucleosynthesis, and then hydro-gravitational structure formation in the plasma epoch, Gibson (1996, 2000). Evidence about formation mechanisms is preserved by cosmic microwave background temperature anisotropies. CMB spectra indicate hydro-gravitational fragmentation at supercluster to galaxy masses in the primordial plasma with space stretched by \\~10^50. Bershadskii and Sreenivasan (2002, 2003) CMB multi-scaling coefficients support a strong turbulence origin for the anisotropies prior to the plasma epoch.

Carl H. Gibson

2005-01-19T23:59:59.000Z

47

Observations of Edge Turbulence  

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

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

48

ARM - Measurement - Atmospheric turbulence  

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

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

49

MHD Turbulence Revisited  

E-Print Network (OSTI)

Kraichnan (1965) proposed that MHD turbulence occurs as a result of collisions between oppositely directed Alfv\\'en wave packets. Recent work has generated some controversy over the nature of non linear couplings between colliding Alfv\\'en waves. We find that the resolution to much of the confusion lies in the existence of a new type of turbulence, intermediate turbulence, in which the cascade of energy in the inertial range exhibits properties intermediate between those of weak and strong turbulent cascades. Some properties of intermediate MHD turbulence are: (i) in common with weak turbulent cascades, wave packets belonging to the inertial range are long lived; (ii) however, components of the strain tensor are so large that, similar to the situation in strong turbulence, perturbation theory is not applicable; (iii) the breakdown of perturbation theory results from the divergence of neighboring field lines due to wave packets whose perturbations in velocity and magnetic fields are localized, but whose perturbations in displacement are not; (iv) 3--wave interactions dominate individual collisions between wave packets, but interactions of all orders $n\\geq 3$ make comparable contributions to the intermediate turbulent energy cascade; (v) successive collisions are correlated since wave packets are distorted as they follow diverging field lines; (vi) in common with the weak MHD cascade, there is no parallel cascade of energy, and the cascade to small perpendicular scales strengthens as it reaches higher wave numbers; (vii) For an appropriate weak excitation, there is a natural progression from a weak, through an intermediate, to a strong cascade.

P. Goldreich; S. Sridhar

1996-12-31T23:59:59.000Z

50

The Influence of Stratification and Nonlocal Turbulent Production on Estuarine Turbulence: An Assessment of Turbulence Closure with Field Observations  

Science Conference Proceedings (OSTI)

Field observations of turbulent kinetic energy (TKE), dissipation rate ?, and turbulent length scale demonstrate the impact of both density stratification and nonlocal turbulent production on turbulent momentum flux. The data were collected in a ...

Malcolm E. Scully; W. Rocky Geyer; John H. Trowbridge

2011-01-01T23:59:59.000Z

51

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

52

Mixing in Thermals with and without Buoyancy Reversal  

Science Conference Proceedings (OSTI)

The mixing characteristics of turbulent thermals were investigated in a water tank via laser-induced fluorescence techniques. The concentration of mixed fluid in the far field of a “classical” thermal is approximately uniform, whereas the near ...

Hamid Johari

1992-08-01T23:59:59.000Z

53

Influence of a New Turbulence Regime on the Global Air–Sea Heat Fluxes  

Science Conference Proceedings (OSTI)

Recent research has found that boundary layer turbulence changes its organization as the stratification approaches neutral from the unstable side. When the thermal forcing weakens in combination with wind speed above approximately 10 m s?1, ...

Erik Sahlée; Ann-Sofi Smedman; Anna Rutgersson; Ulf Högström

2008-11-01T23:59:59.000Z

54

MU Radar and Lidar Observations of Clear-Air Turbulence underneath Cirrus  

Science Conference Proceedings (OSTI)

Turbulence generation mechanisms prevalent in the atmosphere are mainly shear instabilities, breaking of internal buoyancy waves, and convective instabilities such as thermal convection due to heating of the ground. In the present work, clear-air ...

Hubert Luce; Takuji Nakamura; Masayuki K. Yamamoto; Mamoru Yamamoto; Shoichiro Fukao

2010-02-01T23:59:59.000Z

55

A Theory of Baroclinic Turbulence  

Science Conference Proceedings (OSTI)

Understanding the physical mechanism maintaining fluid turbulence remains a fundamental theoretical problem. The two-layer model is an analytically and computationally simple system in which the dynamics of turbulence can be conveniently studied; ...

Brian F. Farrell; Petros J. Ioannou

2009-08-01T23:59:59.000Z

56

Statistical Predictability of Decaying Turbulence  

Science Conference Proceedings (OSTI)

We use statistical models of turbulence with “eddy damping” (EDQNM) in order to study the problem of predictability of freely evolving two- and three-dimensional isotropic turbulent flows.

Olivier Métais; Marcel Lesieur

1986-05-01T23:59:59.000Z

57

Supersaturation Intermittency in Turbulent Clouds  

Science Conference Proceedings (OSTI)

It is hypothesized that bursts of high supersaturation are produced in turbulent, convective clouds through interactions between cloud droplets and the small-scale structure of atmospheric turbulence. This hypothesis is based on the observation ...

Raymond A. Shaw

2000-10-01T23:59:59.000Z

58

The Decay of Convective Turbulence  

Science Conference Proceedings (OSTI)

Using simulations with a large-eddy model we have studied the decay of convective turbulence in the atmospheric boundary layer when the upward surface sensible heat flux is suddenly stopped. The decay of turbulent kinetic energy and temperature ...

F. T. M. Nieuwstadt; R. A. Brost

1986-03-01T23:59:59.000Z

59

turbulence | OpenEI  

Open Energy Info (EERE)

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

60

Quasi-Lagrangian Models of Nascent Thermals  

Science Conference Proceedings (OSTI)

Thermals are modeled by considering their boundaries as self-advecting vortex sheets. Both slab-symmetric and axisymmetiic geometries are considered. Discussion is restricted to the case of a neutral environment, and turbulent processes are not ...

Sandro Rambaldi; David A. Randall

1981-09-01T23:59:59.000Z

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.


61

First Hybrid Turbulence Modeling for Turbine Blade Cooling Sagar Kapadia*  

E-Print Network (OSTI)

First Hybrid Turbulence Modeling for Turbine Blade Cooling Sagar Kapadia* and Subrata Roy turbines require proper cooling mechanism to protect the airfoils from thermal stresses generated by exposure to hot combustion gases. The problem becomes aggravated by the growing trend to use higher turbine

Roy, Subrata

62

Energy flux limitation by tame turbulence  

SciTech Connect

A quasi-linear theory of energy flux limitation by ion acoustic turbulence is presented. This distribution function is modelled by a Maxwellian plus an additional piece which carries a heat flux Q. By taking the fourth moment of the Vlasov equation one finds the anomalous thermal conductivity K approximately 3 v/sub e/ delta/sub De/ (e phi/T/sub e/)$sup -2$. Other moments treated self-consistently include anomalous ion heating, electron cooling, current generation and enhanced inverse bremsstrahlung due to the nonthermal ion fluctuations. (auth)

Manheimer, W.M.

1975-11-01T23:59:59.000Z

63

Modeling Turbulent Flow  

National Nuclear Security Administration (NNSA)

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

64

Fast Turbulent Reconnection  

E-Print Network (OSTI)

Reconnection is the process by which magnetic fields in a conducting fluid change their topology. This process is essential for understanding a wide variety of astrophysical processes, including stellar and galactic dynamos and astrophysical turbulence. To account for solar flares, solar cycles and the structure of the galactic magnetic field reconnection must be fast, propagating with a speed close to the Alfven speed. We show that the presence of a random magnetic field component substantially enhances the reconnection rate and enables fast reconnection, i.e. reconnection that does not depend on fluid resistivity. The enhancement of the reconnection rate is achieved via a combination of two effects. First of all, only small segments of magnetic field lines are subject to direct Ohmic annihilation. Thus the fraction of magnetic energy that goes directly into fluid heating goes to zero as fluid resistivity vanishes. However, the most important enhancement comes from the fact that unlike the laminar fluid case where reconnection is constrained to proceed line by line, the presence of turbulence enables many magnetic field lines to enter the reconnection zone simultaneously. A significant fraction of magnetic energy goes into MHD turbulence and this enhances reconnection rates through an increase in the field stochasticity. In this way magnetic reconnection becomes fast when field stochasticity is accounted for. As a consequence solar and galactic dynamos are also fast, i.e. do not depend on fluid resistivity.

A. Lazarian; E. Vishniac

2000-02-03T23:59:59.000Z

65

Renormalized weak plasma turbulence theory  

SciTech Connect

A renormalized Vlasov turbulence theory, derived by neglecting a mode coupling term in the Direct Interaction Approximation, is discussed. The theory reduces correctly to weak turbulence theory; it predicts both diffusion and polarization effects of the turbulent medium on test particles, as well as the inverse effects of the test particles on the medium. A heuristic, physical algorithm is presented for constructing the equations. The theory of the renormalized dielectric function is reviewed.

Krommes, J.A.; Kleva, R.G.

1979-02-01T23:59:59.000Z

66

Filtering Turbulent Sparsely Observed Geophysical Flows  

Science Conference Proceedings (OSTI)

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

John Harlim; Andrew J. Majda

2010-04-01T23:59:59.000Z

67

Measurements of Enhanced Turbulent Mixing near Highways  

Science Conference Proceedings (OSTI)

In August and September of 2010, measurements of turbulent fluxes and turbulent kinetic energy were made on highways in the Toronto area (Ontario, Canada). In situ turbulence measurements were made with a mobile laboratory while driving on the ...

Mark Gordon; Ralf M. Staebler; John Liggio; Paul Makar; Shao-Meng Li; Jeremy Wentzell; Gang Lu; Patrick Lee; Jeffrey R. Brook

2012-09-01T23:59:59.000Z

68

Simulation of turbulence in fireballs  

SciTech Connect

The ALE technique is applied to the calculation of a small yield, low altitude nuclear explosion. When artificial diffusion effects caused by numerical errors are minimized, the fireball rises too rapidly, reaching an altitude in excess of that which is observed. This suggests that turbulent diffusion and entrainmert may be important. Hence, a turbulence model has been added to later calculations of the fireball dynamics. Some of the more important features of the calculational technique and the turbulence model are discussed. Preliminary results for a set of turbulence parameters and a particular low altitude fireball are presented. (auth)

Ruppel, H.M.; Gentry, R.A.; Daly, B.J.

1973-11-01T23:59:59.000Z

69

Conte Large Flume | Open Energy Information  

Open Energy Info (EERE)

Conte Large Flume Conte Large Flume Overseeing Organization United States Geological Survey, LSC Hydrodynamic Testing Facility Type Flume Length(m) 38.1 Beam(m) 6.1 Depth(m) 5.2 Cost(per day) Contact POC Towing Capabilities Towing Capabilities None Wavemaking Capabilities Wavemaking Capabilities None Channel/Tunnel/Flume Channel/Tunnel/Flume Yes Recirculating No Wind Capabilities Wind Capabilities None Control and Data Acquisition Description National Instruments LabView and other data acquisition systems Number of channels 12 Bandwidth(kHz) 44 Cameras Yes Number of Color Cameras 5 Description of Camera Types Conventional underwater video, 4; high speed (1000 fps), 1 Available Sensors Displacement, Flow, Pressure Range(psi), Thermal, Turbulence, Velocity Data Generation Capability

70

Conte Small Flume | Open Energy Information  

Open Energy Info (EERE)

Small Flume Small Flume Overseeing Organization United States Geological Survey, LSC Hydrodynamic Testing Facility Type Flume Length(m) 38.1 Beam(m) 3.0 Depth(m) 5.2 Cost(per day) Contact POC Towing Capabilities Towing Capabilities None Wavemaking Capabilities Wavemaking Capabilities None Channel/Tunnel/Flume Channel/Tunnel/Flume Yes Recirculating No Wind Capabilities Wind Capabilities None Control and Data Acquisition Description National Instruments LabView and other data acquisition systems Number of channels 12 Bandwidth(kHz) 44 Cameras Yes Number of Color Cameras 5 Description of Camera Types Conventional underwater video, 4; high speed (1000 fps), 1 Available Sensors Displacement, Flow, Pressure Range(psi), Thermal, Turbulence, Velocity Data Generation Capability

71

DeFrees Flume 1 | Open Energy Information  

Open Energy Info (EERE)

Flume 1 Flume 1 Jump to: navigation, search Basic Specifications Facility Name DeFrees Flume 1 Overseeing Organization Cornell University Hydrodynamics Hydrodynamic Testing Facility Type Flume Length(m) 4.5 Beam(m) 0.6 Depth(m) 0.6 Water Type Freshwater Towing Capabilities Towing Capabilities None Wavemaking Capabilities Wavemaking Capabilities None Channel/Tunnel/Flume Channel/Tunnel/Flume Yes Velocity(m/s) 2 Recirculating No Wind Capabilities Wind Capabilities None Control and Data Acquisition Description National Instruments LabView and Mathworks Matlab DAQ systems Number of channels 64+ Bandwidth(kHz) 1000 Cameras Yes Number of Color Cameras 5 Description of Camera Types 1024 x 1024 x 12 bit to 60 fps, 491 x 656 x 8-bit to 100 fps, others Available Sensors Flow, Turbulence, Ultrasonic Wave Height, Acceleration, Pressure Range(psi), Acoustics, Velocity, Displacement, Thermal

72

DeFrees Flume 3 | Open Energy Information  

Open Energy Info (EERE)

Basic Specifications Basic Specifications Facility Name DeFrees Flume 3 Overseeing Organization Cornell University Hydrodynamics Hydrodynamic Testing Facility Type Flume Length(m) 15.0 Beam(m) 2.0 Depth(m) 0.6 Water Type Freshwater Towing Capabilities Towing Capabilities None Wavemaking Capabilities Wavemaking Capabilities None Channel/Tunnel/Flume Channel/Tunnel/Flume Yes Velocity(m/s) 2 Recirculating No Wind Capabilities Wind Capabilities None Control and Data Acquisition Description National Instruments LabView and Mathworks Matlab DAQ systems Number of channels 64+ Cameras Yes Number of Color Cameras 5 Description of Camera Types 1024 x 1024 x 12 bit to 60 fps, 491 x 656 x 8-bit to 100 fps, others Available Sensors Acceleration, Acoustics, Pressure Range(psi), Velocity, Displacement, Turbulence, Flow, Ultrasonic Wave Height, Thermal

73

DeFrees Flume 2 | Open Energy Information  

Open Energy Info (EERE)

DeFrees Flume 2 DeFrees Flume 2 Jump to: navigation, search Basic Specifications Facility Name DeFrees Flume 2 Overseeing Organization Cornell University Hydrodynamics Hydrodynamic Testing Facility Type Flume Length(m) 8.0 Beam(m) 0.6 Depth(m) 0.6 Towing Capabilities Towing Capabilities None Wavemaking Capabilities Wavemaking Capabilities None Channel/Tunnel/Flume Channel/Tunnel/Flume Yes Velocity(m/s) 2 Recirculating No Wind Capabilities Wind Capabilities None Control and Data Acquisition Description National Instruments LabView and Mathworks Matlab DAQ systems Number of channels 64+ Bandwidth(kHz) 1000 Cameras Yes Number of Color Cameras 5 Description of Camera Types 1024 x 1024 x 12 bit to 60 fps, 491 x 656 x 8-bit to 100 fps, others Available Sensors Thermal, Ultrasonic Wave Height, Displacement, Acceleration, Turbulence, Pressure Range(psi), Flow, Acoustics, Velocity

74

Hall MHD Stability and Turbulence in Magnetically Accelerated Plasmas  

Science Conference Proceedings (OSTI)

The object of the research was to develop theory and carry out simulations of the Z pinch and plasma opening switch (POS), and compare with experimental results. In the case of the Z pinch, there was experimental evidence of ion kinetic energy greatly in excess of the ion thermal energy. It was thought that this was perhaps due to fine scale turbulence. The simulations showed that the ion energy was predominantly laminar, not turbulent. Preliminary studies of a new Z pinch experiment with an axial magnetic field were carried out. The axial magnetic is relevant to magneto - inertial fusion. These studies indicate the axial magnetic field makes the Z pinch more turbulent. Results were also obtained on Hall magnetohydrodynamic instability of the POS.

H. R. Strauss

2012-11-27T23:59:59.000Z

75

Turbulent Combustion Properties of Premixed Syngases  

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

Turbulent Combustion Properties of Premixed Syngases Title Turbulent Combustion Properties of Premixed Syngases Publication Type Journal Article Year of Publication 2009 Authors...

76

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

77

Advanced Computational Methods for Turbulence and Combustion...  

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

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

78

Supercomputers Capture Turbulence in the Solar Wind  

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

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

79

Understanding Galaxy Outflows as the Product of Unstable Turbulent Support  

E-Print Network (OSTI)

The interstellar medium is a multiphase gas in which turbulent support is as important as thermal pressure. Sustaining this configuration requires both continuous turbulent stirring and continuous radiative cooling to match the decay of turbulent energy. While this equilibrium can persist for small turbulent velocities, if the one-dimensional velocity dispersion is larger than approximately 35 km/s, the gas moves into an unstable regime that leads to rapid heating. I study the implications of this turbulent runaway, showing that it causes a hot gas outflow to form in all galaxies with a gas surface density above approximately 50 solar masses/pc^2 corresponding to a star formation rate per unit area of 0.1$ solar masses/yr/kpc^2. For galaxies with escape velocities above 200 km/s, the sonic point of this hot outflow should lie interior to the region containing cold gas and stars, while for galaxies with smaller escape velocities, the sonic point should lie outside this region. This leads to efficient cold clou...

Scannapieco, Evan

2013-01-01T23:59:59.000Z

80

Magnetized Turbulent Dynamo in Protogalaxies  

Science Conference Proceedings (OSTI)

The prevailing theory for the origin of cosmic magnetic fields is that they have been amplified to their present values by the turbulent dynamo inductive action in the protogalactic and galactic medium. Up to now, in calculation of the turbulent dynamo, it has been customary to assume that there is no back reaction of the magnetic field on the turbulence, as long as the magnetic energy is less than the turbulent kinetic energy. This assumption leads to the kinematic dynamo theory. However, the applicability of this theory to protogalaxies is rather limited. The reason is that in protogalaxies the temperature is very high, and the viscosity is dominated by magnetized ions. As the magnetic field strength grows in time, the ion cyclotron time becomes shorter than the ion collision time, and the plasma becomes strongly magnetized. As a result, the ion viscosity becomes the Braginskii viscosity. Thus, in protogalaxies the back reaction sets in much earlier, at field strengths much lower than those which correspond to field-turbulence energy equipartition, and the turbulent dynamo becomes what we call the magnetized turbulent dynamo. In this paper we lay the theoretical groundwork for the magnetized turbulent dynamo. In particular, we predict that the magnetic energy growth rate in the magnetized dynamo theory is up to ten times larger than that in the kinematic dynamo theory. We also briefly discuss how the Braginskii viscosity can aid the development of the inverse cascade of magnetic energy after the energy equipartition is reached.

Leonid Malyshkin; Russell M. Kulsrud

2002-01-28T23:59:59.000Z

Note: This page contains sample records for the topic "rangepsi thermal turbulence" from the National Library of EnergyBeta (NLEBeta).
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they are not comprehensive nor are they the most current set.
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81

Advances in compressible turbulent mixing  

Science Conference Proceedings (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

82

Turbulent molecular clouds  

E-Print Network (OSTI)

Stars form within molecular clouds but our understanding of this fundamental process remains hampered by the complexity of the physics that drives their evolution. We review our observational and theoretical knowledge of molecular clouds trying to confront the two approaches wherever possible. After a broad presentation of the cold interstellar medium and molecular clouds, we emphasize the dynamical processes with special focus to turbulence and its impact on cloud evolution. We then review our knowledge of the velocity, density and magnetic fields. We end by openings towards new chemistry models and the links between molecular cloud structure and star--formation rates.

Hennebelle, Patrick

2012-01-01T23:59:59.000Z

83

On Collective Properties of Turbulent QED Plasma  

E-Print Network (OSTI)

Polarization properties of turbulent stochastically inhomogeneous ultrarelativistic QED plasma are studied. It is shown that the sign of nonlinear turbulent Landau damping corresponds to an instability of the spacelike modes and, for sufficiently large turbulent fields, to an actual instability of a system. Modification of plasmon dispersion relations due to turbulent effects are studied.

Martin Kirakosyan; Andrei Leonidov; Berndt Muller

2013-05-19T23:59:59.000Z

84

Turbulence Regimes and Turbulence Intermittency in the Stable Boundary Layer during CASES-99  

Science Conference Proceedings (OSTI)

An investigation of nocturnal intermittent turbulence during the Cooperative Atmosphere–Surface Exchange Study in 1999 (CASES-99) revealed three turbulence regimes at each observation height: 1) regime 1, a weak turbulence regime when the wind ...

Jielun Sun; Larry Mahrt; Robert M. Banta; Yelena L. Pichugina

2012-01-01T23:59:59.000Z

85

Turbulence-Flame Interactions in Type Ia Supernovae  

SciTech Connect

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 x 107 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 x 107 g cm-3 where the nature of the burning changes ualitatively. By 1 x 107 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.

Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 50A-1148, Berkeley, CA 94720 (Authors 1, 2& 3); Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (Author 4); Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794 (Author 5); Aspden, Andrew J; Aspden, Andrew J.; Bell, John B.; Day, Marc S.; Woosley, Stan E.; Zingale, Mike

2008-05-27T23:59:59.000Z

86

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

87

Finescale Parameterizations of Turbulent Dissipation  

Science Conference Proceedings (OSTI)

Fine- and microstructure data from a free fall profiler are analysed to test models that relate the turbulent dissipation rate (?) to characteristics of the internal wave field. The data were obtained from several distinct internal wave ...

Kurt L. Polzin; John M. Toole; Raymond W. Schmitt

1995-03-01T23:59:59.000Z

88

Predictability of Rotating Stratified Turbulence  

Science Conference Proceedings (OSTI)

Although predictability represents one of the fundamental problems in atmospheric science, gaps in our knowledge remain. Theoretical understanding of the inverse error cascade is limited mostly to homogeneous, isotropic turbulence, whereas ...

K. Ngan; P. Bartello; D. N. Straub

2009-05-01T23:59:59.000Z

89

THREE-DIMENSIONAL MAGNETOHYDRODYNAMIC MODELING OF THE SOLAR WIND INCLUDING PICKUP PROTONS AND TURBULENCE TRANSPORT  

Science Conference Proceedings (OSTI)

To study the effects of interstellar pickup protons and turbulence on the structure and dynamics of the solar wind, we have developed a fully three-dimensional magnetohydrodynamic solar wind model that treats interstellar pickup protons as a separate fluid and incorporates the transport of turbulence and turbulent heating. The governing system of equations combines the mean-field equations for the solar wind plasma, magnetic field, and pickup protons and the turbulence transport equations for the turbulent energy, normalized cross-helicity, and correlation length. The model equations account for photoionization of interstellar hydrogen atoms and their charge exchange with solar wind protons, energy transfer from pickup protons to solar wind protons, and plasma heating by turbulent dissipation. Separate mass and energy equations are used for the solar wind and pickup protons, though a single momentum equation is employed under the assumption that the pickup protons are comoving with the solar wind protons. We compute the global structure of the solar wind plasma, magnetic field, and turbulence in the region from 0.3 to 100 AU for a source magnetic dipole on the Sun tilted by 0 Degree-Sign -90 Degree-Sign and compare our results with Voyager 2 observations. The results computed with and without pickup protons are superposed to evaluate quantitatively the deceleration and heating effects of pickup protons, the overall compression of the magnetic field in the outer heliosphere caused by deceleration, and the weakening of corotating interaction regions by the thermal pressure of pickup protons.

Usmanov, Arcadi V.; Matthaeus, William H. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Goldstein, Melvyn L., E-mail: arcadi.usmanov@nasa.gov [Code 673, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2012-07-20T23:59:59.000Z

90

The Influence of Atmospheric Stability on the Budgets of the Reynolds Stress and Turbulent Kinetic Energy within and above a Deciduous Forest  

Science Conference Proceedings (OSTI)

This paper shows that the inclusion of thermal effects is necessary to correctly interpret the physical processes involved in the generation or suppression of Reynolds stress and turbulent kinetic energy inside a form canopy. In both of thew ...

M. Y. Leclerc; R. H. Shaw; G. Den Hartog; H. H. Neumann

1990-09-01T23:59:59.000Z

91

Complex Geometry Creation and Turbulent Conjugate Heat Transfer Modeling  

Science Conference Proceedings (OSTI)

The multiphysics capabilities of COMSOL provide the necessary tools to simulate the turbulent thermal-fluid aspects of the High Flux Isotope Reactor (HFIR). Version 4.1, and later, of COMSOL provides three different turbulence models: the standard k-{var_epsilon} closure model, the low Reynolds number (LRN) k-{var_epsilon} model, and the Spalart-Allmaras model. The LRN meets the needs of the nominal HFIR thermal-hydraulic requirements for 2D and 3D simulations. COMSOL also has the capability to create complex geometries. The circular involute fuel plates used in the HFIR require the use of algebraic equations to generate an accurate geometrical representation in the simulation environment. The best-estimate simulation results show that the maximum fuel plate clad surface temperatures are lower than those predicted by the legacy thermal safety code used at HFIR by approximately 17 K. The best-estimate temperature distribution determined by COMSOL was then used to determine the necessary increase in the magnitude of the power density profile (PDP) to produce a similar clad surface temperature as compared to the legacy thermal safety code. It was determined and verified that a 19% power increase was sufficient to bring the two temperature profiles to relatively good agreement.

Bodey, Isaac T [ORNL; Arimilli, Rao V [ORNL; Freels, James D [ORNL

2011-01-01T23:59:59.000Z

92

Dust Motions Driven by MHD Turbulence  

E-Print Network (OSTI)

We discuss the relative grain motions due to MHD turbulence in interstellar medium. It has been known for decades that turbulent drag is an efficient way to induce grain relative motions. However, earlier treatments disregarded magnetic field and used Kolmogorov turbulence. Unlike hydro turbulence, MHD turbulence is anisotropic on small scales. Moreover, compressible modes are important for MHD and magnetic perturbations can directly interact with grains. We provide calculations of grain relative motion for realistic interstellar turbulence driving that is consistent with the velocity dispersions observed in diffuse gas and for realistic grain charging. We account for the turbulence cutoff arising from abmipolar drag. Our results on grain shattering are consistent with the customary accepted cutoff size. We obtain grain velocities for turbulence with parameters consistent with those in HI and dark clouds. These velocities are smaller than those in earlier papers, where MHD effects were disregarded. Finally, w...

Lazarian, A; Yan, Huirong

2002-01-01T23:59:59.000Z

93

Turbulent Kinetic Energy Budgets over Mountainous Terrain  

Science Conference Proceedings (OSTI)

The objective of this study is to describe the characteristics of the airflow and turbulence structure over mountainous terrain. Turbulent characteristics of the airflow were measured using well-instrumented aircraft. The shear, buoyancy, ...

Theodore S. Karacostas; John D. Marwitz

1980-02-01T23:59:59.000Z

94

Strong Turbulence in the Wave Crest Region  

Science Conference Proceedings (OSTI)

High-resolution vertical velocity profiles in the surface layer of a lake reveal the turbulence structure beneath strongly forced waves. Dissipation rates of turbulence kinetic energy are estimated based on centered second-order structure ...

Johannes Gemmrich

2010-03-01T23:59:59.000Z

95

Turbulent Mixing in Stably Stratified Shear Flows  

Science Conference Proceedings (OSTI)

Vertical mixing of momentum and heat is investigated in turbulent stratified shear flows. It is assumed that the flow has uniform shear and stratification with homogeneous turbulence and that an equilibrium is reached between kinetic and ...

U. Schumann; T. Gerz

1995-01-01T23:59:59.000Z

96

The Canopy Horizontal Array Turbulence Study  

Science Conference Proceedings (OSTI)

The Canopy Horizontal Array Turbulence Study (CHATS) took place in spring 2007 and is the third in the series of Horizontal Array Turbulence Study (HATS) experiments. The HATS experiments have been instrumental in testing and developing subfilterscale (...

Edward G. Patton; Thomas W. Horst; Peter P. Sullivan; Donald H. Lenschow; Steven P. Oncley; William O. J. Brown; Sean P. Burns; Alex B. Guenther; Andreas Held; Thomas Karl; Shane D. Mayor; Luciana V. Rizzo; Scott M. Spuler; Jielun Sun; Andrew A. Turnipseed; Eugene J. Allwine; Steven L. Edburg; Brian K. Lamb; Roni Avissar; Ronald J. Calhoun; Jan Kleissl; William J. Massman; Kyaw Tha Paw U; Jeffrey C. Weil

2011-05-01T23:59:59.000Z

97

Effects of Atmospheric Turbulence on Ballistic Testing  

Science Conference Proceedings (OSTI)

The effects of atmospheric turbulence on munition target scatter are determined from numerical simulations of ballistic trajectories through many realizations of realistic simulated turbulent wind fields. A technique is evaluated for correcting ...

Rod Frehlich; Robert Sharman; Charles Clough; Michael Padovani; Kelly Fling; Ward Boughers; W. Scott Walton

2008-05-01T23:59:59.000Z

98

RESONANCE BROADENING AND HEATING OF CHARGED PARTICLES IN MAGNETOHYDRODYNAMIC TURBULENCE  

SciTech Connect

The heating, acceleration, and pitch-angle scattering of charged particles by magnetohydrodynamic (MHD) turbulence are important in a wide range of astrophysical environments, including the solar wind, accreting black holes, and galaxy clusters. We simulate the interaction of high-gyrofrequency test particles with fully dynamical simulations of subsonic MHD turbulence, focusing on the parameter regime with {beta} {approx} 1, where {beta} is the ratio of gas to magnetic pressure. We use the simulation results to calibrate analytical expressions for test particle velocity-space diffusion coefficients and provide simple fits that can be used in other work. The test particle velocity diffusion in our simulations is due to a combination of two processes: interactions between particles and magnetic compressions in the turbulence (as in linear transit-time damping; TTD) and what we refer to as Fermi Type-B (FTB) interactions, in which charged particles moving on field lines may be thought of as beads sliding along moving wires. We show that test particle heating rates are consistent with a TTD resonance that is broadened according to a decorrelation prescription that is Gaussian in time (but inconsistent with Lorentzian broadening due to an exponential decorrelation function, a prescription widely used in the literature). TTD dominates the heating for v{sub s} >> v{sub A} (e.g., electrons), where v{sub s} is the thermal speed of species s and v{sub A} is the Alfven speed, while FTB dominates for v{sub s} << v{sub A} (e.g., minor ions). Proton heating rates for {beta} {approx} 1 are comparable to the turbulent cascade rate. Finally, we show that velocity diffusion of collisionless, large gyrofrequency particles due to large-scale MHD turbulence does not produce a power-law distribution function.

Lynn, Jacob W. [Physics Department, University of California, Berkeley, CA 94720 (United States); Parrish, Ian J.; Quataert, Eliot [Astronomy Department and Theoretical Astrophysics Center, University of California, Berkeley, CA 94720 (United States); Chandran, Benjamin D. G., E-mail: jacob.lynn@berkeley.edu [Space Science Center and Department of Physics, University of New Hampshire, Durham, NH 03824 (United States)

2012-10-20T23:59:59.000Z

99

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 and, unexpectedly, we also find a dependence upon 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

2013-10-21T23:59:59.000Z

100

Thermally Indirect Motions in the Convective Atmospheric Boundary Layer  

Science Conference Proceedings (OSTI)

The energetics of the dry convective boundary layer is studied by partitioning the turbulent heat flux into thermally indirect (w???thermally direct (w???>0) components as a function of z/Zi. It is found that except for the inversion ...

J. M. Wilczak; Joost A. Businger

1983-02-01T23:59:59.000Z

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

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

DOE Green Energy (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

102

Velocity-Space Proton Diffusion in the Solar Wind Turbulence  

E-Print Network (OSTI)

We study a velocity-space quasilinear diffusion of the solar wind protons driven by oblique Alfven turbulence at proton kinetic scales. Turbulent fluctuations at these scales possess properties of kinetic Alfven waves (KAWs) that are efficient in Cherenkov resonant interactions. The proton diffusion proceeds via Cherenkov kicks and forms a quasilinear plateau - nonthermal proton tail in the velocity distribution function (VDF). The tails extend in velocity space along the mean magnetic field from 1 to (1.5-3) VA, depending on the spectral break position, turbulence amplitude at the spectral break, and spectral slope after the break. The most favorable conditions for the tail generation occur in the regions where the proton thermal and Alfven velocities are about the same, VTp/VA = 1. The estimated formation times are within 1-2 h for typical tails at 1 AU, which is much shorter than the solar wind expansion time. Our results suggest that the nonthermal proton tails, observed in-situ at all heliocentric distan...

Voitenko, Yuriy

2013-01-01T23:59:59.000Z

103

Parallel electric field generation by Alfven wave turbulence  

E-Print Network (OSTI)

{This work aims to investigate the spectral structure of the parallel electric field generated by strong anisotropic and balanced Alfvenic turbulence in relation with the problem of electron acceleration from the thermal population in solar flare plasma conditions.} {We consider anisotropic Alfvenic fluctuations in the presence of a strong background magnetic field. Exploiting this anisotropy, a set of reduced equations governing non-linear, two-fluid plasma dynamics is derived. The low-$\\beta$ limit of this model is used to follow the turbulent cascade of the energy resulting from the non-linear interaction between kinetic Alfven waves, from the large magnetohydrodynamics (MHD) scales with $k_{\\perp}\\rho_{s}\\ll 1$ down to the small "kinetic" scales with $k_{\\perp}\\rho_{s} \\gg 1$, $\\rho_{s}$ being the ion sound gyroradius.} {Scaling relations are obtained for the magnitude of the turbulent electromagnetic fluctuations, as a function of $k_{\\perp}$ and $k_{\\parallel}$, showing that the electric field develops ...

Bian, N H; Brown, J C

2010-01-01T23:59:59.000Z

104

Dust Motions Driven by MHD Turbulence  

E-Print Network (OSTI)

We discuss the relative grain motions due to MHD turbulence in interstellar medium. It has been known for decades that turbulent drag is an efficient way to induce grain relative motions. However, earlier treatments disregarded magnetic field and used Kolmogorov turbulence. Unlike hydro turbulence, MHD turbulence is anisotropic on small scales. Moreover, compressible modes are important for MHD and magnetic perturbations can directly interact with grains. We provide calculations of grain relative motion for realistic interstellar turbulence driving that is consistent with the velocity dispersions observed in diffuse gas and for realistic grain charging. We account for the turbulence cutoff arising from abmipolar drag. Our results on grain shattering are consistent with the customary accepted cutoff size. We obtain grain velocities for turbulence with parameters consistent with those in HI and dark clouds. These velocities are smaller than those in earlier papers, where MHD effects were disregarded. Finally, we consider grain velocities arising from photoelectric emission, radiation pressure and the thrust due to molecular hydrogen formation. These are lower than relative velocities induced by turbulence. We conclude that turbulence should prevent these mechanisms from segregating grains by size.

A. Lazarian; Huirong Yan

2002-05-17T23:59:59.000Z

105

Active control for turbulent premixed flame simulations  

Science Conference Proceedings (OSTI)

Many turbulent premixed flames of practical interest are statistically stationary. They occur in combustors that have anchoring mechanisms to prevent blow-off and flashback. The stabilization devices often introduce a level of geometric complexity that is prohibitive for detailed computational studies of turbulent flame dynamics. As a result, typical detailed simulations are performed in simplified model configurations such as decaying isotropic turbulence or inflowing turbulence. In these configurations, the turbulence seen by the flame either decays or, in the latter case, increases as the flame accelerates toward the turbulent inflow. This limits the duration of the eddy evolutions experienced by the flame at a given level of turbulent intensity, so that statistically valid observations cannot be made. In this paper, we apply a feedback control to computationally stabilize an otherwise unstable turbulent premixed flame in two dimensions. For the simulations, we specify turbulent in flow conditions and dynamically adjust the integrated fueling rate to control the mean location of the flame in the domain. We outline the numerical procedure, and illustrate the behavior of the control algorithm. We use the simulations to study the propagation and the local chemical variability of turbulent flame chemistry.

Bell, John B.; Day, Marcus S.; Grcar, Joseph F.; Lijewski, Michael J.

2004-03-26T23:59:59.000Z

106

Magnetic shear-driven instability and turbulent mixing in magnetized protostellar disks  

E-Print Network (OSTI)

Observations of protostellar disks indicate the presence of the magnetic field of thermal (or superthermal) strength. In such a strong magnetic field, many MHD instabilities responsible for turbulent transport of the angular momentum are suppressed. We consider the shear-driven instability that can occur in protostellar disks even if the field is superthermal. This instability is caused by the combined influence of shear and compressibility in a magnetized gas and can be an efficient mechanism to generate turbulence in disks. The typical growth time is of the order of several rotation periods.

Bonanno, Alfio

2008-01-01T23:59:59.000Z

107

Measurements of Nonlinear Energy Transfer in Turbulence in the Tokamak Fusion Test Reactor  

SciTech Connect

The application of a new bispectral analysis technique to density fluctuation measurements in the core of the Tokamak Fusion Test Reactor indicates that the peak in the autopower spectrum usually lies in a region of linear stability. Large changes in the linear and nonlinear characteristics of the turbulence are observed as the plasma toroidal rotation and/or confinement properties are varied, while estimates of the turbulence-driven diffusivity varies only slightly with rotation. These observations are consistent with the operation of a global organizing property that may be related to the observation of Bohm-like scaling of ion thermal transport. {copyright} {ital 1997} {ital The American Physical Society}

Kim, J.S.; Fonck, R.J.; Durst, R.D. [Department of Nuclear Engineering and Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States)] [Department of Nuclear Engineering and Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States); Fernandez, E.; Terry, P.W. [Department of Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States)] [Department of Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States); Paul, S.F.; Zarnstorff, M.C. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)] [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

1997-08-01T23:59:59.000Z

108

Reflective ghost imaging through turbulence  

SciTech Connect

Recent work has indicated that ghost imaging may have applications in standoff sensing. However, most theoretical work has addressed transmission-based ghost imaging. To be a viable remote-sensing system, the ghost imager needs to image rough-surfaced targets in reflection through long, turbulent optical paths. We develop, within a Gaussian-state framework, expressions for the spatial resolution, image contrast, and signal-to-noise ratio of such a system. We consider rough-surfaced targets that create fully developed speckle in their returns and Kolmogorov-spectrum turbulence that is uniformly distributed along all propagation paths. We address both classical and nonclassical optical sources, as well as a computational ghost imager.

Hardy, Nicholas D.; Shapiro, Jeffrey H. [Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2011-12-15T23:59:59.000Z

109

Fluid dynamics of bacterial turbulence  

E-Print Network (OSTI)

Self-sustained turbulent structures have been observed in a wide range of living fluids, yet no quantitative theory exists to explain their properties. We report experiments on active turbulence in highly concentrated 3D suspensions of Bacillus subtilis and compare them with a minimal fourth-order vector-field theory for incompressible bacterial dynamics. Velocimetry of bacteria and surrounding fluid, determined by imaging cells and tracking colloidal tracers, yields consistent results for velocity statistics and correlations over two orders of magnitude in kinetic energy, revealing a decrease of fluid memory with increasing swimming activity and linear scaling between energy and enstrophy. The best-fit model parameters allow for quantitative agreement with experimental data.

Jörn Dunkel; Sebastian Heidenreich; Knut Drescher; Henricus H. Wensink; Markus Bär; Raymond E. Goldstein

2013-02-21T23:59:59.000Z

110

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

111

A Numerical Study of Thermal Effects on Flow and Pollutant Dispersion in Urban Street Canyons  

Science Conference Proceedings (OSTI)

This study investigates thermal effects on the flow and pollutant dispersion in urban street canyons. A two-dimensional numerical model with a k–? turbulent closure scheme is developed, and the heat transfer between the air and the building wall ...

Jae-Jin Kim; Jong-Jin Baik

1999-09-01T23:59:59.000Z

112

Quantifying Turbulence for Tidal Power Applications  

SciTech Connect

Using newly collected data from a tidal power site in Puget Sound, WA, metrics for turbulence quantification are assessed and discussed. The quality of raw ping Acoustic Doppler Current Profiler (ADCP) data for turbulence studies is evaluated against Acoustic Doppler Velocimeter (ADV) data at a point. Removal of Doppler noise from the raw ping data is shown to be a crucial step in turbulence quantification. Excluding periods of slack tide, the turbulent intensity estimates at a height of 4.6 m above the seabed are 8% and 11% from the ADCP and ADV, respectively. Estimates of the turbulent dissipation rate are more variable, from 10e-3 to 10e-1 W/m^3. An example analysis of coherent Turbulent Kinetic Energy (TKE) is presented.

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

2010-08-01T23:59:59.000Z

113

A SHELL MODEL TURBULENT DYNAMO  

Science Conference Proceedings (OSTI)

Turbulent dynamo phenomena, observed almost everywhere in astrophysical objects and also in the laboratory in the recent VKS2 experiment, are investigated using a shell model technique to describe magnetohydrodynamic turbulence. Detailed numerical simulations at very high Rossby numbers ({alpha}{sup 2} dynamo) show that as the magnetic Reynolds number increases, the dynamo action starts working and different regimes are observed. The model, which displays different large-scale coherent behaviors corresponding to different regimes, is able to reproduce the magnetic field reversals observed both in a geomagnetic dynamo and in the VKS2 experiment. While rough quantitative estimates of typical times associated with the reversal phenomenon are consistent with paleomagnetic data, the analysis of the transition from oscillating intermittent through reversal and finally to stationary behavior shows that the nature of the reversals we observe is typical of {alpha}{sup 2} dynamos and completely different from VKS2 reversals. Finally, the model shows that coherent behaviors can also be naturally generated inside the many-mode dynamical chaotic model, which reproduces the complexity of fluid turbulence, as described by the shell technique.

Perrone, D.; Nigro, G.; Veltri, P. [Universita della Calabria, Dipartimento di Fisica and Centro Nazionale Interuniversitario Struttura della Materia, Unita di Cosenza, I-87030 Arcavacata di Rende (Italy)

2011-07-10T23:59:59.000Z

114

Probability Densities in Strong Turbulence  

E-Print Network (OSTI)

According to modern developments in turbulence theory, the "dissipation" scales (u.v. cut-offs) $\\eta$ form a random field related to velocity increments $\\delta_{\\eta}u$. In this work we, using Mellin's transform combined with the Gaussain large -scale boundary condition, calculate probability densities (PDFs) of velocity increments $P(\\delta_{r}u,r)$ and the PDF of the dissipation scales $Q(\\eta, Re)$, where $Re$ is the large-scale Reynolds number. The resulting expressions strongly deviate from the Log-normal PDF $P_{L}(\\delta_{r}u,r)$ often quoted in the literature. It is shown that the probability density of the small-scale velocity fluctuations includes information about the large (integral) scale dynamics which is responsible for deviation of $P(\\delta_{r}u,r)$ from $P_{L}(\\delta_{r}u,r)$. A framework for evaluation of the PDFs of various turbulence characteristics involving spatial derivatives is developed. The exact relation, free of spurious Logarithms recently discussed in Frisch et al (J. Fluid Mech. {\\bf 542}, 97 (2005)), for the multifractal probability density of velocity increments, not based on the steepest descent evaluation of the integrals is obtained and the calculated function $D(h)$ is close to experimental data. A novel derivation (Polyakov, 2005), of a well-known result of the multi-fractal theory [Frisch, "Turbulence. {\\it Legacy of A.N.Kolmogorov}", Cambridge University Press, 1995)), based on the concepts described in this paper, is also presented.

Victor Yakhot

2005-12-12T23:59:59.000Z

115

Characteristics of Langmuir Turbulence in the Ocean Mixed Layer  

Science Conference Proceedings (OSTI)

This study uses large-eddy simulation (LES) to investigate the characteristics of Langmuir turbulence through the turbulent kinetic energy (TKE) budget. Based on an analysis of the TKE budget a velocity scale for Langmuir turbulence is proposed. ...

Alan L. M. Grant; Stephen E. Belcher

2009-08-01T23:59:59.000Z

116

Kinetic Energy Transfer between Internal Gravity Waves and Turbulence  

Science Conference Proceedings (OSTI)

We describe a reliable method for distinguishing the mean, wave and turbulence fields when internal waves with changing amplitude perturb the turbulent boundary layer. By integrating the component wave and turbulence kinetic energy budgets ...

J. J. Finnigan

1988-02-01T23:59:59.000Z

117

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

2004-07-13T23:59:59.000Z

118

Visualizing the unseen forces of turbulence  

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

Grasping the vast power of turbulence could help researchers design better weather forecasts, more efficient cars, quieter helicopters and even faster ships that "float" through...

119

Supercomputers Capture Turbulence in the Solar Wind  

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

Provide Web Site Feedback: info@es.net Supercomputers Capture Turbulence in the Solar Wind Berkeley Lab visualizations could help scientists forecast destructive space...

120

A Total Turbulent Energy Closure Model for Neutrally and Stably Stratified Atmospheric Boundary Layers  

Science Conference Proceedings (OSTI)

This paper presents a turbulence closure for neutral and stratified atmospheric conditions. The closure is based on the concept of the total turbulent energy. The total turbulent energy is the sum of the turbulent kinetic energy and turbulent ...

Thorsten Mauritsen; Gunilla Svensson; Sergej S. Zilitinkevich; Igor Esau; Leif Enger; Branko Grisogono

2007-11-01T23:59:59.000Z

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.


121

THERMAL RECOVERY  

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

THERMAL RECOVERY Thermal recovery comprises the techniques of steamflooding, cyclic steam stimulation, and in situ combustion. In steamflooding, high-temperature steam is injected...

122

Turbulent Heating in the Solar Wind and in the Solar Corona  

E-Print Network (OSTI)

In this paper we calculate the turbulent heating rates in the solar wind using the Kolmogorov-like MHD turbulence phenomenology with Kolmogorov's constants calculated by {\\it Verma and Bhattacharjee }[1995b,c]. We find that the turbulent heating can not account for the total heating of the nonAlfv\\'enic streams in the solar wind. We show that dissipation due to thermal conduction is also a potential heating source. Regarding the Alfv\\'enic streams, the predicted turbulent heating rates using the constants of {\\it Verma and Bhattacharjee }[1995c] are higher than the observed heating rates; the predicted dissipation rates are probably overestimates because Alfv\\'enic streams have not reached steady-state. We also compare the predicted turbulent heating rates in the solar corona with the observations; the Kolmogorov-like phenomenology predicts dissipation rates comparable to the observed heating rates in the corona [{\\it Hollweg, }% 1984], but Dobrowoly et al.'s generalized Kraichnan model yields heating rates much less than that required.

Mahendra K. Verma

1995-09-05T23:59:59.000Z

123

Turbulent Heating in the Solar Wind and in the Solar Corona  

E-Print Network (OSTI)

In this paper we calculate the turbulent heating rates in the solar wind using the Kolmogorov-like MHD turbulence phenomenology with Kolmogorov’s constants calculated by Verma and Bhattacharjee [1995b,c]. We find that the turbulent heating can not account for the total heating of the nonAlfvénic streams in the solar wind. We show that dissipation due to thermal conduction is also a potential heating source. Regarding the Alfvénic streams, the predicted turbulent heating rates using the constants of Verma and Bhattacharjee [1995c] are higher than the observed heating rates; the predicted dissipation rates are probably overestimates because Alfvénic streams have not reached steady-state. We also compare the predicted turbulent heating rates in the solar corona with the observations; the Kolmogorov-like phenomenology predicts dissipation rates comparable to the observed heating rates in the corona [Hollweg, 1984], but Dobrowoly et al.’s generalized Kraichnan model yields heating rates much less than that required. 1 1

Mahendra K. Verma

2008-01-01T23:59:59.000Z

124

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

125

A Quadratic Closure for Compressible Turbulence  

Science Conference Proceedings (OSTI)

We have investigated a one-point closure model for compressible turbulence based on third- and higher order cumulant discard for systems undergoing rapid deformation, such as might occur downstream of a shock or other discontinuity. In so doing, we find the lowest order contributions of turbulence to the mean flow, which lead to criteria for Adaptive Mesh Refinement. Rapid distortion theory (RDT) as originally applied by Herring closes the turbulence hierarchy of moment equations by discarding third order and higher cumulants. This is similar to the fourth-order cumulant discard hypothesis of Millionshchikov, except that the Millionshchikov hypothesis was taken to apply to incompressible homogeneous isotropic turbulence generally, whereas RDT is applied only to fluids undergoing a distortion that is 'rapid' in the sense that the interaction of the mean flow with the turbulence overwhelms the interaction of the turbulence with itself. It is also similar to Gaussian closure, in which both second and fourth-order cumulants are retained. Motivated by RDT, we develop a quadratic one-point closure for rapidly distorting compressible turbulence, without regard to homogeneity or isotropy, and make contact with two equation turbulence models, especially the K-{var_epsilon} and K-L models, and with linear instability growth. In the end, we arrive at criteria for Adaptive Mesh Refinement in Finite Volume simulations.

Futterman, J A

2008-09-16T23:59:59.000Z

126

The Turbulence Structure of Nocturnal Slope Flow  

Science Conference Proceedings (OSTI)

Measurements of the turbulence structure of nocturnal slope flow are used to test the hypothesis that slope flow turbulence in the region above the low-level wind maximum is decoupled from the surface and has a local structure similar to that ...

T. W. Horst; J. C. Doran

1988-02-01T23:59:59.000Z

127

Electromagnetic weak turbulence theory revisited  

SciTech Connect

The statistical mechanical reformulation of weak turbulence theory for unmagnetized plasmas including fully electromagnetic effects was carried out by Yoon [Phys. Plasmas 13, 022302 (2006)]. However, the wave kinetic equation for the transverse wave ignores the nonlinear three-wave interaction that involves two transverse waves and a Langmuir wave, the incoherent analogue of the so-called Raman scattering process, which may account for the third and higher-harmonic plasma emissions. The present paper extends the previous formalism by including such a term.

Yoon, P. H. [IPST, University of Maryland, College Park, Maryland 20742 (United States); Ziebell, L. F. [Instituto de Fisica, UFRGS, Porto Alegre, RS (Brazil); Gaelzer, R.; Pavan, J. [Instituto de Fisica e Matematica, UFPel, Pelotas, RS (Brazil)

2012-10-15T23:59:59.000Z

128

Spectrum of gravitational radiation from primordial turbulence  

Science Conference Proceedings (OSTI)

Energy injection into the early universe can induce turbulent motions of the primordial plasma, which in turn act as a source for gravitational radiation. Earlier work computed the amplitude and characteristic frequency of the relic gravitational wave background, as a function of the total energy injected and the stirring scale of the turbulence. This paper computes the frequency spectrum of relic gravitational radiation from a turbulent source of the stationary Kolmogoroff form which acts for a given duration, making no other approximations. We also show that the limit of long source wavelengths, commonly employed in aeroacoustic problems, is an excellent approximation. The gravitational waves from cosmological turbulence around the electroweak energy scale will be detectable by future space-based laser interferometers for a substantial range of turbulence parameters.

Gogoberidze, Grigol [Centre for Plasma Astrophysics, K.U. Leuven, Celestijnenlaan 200B, 3001 Leuven (Belgium); National Abastumani Astrophysical Observatory, 2A Kazbegi Ave, GE-0160 Tbilisi (Georgia); Kahniashvili, Tina [Center for Cosmology and Particle Physics, New York University, 4 Washington Plaza, New York, New York 10003 (United States); National Abastumani Astrophysical Observatory, 2A Kazbegi Ave, GE-0160 Tbilisi (Georgia); Kosowsky, Arthur [Department of Physics and Astronomy, University of Pittsburgh, 3941 O'Hara Street, Pittsburgh, Pennsylvania 15260 (United States)

2007-10-15T23:59:59.000Z

129

Lagrangian formulation of turbulent premixed combustion  

E-Print Network (OSTI)

The Lagrangian point of view is adopted to study turbulent premixed combustion. The evolution of the volume fraction of combustion products is established by the Reynolds transport theorem. It emerges that the burned-mass fraction is led by the turbulent particle motion, by the flame front velocity, and by the mean curvature of the flame front. A physical requirement connecting particle turbulent dispersion and flame front velocity is obtained from equating the expansion rates of the flame front progression and of the unburned particles spread. The resulting description compares favorably with experimental data. In the case of a zero-curvature flame, with a non-Markovian parabolic model for turbulent dispersion, the formulation yields the Zimont equation extended to all elapsed times and fully determined by turbulence characteristics. The exact solution of the extended Zimont equation is calculated and analyzed to bring out different regimes.

Pagnini, Gianni

2011-01-01T23:59:59.000Z

130

Anisotropic MHD Turbulence in the Interstellar Medium and Solar Wind  

E-Print Network (OSTI)

Anisotropic MHD Turbulence in the Interstellar Medium and Solar Wind C. S. Ng Center for Magnetic (MHD) turbulence Observations in ISM and solar wind · Anisotropy due to magnetic field · Electron MHD turbulence #12;Interstellar turbulence From Cordes (1999) Observation: power law relation between electron

Ng, Chung-Sang

131

Modeling the motion of a hot, turbulent gas  

Science Conference Proceedings (OSTI)

Keywords: animation, convection, gas simulations, gaseous phenomena, physics-based modeling, smoke, steam, turbulent flow

Nick Foster; Dimitris Metaxas

1997-08-01T23:59:59.000Z

132

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

SciTech Connect

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

133

Experimental Study of an Artificial Thermal Plume in the Boundary Layer. Part II: Some Aspects of the Plume Thermodynamical Structure  

Science Conference Proceedings (OSTI)

Some aspects of the mean and turbulent structures of artificial thermal plumes in the boundary layer (BL) are presented. This analysis is based mainly on measurements with an instrumented aircraft. As initial conditions for plume rise, the ...

J. Noilhan; B. Bénech; G. Letrenne; A. Druilhet; A. Saab

1986-04-01T23:59:59.000Z

134

Wind turbulence characterization for wind energy development  

DOE Green Energy (OSTI)

As part of its support of the US Department of Energy's (DOE's) Federal Wind Energy Program, the Pacific Northwest Laboratory (PNL) has initiated an effort to work jointly with the wind energy community to characterize wind turbulence in a variety of complex terrains at existing or potential sites of wind turbine installation. Five turbulence characterization systems were assembled and installed at four sites in the Tehachapi Pass in California, and one in the Green Mountains near Manchester, Vermont. Data processing and analyses techniques were developed to allow observational analyses of the turbulent structure; this analysis complements the more traditional statistical and spectral analyses. Preliminary results of the observational analyses, in the rotating framework or a wind turbine blade, show that the turbulence at a site can have two major components: (1) engulfing eddies larger than the rotor, and (2) fluctuating shear due to eddies smaller than the rotor disk. Comparison of the time series depicting these quantities at two sites showed that the turbulence intensity (the commonly used descriptor of turbulence) did not adequately characterize the turbulence at these sites. 9 refs., 10 figs.,

Wendell, L.L.; Gower, G.L.; Morris, V.R.; Tomich, S.D.

1991-09-01T23:59:59.000Z

135

Gauge turbulence, topological defect dynamics, and condensation in Higgs models  

E-Print Network (OSTI)

The real-time dynamics of topological defects and turbulent configurations of gauge fields for electric and magnetic confinement are studied numerically within a 2+1D Abelian Higgs model. It is shown that confinement is appearing in such systems equilibrating after a strong initial quench such as the overpopulation of the infrared modes. While the final equilibrium state does not support confinement, metastable vortex defect configurations appear in the gauge field which are found to be closely related to the appearance of physically observable confined electric and magnetic charges. These phenomena are seen to be intimately related to the approach of a non-thermal fixed point of the far-from-equilibrium dynamical evolution, signalled by universal scaling in the gauge-invariant correlation function of the Higgs field. Even when the parameters of the Higgs action do not support condensate formation in the vacuum, during this approach, transient Higgs condensation is observed. We discuss implications of these results for the far-from-equilibrium dynamics of Yang-Mills fields and potential mechanisms how confinement and condensation in non-abelian gauge fields can be understood in terms of the dynamics of Higgs models. These suggest that there is an interesting new class of dynamics of strong coherent turbulent gauge fields with condensates.

Thomas Gasenzer; Larry McLerran; Jan M. Pawlowski; Dénes Sexty

2013-07-19T23:59:59.000Z

136

Radar Detection of Turbulence in Precipitation Environments  

Science Conference Proceedings (OSTI)

Imperfect particle tracer response is incorporated into the relations describing the turbulent air motion contribution to Doppler radar spectrum mean and variance. Tracer effects on radar estimates of the eddy dissipation rate (?) increase with ...

Alan R. Bohne

1982-08-01T23:59:59.000Z

137

An Analysis of Wave-Turbulence Interaction  

Science Conference Proceedings (OSTI)

We present the results of an analytical and numerical calculation of the interaction between an internal gravity wave and a wave-induced turbulence. The initial atmospheric state, assumed horizontally homogeneous, is statically and dynamically ...

D. Fua; G. Chimonas; F. Einaudi; O. Zeman

1982-11-01T23:59:59.000Z

138

A LES-Langevin model for turbulence  

E-Print Network (OSTI)

We propose a new model of turbulence for use in large-eddy simulations (LES). The turbulent force, represented here by the turbulent Lamb vector, is divided in two contributions. The contribution including only subfilter fields is deterministically modeled through a classical eddy-viscosity. The other contribution including both filtered and subfilter scales is dynamically computed as solution of a generalized (stochastic) Langevin equation. This equation is derived using Rapid Distortion Theory (RDT) applied to the subfilter scales. The general friction operator therefore includes both advection and stretching by the resolved scale. The stochastic noise is derived as the sum of a contribution from the energy cascade and a contribution from the pressure. The LES model is thus made of an equation for the resolved scale, including the turbulent force, and a generalized Langevin equation integrated on a twice-finer grid. The model is validated by comparison to DNS and is tested against classical LES models for i...

Laval, J P; Dubrulle, Berengere; Laval, Jean-Philippe

2006-01-01T23:59:59.000Z

139

Supercomputers Capture Turbulence in the Solar Wind  

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

Supercomputers Supercomputers Capture Turbulence in the Solar Wind Supercomputers Capture Turbulence in the Solar Wind Berkeley Lab visualizations could help scientists forecast destructive space weather December 16, 2013 Linda Vu, +1 510 495 2402, lvu@lbl.gov eddies1.jpg This visualization zooms in on current sheets revealing the "cascade of turbulence" in the solar wind occurring down to electron scales. This is a phenomenon common in fluid dynamics-turbulent energy injected at large eddies is transported to successively smaller scales until it is dissipated as heat. (Image by Burlen Loring, Berkeley Lab) As inhabitants of Earth, our lives are dominated by weather. Not just in the form of rain and snow from atmospheric clouds, but also a sea of charged particles and magnetic fields generated by a star sitting 93

140

Generation of Turbulence by Atmospheric Gravity Waves  

Science Conference Proceedings (OSTI)

The standard current criterion for the generation of turbulence by atmospheric gravity waves and for the associated limitation on wave growth is based upon the standard criterion for static instability of the unperturbed atmosphere, namely, that ...

Colin O. Hines

1988-04-01T23:59:59.000Z

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.


141

Tracer dispersion in the turbulent convective layer  

Science Conference Proceedings (OSTI)

Experimental results for passive tracer dispersion in the turbulent surface layer under convective conditions are presented. In this case, the dispersion of tracer particles is determined by the interplay of two mechanisms: buoyancy and advection. ...

Alex Skvortsov; Milan Jamriska; Timothy C. DuBois

142

Turbulence and Diapycnal Mixing in Drake Passage  

Science Conference Proceedings (OSTI)

Direct measurements of turbulence levels in the Drake Passage region of the Southern Ocean show a marked enhancement over the Phoenix Ridge. At this site, the Antarctic Circumpolar Current (ACC) is constricted in its flow between the southern tip ...

L. St. Laurent; A. C. Naveira Garabato; J. R. Ledwell; A. M. Thurnherr; J. M. Toole; A. J. Watson

2012-12-01T23:59:59.000Z

143

Stratified Turbulence near a Critical Dissipation Rate  

Science Conference Proceedings (OSTI)

Turbulence in the thermocline was investigated using data observed by the submarine Dolphin. Various length scales, the Reynolds and the Froude numbers of the Dolphin data were compared to those values of a laboratory experiment presented in ...

Hidekatsu Yamazaki

1990-10-01T23:59:59.000Z

144

Estimating Oceanic Turbulence Dissipation from Seismic Images  

Science Conference Proceedings (OSTI)

Seismic images of oceanic thermohaline finestructure record vertical displacements from internal waves and turbulence over large sections at unprecedented horizontal resolution. Where reflections follow isopycnals, their displacements can be used ...

W. Steven Holbrook; Ilker Fer; Raymond W. Schmitt; Daniel Lizarralde; Jody M. Klymak; L. Cody Helfrich; Robert Kubichek

145

Ertel's Potential Vorticity in Unstratified Turbulence  

Science Conference Proceedings (OSTI)

The evolution of Ertel's potential vorticity (PV) is examined in direct numerical simulations (DNS) of decaying turbulence advecting passive scalars and in a generalized Taylor-Green vortex (TGV). It is noted that although PV itself is advected ...

J. R. Herring; R. M. Kerr; R. Rotunno

1994-01-01T23:59:59.000Z

146

Observations of Turbulence in Stratified Flow  

Science Conference Proceedings (OSTI)

Various theoretical properties of the structure function are evaluated. Additional functions are constructed to describe the overall influence of stratification, the anisotropy and intermittency of the turbulence, and the asymmetry of the main ...

L. Mahrt; N. Gamage

1987-04-01T23:59:59.000Z

147

Example of Reduced Turbulence during Thunderstorm Outflow  

Science Conference Proceedings (OSTI)

The vertical structures of turbulence, winds, and temperatures are analyzed from a 92-m instrumented tower and a collocated acoustic sodar during an outflow episode from a weak thunderstorm over sloping terrain in northern New Mexico. Prior to ...

Brent M. Bowen

1996-06-01T23:59:59.000Z

148

A Comparison of Turbulence Measurements from Aircraft  

Science Conference Proceedings (OSTI)

A performance analysis of the three turbulence-measuring aircraft which participated in the GATE is presented. These aircraft were a Lockheed C-130 operated by the Meteorological Research Flight Centre of the U.K. Meteorological Office, a Douglas ...

Margaret A. Lemone; William T. Pennell

1980-12-01T23:59:59.000Z

149

Marine Stratocumulus Layers. Part II: Turbulence Budgets  

Science Conference Proceedings (OSTI)

This paper discusses the turbulence profiles and budgets for two days of radiation, dynamical and thermodynamical observations by the NCAR Electra in shallow marine stratocumulus off the California coast in June 1976.

R. A. Brost; J. C. Wyngaard; D. H. Lenschow

1982-04-01T23:59:59.000Z

150

ENERGETIC PARTICLE DIFFUSION IN STRUCTURED TURBULENCE  

Science Conference Proceedings (OSTI)

In the full-orbit particle simulations of energetic particle transport in plasmas, the plasma turbulence is typically described as a homogeneous superposition of linear Fourier modes. The turbulence evolution is, however, typically a nonlinear process, and, particularly in the heliospheric context, the solar wind plasma is inhomogeneous due to the transient structures, as observed by remote and in situ measurements. In this work, we study the effects of the inhomogeneities on energetic particle transport by using spatially distributed, superposed turbulence envelopes. We find that the cross-field transport is significantly reduced, when compared to the results obtained with homogeneous turbulence. The reduction can reach an order of magnitude when the enveloping breaks the wave phase coherence along the mean magnetic field direction.

Laitinen, T.; Dalla, S.; Kelly, J. [Jeremiah Horrocks Institute, University of Central Lancashire, PR1 2HE Preston (United Kingdom)

2012-04-20T23:59:59.000Z

151

An Improved Model for the Turbulent PBL  

Science Conference Proceedings (OSTI)

Second-order turbulence models of the Mellor and Yamada type have been widely used to simulate the planetary boundary layer (PBL). It is, however, known that these models have several deficiencies. For example, assuming the production of the ...

Y. Cheng; V. M. Canuto; A. M. Howard

2002-05-01T23:59:59.000Z

152

Can Quasigeostrophic Turbulence Be Modeled Stochastically?  

Science Conference Proceedings (OSTI)

Numerically generated data of quasigeostrophic turbulence in an equilibrated shear flow are analyzed to determine the extent to which they can be modeled by a Markov model. The time lagged covariances are collected into a matrix, C?, and are ...

Timothy DelSole

1996-06-01T23:59:59.000Z

153

k-? turbulence modeling for a wind turbine.  

E-Print Network (OSTI)

?? In this report we discuss the use of k-? RANS (Reynolds-averaged Navier-Stokes equations) turbulence model for wind turbine applications. This model has been implemented… (more)

EREK, ERMAN

2011-01-01T23:59:59.000Z

154

Active control for turbulent premixed flame simulations  

E-Print Network (OSTI)

Poinsot, T. J. , Combust. Flame, 121:395–417 [8] Trouve, A.Rutland, C. J. , Combust. Flame, 102:447–461 (1995). [10]Control for Turbulent Premixed Flame Simulations J. B. Bell,

Bell, John B.; Day, Marcus S.; Grcar, Joseph F.; Lijewski, Michael J.

2004-01-01T23:59:59.000Z

155

Dispersion of Heavy Particles by Turbulent Motion  

Science Conference Proceedings (OSTI)

Accurate prediction of heavy particle dispersion in turbulent flows requires a simultaneous consideration of particle's inertia and particle's drift velocity. A mathematically simple and physically comprehensive analysis was developed to solve ...

Lian-Ping Wang; Davd E. Stock

1993-07-01T23:59:59.000Z

156

Is there a statistical mechanics of turbulence  

SciTech Connect

The statistical-mechanical treatment of turbulence is made questionable by strong nonlinearity and strong disequilibrium that result in the creation of ordered structures imbedded in disorder. Model systems are described which may provide some hope that a compact, yet faithful, statistical description of turbulence nevertheless is possible. Some essential dynamic features of the models are captured by low-order statistical approximations despite strongly non-Gaussian behavior. 31 refs., 5 figs.

Kraichnan, R.H.; Chen, S.Y.

1988-09-01T23:59:59.000Z

157

Quantum light in the turbulent atmosphere  

E-Print Network (OSTI)

Nonclassical properties of light propagating through the turbulent atmosphere are studied. We demonstrate by numerical simulation that the probability distribution of the transmission coefficient, which characterizes the effects of the atmosphere on the quantum state of light, can be reconstructed by homodyne detection. Nonclassical photon-statistics and, more generally, nonclassical Glauber-Sudarshan functions appear to be more robust against turbulence for weak light fields rather than for bright ones.

A. A. Semenov; W. Vogel

2009-02-24T23:59:59.000Z

158

FORMATION OF TURBULENT AND MAGNETIZED MOLECULAR CLOUDS VIA ACCRETION FLOWS OF H I CLOUDS  

Science Conference Proceedings (OSTI)

Using three-dimensional magnetohydrodynamic simulations, including the effects of radiative cooling/heating, chemical reactions, and thermal conduction, we investigate the formation of molecular clouds in the multi-phase interstellar medium. As suggested by recent observations, we consider the formation of molecular clouds due to accretion of H I clouds. Our simulations show that the initial H I medium is piled up behind the shock waves induced by accretion flows. Since the initial medium is highly inhomogeneous as a consequence of thermal instability, a newly formed molecular cloud becomes very turbulent owing to the development of the Richtmyer-Meshkov instability. The kinetic energy of the turbulence dominates the thermal, magnetic, and gravitational energies throughout the entire 10 Myr evolution. However, the kinetic energy measured using CO-fraction-weighted densities is comparable to the other energies, once the CO molecules are sufficiently formed as a result of UV shielding. This suggests that the true kinetic energy of turbulence in molecular clouds as a whole can be much larger than the kinetic energy of turbulence estimated using line widths of molecular emission. We find that clumps in a molecular cloud show the following statistically homogeneous evolution: the typical plasma {beta} of the clumps is roughly constant ({beta}) {approx_equal} 0.4; the size-velocity dispersion relation is {Delta}v {approx_equal} 1.5 km s{sup -1} (l/1 pc){sup 0.5}, irrespective of the density; the clumps evolve toward magnetically supercritical, gravitationally unstable cores; and the clumps seem to evolve into cores that satisfy the condition for fragmentation into binaries. These statistical properties may represent the initial conditions of star formation.

Inoue, Tsuyoshi [Department of Physics and Mathematics, Aoyama Gakuin University, Fuchinobe, Chuou-ku, Sagamihara 252-5258 (Japan); Inutsuka, Shu-ichiro, E-mail: inouety@phys.aoyama.ac.jp [Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602 (Japan)

2012-11-01T23:59:59.000Z

159

The Efficiency of Second-Order Fermi Acceleration by Weakly Compressible MHD Turbulence  

E-Print Network (OSTI)

We investigate the effects of pitch-angle scattering on the efficiency of particle heating and acceleration by MHD turbulence using phenomenological estimates and simulations of non-relativistic test particles interacting with strong, subsonic MHD turbulence. We include an imposed pitch-angle scattering rate, which is meant to approximate the effects of high frequency plasma waves and/or velocity space instabilities. We focus on plasma parameters similar to those found in the near-Earth solar wind, though most of our results are more broadly applicable. An important control parameter is the size of the particle mean free path lambda_{mfp} relative to the scale of the turbulent fluctuations L. For small scattering rates, particles interact quasi-resonantly with turbulent fluctuations in magnetic field strength. Scattering increases the long-term efficiency of this resonant heating by factors of a few-10, but the distribution function does not develop a significant non-thermal power-law tail. For higher scatter...

Lynn, Jacob W; Chandran, Benjamin D G; Parrish, Ian J

2013-01-01T23:59:59.000Z

160

Experimental Study of Parametric Dependence of Electron-scale Turbulence in a Spherical Tokamak  

Science Conference Proceedings (OSTI)

Electron-scale turbulence is predicted to drive anomalous electron thermal transport. However, experimental study of its relation with transport is still in its early stage. On the National Spherical Tokamak eXperiment (NSTX), electron-scale density ?uctuations are studied with a novel tangen- tial microwave scattering system with high radial resolution of ±2 cm. Here, we report a study of parametric dependence of electron-scale turbulence in NSTX H-mode plasmas. The dependence on density gradient is studied through the observation of a large density gradient variation in the core induced by an ELM event, where we found the ?rst clear experimental evidence of density gradient stabilization of electron-gyro scale turbulence in a fusion plasma. This observation, cou- pled with linear gyro-kinetic calculations, leads to the identi?cation of the observed instability as toroidal Electron Temperature Gradient (ETG) modes. It is observed that longer wavelength ETG modes, k??s electron temperature and k? is the wavenumber perpendicular to local equilibrium magnetic ?eld), are most stabilized by density gradient, and the stabilization is accompanied by about a factor of two decrease in electron thermal di?usivity. Comparisons with nonlinear ETG gyrokinetic simulations shows ETG turbulence may be able to explain the experimental electron heat ?ux observed before the ELM event. The collisionality dependence of electron-scale turbulence is also studied by systematically varying plasma current and toroidal ?eld, so that electron gyroradius (?e ), electron beta (?e ) and safety factor (q95 ) are kept approximately constant. More than a factor of two change in electron collisionality, ? ?e, was achieved, and we found that the spectral power of electron-scale turbulence appears to increase as ? ?e is decreased in this collisonality scan. However, both linear and nonlinear simulations show no or weak dependence with the electron-ion collision frequency, ? e/i . Instead, other equilibrium parameters (safety factor, electron density gradient, for example) a?ect ETG linear growth rate and electron thermal transport more than ? e/i does. Furthermore, electron heat ?ux predicted by the simulations is found to have an order-of-magnitude spatial variation in the experimental mea- surement region and is also found to be much smaller than experimental levels except at one radial location we evaluated. The predicted electron heat ?ux is shown to be strongly anti-correlated with density gradient which varies for a factor of three in the measurement region, which is in agreement with the density gradient dependence study reported in this paper.

Ren, Y; Kaye, S M; Mazzucato, E; Bell, R E; Diallo, A; Domier, C W; LeBlanc, B P; Lee, K C; Smith, D R

2012-05-23T23:59:59.000Z

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

Experimental Study of Parametric Dependence of Electron-scale Turbulence in a Spherical Tokamak  

SciTech Connect

Electron-scale turbulence is predicted to drive anomalous electron thermal transport. However, experimental study of its relation with transport is still in its early stage. On the National Spherical Tokamak eXperiment (NSTX), electron-scale density ?uctuations are studied with a novel tangen- tial microwave scattering system with high radial resolution of ±2 cm. Here, we report a study of parametric dependence of electron-scale turbulence in NSTX H-mode plasmas. The dependence on density gradient is studied through the observation of a large density gradient variation in the core induced by an ELM event, where we found the ?rst clear experimental evidence of density gradient stabilization of electron-gyro scale turbulence in a fusion plasma. This observation, cou- pled with linear gyro-kinetic calculations, leads to the identi?cation of the observed instability as toroidal Electron Temperature Gradient (ETG) modes. It is observed that longer wavelength ETG modes, k??s < 10 (?s is the ion gyroradius at electron temperature and k? is the wavenumber perpendicular to local equilibrium magnetic ?eld), are most stabilized by density gradient, and the stabilization is accompanied by about a factor of two decrease in electron thermal di?usivity. Comparisons with nonlinear ETG gyrokinetic simulations shows ETG turbulence may be able to explain the experimental electron heat ?ux observed before the ELM event. The collisionality dependence of electron-scale turbulence is also studied by systematically varying plasma current and toroidal ?eld, so that electron gyroradius (?e ), electron beta (?e ) and safety factor (q95 ) are kept approximately constant. More than a factor of two change in electron collisionality, ? ?e, was achieved, and we found that the spectral power of electron-scale turbulence appears to increase as ? ?e is decreased in this collisonality scan. However, both linear and nonlinear simulations show no or weak dependence with the electron-ion collision frequency, ? e/i . Instead, other equilibrium parameters (safety factor, electron density gradient, for example) a?ect ETG linear growth rate and electron thermal transport more than ? e/i does. Furthermore, electron heat ?ux predicted by the simulations is found to have an order-of-magnitude spatial variation in the experimental mea- surement region and is also found to be much smaller than experimental levels except at one radial location we evaluated. The predicted electron heat ?ux is shown to be strongly anti-correlated with density gradient which varies for a factor of three in the measurement region, which is in agreement with the density gradient dependence study reported in this paper.

Ren, Y; Kaye, S M; Mazzucato, E; Bell, R E; Diallo, A; Domier, C W; LeBlanc, B P; Lee, K C; Smith, D R

2012-05-23T23:59:59.000Z

162

On the Nature of Turbulence in a Stratified Fluid. Part I: The Energetics of Mixing  

Science Conference Proceedings (OSTI)

The definition of the flux Richardson number Rf is generalized to be the ratio of the turbulent buoyancy flux b to the net turbulent mechanical energy m available from all sources. For mechanically energized turbulence where turbulence kinetic ...

G. N. Ivey; J. Imberger

1991-05-01T23:59:59.000Z

163

Evidence of critical balance in kinetic Alfven wave turbulence simulations  

Science Conference Proceedings (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

164

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

DOE Green Energy (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

165

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

166

Clustering of Aerosols in Atmospheric Turbulent Flow  

E-Print Network (OSTI)

A mechanism of formation of small-scale inhomogeneities in spatial distributions of aerosols and droplets associated with clustering instability in the atmospheric turbulent flow is discussed. The particle clustering is a consequence of a spontaneous breakdown of their homogeneous space distribution due to the clustering instability, and is caused by a combined effect of the particle inertia and a finite correlation time of the turbulent velocity field. In this paper a theoretical approach proposed in Phys. Rev. E 66, 036302 (2002) is further developed and applied to investigate the mechanisms of formation of small-scale aerosol inhomogeneities in the atmospheric turbulent flow. The theory of the particle clustering instability is extended to the case when the particle Stokes time is larger than the Kolmogorov time scale, but is much smaller than the correlation time at the integral scale of turbulence. We determined the criterion of the clustering instability for the Stokes number larger than 1. We discussed applications of the analyzed effects to the dynamics of aerosols and droplets in the atmospheric turbulent flow.

T. Elperin; N. Kleeorin; M. A. Liberman; V. L'vov; I. Rogachevskii

2007-02-15T23:59:59.000Z

167

Turbulence Closure, Steady State, and Collapse into Waves  

Science Conference Proceedings (OSTI)

A new simple two-equation turbulence closure is constructed by hypothesizing that there is an extra energy sink in the turbulent kinetic energy (k) equation representing the transfer of energy from k to internal waves and other nonturbulent ...

Helmut Baumert; Hartmut Peters

2004-02-01T23:59:59.000Z

168

Comments on “Turbulence Closure, Steady State, and Collapse into Waves”  

Science Conference Proceedings (OSTI)

Two-equation models are being increasingly used to model turbulence in geophysical flows. A salient aspect of these flows is the stable gravitational stratification, which implies that turbulent fluctuations can generate internal waves that drain ...

Lakshmi H. Kantha

2005-01-01T23:59:59.000Z

169

Recent Advances in the Understanding of Near-Cloud Turbulence  

Science Conference Proceedings (OSTI)

Anyone who has flown in a commercial aircraft is familiar with turbulence. Unexpected encounters with turbulence pose a safety risk to airline passengers and crew, can occasionally damage aircraft, and indirectly increase the cost of air travel. Deep ...

Todd P. Lane; Robert D. Sharman; Stanley B. Trier; Robert G. Fovell; John K. Williams

2012-04-01T23:59:59.000Z

170

Velcro Measurement of Turbulence Kinetic Energy Dissipation Rate ?  

Science Conference Proceedings (OSTI)

Turbulence in the ocean results from many different processes operating over a wide range of space scales and timescales, with spatial and temporal variability particularly extreme in coastal oceans. If the origins and effects of turbulent ...

Ann E. Gargett

1999-12-01T23:59:59.000Z

171

Observations of the Surf-Zone Turbulent Dissipation Rate  

Science Conference Proceedings (OSTI)

The contributions of surface (breaking wave) boundary layer (SBL) and bottom (velocity shear) boundary layer (BBL) processes to surf-zone turbulence is studied here. The turbulent dissipation rate ?, estimated on a 160-m-long cross-shore ...

Falk Feddersen

2012-03-01T23:59:59.000Z

172

Wave–Turbulence Interactions in a Breaking Mountain Wave  

Science Conference Proceedings (OSTI)

The mean and turbulent structures in a breaking mountain wave are considered through an ensemble of high-resolution (essentially large-eddy simulation) wave-breaking calculations. Of particular interest are the turbulent heat and momentum fluxes ...

Craig C. Epifanio; Tingting Qian

2008-10-01T23:59:59.000Z

173

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

174

Dispersion of Marked Fluid Elements in a Turbulent Ekman Layer  

Science Conference Proceedings (OSTI)

A stochastic model is derived for studying shear-dispersion in a horizontally homogeneous, turbulent Ekman layer that is evolving in time. It is based on a one-dimensional model including an advanced turbulence closure (k = ?) model, which yields ...

Lars-Arne Rahm; Urban Svensson

1986-12-01T23:59:59.000Z

175

Modeling Optical Turbulence and Seeing over Mauna Kea  

Science Conference Proceedings (OSTI)

Atmospheric turbulence is a primary concern for astronomers. Turbulence causes amplitude and phase fluctuations in electromagnetic waves propagating through the atmosphere, constraining the maximum telescope resolution and resulting in telescope ...

T. Cherubini; S. Businger; R. Lyman; M. Chun

2008-04-01T23:59:59.000Z

176

Effective Roughness Length for Turbulent Flow over a Wavy Surface  

Science Conference Proceedings (OSTI)

A two-equation turbulence model is used to calculate the effective roughness length for two-dimensional turbulent flow over small amplitude, wavy surface topography. The governing equations are solved using the method of matched asymptotic ...

S. J. Jacobs

1989-07-01T23:59:59.000Z

177

Statistics and Dynamics of Aircraft Encounters of Turbulence over Greenland  

Science Conference Proceedings (OSTI)

Historical records of aviation turbulence encounters above Greenland are examined for the period from 2000 to 2006. These data identify an important flow regime that contributes to the occurrence of aircraft turbulence encounters, associated with ...

Todd P. Lane; James D. Doyle; Robert D. Sharman; Melvyn A. Shapiro; Campbell D. Watson

2009-08-01T23:59:59.000Z

178

An Investigation of Turbulence Generation Mechanisms above Deep Convection  

Science Conference Proceedings (OSTI)

An investigation of the generation of turbulence above deep convection is presented. This investigation is motivated by an encounter between a commercial passenger aircraft and severe turbulence above a developing thunderstorm near Dickinson, ...

Todd P. Lane; Robert D. Sharman; Terry L. Clark; Hsiao-Ming Hsu

2003-05-01T23:59:59.000Z

179

Statistical theory of Langmuir turbulence. [Direct interaction approximation  

SciTech Connect

A statistical theory of Langmuir turbulence is developed by applying a generalization of the direction interaction approximation (DIA) of Kraichnan to the Zakharov equations describing Langmuir turbulence. 7 references.

DuBois, D.F.; Rose, H.A.; Goldman, M.V.

1979-01-01T23:59:59.000Z

180

Boils and Turbulence in a Weakly Stratified Shallow Tidal Sea  

Science Conference Proceedings (OSTI)

Measurements of turbulence are made in a weakly but variably stratified region of tidal straining in the eastern Irish Sea using turbulence sensors profiling vertically through the water column on the Fast Light Yo-yo (FLY) profiler and ...

S. A. Thorpe; J. A. M. Green; J. H. Simpson; T. R. Osborn; W. A. M. Nimmo Smith

2008-08-01T23:59:59.000Z

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

The New Cardington Balloon-Borne Turbulence Probe System  

Science Conference Proceedings (OSTI)

A new instrument package has been developed to measure turbulence at various heights in the boundary layer. The package or “turbulence probe” is designed to be attached to the tethering cable of a balloon. In contrast to previous balloon borne ...

A. J. Lapworth; P. J. Mason

1988-12-01T23:59:59.000Z

182

Modeling Turbulent Flow in an Urban Central Business District  

Science Conference Proceedings (OSTI)

The Realistic Urban Spread and Transport of Intrusive Contaminants (RUSTIC) model has been developed as a simplified computational fluid dynamics model with a k–? turbulence model to be used to provide moderately fast simulations of turbulent ...

Donald A. Burrows; Eric A. Hendricks; Steve R. Diehl; Robert Keith

2007-12-01T23:59:59.000Z

183

Turbulence Sensor Dynamic Calibration Using Real-Time Spectral Computations  

Science Conference Proceedings (OSTI)

The integration of plug-in Fast Fourier Transform (FFT) boards in data acquisition computers allows a considerable development in the dynamic calibration of turbulence sensors. The spectral transfer function of a fast and sensitive turbulence ...

P. G. Mestayer; S. E. Larsen; C. W. Fairall; J. B. Edson

1990-12-01T23:59:59.000Z

184

Turbulent Condensation of Droplets: Direct Simulation and a Stochastic Model  

Science Conference Proceedings (OSTI)

The effect of turbulent mixing on droplet condensation is studied via direct numerical simulations of a population of droplets in a periodic box of homogeneous isotropic turbulence. Each droplet is tracked as a fluid particle whose radius grows ...

Roberto Paoli; Karim Shariff

2009-03-01T23:59:59.000Z

185

Observations of Quasi-Two-Dimensional Turbulence in Tidal Currents  

Science Conference Proceedings (OSTI)

Observational evidence for the existence of quasi-two-dimensional turbulence in tidal currents is derived from the auto- and cross-correlation spectra of vertically separated current meters. The observed quasi- two-dimensional turbulence seems to ...

C. Veth; J. T. F. Zimmerman

1981-10-01T23:59:59.000Z

186

Observations of Turbulence within a Natural Surf Zone  

Science Conference Proceedings (OSTI)

Here, the Reynolds stresses u?w? and ??w?, where u?, ??, and w? are the cross-shore, alongshore, and vertical turbulence velocities, respectively, and the angle brackets represent time averaging, are used to diagnose turbulence dynamics ...

B. G. Ruessink

2010-12-01T23:59:59.000Z

187

Turbulent burning rates of methane and methane-hydrogen mixtures  

Science Conference Proceedings (OSTI)

Methane and methane-hydrogen (10%, 20% and 50% hydrogen by volume) mixtures have been ignited in a fan stirred bomb in turbulence and filmed using high speed cine schlieren imaging. Measurements were performed at 0.1 MPa (absolute) and 360 K. A turbulent burning velocity was determined for a range of turbulence velocities and equivalence ratios. Experimental laminar burning velocities and Markstein numbers were also derived. For all fuels the turbulent burning velocity increased with turbulence velocity. The addition of hydrogen generally resulted in increased turbulent and laminar burning velocity and decreased Markstein number. Those flames that were less sensitive to stretch (lower Markstein number) burned faster under turbulent conditions, especially as the turbulence levels were increased, compared to stretch-sensitive (high Markstein number) flames. (author)

Fairweather, M. [School of Process, Environmental and Materials Engineering, University of Leeds, Leeds LS2 9JT (United Kingdom); Ormsby, M.P.; Sheppard, C.G.W. [School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT (United Kingdom); Woolley, R. [Department of Mechanical Engineering, University of Sheffield, Sheffield S1 3JD (United Kingdom)

2009-04-15T23:59:59.000Z

188

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

189

Collision Rates of Cloud Droplets in Turbulent Flow  

Science Conference Proceedings (OSTI)

Direct numerical simulations of an evolving turbulent flow field have been performed to explore how turbulence affects the motion and collisions of cloud droplets. Large numbers of droplets are tracked through the flow field and their positions, ...

Charmaine N. Franklin; Paul A. Vaillancourt; M. K. Yau; Peter Bartello

2005-07-01T23:59:59.000Z

190

Perpendicular Ion Heating by Low-Frequency Alfven-Wave Turbulence in the Solar Wind  

E-Print Network (OSTI)

We consider ion heating by turbulent Alfven waves (AWs) and kinetic Alfven waves (KAWs) with perpendicular wavelengths comparable to the ion gyroradius and frequencies smaller than the ion cyclotron frequency. When the turbulence amplitude exceeds a certain threshold, an ion's orbit becomes chaotic. The ion then interacts stochastically with the time-varying electrostatic potential, and the ion's energy undergoes a random walk. Using phenomenological arguments, we derive an analytic expression for the rates at which different ion species are heated, which we test by simulating test particles interacting with a spectrum of randomly phased AWs and KAWs. We find that the stochastic heating rate depends sensitively on the quantity epsilon = dv/vperp, where vperp is the component of the ion velocity perpendicular to the background magnetic field B0, and dv (dB) is the rms amplitude of the velocity (magnetic-field) fluctuations at the gyroradius scale. In the case of thermal protons, when epsilon eps1, the proton ...

Chandran, Benjamin D G; Rogers, Barrett N; Quataert, Eliot; Germaschewski, Kai

2010-01-01T23:59:59.000Z

191

Supercomputers Capture Turbulence in the Solar Wind  

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

Supercomputers Capture Supercomputers Capture Turbulence in the Solar Wind News & Publications ESnet in the News ESnet News Media & Press Publications and Presentations Galleries ESnet Awards and Honors Contact Us Technical Assistance: 1 800-33-ESnet (Inside the US) 1 800-333-7638 (Inside the US) 1 510-486-7600 (Globally) 1 510-486-7607 (Globally) Report Network Problems: trouble@es.net Provide Web Site Feedback: info@es.net Supercomputers Capture Turbulence in the Solar Wind Berkeley Lab visualizations could help scientists forecast destructive space weather December 16, 2013 | Tags: ESnet News, National Energy Research Scientific Computing Linda Vu, +1 510 495 2402, lvu@lbl.gov eddies1.jpg This visualization zooms in on current sheets revealing the "cascade of turbulence" in the solar wind occurring down to electron scales. This is

192

Boundary Plasma Turbulence Simulations for Tokamaks  

SciTech Connect

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

193

Turbulent Density Spectrum in Solar Wind Plasma  

E-Print Network (OSTI)

The density fluctuation spectrum in the solar wind reveals a Kolmogorov-like scaling with a spectral slope of -5/3 in wavenumber space. The energy transfer process in the magnetized solar wind, characterized typically by MHD turbulence, over extended length-scales remains an unresolved paradox of modern turbulence theories, raising the question of how a compressible magnetofluid exhibits a turbulent spectrum that is characteristic of an incompressible hydrodynamic fluid. To address these questions, we have undertaken three-dimensional time dependent numerical simulations of a compressible magnetohydrodynamic fluid describing super-Alfv\\'enic, supersonic and strongly magnetized plasma fluid. It is shown that a Kolmogorov-like density spectrum can develop by plasma motions that are dominated by Alfv\\'enic cascades whereas compressive modes are dissipated.

Shaikh, Dastgeer

2009-01-01T23:59:59.000Z

194

Turbulent Spectra in the Solar Wind Plasma  

E-Print Network (OSTI)

Observations of interstellar scintillations at radio wavelengths reveal a Kolmogorov-like scaling of the electron density spectrum with a spectral slope of -5/3 over six decades in wavenumber space. A similar turbulent density spectrum in the solar wind plasma has been reported. The energy transfer process in the magnetized solar wind plasma over such extended length-scales remains an unresolved paradox of modern turbulence theories raising the especially intriguing question of how a compressible magnetized solar wind exhibits a turbulent spectrum that is a characteristic of an incompressible hydrodynamic fluid. To address these questions, we have undertaken three-dimensional time dependent numerical simulations of a compressible magnetohydrodynamic fluid describing super-Alfv\\'enic, supersonic and strongly magnetized plasma. It is shown that the observed Kolmogorov-like (-5/3) spectrum can develop in the solar wind plasma by supersonic plasma motions that dissipate into highly subsonic motion that passively ...

Shaikh, Dastgeer

2009-01-01T23:59:59.000Z

195

Statistical theory of turbulent incompressible multimaterial flow  

Science Conference Proceedings (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

196

Turbulence-Induced Instabilities in EP and QGP  

E-Print Network (OSTI)

Polarization properties of turbulent stochastically inhomogeneous ultrarelativistic QED plasma are studied. It is shown that the sign of nonlinear turbulent Landau damping corresponds to an instability of the spacelike modes and, for sufficiently large turbulent fields, to an actual instability of a system.

Martin Kirakosyan; Andrei Leonidov; Berndt Muller

2012-12-28T23:59:59.000Z

197

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

SciTech Connect

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

198

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

E-Print Network (OSTI)

The technical feasibility of hypersonic flight (i.e., re-entry, hypersonic flight vehicles, cruise missiles, etc.) hinges on our ability to understand, predict, and control the transport of turbulence in the presence of non-equilibrium effects. A theoretical analysis of the governing equations suggests a mechanism by which fluctuations in internal energy are coupled to the transport of turbulence. Numerical studies of these flows have been conducted, but limited computational power results in reduced fidelity. Experimental studies are exceedingly rare and, consequently, experimental data available to build and evaluate turbulence models is nearly non-existent. The Decaying Mesh Turbulence (DMT) facility was designed and constructed to generate a fundamental decaying mesh turbulent flow field with passive grids. Vibrational non-equilibrium was achieved via a capacitively-coupled radio-frequency (RF) plasma discharge which required an operating pressure of 30 Torr. The flow velocity was 30 m/s. Data was recorded with each grid at multiple plasma powers (Off, 150 W, and 300 W). Over two terabytes of highly resolved (3,450 image pairs) two-dimensional particle image velocimetry (PIV) was acquired and archived. Temperature measurements were carried out using coherent anti-Stokes Raman spectroscopy (CARS). The primary objective of this study was to answer 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. The trends observed agree with those expected based on an analysis of the Reynolds stress transport equations, which provides confidence in transport equation-based modeling. A non-trivial reduction (~30%) in the decay rate downstream of the 300 W plasma discharge was observed. The data also show that the decay of TKE downstream of the plasma discharge was delayed (~20% downstream shift). In addition, the thermal non-equilbrium was observed to have no effect on the transverse stress. This suggests that, for this flow, the energy dilatation terms are small and unaffected by the plasma discharge, which simplifies modeling.

Fuller, T. J.

2009-08-01T23:59:59.000Z

199

Atmospheric Gravity Waves and Aircraft Turbulence Encounters  

Science Conference Proceedings (OSTI)

We describe aircraft turbulence-atmospheric gravity wave events which occurred during a 2-day period over the Continental Divide. The waves are observed by two microbarograph networks an each side of the divide and last for several hours at a ...

A. J. Bedard Jr.; F. Canavero; F. Einaudi

1986-12-01T23:59:59.000Z

200

Cup Anemometer Behavior in Turbulent Environments  

Science Conference Proceedings (OSTI)

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

Leif Kristensen

1998-02-01T23:59:59.000Z

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

Formation of Jets by Baroclinic Turbulence  

Science Conference Proceedings (OSTI)

Turbulent fluids are frequently observed to spontaneously self-organize into large spatial-scale jets; geophysical examples of this phenomenon include the Jovian banded winds and the earth’s polar-front jet. These relatively steady large-scale ...

Brian F. Farrell; Petros J. Ioannou

2008-11-01T23:59:59.000Z

202

Turbulence Characteristics in a Tidal Channel  

Science Conference Proceedings (OSTI)

A broadband ADCP and a moored microstructure instrument (TAMI) were deployed in a tidal channel of 30-m depth and with peak speeds of 1 m s?1. The measurements enable us to derive profiles of stress, turbulent kinetic energy (TKE), the rate of ...

Youyu Lu; Rolf G. Lueck; Daiyan Huang

2000-05-01T23:59:59.000Z

203

Shock wave / turbulent boundary layer interactions  

Science Conference Proceedings (OSTI)

This visualization shows the results of the simulation of a Mach 4 flow into two cone nosed cylindrical bodies adjacent to a flat plate. The analysis was computed with a Reynolds Averaged Navier Stokes (RANS) code utilizing a Spalart-Allmaras Turbulent ... Keywords: CFD, blender, raytracing, scientific visualization, visit, volume rendering

Michael A. Matheson; Allan D. Grosvenor; Alexander A. Zheltovodov

2011-11-01T23:59:59.000Z

204

Wavelet Turbulence for Fluid Simulation Theodore Kim  

E-Print Network (OSTI)

in the running time. We instead propose an algorithm that generates small-scale fluid de- tail procedurally. We of the key results of Kolmogorov the- ory is that the energy spectrum of a turbulent fluid approaches a five spectra [Perrier et al. 1995], and the sub- stitution is common in fluid dynamics [Farge et al. 1996

California at Santa Barbara, University of

205

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 ther...

Howes, G G

2007-01-01T23:59:59.000Z

206

Premixed turbulent combustion to opposed streams  

DOE Green Energy (OSTI)

Premixed turbulent combustion in opposed streams has been studied experimentally by the use of two component laser doppler aneomometry. This flow geometry is part of a class of stagnating flows used to study turbulent combustion in recent years. It does not involve any surface near the flames because of the flow symmetry thus circumventing many of the effects of flame surface interaction. The mean non-reacting flow is found to be self-similar for all the conditions studied in this and the stagnation plate configuration. A homogeneous region of plane straining is produced in the vicinity of the stagnation and there is a strong interaction between the turbulence in the flow and the mean straining which can increase the rms velocity as the flow stagnates. The reacting flow fields are found to be symmetric about the free stagnation point. The traverses of mean axial velocity in the stagnation streamlines for reaction flows are not dramatically different from the non-reaction flows. These results differ from turbulent combustion experiments where the flow is stagnated by a flat plate. The extinction limits was studied for propane:air mixtures. 11 refs.

Kostiuk, L.W.; Cheng, R.K.

1992-03-01T23:59:59.000Z

207

Chaotic radiation/turbulence interactions in flames  

SciTech Connect

In this paper, the authors present a review of their recent efforts to model chaotic radiation-turbulence interactions in flames. The main focus is to characterize soot volume fraction fluctuations in turbulent diffusion flames, as they strongly contribute to these interaction. The approach is based on the hypothesis that the fluctuations of properties in turbulent flames are deterministic in nature, rather than random. The authors first discuss the theoretical details and then they briefly outline the experiments conducted to measure the scattered light signals from fluctuating soot particles along the axis of an ethylene-air diffusion flame. They compare the power spectra and time series obtained from experiments against the ad-hoc and rigorous models derived using a series of logistic maps. These logistic maps can be used in simulation of the fluctuations in these type of flames, without extensive computational effort or sacrifice of physical detail. Availability of accurate models of these kinds allows investigation of radiation-turbulence interactions at a more fundamental level than it was previously possible.

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

1998-11-01T23:59:59.000Z

208

LES algorithm for turbulent reactive flows simulation  

Science Conference Proceedings (OSTI)

The paper presents the development and implementation of a Large Eddy Simulation numerical algorithm for simulating turbulent reactive flows. The numerical algorithm is based on a 5 step modified Runge - Kutta numerical scheme with a dual time stepping ... Keywords: Runge - Kutta numerical scheme, large eddy simulation, linear eddy model

Ionut Porumbel; Cristian Cârl?nescu; Florin Gabriel Florean; Constantin Eusebiu Hritcu

2010-10-01T23:59:59.000Z

209

Petascale Direct Numerical Simulations of Turbulent Channel Flow  

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

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

210

Compressible Turbulence and Interactions with Shock Waves and Material  

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

Compressible Turbulence Compressible Turbulence and Interactions with Shock Waves and Material Interfaces Compressible Turbulence and Interactions with Shock Waves and Material Interfaces Lele.jpg Alternate Title: High-fidelity simulations of supersonic turbulent mixing and combustion Key Challenges: Direct numerical simulation (DNS) of isotropic turbulence interacting with a normal shock wave and turbulent multi-material mixing in the Richtmyer-Meshkov instability (RMI) Why it Matters: Shock/turbulence interaction is a fundamental phenomenon in fluid mechanics that occurs in a wide range of interesting problems in various disciplines, including supernova explosions, inertial confinement fusion, hypersonic flight and propulsion, and shock wave lithotripsy. Accomplishments: A novel solution-adaptive algorithm that applies different

211

Literature Review of Airflow Fluid Characteristics and their Impact on Human Thermal Comfort  

E-Print Network (OSTI)

Airflow dynamics significantly impact indoor thermal environment and human thermal comfort. Studies on the effects of airflow fluctuations on thermal comfort mainly focus on the effects of turbulence intensity and fluctuation frequency. The fluctuant characteristics of natural wind and mechanical wind are obviously different. However, the fluctuant characteristics of mechanical wind can shift to those of natural wind in some conditions. With the development of turbulence statistical theory, chaos and fractal theory, researchers began to use these theories to describe the structural characteristics of the fluctuating airflow in different environments or by different generating sources. The results of studies on airflow fluctuation and thermal environment are reviewed in this paper from two aspects: 1) the effect of the airflow fluctuations on thermal comfort, and 2) the physical structure of airflow fluctuations. This paper first reviews these achievements, and then summarizes studies conducted at Tsinghua University.

Zhao, R.; Zhang, Y.; Yu, N.; Di, H.

2006-01-01T23:59:59.000Z

212

Thermal hydraulics development for CASL  

SciTech Connect

This talk will describe the technical direction of the Thermal-Hydraulics (T-H) Project within the Consortium for Advanced Simulation of Light Water Reactors (CASL) Department of Energy Innovation Hub. CASL is focused on developing a 'virtual reactor', that will simulate the physical processes that occur within a light-water reactor. These simulations will address several challenge problems, defined by laboratory, university, and industrial partners that make up CASL. CASL's T-H efforts are encompassed in two sub-projects: (1) Computational Fluid Dynamics (CFD), (2) Interface Treatment Methods (ITM). The CFD subproject will develop non-proprietary, scalable, verified and validated macroscale CFD simulation tools. These tools typically require closures for their turbulence and boiling models, which will be provided by the ITM sub-project, via experiments and microscale (such as DNS) simulation results. The near-term milestones and longer term plans of these two sub-projects will be discussed.

Lowrie, Robert B [Los Alamos National Laboratory

2010-12-07T23:59:59.000Z

213

The Evolving Magnetic Scales of the Outer Solar Atmosphere and Their Potential Impact on Heliospheric Turbulence  

E-Print Network (OSTI)

The presence of turbulent phenomena in the outer solar atmosphere is a given. However, because we are reduced to remotely sensing the atmosphere of a star with instruments of limited spatial and/or spectral resolution, we can only infer the physical progression from macroscopic to microscopic phenomena. Even so, we know that many, if not all, of the turbulent phenomena that pervade interplanetary space have physical origins at the Sun and so in this brief article we consider some recent measurements which point to sustained potential source(s) of heliospheric turbulence in the magnetic and thermal domains. In particular, we look at the scales of magnetism that are imprinted on the outer solar atmosphere by the relentless magneto-convection of the solar interior and combine state-of-the-art observations from the Solar Dynamics Observatory (SDO) and the Coronal Multi-channel Polarimeter (CoMP) which are beginning to hint at the origins of the wave/plasma interplay prevalent closer to the Earth. While linking th...

McIntosh, Scott W; Threlfall, James; De Moortel, Ineke; Leamon, Robert J; Tian, Hui

2013-01-01T23:59:59.000Z

214

Thermal laminarization of a stratified pipe flow  

SciTech Connect

The present work constitutes a new program that grew out of a scoping assessment by ANL to determine the propensity for pipe stratification to occur in the reactor outlet nozzles and hot-leg piping of a generic LMFBR during events producing reverse pipe flow. This paper focuses on the role that thermal buoyancy plays relative to being able to laminarize a turbulent stratified shear zone in a horizontal pipe. The preceeding can influence the behavior of a pipe stratified-backflow-recirculation zone (cold plenum water down into the hot pipe flow) which developes as the result of a temperature difference between the pipe flow and the plenum.

Oras, J.J.; Kasza, K.E.

1984-01-01T23:59:59.000Z

215

Cosmic ray propagation in galactic turbulence  

E-Print Network (OSTI)

We revisit propagation of galactic cosmic rays in light of recent advances in cosmic ray diffusion theory in realistic interstellar turbulence. We use tested model of turbulence in which it has been shown that fast modes dominate scattering of cosmic rays. As a result, propagation becomes inhomogeneous and environment dependent. By adopting the formalism of the nonlinear theory (NLT) developed by Yan & Lazarian (2008), we calculate diffusion of cosmic rays self-consistently from first principles. We assume a two-phase model for the Galaxy to account for different damping mechanisms of the fast modes, and we find that the energy dependence of the diffusion coefficient is mainly affected by medium properties. We show that it gives a correct framework to interpret some of the recent CR puzzles.

Evoli, Carmelo

2013-01-01T23:59:59.000Z

216

Causality detection and turbulence in fusion plasmas  

E-Print Network (OSTI)

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

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

2013-01-01T23:59:59.000Z

217

Turbulence in the Molecular Interstellar Medium  

E-Print Network (OSTI)

Abstract. The observational record of turbulence within the molecular gas phase of the interstellar medium is summarized. We briefly review the analysis methods used to recover the velocity structure function from spectroscopic imaging and the application of these tools on sets of cloud data. These studies identify a near-invariant velocity structure function that is independent of local the environment and star formation activity. Such universality accounts for the cloud-to-cloud scaling law between the global line-width and size of molecular clouds found by Larson (1981) and constrains the degree to which supersonic turbulence can regulate star formation. In addition, the evidence for large scale driving sources necessary to sustain supersonic flows is summarized.

Mark H. Heyer; Chris Brunt

2006-01-01T23:59:59.000Z

218

Three-dimensional electromagnetic strong turbulence. I. Scalings, spectra, and field statistics  

SciTech Connect

The first fully three-dimensional (3D) simulations of large-scale electromagnetic strong turbulence (EMST) are performed by numerically solving the electromagnetic Zakharov equations for electron thermal speeds {nu}{sub e} with {nu}{sub e}/c{>=}0.025. The results of these simulations are presented, focusing on scaling behavior, energy density spectra, and field statistics of the Langmuir (longitudinal) and transverse components of the electric fields during steady-state strong turbulence, where multiple wave packets collapse simultaneously and the system is approximately statistically steady in time. It is shown that for {nu}{sub e}/c > or approx. 0.17 strong turbulence is approximately electrostatic and can be explained using the electrostatic two-component model. For v{sub e}/c > or approx. 0.17 the power-law behaviors of the scalings, spectra, and field statistics differ from the electrostatic predictions and results because {nu}{sub e}/c is sufficiently high to allow transverse modes to become trapped in density wells. The results are compared with those of past 3D electrostatic strong turbulence (ESST) simulations and 2D EMST simulations. For number density perturbations, the scaling behavior, spectra, and field statistics are shown to be only weakly dependent on {nu}{sub e}/c, whereas the Langmuir and transverse scalings, spectra, and field statistics are shown to be strongly dependent on {nu}{sub e}/c. Three-dimensional EMST is shown to have features in common with 2D EMST, such as a two-component structure and trapping of transverse modes which are dependent on {nu}{sub e}/c.

Graham, D. B.; Robinson, P. A.; Cairns, Iver H. [School of Physics, University of Sydney, New South Wales 2006 (Australia); Skjaeraasen, O. [ProsTek, Institute for Energy Technology, P.O. Box 40, N-2027 Kjeller (Norway)

2011-06-15T23:59:59.000Z

219

Gravitational Runaway and Turbulence Driving in Star-Gas Galactic Disks  

E-Print Network (OSTI)

Galactic disks consist of both stars and gas. The gas is more dynamically responsive than the stars, and strongly nonlinear structures and velocities can develop in the ISM even while stellar surface density perturbations remain fractionally small. We use 2D numerical simulations to explore formation of bound clouds and turbulence generation in the gas of two-component galactic disks. We represent the stars with collisionless particles and follow their orbits using a PM method, and treat the gas as an isothermal, unmagnetized fluid. The two components interact through a combined gravity. Using stellar parameters typical of mid-disk conditions, we find that models with gaseous Toomre parameter Q_g gas-only models, indicating that the destabilizing effect of live stars is offsets the reduced self-gravity of thick disks. This result is also consistent with empirical studies showing that star formation is suppressed when Q_g > 1-2. The bound gaseous clouds that form have mass 6x10^7 Msun each; these represent superclouds that would subsequently fragment into GMCs. Self-gravity and sheared rotation also interact to drive turbulence in the gas when Q_g > Q_c. This turbulence is anisotropic, with more power in sheared than compressive motions. The gaseous velocity dispersion is ~ 0.6 times the thermal speed when Q_g ~ Q_c. This suggests that gravity is important in driving ISM turbulence in many spiral galaxies, since the low efficiency of star formation naturally leads to a state of marginal instability.

Woong-Tae Kim; Eve C. Ostriker

2007-01-26T23:59:59.000Z

220

Cascade and Damping of Alfvén-Cyclotron Fluctuations: Application to Solar Wind Turbulence Spectrum  

E-Print Network (OSTI)

With the diffusion approximation, we study the cascade and damping of Alfv\\'{e}n-cyclotron fluctuations in solar plasmas numerically. Motivated by wave-wave couplings and nonlinear effects, we test several forms of the diffusion tensor. For a general locally anisotropic and inhomogeneous diffusion tensor in the wave vector space, the turbulence spectrum in the inertial range can be fitted with power-laws with the power-law index varying with the wave propagation direction. For several locally isotropic but inhomogeneous diffusion coefficients, the steady-state turbulence spectra are nearly isotropic in the absence of damping and can be fitted by a single power-law function. However, the energy flux is strongly polarized due to the inhomogeneity that leads to an anisotropic cascade. Including the anisotropic thermal damping, the turbulence spectrum cuts off at the wave numbers, where the damping rates become comparable to the cascade rates. The combined anisotropic effects of cascade and damping make this cutoff wave number dependent on the wave propagation direction, and the propagation direction integrated turbulence spectrum resembles a broken power-law, which cuts off at the maximum of the cutoff wave numbers or the $^4$He cyclotron frequency. Taking into account the Doppler effects, the model can naturally reproduce the broken power-law wave spectra observed in the solar wind and predicts that a higher break frequency is aways accompanied with a greater spectral index change that may be caused by the increase of the Alfv\\'{e}n Mach number, the reciprocal of the plasma beta, and/or the angle between the solar wind velocity and the mean magnetic field. These predictions can be tested by future observations.

Yan Wei Jiang; Siming Liu; Vahé Petrosian; Christopher L. Fryer

2008-02-07T23:59:59.000Z

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

A Baroclinic Model of turbulent dusty flows  

SciTech Connect

The problem considered here is the numerical simulation of the turbulent dusty flow induced by explosions over soil surfaces. Some of the unresolved issues are: (1) how much dust is scoured from such surfaces; (2) where does the dust go in the boundary layer; (3) what is the dusty boundary layer height versus time; (4) what are the dusty boundary layer profiles; (5) how much of the dust mass becomes entrained into the dust stem; and (6) where does the dust go in the buoyant cloud? The author proposes a Baroclinic Model for flows with large density variations that actually calculates the turbulent mixing and transport of dust on an adaptive grid. The model is based on the following idealizations: (1) a loose dust bed; (2) an instantaneous shock fluidization of the dust layer; (3) the dust and air are in local equilibrium (so air viscosity enforces the no-slip condition); (4) the dust-air mixture is treated as a continuum dense fluid with zero viscosity; and (5) the turbulent mixing is dominated by baroclinically-generated vorticity. These assumptions lead to an inviscid set of conservation laws for the mixture, which are solved by means of a high-order Godunov algorithm for gasdynamics. Adaptive Mesh Refinement (AMR) is used to capture the turbulent mixing processes on the grid. One of the unique characteristics of these flows is that mixing occurs because vorticity is produced by an inviscid, baroclinic mechanism. A number of examples are presented to illustrate these baroclinic effects including shock interactions with dense-gas layers and dust beds, and dusty wall jets of airblast precursors. The conclusion of these studies is that dusty boundary layers grow because of mass entrainment from the fluidized bed (and not because of viscous wall drag) as proven by the Mass Integral Equation.

Kuhl, A.L.

1992-04-01T23:59:59.000Z

222

Displacement speeds in turbulent premixed flame simulations  

SciTech Connect

The theory of turbulent premixed flames is based on acharacterization of the flame as a discontinuous surface propagatingthrough the fluid. The displacement speed, defined as the local speed ofthe flame front normal to itself, relative to the unburned fluid,provides one characterization of the burning velocity. In this paper, weintroduce a geometric approach to computing displacement speed anddiscuss the efficacy of the displacement speed for characterizing aturbulent flame.

Day, Marcus S.; Shepherd, Ian G.; Bell, J.; Grcar, Joseph F.; Lijewski, Michael J.

2007-07-01T23:59:59.000Z

223

The Statistics of Supersonic Isothermal Turbulence  

E-Print Network (OSTI)

We present results of large-scale three-dimensional simulations of supersonic Euler turbulence with the piecewise parabolic method (PPM) and multiple grid resolutions up to 2048^3 points. Our numerical experiments describe non-magnetized driven turbulent flows with an isothermal equation of state and an rms Mach number of 6. We discuss numerical resolution issues and demonstrate convergence, in a statistical sense, of the inertial range dynamics in simulations on grids larger than 512^3 points. The simulations allowed us to measure the absolute velocity scaling exponents for the first time. The inertial range velocity scaling in this strongly compressible regime deviates substantially from the incompressible Kolmogorov laws. The slope of the velocity power spectrum, for instance, is -1.95 compared to -5/3 in the incompressible case. The exponent of the third-order velocity structure function is 1.28, while in incompressible turbulence it is known to be unity. We propose a natural extension of Kolmogorov's phe...

Kritsuk, Alexei G; Padoan, Paolo; Wagner, Rick

2007-01-01T23:59:59.000Z

224

Closure in Turbulence from first principles  

E-Print Network (OSTI)

It has been recently demonstrated, [3], that according to the principle of release of constraints, absence of shear stresses in the Euler equations must be compensated by additional degrees of freedom, and that led to a Reynolds-type enlarged Euler equations (EE equations) with a doublevalued velocity field that do not require any closures. In the first part of the paper, the theory is applies to turbulent mixing and illustrated by propagation of mixing zone triggered by a tangential jump of velocity. A comparison of the proposed solution with the Prandtl's solutions is performed and discussed. In the second part of the paper, a semi-viscose version of the Navier-Stokes equations is introduced. The model does not require any closures since the number of equations is equal to the number of unknowns. Special attention is paid to transition from laminar to turbulent state. The analytical solution for this transition demonstrates the turbulent mean velocity profile that qualitatively similar to the celebrated logarithmic law.

Michail Zak

2012-12-26T23:59:59.000Z

225

Coherent and turbulent fluctuations in TFTR  

SciTech Connect

Classification of the sawteeth observed in the TFTR tokamak has been carried out to highlight the differences between the many types observed. Three types of sawteeth are discussed: ''simple,'' ''small,'' and ''compound.'' During the enhanced confinement discharges on TFTR, sawteeth related to q = 1 are usually not present, but a sawtooth-like event is sometimes observed. ..beta.. approaches the Troyon limit only at low q/sub cyl/ with a clear reduction of achievable ..beta../sub n/ at high q/sub cyl/. This suggests that a ..beta../sub p/ limit, rather than the Troyon-Gruber limit, applies at high q/sub cyl/ in the enhanced confinement discharges. These discharges also reach the stability boundary for n ..-->.. infinity ideal MHD ballooning modes. Turbulence measurements in the scrape-off region with Langmuir and magnetic probes show strong edge density turbulence n-tilde/n = 0.3 - 0.5, with weak magnetic turbulence B-tilde/sub theta/B/sub theta/ > 5 x 10/sup -6/ measured at the wall, but these measurements are very sensitive to local edge conditions.

McGuire, K.; Arunasalam, V.; Bell, M.G.; Bitter, M.; Blanchard, W.R.; Bretz, N.L.; Budny, R.; Bush, C.E.; Callen, J.D.; Chance, M.

1987-04-01T23:59:59.000Z

226

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

227

INTERMITTENCE OF THE MAP OF THE KINETIC SUNYAEV-ZEL'DOVICH EFFECT AND TURBULENCE OF THE INTERGALACTIC MEDIUM  

Science Conference Proceedings (OSTI)

We investigate the possibility of detecting the turbulent state of the intergalactic medium (IGM) with the kinetic Sunyaev-Zel'dovich (kSZ) effect. Being sensitive to the divergence-free component of the momentum field of the IGM, the kSZ effect might be used to probe the vorticity of the turbulent IGM. With cosmological hydrodynamical simulation in the concordance {Lambda}CDM universe, we find that the structure functions of two-dimensional kSZ maps show strong intermittence, and the intermittent exponents follow a law similar to the She-Leveque scaling formula of fully developed turbulence. We also find that the intermittence is weak in the maps of thermal Sunyaev-Zel'dovich (tSZ) effect. Nevertheless, the superposition of the kSZ and tSZ effects still contain significant intermittence. We conclude that the turbulent behavior of the IGM may be revealed by the observation of the SZ effect on angular scales equal to or less than 0.5 arcmin, corresponding to the multipole parameter l {>=} 2 x 10{sup 4}.

Zhu Weishan; Feng Longlong [Purple Mountain Observatory, Nanjing, 210008 (China); Fang Lizhi [Department of Physics, University of Arizona, Tucson, AZ 85721 (United States)

2011-06-10T23:59:59.000Z

228

Thermal Properties  

Science Conference Proceedings (OSTI)

Table 12   Thermal conductivities of polymers and other materials...40,000 2.8 Aluminum 24,000 1.7 Steel 5000 0.35 Granite 350 0.02 Crown glass (75 wt% silica) 90 0.006 Source: Ref 4...

229

Weak and strong regimes of incompressible magnetohydrodynamic turbulence  

Science Conference Proceedings (OSTI)

It is shown that in the framework of the weak turbulence theory, the autocorrelation and cascade time scales are always of the same order of magnitude. This means that, contrary to the general belief, any model of turbulence that implies a large number of collisions among wave packets for an efficient energy cascade (such as the Iroshnikov-Kraichnan model) is not compatible with the weak turbulence theory.

Gogoberidze, G. [Centre for Plasma Astrophysics, K. U. Leuven, Celestijnenlaan 200B, 3001 Leuven (Belgium); Georgian National Astrophysical Observatory, 2a Kazbegi Ave., 0160 Tbilisi, Georgia (United States); Mahajan, S. M. [Institute for Fusion Studies, University of Texas at Austin, Austin, Texas 78712 (United States); Poedts, S. [Centre for Plasma Astrophysics, K. U. Leuven, Celestijnenlaan 200B, 3001 Leuven (Belgium)

2009-07-15T23:59:59.000Z

230

Spatial redistribution of turbulent and mean kinetic energy  

Science Conference Proceedings (OSTI)

The turbulent spatial redistribution of turbulent and mean kinetic energy and its exchange is investigated in the framework of an K-{epsilon} model in a magnetized plasma column. The kinetic energy is transferred from the turbulence into the zonal flow around the shear layer. The Reynolds stress profile adjusts to the shear layer, which results in a transport of mean kinetic energy from the region around the shear layer into the shear layer.

Manz, P.; Xu, M.; Fedorczak, N.; Thakur, S. C.; Tynan, G. R. [Center for Momentum Transport and Flow Organization,University of California at San Diego, San Diego, California 92093 (United States); Center for Energy Research, University of California at San Diego, San Diego, California 92093 (United States)

2012-01-15T23:59:59.000Z

231

Measurement and theory of turbulence in RR Lyrae  

SciTech Connect

CORAVEL observations of time-dependent turbulence in RR Lyrae are presented. Variation in the width of the mean velocity correlation function implies turbulent velocities that peak at 10 to 15 km/sec for a brief interval of phase near minimum radius. Comparison with a nonlinear pulsation model shows that these amplitudes of the turbulent velocity are expected near the hydrogen ionization zone, again only near minimum radius.

Benz, W.; Stellingwerf, R.F.

1985-01-01T23:59:59.000Z

232

Collisionless inter-species energy transfer and turbulent heating in drift wave turbulence  

Science Conference Proceedings (OSTI)

We reconsider the classic problems of calculating 'turbulent heating' and collisionless inter-species transfer of energy in drift wave turbulence. These issues are of interest for low collisionality, electron heated plasmas, such as ITER, where collisionless energy transfer from electrons to ions is likely to be significant. From the wave Poynting theorem at steady state, a volume integral over an annulus r{sub 1}heating as {integral}{sub r{sub 1}} {sup r{sub 2}} dr=-S{sub r}|{sub r{sub 1}{sup r{sub 2}}}{ne}0. Here S{sub r} is the wave energy density flux in the radial direction. Thus, a wave energy flux differential across an annular region indeed gives rise to a net heating, in contrast to previous predictions. This heating is related to the Reynolds work by the zonal flow, since S{sub r} is directly linked to the zonal flow drive. In addition to net heating, there is inter-species heat transfer. For collisionless electron drift waves, the total turbulent energy source for collisionless heat transfer is due to quasilinear electron cooling. Subsequent quasilinear ion heating occurs through linear ion Landau damping. In addition, perpendicular heating via ion polarization currents contributes to ion heating. Since at steady state, Reynolds work of the turbulence on the zonal flow must balance zonal flow frictional damping ({approx}{nu}{sub ii}{sup 2}{approx}|(e{phi}(tilde sign)/T)|{sup 4}), it is no surprise that zonal flow friction appears as an important channel for ion heating. This process of energy transfer via zonal flow has not previously been accounted for in analyses of energy transfer. As an application, we compare the rate of turbulent energy transfer in a low collisionality plasma with the rate of the energy transfer by collisions. The result shows that the collisionless turbulent energy transfer is a significant energy coupling process for ITER plasma.

Zhao, L. [Center for Astrophysics and Space Sciences and Department of Physics, University of California at San Diego, La Jolla, California 92093-0424 (United States); Diamond, P. H. [Center for Astrophysics and Space Sciences and Department of Physics, University of California at San Diego, La Jolla, California 92093-0424 (United States); WCI Center for Fusion Theory, National Fusion Research Institute, Gwahangno113, Yuseong-gu, Daejeon 305-333 (Korea, Republic of)

2012-08-15T23:59:59.000Z

233

On the Mellor–Yamada Turbulence Closure Scheme: The Surface Boundary Condition for q2  

Science Conference Proceedings (OSTI)

A numerical model that uses a level-2½ turbulence closure scheme is used to compare two boundary conditions for the turbulent energy at the air–sea interface. One boundary condition, the most commonly used, sets the turbulent kinetic energy ...

Michael W. Stacey; Stephen Pond

1997-10-01T23:59:59.000Z

234

Applicability of Boussinesq approximation in a turbulent fluid with constant properties  

E-Print Network (OSTI)

The equations of motion describing buoyant fluids are often simplified using a set of approximations proposed by J. Boussinesq one century ago. To resume, they consist in assuming constant fluid properties, incompressibility and conservation of calories during heat transport. Assuming fulfilment of the first requirement (constant fluid properties), we derive a set of 4 criteria for assessing the validity of the two other requirements in turbulent Rayleigh-B\\'enard convection. The first criterion $\\alpha \\Delta \\ll 1 $ simply results from the incompressibility condition in the thermal boundary layer ($\\alpha$ and $\\Delta$ are the thermal expansion coefficient and the temperature difference driving the flow). The 3 other criteria are proportional or quadratic with the density stratification or, equivalently with the temperature difference resulting from the adiabatic gradient across the cell $\\Delta_{h}$. Numerical evaluations with air, water and cryogenic helium show that most laboratory experiments are free f...

Roche, Philippe-Emmanuel P -E

2007-01-01T23:59:59.000Z

235

Gyrokinetic simulations of turbulent transport in fusion plasmas  

Science Conference Proceedings (OSTI)

This is the final report for a DOE award that was targeted at understanding and simulating turbulence and transport in plasma fusion devices such as tokamaks.

Rogers, Barrett Neil [Dartmouth] [Dartmouth

2013-05-30T23:59:59.000Z

236

Gravitational radiation from primordial helical inverse cascade magnetohydrodynamic turbulence  

SciTech Connect

We consider the generation of gravitational waves by primordial helical inverse-cascade magnetohydrodynamic (MHD) turbulence produced by bubble collisions at the electroweak phase transition. We extend the previous study 1 by considering both currently discussed models of MHD turbulence. For popular electroweak phase transition parameter values, the generated gravitational wave spectrum is only weakly dependent on the MHD turbulence model. Compared with the unmagnetized electroweak phase transition case, the spectrum of MHD-turbulence-generated gravitational waves peaks at lower frequency with larger amplitude and can be detected by the proposed Laser Interferometer Space Antenna.

Kahniashvili, Tina [Department of Physics, Kansas State University, 116 Cardwell Hall, Manhattan, Kansas 66506 (United States); Department of Physics, Laurentian University, Ramsey Lake Road, Sudbury, ON P3E 2C6 (Canada); National Astrophysical Observatory, Ilia Chavchavadze State University, 2A Kazbegi Ave, Tbilisi, GE-0160 (Georgia); Campanelli, Leonardo [Dipartimento di Fisica, Universita di Bari, I-70126 Bari (Italy); INFN - Sezione di Bari, I-70126 Bari (Italy); Gogoberidze, Grigol [Department of Physics, Kansas State University, 116 Cardwell Hall, Manhattan, Kansas 66506 (United States); National Astrophysical Observatory, Ilia Chavchavadze State University, 2A Kazbegi Ave, Tbilisi, GE-0160 (Georgia); Centre for Plasma Astrophysics, K.U. Leuven, Celestijnenlaan 200B, 3001 Leuven (Belgium); Maravin, Yurii; Ratra, Bharat [Department of Physics, Kansas State University, 116 Cardwell Hall, Manhattan, Kansas 66506 (United States)

2008-12-15T23:59:59.000Z

237

Flashback, Blow out, Emissions and Turbulent Displacement Flame...  

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

driving physics relating turbulent flame speeds to flashback at conditions relevant to gas turbine engines. Testing was conducted in an optically accessible single nozzle...

238

Vertical stratified turbulent transport mechanism indicated by remote sensing  

E-Print Network (OSTI)

Satellite and shipboard data reveal the intermittent vertical information transport mechanism of turbulence and internal waves that mixes the ocean, atmosphere, planets and stars.

Gibson, Carl H; Bondur, Valery G

2007-01-01T23:59:59.000Z

239

Vertical stratified turbulent transport mechanism indicated by remote sensing  

E-Print Network (OSTI)

Satellite and shipboard data reveal the intermittent vertical information transport mechanism of turbulence and internal waves that mixes the ocean, atmosphere, planets and stars.

Carl H. Gibson; R. Norris Keeler; Valery G. Bondur

2007-12-02T23:59:59.000Z

240

Numerical Simulation of Electro-magnetic Turbulent Inhibitor ...  

Science Conference Proceedings (OSTI)

Numerical Modeling of Centrifugally Cast HSS Rolls · Numerical Simulation of Electro-magnetic Turbulent Inhibitor Technology in a Tundish · Optimizing the ...

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

First Mira Runs Break New Ground with Turbulence Simulations...  

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

First Mira Runs Break New Ground with Turbulence Simulations July 16, 2013 Printer-friendly version Shortly after Mira, the ALCF's new 10-petaflops supercomputer, entered...

242

Generalized similarity in finite range solar wind magnetohydrodynamic turbulence  

E-Print Network (OSTI)

Extended or generalized similarity is a ubiquitous but not well understood feature of turbulence that is realized over a finite range of scales. ULYSSES spacecraft solar polar passes at solar minimum provide \\textit{in situ} observations of evolving anisotropic magnetohydrodynamic turbulence in the solar wind under ideal conditions of fast quiet flow. We find a single generalized scaling function characterises this finite range turbulence and is insensitive to plasma conditions. The recent unusually inactive solar minimum -with turbulent fluctuations down by a factor of $\\sim 2$ in power- provides a test of this invariance.

Chapman, S C

2009-01-01T23:59:59.000Z

243

Experimental study on turbulent natural convection heat transfer in ...  

Science Conference Proceedings (OSTI)

Feb 16, 2010 ... ments are conducted to investigate flow and heat transfer ... turbulent region, the heat transfer deterioration occurs for a bubble flow rate Q = 33 ...

244

Experimental study of premixed flames in intense isotropic turbulence  

SciTech Connect

A methodology for investigating premixed turbulent flames propagating in intense isotropic turbulence has been developed. The burner uses a turbulence generator developed by Videto and Santavicca and the flame is stabilized by weak-swirl generated by air injectors. This set-up produces stable premixed turbulent flames under a wide range of mixture conditions and turbulence intensities. The experiments are designed to investigate systematically the changes in flame structures for conditions which can be classified as wrinkled laminar flames, corrugated flames and flames with distributed reaction zones. Laser Doppler anemometry and Rayleigh scattering techniques are used to determine the turbulence and scalar statistics. In the intense turbulence, the flames are found to produce very little changes in the mean and rams velocities. Their flame speed increase linearly with turbulence intensity as for wrinkled laminar flames. The Rayleigh scattering pdfs for flames within the distributed reaction zone regime are distinctly bimodal. The probabilities of the reacting states (i.e. contributions from within the reaction zone) is not higher than those of wrinkled laminar flame. These results show that there is no drastic changes in flame structures at Karlovitz number close to unity. This suggest that the Klimov-Williams criterion under-predicts the resilience of wrinkled flamelets to intense turbulence.

Bedat, B.; Cheng, R.K.

1994-04-01T23:59:59.000Z

245

Turbulence-Flame Interactions in Type Ia Supernovae  

E-Print Network (OSTI)

Turbulence-Flame Interactions in Type Ia Supernovae A. J.Normalised time (e) Normalised flame speed Normalised time (length scale (cm) Laminar flame width Gibson scale Cell

Aspden, Andrew J; Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 50A-1148, Berkeley, CA 94720 (Authors 1, 2 & 3); Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (Author 4); Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794 (Author 5)

2008-01-01T23:59:59.000Z

246

High Frequency Acoustic Wave Scattering From Turbulent Premixed Flames .  

E-Print Network (OSTI)

??This thesis describes an experimental investigation of high frequency acoustic wave scattering from turbulent premixed flames. The objective of this work was to characterize the… (more)

Narra, Venkateswarlu

2008-01-01T23:59:59.000Z

247

Analysis of the Wave Scattering From Turbulent Premixed Flame .  

E-Print Network (OSTI)

??A theoretical investigation of acoustic wave interactions with turbulent premixed flames was performed. Such interactions affect the characteristic unsteadiness of combustion processes, e.g., combustion instabilities.… (more)

Cho, Ju Hyeong

2006-01-01T23:59:59.000Z

248

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

249

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

250

Adaptive LES Methodology for Turbulent Flow Simulations  

Science Conference Proceedings (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

251

Experimental study of parametric dependence of electron-scale turbulence in a spherical tokamak  

Science Conference Proceedings (OSTI)

Electron-scale turbulence is predicted to drive anomalous electron thermal transport. However, experimental study of its relation with transport is still in its early stage. On the National Spherical Tokamak Experiment (NSTX), electron-scale density fluctuations are studied with a novel tangential microwave scattering system with high radial resolution of {+-}2 cm. Here, we report a study of parametric dependence of electron-scale turbulence in NSTX H-mode plasmas. The dependence on density gradient is studied through the observation of a large density gradient variation in the core induced by an edge localized mode (ELM) event, where we found the first clear experimental evidence of density gradient stabilization of electron-gyro scale turbulence in a fusion plasma. This observation, coupled with linear gyro-kinetic calculations, leads to the identification of the observed instability as toroidal electron temperature gradient (ETG) modes. It is observed that longer wavelength ETG modes, k{sub Up-Tack }{rho}{sub s} Less-Than-Or-Equivalent-To 10 ({rho}{sub s} is the ion gyroradius at electron temperature and k{sub Up-Tack} is the wavenumber perpendicular to local equilibrium magnetic field), are most stabilized by density gradient, and the stabilization is accompanied by about a factor of two decrease in electron thermal diffusivity. Comparisons with nonlinear ETG gyrokinetic simulations show ETG turbulence may be able to explain the experimental electron heat flux observed before the ELM event. The collisionality dependence of electron-scale turbulence is also studied by systematically varying plasma current and toroidal field, so that electron gyroradius ({rho}{sub e}), electron beta ({beta}{sub e}), and safety factor (q{sub 95}) are kept approximately constant. More than a factor of two change in electron collisionality, {nu}{sub e}{sup *}, was achieved, and we found that the spectral power of electron-scale turbulence appears to increase as {nu}{sub e}{sup *} is decreased in this collisonality scan. However, both linear and nonlinear simulations show no or weak dependence with the electron-ion collision frequency, {nu}{sup e/i}. Instead, other equilibrium parameters (safety factor, electron density gradient, for example) affect ETG linear growth rate and electron thermal transport more than {nu}{sup e/i} does. Furthermore, electron heat flux predicted by the simulations is found to have an order-of-magnitude spatial variation in the experimental measurement region and is also found to be much smaller than experimental levels except at one radial location we evaluated. The predicted electron heat flux is shown to be strongly anti-correlated with density gradient, which varies for a factor of three in the measurement region, which is in agreement with the density gradient dependence study reported in this paper.

Ren, Y.; Guttenfelder, W.; Kaye, S. M.; Mazzucato, E.; Bell, R. E.; Diallo, A.; LeBlanc, B. P. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Domier, C. W.; Lee, K. C. [University of California at Davis, Davis, California 95616 (United States); Smith, D. R. [University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Yuh, H. [Nova Photonics, Inc., Princeton, New Jersey 08540 (United States)

2012-05-15T23:59:59.000Z

252

Co-existence of whistler waves with kinetic Alfven wave turbulence for the high-beta solar wind plasma  

SciTech Connect

It is shown that the dispersion relation for whistler waves is identical for a high or low beta plasma. Furthermore, in the high-beta solar wind plasma, whistler waves meet the Landau resonance with electrons for velocities less than the thermal speed, and consequently, the electric force is small compared to the mirror force. As whistlers propagate through the inhomogeneous solar wind, the perpendicular wave number increases through refraction, increasing the Landau damping rate. However, the whistlers can survive because the background kinetic Alfven wave (KAW) turbulence creates a plateau by quasilinear (QL) diffusion in the solar wind electron distribution at small velocities. It is found that for whistler energy density of only {approx}10{sup -3} that of the kinetic Alfven waves, the quasilinear diffusion rate due to whistlers is comparable to KAW. Thus, very small amplitude whistler turbulence can have a significant consequence on the evolution of the solar wind electron distribution function.

Mithaiwala, Manish; Crabtree, Chris; Ganguli, Gurudas [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375-5346 (United States); Rudakov, Leonid [Icarus Research Inc., P.O. Box 30780, Bethesda, Maryland 20824-0780 (United States)

2012-10-15T23:59:59.000Z

253

TEMPEST. Transient 3-D Thermal-Hydraulic  

SciTech Connect

TEMPEST is a transient, three-dimensional, hydrothermal program that is designed to analyze a range of coupled fluid dynamic and heat transfer systems of particular interest to the Fast Breeder Reactor (FBR) thermal-hydraulic design community. The full three-dimensional, time-dependent equations of motion, continuity, and heat transport are solved for either laminar or turbulent fluid flow, including heat diffusion and generation in both solid and liquid materials. The equations governing mass, momentum, and energy conservation for incompressible flows and small density variations (Boussinesq approximation) are solved using finite-difference techniques. Analyses may be conducted in either cylindrical or Cartesian coordinate systems. Turbulence is treated using a two-equation model. Two auxiliary plotting programs, SEQUEL and MANPLOT, for use with TEMPEST output are included. SEQUEL may be operated in batch or interactive mode; it generates data required for vector plots, contour plots of scalar quantities, line plots, grid and boundary plots, and time-history plots. MANPLOT reads the SEQUEL-generated data and creates the hardcopy plots. TEMPEST can be a valuable hydrothermal design analysis tool in areas outside the intended FBR thermal-hydraulic design community.

Eyler, L.L. [Pacific Northwest Lab., Richland, WA (United States)

1992-01-31T23:59:59.000Z

254

The Statistics of Supersonic Isothermal Turbulence  

E-Print Network (OSTI)

We present results of large-scale three-dimensional simulations of supersonic Euler turbulence with the piecewise parabolic method and multiple grid resolutions up to 2048^3 points. Our numerical experiments describe non-magnetized driven turbulent flows with an isothermal equation of state and an rms Mach number of 6. We discuss numerical resolution issues and demonstrate convergence, in a statistical sense, of the inertial range dynamics in simulations on grids larger than 512^3 points. The simulations allowed us to measure the absolute velocity scaling exponents for the first time. The inertial range velocity scaling in this strongly compressible regime deviates substantially from the incompressible Kolmogorov laws. The slope of the velocity power spectrum, for instance, is -1.95 compared to -5/3 in the incompressible case. The exponent of the third-order velocity structure function is 1.28, while in incompressible turbulence it is known to be unity. We propose a natural extension of Kolmogorov's phenomenology that takes into account compressibility by mixing the velocity and density statistics and preserves the Kolmogorov scaling of the power spectrum and structure functions of the density-weighted velocity v=\\rho^{1/3}u. The low-order statistics of v appear to be invariant with respect to changes in the Mach number. For instance, at Mach 6 the slope of the power spectrum of v is -1.69, and the exponent of the third-order structure function of v is unity. We also directly measure the mass dimension of the "fractal" density distribution in the inertial subrange, D_m = 2.4, which is similar to the observed fractal dimension of molecular clouds and agrees well with the cascade phenomenology.

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

2007-04-29T23:59:59.000Z

255

Similarity Solutions for the Stratified Turbulent Rayleigh Problem  

Science Conference Proceedings (OSTI)

The type of stratified flow suggested by the Kantha Phillips and Azad experiment is examined analytically and shown to be a self-similar, turbulent flow which includes the well-documented fiat-plate, turbulent boundary-layer case. Some relevant ...

George Mellor; Paul T. Strub

1980-03-01T23:59:59.000Z

256

Verification of clear-air turbulence forecasts June 2002, KNMI  

E-Print Network (OSTI)

to increase potential energy. Under these conditions turbulence will increase in intensity until different weather conditions. It often occurs in relatively clear skies and is then referred to as clear-airVerification of clear-air turbulence forecasts A. Overeem June 2002, KNMI Technisch rapport #12

Stoffelen, Ad

257

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

258

Light reradiation in a parametrically turbulent laser plasma  

SciTech Connect

The intensity and spectrum of the light reradiated in a laser plasma are estimated from the theory of parametric turbulence. The possibility of determining the turbulence characteristics from the reradiation spectrum is discussed. It is suggested that the diffuse reflection observed experimentally is related to reradiation.

Krupnova, L.V.; Silin, V.P.; Tikhonchuk, V.T.

1979-03-01T23:59:59.000Z

259

High-Performance Computing and Visualization of Unsteady Turbulent Flows  

Science Conference Proceedings (OSTI)

The history of high-performance computing in turbulent flows is reviewed and their recent topics in industrial use are addressed. Special attention is paid to the validity of the method in flow visualization, and three-dimensional unsteady simulation ... Keywords: CAE, DNS, HPC, LES, turbulence

T. Kobayashi; M. Tsubokura; N. Oshima

2008-01-01T23:59:59.000Z

260

Identification of Wind Turbine Response to Turbulent Inflow Structures: Preprint  

DOE Green Energy (OSTI)

The National Renewable Energy Laboratory conducted an experiment to obtain detailed wind measurements and corresponding wind turbine measurements in order to establish a causal relationship between coherent turbulent structures and wind turbine blade fatigue loads. Data were collected for one entire wind season from October 2000 to May 2001. During this period, the wind turbine operated under atmospheric conditions that support the formation of coherent turbulent structures 31% of the time. Using the equivalent fatigue load parameter as a measure of wind turbine blade fatigue and using statistical measures of the turbulent fluctuations of the wind, general correlation between the turbulence and the wind turbine response is shown. Direct correlation cannot be resolved with 10-minute statistics for several reasons. Multiple turbulent structures can exist within a 10-minute record, and the equivalent fatigue load parameter is essentially a 10-minute statistic that cannot estimate turbine response to individual turbulent structures. Large-magnitude turbulent fluctuations in the form of instantaneous Reynolds stresses do not necessarily correspond directly to large-magnitude blade root moment amplitudes. Thus, additional work must be done to quantify the negative turbine response and to correlate this response to turbulent inflow parameters over time scales less than 10 minutes.

Hand, M. M.; Kelley, N. D.; Balas, M. J.

2003-06-01T23:59:59.000Z

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

On the Turbulent Mixing Length in the Oceanic Boundary Layer  

Science Conference Proceedings (OSTI)

Turbulence measurements from under drifting pack ice illustrate the distribution of turbulent mixing length in the well-mixed layer of the upper ocean. Mixing length (? ? K/u*, where K and u* are the local eddy viscosity and square root of ...

Miles G. Mcphee

1994-09-01T23:59:59.000Z

262

Nonperturbative models of intermittency in edge turbulence  

SciTech Connect

A theory of the probability distribution function (PDF) tails of the blob density in plasma edge turbulence is provided. A simplified model of the fast convective radial transport is used. The theoretically predicted PDF tails corroborate earlier measurements of edge transport, further confirming the strongly non-Gaussian feature of edge transport. It is found that increasing the cross-sectional spatial scale length (L{sub x} and L{sub y}) of the blob results in larger transport, whereas increasing the toroidal scale length (L{sub z}) decreases the PDF. The results imply that the PDF decreases for larger blob speed v{sub b}.

Anderson, Johan; Kim, Eun-jin [Department of Applied Mathematics, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom)

2008-12-15T23:59:59.000Z

263

SPECTRUM OF KINETIC-ALFVEN TURBULENCE  

Science Conference Proceedings (OSTI)

A numerical study of strong kinetic-Alfven turbulence at scales smaller than the ion gyroscale is presented, and a phenomenological model is proposed that argues that magnetic and density fluctuations are concentrated mostly in two-dimensional structures, which leads to their Fourier energy spectra E(k ){proportional_to}k {sup -8/3} , where k is the wavevector component normal to the strong background magnetic field. The results may provide an explanation for recent observations of magnetic and density fluctuations in the solar wind at sub-proton scales.

Boldyrev, Stanislav; Perez, Jean Carlos [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States)

2012-10-20T23:59:59.000Z

264

Rain initiation time in turbulent warm clouds  

E-Print Network (OSTI)

We present a mean-field model that describes droplet growth due to condensation and collisions and droplet loss due to fallout. The model allows for an effective numerical simulation. We study how the rain initiation time depends on different parameters. We also present a simple model that allows one to estimate the rain initiation time for turbulent clouds with an inhomogeneous concentration of cloud condensation nuclei. In particular, we show that over-seeding even a part of a cloud by small hygroscopic nuclei one can substantially delay the onset of precipitation.

Falkovich, G; Vucelja, M

2004-01-01T23:59:59.000Z

265

Rain initiation time in turbulent warm clouds  

E-Print Network (OSTI)

We present a mean-field model that describes droplet growth due to condensation and collisions and droplet loss due to fallout. The model allows for an effective numerical simulation. We study how the rain initiation time depends on different parameters. We also present a simple model that allows one to estimate the rain initiation time for turbulent clouds with an inhomogeneous concentration of cloud condensation nuclei. In particular, we show that over-seeding even a part of a cloud by small hygroscopic nuclei one can substantially delay the onset of precipitation.

G. Falkovich; M. G. Stepanov; M. Vucelja

2004-11-22T23:59:59.000Z

266

Visualizing Magneto-Rotational Instability and Turbulent Angular Momentum  

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

Turbulent Angular Momentum Transport Turbulent Angular Momentum Transport Magneto-Rotational Instability and Turbulent Angular Momentum Transport hydroentropyvisit0400.s.x2005.png In space, gases and other matter often form swirling disks around attracting central objects such as newly formed stars. The presence of magnetic fields can cause the disks to become unstable and develop turbulence, causing the disk material to fall onto the central object. This project will carry out large-scale simulations to test theories on how turbulence can develop in such a scenario. These simulations may provide insights into magnetically caused instabilities being studied on a smaller scale in laboratory experiments. In this image volume rendering has been used to visualize the time evolution of hydrodynamic entropy. The color

267

Gyrokinetic turbulence: a nonlinear route to dissipation through phase space  

E-Print Network (OSTI)

This paper describes a conceptual framework for understanding kinetic plasma turbulence as a generalized form of energy cascade in phase space. It is emphasized that conversion of turbulent energy into thermodynamic heat is only achievable in the presence of some (however small) degree of collisionality. The smallness of the collision rate is compensated by the emergence of small-scale structure in the velocity space. For gyrokinetic turbulence, a nonlinear perpendicular phase mixing mechanism is identified and described as a turbulent cascade of entropy fluctuations simultaneously occurring at spatial scales smaller than the ion gyroscale and in velocity space. Scaling relations for the resulting fluctuation spectra are derived. An estimate for the collisional cutoff is provided. The importance of adequately modeling and resolving collisions in gyrokinetic simulations is biefly discussed, as well as the relevance of these results to understanding the dissipation-range turbulence in the solar wind and the electrostatic microturbulence in fusion plasmas.

A. A. Schekochihin; S. C. Cowley; W. Dorland; G. W. Hammett; G. G. Howes; G. G. Plunk; E. Quataert; T. Tatsuno

2008-06-05T23:59:59.000Z

268

Lagrangian Frequency Spectrum as a Diagnostic for Magnetohydrodynamic Turbulence Dynamics  

SciTech Connect

For the phenomenological description of magnetohydrodynamic turbulence competing models exist, e.g., Boldyrev [Phys. Rev. Lett. 96, 115002 (2006)] and Gogoberidze [Phys. Plasmas 14, 022304 (2007)], which predict the same Eulerian inertial-range scaling of the turbulent energy spectrum although they employ fundamentally different basic interaction mechanisms. A relation is found that links the Lagrangian frequency spectrum with the autocorrelation time scale of the turbulent fluctuations {tau}{sub ac} and the associated cascade time scale {tau}{sub cas}. Thus, the Lagrangian energy spectrum can serve to identify weak ({tau}{sub ac}<<{tau}{sub cas}) and strong ({tau}{sub ac{approx}{tau}cas}) interaction mechanisms providing insight into the turbulent energy cascade. The new approach is illustrated by results from direct numerical simulations of two- and three-dimensional incompressible MHD turbulence.

Busse, Angela; Mueller, Wolf-Christian; Gogoberidze, Grigol [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstrasse 2, 85748 Garching (Germany); Georgian National Astrophysical Observatory, 2a Kazbegi Avenue, 0160 Tbilisi (Georgia) and Centre for Plasma Astrophysics, University of Leuven, B-3001 Leuven (Belgium)

2010-12-03T23:59:59.000Z

269

Reconnection events in two-dimensional Hall magnetohydrodynamic turbulence  

Science Conference Proceedings (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

270

DRIFT COEFFICIENTS OF CHARGED PARTICLES IN TURBULENT MAGNETIC FIELDS  

Science Conference Proceedings (OSTI)

Using test-particle simulations, the off-diagonal elements of the diffusion tensor are evaluated numerically. The comparison of the so-obtained time-dependent drift coefficients with analytical approximations shows that, for weak turbulence strengths or for slab turbulence geometry, the weak scattering result provides an excellent agreement with the numerical results. For two- or three-dimensional turbulence geometry, however, neither the classical scattering result nor alternative analytical approaches provide an accurate description of the numerically obtained values. Furthermore, the influence is discussed of a non-constant energy range in the turbulence spectrum and of non-static turbulence, for which the time dependence is modeled using magnetohydrodynamic plasma waves.

Tautz, R. C. [Zentrum fuer Astronomie und Astrophysik, Technische Universitaet Berlin, Hardenbergstrasse 36, D-10623 Berlin (Germany); Shalchi, A., E-mail: rct@tp4.rub.de, E-mail: andreasm4@yahoo.com [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada)

2012-01-10T23:59:59.000Z

271

Gyrokinetic Simulation of Global Turbulent Transport Properties in Tokamak Experiments  

SciTech Connect

A general geometry gyro-kinetic model for particle simulation of plasma turbulence in tokamak experiments is described. It incorporates the comprehensive influence of noncircular cross section, realistic plasma profiles, plasma rotation, neoclassical (equilibrium) electric fields, and Coulomb collisions. An interesting result of global turbulence development in a shaped tokamak plasma is presented with regard to nonlinear turbulence spreading into the linearly stable region. The mutual interaction between turbulence and zonal flows in collisionless plasmas is studied with a focus on identifying possible nonlinear saturation mechanisms for zonal flows. A bursting temporal behavior with a period longer than the geodesic acoustic oscillation period is observed even in a collisionless system. Our simulation results suggest that the zonal flows can drive turbulence. However, this process is too weak to be an effective zonal flow saturation mechanism.

Wang, W.X.; Lin, Z.; Tang, W.M.; Lee, W.W.; Ethier, S.; Lewandowski, J.L.V.; Rewoldt, G.; Hahm, T.S.; Manickam, J.

2006-01-01T23:59:59.000Z

272

Ignition of hydrogen/air mixing layer in turbulent flows  

DOE Green Energy (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

273

One-dimensional turbulence model simulations of autoignition of hydrogen/carbon monoxide fuel mixtures in a turbulent jet  

Science Conference Proceedings (OSTI)

The autoignition of hydrogen/carbon monoxide in a turbulent jet with preheated co-flow air is studied using the one-dimensional turbulence (ODT) model. The simulations are performed at atmospheric pressure based on varying the jet Reynolds number and the oxidizer preheat temperature for two compositions corresponding to varying the ratios of H{sub 2} and CO in the fuel stream. Moreover, simulations for homogeneous autoignition are implemented for similar mixture conditions for comparison with the turbulent jet results. The results identify the key effects of differential diffusion and turbulence on the onset and eventual progress of autoignition in the turbulent jets. The differential diffusion of hydrogen fuels results in a reduction of the ignition delay relative to similar conditions of homogeneous autoignition. Turbulence may play an important role in delaying ignition at high-turbulence conditions, a process countered by the differential diffusion of hydrogen relative to carbon monoxide; however, when ignition is established, turbulence enhances the overall rates of combustion of the non-premixed flame downstream of the ignition point. (author)

Gupta, Kamlesh G.; Echekki, Tarek [Department of Mechanical and Aerospace Engineering, North Carolina State University, NC (United States)

2011-02-15T23:59:59.000Z

274

Scrape-off layer tokamak plasma turbulence  

Science Conference Proceedings (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

275

Study of Flow, Turbulence and Transport on the Large Plasma Device  

E-Print Network (OSTI)

Axial versus Radial Transport . . . . . . . . . . . . .223 A LAPD Transport172 Turbulence and Transport

Schaffner, David A.

2013-01-01T23:59:59.000Z

276

A parallel solution - adaptive method for three-dimensional turbulent non-premixed combusting flows  

Science Conference Proceedings (OSTI)

A parallel adaptive mesh refinement (AMR) algorithm is proposed and applied to the prediction of steady turbulent non-premixed compressible combusting flows in three space dimensions. The parallel solution-adaptive algorithm solves the system of partial-differential ... Keywords: Adaptive mesh refinement, Parallel solution-adaptive algorithm, Turbulent combustion, Turbulent diffusion flames, Turbulent non-premixed flames

Xinfeng Gao; Clinton P. T. Groth

2010-05-01T23:59:59.000Z

277

Nonlinear Flow Generation By Electrostatic Turbulence In Tokamaks  

SciTech Connect

Global gyrokinetic simulations have revealed an important nonlinear flow generation process due to the residual stress produced by electrostatic turbulence of ion temperature gradient (ITG) modes and trapped electron modes (TEM). In collisionless TEM (CTEM) turbulence, nonlinear residual stress generation by both the fluctuation intensity and the intensity gradient in the presence of broken symmetry in the parallel wave number spectrum is identified for the first time. Concerning the origin of the symmetry breaking, turbulence self-generated low frequency zonal flow shear has been identified to be a key, universal mechanism in various turbulence regimes. Simulations reported here also indicate the existence of other mechanisms beyond E × B shear. The ITG turbulence driven “intrinsic” torque associated with residual stress is shown to increase close to linearly with the ion temperature gradient, in qualitative agreement with experimental observations in various devices. In CTEM dominated regimes, a net toroidal rotation is driven in the cocurrent direction by “intrinsic” torque, consistent with the experimental trend of observed intrinsic rotation. The finding of a “flow pinch” in CTEM turbulence may offer an interesting new insight into the underlying dynamics governing the radial penetration of modulated flows in perturbation experiments. Finally, simulations also reveal highly distinct phase space structures between CTEM and ITG turbulence driven momentum, energy and particle fluxes, elucidating the roles of resonant and non-resonant particles.

W.X. Wang, P.H. Diamond, T.S. Hahm, S. Ethier, G. Rewoldt, and W.M. Tang

2010-07-07T23:59:59.000Z

278

Nonlinear flow generation by electrostatic turbulence in tokamaks  

SciTech Connect

Global gyrokinetic simulations have revealed an important nonlinear flow generation process due to the residual stress produced by electrostatic turbulence of ion temperature gradient (ITG) modes and trapped electron modes (TEMs). In collisionless TEM (CTEM) turbulence, nonlinear residual stress generation by both the fluctuation intensity and the intensity gradient in the presence of broken symmetry in the parallel wavenumber spectrum is identified for the first time. Concerning the origin of the symmetry breaking, turbulence self-generated low frequency zonal flow shear has been identified to be a key, universal mechanism in various turbulence regimes. Simulations reported here also indicate the existence of other mechanisms beyond ExB shear. The ITG turbulence driven 'intrinsic' torque associated with residual stress is shown to increase close to linearly with the ion temperature gradient, in qualitative agreement with experimental observations in various devices. In CTEM dominated regimes, a net toroidal rotation is driven in the cocurrent direction by intrinsic torque, consistent with the experimental trend of observed intrinsic rotation. The finding of a 'flow pinch' in CTEM turbulence may offer an interesting new insight into the underlying dynamics governing the radial penetration of modulated flows in perturbation experiments. Finally, simulations also reveal highly distinct phase space structures between CTEM and ITG turbulence driven momentum, energy, and particle fluxes, elucidating the roles of resonant and non-resonant particles.

Wang, W. X.; Hahm, T. S.; Ethier, S.; Rewoldt, G.; Tang, W. M. [Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, New Jersey 08543 (United States); Diamond, P. H. [University of California, San Diego, La Jolla, California 92093 (United States)

2010-07-15T23:59:59.000Z

279

COLLISIONLESS DAMPING AT ELECTRON SCALES IN SOLAR WIND TURBULENCE  

SciTech Connect

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

280

Thermal conductivity of thermal-battery insulations  

DOE Green Energy (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

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281

Rotational intermittency and turbulence induced lift experienced by large particles in a turbulent flow  

E-Print Network (OSTI)

The motion of a large, neutrally buoyant, particle, freely advected by a turbulent flow is determined experimentally. We demonstrate that both the translational and angular accelerations exhibit very wide probability distributions, a manifestation of intermittency. The orientation of the angular velocity with respect to the trajectory, as well as the translational acceleration conditioned on the spinning velocity provide evidence of a lift force acting on the particle.

Zimmermann, Robert; Bourgoin, Mickael; Volk, Romain; Pumir, Alain; Pinton, Jean-Francois

2010-01-01T23:59:59.000Z

282

HIERARCHICAL STRUCTURE OF MAGNETOHYDRODYNAMIC TURBULENCE IN POSITION-POSITION-VELOCITY SPACE  

SciTech Connect

Magnetohydrodynamic turbulence is able to create hierarchical structures in the interstellar medium (ISM) that are correlated on a wide range of scales via the energy cascade. We use hierarchical tree diagrams known as dendrograms to characterize structures in synthetic position-position-velocity (PPV) emission cubes of isothermal magnetohydrodynamic turbulence. We show that the structures and degree of hierarchy observed in PPV space are related to the presence of self-gravity and the global sonic and Alfvenic Mach numbers. Simulations with higher Alfvenic Mach number, self-gravity and supersonic flows display enhanced hierarchical structure. We observe a strong dependency on the sonic and Alfvenic Mach numbers and self-gravity when we apply the statistical moments (i.e., mean, variance, skewness, kurtosis) to the leaf and node distribution of the dendrogram. Simulations with self-gravity, larger magnetic field and higher sonic Mach number have dendrogram distributions with higher statistical moments. Application of the dendrogram to three-dimensional density cubes, also known as position-position-position (PPP) cubes, reveals that the dominant emission contours in PPP and PPV are related for supersonic gas but not for subsonic. We also explore the effects of smoothing, thermal broadening, and velocity resolution on the dendrograms in order to make our study more applicable to observational data. These results all point to hierarchical tree diagrams as being a promising additional tool for studying ISM turbulence and star forming regions for obtaining information on the degree of self-gravity, the Mach numbers and the complicated relationship between PPV and PPP data.

Burkhart, Blakesley; Lazarian, A. [Astronomy Department, University of Wisconsin, Madison, 475 N. Charter St., WI 53711 (United States); Goodman, Alyssa [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-78, Cambridge, MA 02138 (United States); Rosolowsky, Erik [University of British Columbia, Okanagan Campus, 3333 University Way, Kelowna BC V1V 1V7 (Canada)

2013-06-20T23:59:59.000Z

283

CLUSTERED STAR FORMATION IN MAGNETIC CLOUDS: PROPERTIES OF DENSE CORES FORMED IN OUTFLOW-DRIVEN TURBULENCE  

Science Conference Proceedings (OSTI)

We investigate the physical properties of dense cores formed in turbulent, magnetized, parsec-scale clumps of molecular clouds, using three-dimensional numerical simulations that include protostellar outflow feedback. The dense cores are identified in the simulated density data cube through a clumpfind algorithm. We find that the core velocity dispersion does not show any clear dependence on the core size, in contrast to Larson's linewidth-size relation, but consistent with recent observations. In the absence of a magnetic field, the majority of the cores have supersonic velocity dispersions. A moderately strong magnetic field reduces the dispersion to a subsonic or at most transonic value typically. Most of the cores are out of virial equilibrium, with the external pressure dominating the self-gravity. The implication is that the core evolution is largely controlled by the outflow-driven turbulence. Even an initially weak magnetic field can retard star formation significantly, because the field is amplified by the outflow-driven turbulence to an equipartition strength, with the distorted field component dominating the uniform one. In contrast, for a moderately strong field, the uniform component remains dominant. Such a difference in the magnetic structure is evident in our simulated polarization maps of dust thermal emission; it provides a handle on the field strength. Recent polarization measurements show that the field lines in cluster-forming clumps are spatially well ordered. It is indicative of a moderately strong, dynamically important field which, in combination with outflow feedback, can keep the rate of star formation in embedded clusters at the observationally inferred, relatively slow rate of several percent per free-fall time.

Nakamura, Fumitaka [National Astronomical Observatory, Mitaka, Tokyo 181-8588 (Japan); Li Zhiyun, E-mail: fumitaka.nakamura@nao.ac.jp, E-mail: zl4h@virginia.edu [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904 (United States)

2011-10-10T23:59:59.000Z

284

Modeling H2 formation in the turbulent ISM: Solenoidal versus compressive turbulent forcing  

E-Print Network (OSTI)

We present results from high-resolution three-dimensional simulations of the turbulent interstellar medium that study the influence of the nature of the turbulence on the formation of molecular hydrogen. We have examined both solenoidal (divergence-free) and compressive (curl-free) turbulent driving, and show that compressive driving leads to faster H2 formation, owing to the higher peak densities produced in the gas. The difference in the H2 formation rate can be as much as an order of magnitude at early times, but declines at later times as the highest density regions become fully molecular and stop contributing to the total H2 formation rate. We have also used our results to test a simple prescription suggested by Gnedin et al. (2009) for modeling the influence of unresolved density fluctuations on the H2 formation rate in large-scale simulations of the ISM. We find that this approach works well when the H2 fraction is small, but breaks down once the highest density gas becomes fully molecular.

Milosavljevic, Milica; Federrath, Christoph; Klessen, Ralf S

2011-01-01T23:59:59.000Z

285

Electron and proton heating by solar wind turbulence  

E-Print Network (OSTI)

Previous formulations of heating and transport associated with strong magnetohydrodynamic (MHD) turbulence are generalized to incorporate separate internal energy equations for electrons and protons. Electron heat conduction is included. Energy is supplied by turbulent heating that affects both electrons and protons, and is exchanged between them via collisions. Comparison to available Ulysses data shows that a reasonable accounting for the data is provided when (i) the energy exchange timescale is very long and (ii) the deposition of heat due to turbulence is divided, with 60% going to proton heating and 40% into electron heating. Heat conduction, determined here by an empirical fit, plays a major role in describing the electron data.

Breech, B; Cranmer, S R; Kasper, J C; Oughton, S

2009-01-01T23:59:59.000Z

286

Edge Turbulence Velocity Changes with Lithium Coating on NSTX  

SciTech Connect

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. __________________________________________________

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

2012-08-10T23:59:59.000Z

287

Hard particle spectra from parallel shocks due to turbulence transmission  

E-Print Network (OSTI)

If taken into account, the transmission of the particle-scattering turbulence --in addition to just the particles-- through the shock front can change the effective compression ratio felt by the accelerating particles significantly from the compression of the underlying plasma. This can lead to significantly harder energy spectra than what are traditionally predicted assuming frozen-in turbulence. I consider the applicability and limitations of turbulence transmission scenario in parallel shock waves of different thickness, its consequences in AGN and microquasar environments, and discuss the possible effects to the spectrum of the accelerated particles.

Joni Tammi

2007-12-11T23:59:59.000Z

288

On apparent temperature in low-frequency Alfvenic turbulence  

SciTech Connect

Low-frequency, parallel propagating Alfvenic turbulence in collisionless plasmas is theoretically studied. Alfvenic turbulence is derived as an equilibrium state (Beltrami field) in the magnetohydrodynamic equations with the pressure anisotropy and multi-species of ions. It is shown that the conservation of the total 'apparent temperature' corresponds to the Bernoulli law. A simple model of the radially expanding solar wind including Alfvenic turbulence is also discussed. The conversion of the wave energy in the 'apparent temperature' into the 'real temperature' is facilitated with increasing radial distance.

Nariyuki, Yasuhiro [Faculty of Human Development, University of Toyama, 3190, Toyama City, Toyama 930-8555 (Japan)

2012-08-15T23:59:59.000Z

289

Turbulence driven particle transport in Texas Helimak  

E-Print Network (OSTI)

We analyze the turbulence driven particle transport in Texas Helimak (K. W. Gentle and Huang He, Plasma Sci. and Technology, 10, 284 (2008)), a toroidal plasma device with one-dimensional equilibrium with magnetic curvature and shear. Alterations on the radial electric field, through an external voltage bias, change spectral plasma characteristics inducing a dominant frequency for negative bias values and a broad band frequency spectrum for positive bias values. For negative biased plasma discharges, the transport is high where the waves propagate with phase velocities near the plasma flow velocity, an indication that the transport is strongly affected by a wave particle resonant interaction. On the other hand, for positive bias the plasma has a reversed shear flow and we observe that the transport is almost zero in the shearless radial region, an evidence of a transport barrier in this region.

Toufen, Dennis L; Caldas, Iberê L; Marcus, Francisco A; Gentle, Kenneth W

2011-01-01T23:59:59.000Z

290

Numerical simulations to study solar wind turbulence  

Science Conference Proceedings (OSTI)

Numerical simulation of coupled equations of kinetic Alfven wave (KAW) and ion acoustic wave is presented in the solar wind. The nonlinear dynamical equations satisfy the modified Zakharov system of equations by taking the nonadiabatic response of the background density. The ponderomotive nonlinearity is incorporated in the wave dynamics. The effect of Landau damping of KAW is taken into account. Localization of magnetic field intensity and the wavenumber spectra (perpendicular and parallel) of magnetic fluctuations are studied in solar plasmas around 1 a.u. Our results reveal the formation of damped localized structures and the steeper spectra that are in good agreement with the observations. These damped structures and steeper turbulent spectra can be responsible for plasma heating and particle acceleration in solar wind.

Sharma, R. P.; Sharma, Nidhi; Kumar, Sanjay [Centre for Energy Studies, Indian Institute of Technology Delhi, Delhi 110016 (India); Kumar, Sachin [Department of Applied Sciences and Humanities, Ajay Kumar Garg Engineering College, Ghaziabad 201009 (India); Singh, H. D. [Department of Physical Sciences, School of Physical and Chemical Sciences, Sikkim University, Sikkim 737102 (India)

2011-02-15T23:59:59.000Z

291

Renormalized Resonance Quartets in Dispersive Wave Turbulence  

Science Conference Proceedings (OSTI)

Using the (1+1)D Majda-McLaughlin-Tabak model as an example, we present an extension of the wave turbulence (WT) theory to systems with strong nonlinearities. We demonstrate that nonlinear wave interactions renormalize the dynamics, leading to (i) a possible destruction of scaling structures in the bare wave systems and a drastic deformation of the resonant manifold even at weak nonlinearities, and (ii) creation of nonlinear resonance quartets in wave systems for which there would be no resonances as predicted by the linear dispersion relation. Finally, we derive an effective WT kinetic equation and show that our prediction of the renormalized Rayleigh-Jeans distribution is in excellent agreement with the simulation of the full wave system in equilibrium.

Lee, Wonjung [Courant Institute of Mathematical Sciences, New York University, 251 Mercer Street, New York, New York 10012 (United States); Kovacic, Gregor [Mathematical Sciences Department, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180 (United States); Cai, David [Courant Institute of Mathematical Sciences, New York University, 251 Mercer Street, New York, New York 10012 (United States); Mathematics Department, Shanghai Jiao Tong University, Shanghai 200240 (China)

2009-07-10T23:59:59.000Z

292

Relativistic Fermi acceleration with shock compressed turbulence  

E-Print Network (OSTI)

This paper presents numerical simulations of test particle Fermi acceleration at relativistic shocks of Lorentz factor Gamma_sh = 2-60, using a realistic downstream magnetic structure obtained from the shock jump conditions. The upstream magnetic field is described as pure Kolmogorov turbulence; the corresponding downstream magnetic field lies predominantly in the plane tangential to the shock surface and the coherence length is smaller along the shock normal than in the tangential plane. Acceleration is nonetheless efficient and leads to powerlaw spectra with index s = 2.6-2.7 at large shock Lorentz factor Gamma_sh >> 1, markedly steeper than for isotropic scattering downstream. The acceleration timescale t_acc in the upstream rest frame becomes a fraction of Larmor time t_L in the ultra-relativistic limit, t_acc ~ 10 t_L/Gamma_sh. Astrophysical applications are discussed, in particular the acceleration in gamma-ray bursts internal and external shocks.

Martin Lemoine; Benoit Revenu

2005-10-18T23:59:59.000Z

293

Turbulence driven particle transport in Texas Helimak  

SciTech Connect

We analyze the turbulence driven particle transport in Texas Helimak [K. W. Gentle and H. He, Plasma Sci. Technol. 10, 284 (2008)], a toroidal plasma device with a one-dimensional equilibrium with magnetic curvature and shear. Alterations on the radial electric field, through an external voltage bias, change the spectral plasma characteristics inducing a dominant frequency for negative bias values and a broad band frequency spectrum for positive bias values. When applying a negative bias, the transport is high where the waves propagate with phase velocities near the plasma flow velocity, an indication that the transport is strongly affected by a wave particle resonant interaction. On the other hand, for positive bias values, the plasma has a reversed shear flow, and we observe that the transport is almost zero in the shearless radial region, an evidence of a transport barrier in this region.

Toufen, D. L. [Institute of Physics, University of Sao Paulo, C.P. 66318, 05315-970 Sao Paulo, Sao Paulo (Brazil); Federal Institute of Education, Science and Technology of Sao Paulo--IFSP, 07115-000 Guarulhos, Sao Paulo (Brazil); Guimaraes-Filho, Z. O.; Marcus, F. A. [Aix-Marseille Univ., International Institute for Fusion Science, CNRS-PIIM UMR 7345, Marseille (France); Caldas, I. L. [Institute of Physics, University of Sao Paulo, C.P. 66318, 05315-970 Sao Paulo, Sao Paulo (Brazil); Gentle, K. W. [Department of Physics and Institute for Fusion Studies, University of Texas at Austin, Austin, Texas 78712 (United States)

2012-01-15T23:59:59.000Z

294

Dynamic Multiscale Averaging (DMA) of Turbulent Flow  

SciTech Connect

A new approach called dynamic multiscale averaging (DMA) for computing the effects of turbulent flow is described. The new method encompasses multiple applications of temporal and spatial averaging, that is, multiscale operations. Initially, a direct numerical simulation (DNS) is performed for a relatively short time; it is envisioned that this short time should be long enough to capture several fluctuating time periods of the smallest scales. The flow field variables are subject to running time averaging during the DNS. After the relatively short time, the time-averaged variables are volume averaged onto a coarser grid. Both time and volume averaging of the describing equations generate correlations in the averaged equations. These correlations are computed from the flow field and added as source terms to the computation on the next coarser mesh. They represent coupling between the two adjacent scales. Since they are computed directly from first principles, there is no modeling involved. However, there is approximation involved in the coupling correlations as the flow field has been computed for only a relatively short time. After the time and spatial averaging operations are applied at a given stage, new computations are performed on the next coarser mesh using a larger time step. The process continues until the coarsest scale needed is reached. New correlations are created for each averaging procedure. The number of averaging operations needed is expected to be problem dependent. The new DMA approach is applied to a relatively low Reynolds number flow in a square duct segment. Time-averaged stream-wise velocity and vorticity contours from the DMA approach appear to be very similar to a full DNS for a similar flow reported in the literature. Expected symmetry for the final results is produced for the DMA method. The results obtained indicate that DMA holds significant potential in being able to accurately compute turbulent flow without modeling for practical engineering applications.

Richard W. Johnson

2012-09-01T23:59:59.000Z

295

Spark Ignited Turbulent Flame Kernel Growth  

DOE Green Energy (OSTI)

An experimental study of the effects of spark power and of incomplete fuel-air mixing on spark-ignited flame kernel growth was conducted in turbulent propane-air mixtures at 1 atm, 300K conditions. The results showed that increased spark power resulted in an increased growth rate, where the effect of short duration breakdown sparks was found to persist for times of the order of milliseconds. The effectiveness of increased spark power was found to be less at high turbulence and high dilution conditions. Increased spark power had a greater effect on the 0-5 mm burn time than on the 5-13 mm burn time, in part because of the effect of breakdown energy on the initial size of the flame kernel. And finally, when spark power was increased by shortening the spark duration while keeping the effective energy the same there was a significant increase in the misfire rate, however when the spark power was further increased by increasing the breakdown energy the misfire rate dropped to zero. The results also showed that fluctuations in local mixture strength due to incomplete fuel-air mixing cause the flame kernel surface to become wrinkled and distorted; and that the amount of wrinkling increases as the degree of incomplete fuel-air mixing increases. Incomplete fuel-air mixing was also found to result in a significant increase in cyclic variations in the flame kernel growth. The average flame kernel growth rates for the premixed and the incompletely mixed cases were found to be within the experimental uncertainty except for the 33%-RMS-fluctuation case where the growth rate was significantly lower. The premixed and 6%-RMS-fluctuation cases had a 0% misfire rate. The misfire rates were 1% and 2% for the 13%-RMS-fluctuation and 24%-RMS-fluctuation cases, respectively; however, it drastically increased to 23% in the 33%-RMS-fluctuation case.

Santavicca, D.A.

1995-06-01T23:59:59.000Z

296

MODEL FOR ALFVEN WAVE TURBULENCE IN SOLAR CORONAL LOOPS: HEATING RATE PROFILES AND TEMPERATURE FLUCTUATIONS  

Science Conference Proceedings (OSTI)

It has been suggested that the solar corona may be heated by dissipation of Alfven waves that propagate up from the solar photosphere. According to this theory, counterpropagating Alfven waves are subject to nonlinear interactions that lead to turbulent decay of the waves and heating of the chromospheric and coronal plasma. To test this theory, better models for the dynamics of Alfven waves in coronal loops are required. In this paper, we consider wave heating in an active region observed with the Solar Dynamics Observatory in 2010 May. First a three-dimensional (3D) magnetic model of the region is constructed, and ten magnetic field lines that match observed coronal loops are selected. For each loop we construct a 3D magnetohydrodynamic model of the Alfven waves near the selected field line. The waves are assumed to be generated by footpoint motions inside the kilogauss magnetic flux elements at the two ends of the loop. Based on such models, we predict the spatial and temporal profiles of the heating along the selected loops. We also estimate the temperature fluctuations resulting from such heating. We find that the Alfven wave turbulence model can reproduce the observed characteristics of the hotter loops in the active region core, but the loops at the periphery of the region have large expansion factors and are predicted to be thermally unstable.

Asgari-Targhi, M.; Van Ballegooijen, A. A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street MS-15, Cambridge, MA 02138 (United States)

2012-02-10T23:59:59.000Z

297

Large-eddy simulations of turbulent flow for grid-to-rod fretting in nuclear reactors  

E-Print Network (OSTI)

The grid-to-rod fretting (GTRF) problem in pressurized water reactors is a flow-induced vibration problem that results in wear and failure of the fuel rods in nuclear assemblies. In order to understand the fluid dynamics of GTRF and to build an archival database of turbulence statistics for various configurations, implicit large-eddy simulations of time-dependent single-phase turbulent flow have been performed in 3x3 and 5x5 rod bundles with a single grid spacer. To assess the computational mesh and resolution requirements, a method for quantitative assessment of unstructured meshes with no-slip walls is described. The calculations have been carried out using Hydra-TH, a thermal-hydraulics code developed at Los Alamos for the Consortium for Advanced Simulation of Light water reactors, a United States Department of Energy Innovation Hub. Hydra-TH uses a second-order implicit incremental projection method to solve the single-phase incompressible Navier-Stokes equations. The simulations explicitly resolve the la...

Bakosi, J; Lowrie, R B; Pritchett-Sheats, L A; Nourgaliev, R R

2013-01-01T23:59:59.000Z

298

Global NOx Measurements in Turbulent Nitrogen-Diluted Hydrogen Jet Flames  

DOE Green Energy (OSTI)

Turbulent hydrogen diffusion flames diluted with nitrogen are currently being studied to assess their ability to achieve the DOE Turbine Program’s aggressive emissions goal of 2 ppm NOx in a hydrogen-fueled IGCC gas turbine combustor. Since the unstrained adiabatic flame temperatures of these diluted flames are not low enough to eliminate thermal NOx formation the focus of the current work is to study how the effects of flame residence time and global flame strain can be used to help achieve the stated NOx emissions goal. Dry NOx measurements are presented as a function of jet diameter nitrogen dilution and jet velocity for a turbulent hydrogen/nitrogen jet issuing from a thin-lipped tube in an atmospheric pressure combustor. The NOx emission indices from these experiments are normalized by the flame residence time to ascertain the effects of global flame strain and fuel Lewis Number on the NOx emissions. In addition dilute hydrogen diffusion flame experiments were performed in a high-pressure combustor at 2 4 and 8 atm. The NOx emission data from these experiments are discussed as well as the results from a Computational Fluid Dynamics modeling effort currently underway to help explain the experimental data.

Weiland, N.T.; Strakey, P.A.

2007-03-01T23:59:59.000Z

299

Combustion chamber and thermal vapor stream producing apparatus and method  

DOE Patents (OSTI)

A new and improved method and apparatus for burning a hydrocarbon fuel for producing a high pressure thermal vapor stream comprising steam and combustion gases for injecting into a subterranean formation for the recovery of liquefiable minerals therefrom, wherein a high pressure combustion chamber having multiple refractory lined combustion zones of varying diameters is provided for burning a hydrocarbon fuel and pressurized air in predetermined ratios injected into the chamber for producing hot combustion gases essentially free of oxidizing components and solid carbonaceous particles. The combustion zones are formed by zones of increasing diameters up a final zone of decreasing diameter to provide expansion zones which cause turbulence through controlled thorough mixing of the air and fuel to facilitate complete combustion. The high pressure air and fuel is injected into the first of the multiple zones where ignition occurs with a portion of the air injected at or near the point of ignition to further provide turbulence and more complete combustion.

Sperry, John S. (Houston, TX); Krajicek, Richard W. (Sugar Land, TX); Cradeur, Robert R. (Spring, TX)

1978-01-01T23:59:59.000Z

300

Seasonal thermal energy storage  

DOE Green Energy (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

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

Petascale Simulations of Inhomogeneous Alfven Turbulence in the Solar Wind  

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

A snapshot of turbulent magnetic field lines (red) inside a coronal hole that expands from a small patch on the solar surface to 5 solar radii A snapshot of turbulent magnetic field lines (red) inside a coronal hole that expands from a small patch on the solar surface to 5 solar radii A snapshot of turbulent magnetic field lines (red) inside a coronal hole that expands from a small patch on the solar surface to 5 solar radii. Alfven waves (AW), launched by convective motions on the photosphere, propagate in the inhomogeneous Solar atmosphere producing primary reflected waves that interact non-linearly with the outward waves, driving a turbulent cascade. This cascade continues with secondary reflections in a very complex interplay between wave reflections and nonlinear interactions. Selected slices across the simulation domain show contours of plasma current, indicating the generation of small scale structures where the

302

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

303

Effects of Wind Turbulence on Coherent Doppler Lidar Performance  

Science Conference Proceedings (OSTI)

The effects of wind turbulence on pulsed coherent Doppler lidar performance are investigated theoretically and with computer simulations. The performance of velocity estimators is determined for the case of a single realization of a wind field ...

Rod Frehlich

1997-02-01T23:59:59.000Z

304

Microsoft PowerPoint - Tokamak_turbulence3.pptx  

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

Fusion Energy Sciences Aug. 3-4, 2010, Washington DC g , , g Plasma Turbulence and Transport C.S. Chang a) , J. Candy b) , S. Ethier/W. Wang c) , and Z. Lin d) a) Courant Institute of Mathematical Sciences, New York U. b) G l At i b) General Atomics c) Princeton Plasma Physics Laboratory, Princeton U. d) U. California, Irvine Introduction * Tokamak confinement in the low confinement mode (L- mode) is dominated by turbulent transport. ) y p * In the high confinement mode (H-mode), the ion turbulent transport is subdued, at least, in some layers (internal and edge transport barriers); and the magnetic curvature edge transport barriers); and the magnetic curvature- driven neoclassical transport determines the ion confinement. * Electron transport is found to be always turbulent. * Toroidal rotation appears to be generated/transported by

305

Abnormal heart rate turbulence predicts the initiation of ventricular arrhythmias  

E-Print Network (OSTI)

atrial pacing with onset heart rate = 99 beats/min. (C)Thonet G, Vesin J-M, et al. Heart rate dynamics at the on-M, Barthel P, et al. Heart-rate turbulence after ventricular

Iwasa, Atsushi; Hwa, Michael; Hassankhani, Alborz; Liu, Taylor; Narayan, Sanjiv M

2005-01-01T23:59:59.000Z

306

A Nonlinear Statistical Model of Turbulent Air–Sea Fluxes  

Science Conference Proceedings (OSTI)

Most of the bulk algorithms used to calculate turbulent air–sea fluxes of momentum and heat are iterative algorithms whose convergence is slow and not always achieved. To avoid these drawbacks that are critical when large datasets must be ...

Denis Bourras; Gilles Reverdin; Guy Caniaux; Sophie Belamari

2007-03-01T23:59:59.000Z

307

Turbulence and Gravity Waves within an Upper-Level Front  

Science Conference Proceedings (OSTI)

High-resolution dropwindsonde and in-flight measurements collected by a research aircraft during the Severe Clear-Air Turbulence Colliding with Aircraft Traffic (SCATCAT) experiment and simulations from numerical models are analyzed for a clear-...

Steven E. Koch; Brian D. Jamison; Chungu Lu; Tracy L. Smith; Edward I. Tollerud; Cecilia Girz; Ning Wang; Todd P. Lane; Melvyn A. Shapiro; David D. Parrish; Owen R. Cooper

2005-11-01T23:59:59.000Z

308

Large-Eddy Simulation of Decaying Stably Stratified Turbulence  

Science Conference Proceedings (OSTI)

A large-eddy simulation (LES) model is developed and employed to study the interactions among turbulent and internal gravity wave motions in a uniformly stratified fluid at oceanic space and time scales. The decay of a random initial energy ...

David A. Siegel; J. Andrzej Domaradzki

1994-11-01T23:59:59.000Z

309

Application of Transilient Turbulence Theory to Mesoscale Numerical Weather Forecasting  

Science Conference Proceedings (OSTI)

In this study we show that a unified turbulence parameterization, when divorced from the smoothing procedures needed for numerical stability of the host model, can be implemented in a numerical weather prediction model. Our host model is the 15-...

William H. Raymond; Roland B. Stull

1990-12-01T23:59:59.000Z

310

The NCAR Atmosphere-Surface Turbulent Exchange Research (ASTER) Facility  

Science Conference Proceedings (OSTI)

The Atmosphere-Surface Turbulent Exchange Research (ASTER) facility developed at the National Center for Atmospheric Research (NCAR) will support observational research on the structure of the atmospheric surface layer. ASTER will provide state-...

J. A. Businger; W. F. Dabberdt; A. C. Delany; T. W. Horst; C. L. Martin; S. P. Oncley; S. R. Semmer

1990-07-01T23:59:59.000Z

311

Generation of residual energy in the turbulent solar wind  

SciTech Connect

In situ observations of the fluctuating solar wind flow show that the energy of magnetic field fluctuations always exceeds that of the kinetic energy, and therefore the difference between the kinetic and magnetic energies, known as the residual energy, is always negative. The same behaviour is found in numerical simulations of magnetohydrodynamic turbulence. We study the dynamics of the residual energy for strong, anisotropic, critically balanced magnetohydrodynamic turbulence using the eddy damped quasi-normal Markovian approximation. Our analysis shows that for stationary critically balanced magnetohydrodynamic turbulence, negative residual energy will always be generated by nonlinear interacting Alfven waves. This offers a general explanation for the observation of negative residual energy in solar wind turbulence and in the numerical simulations.

Gogoberidze, G. [Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry CV4 7AL (United Kingdom); Institute of Theoretical Physics, Ilia State University, 3/5 Cholokashvili Ave., 0162 Tbilisi (Georgia); Chapman, S. C.; Hnat, B. [Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry CV4 7AL (United Kingdom)

2012-10-15T23:59:59.000Z

312

A Numerical Simulation of Convectively Induced Turbulence above Deep Convection  

Science Conference Proceedings (OSTI)

At 1034 UTC 2 September 2007, a commercial aircraft flying from Jeju, South Korea, to Osaka, Japan, at an altitude of approximately 11.2 km encountered severe turbulence above deep convection. To investigate the characteristics and generation ...

Jung-Hoon Kim; Hye-Yeong Chun

2012-06-01T23:59:59.000Z

313

Dissipation and Heating in Supersonic Hydrodynamic and MHD Turbulence  

E-Print Network (OSTI)

We study energy dissipation and heating by supersonic MHD turbulence in molecular clouds using Athena, a new higher-order Godunov code. We analyze the dependence of the saturation amplitude, energy dissipation characteristics, power spectra, sonic scaling, and indicators of intermittency in the turbulence on factors such as the magnetic field strength, driving scale, energy injection rate, and numerical resolution. While convergence in the energies is reached at moderate resolutions, we find that the power spectra require much higher resolutions that are difficult to obtain. In a 1024^3 hydro run, we find a power law relationship between the velocity dispersion and the spatial scale on which it is measured, while for an MHD run at the same resolution we find no such power law. The time-variability and temperature intermittency in the turbulence both show a dependence on the driving scale, indicating that numerically driving turbulence by an arbitrary mechanism may not allow a realistic representation of these...

Lemaster, M Nicole

2008-01-01T23:59:59.000Z

314

Turbulent Mixing with Chemical Reaction in the Planetary Boundary Layer  

Science Conference Proceedings (OSTI)

Detailed statistics of the fluctuating concentration field produced by large-eddy simulations (LES) of the chemically reactive mixing of two species in a convectively driven mixed layer are presented. The effect of the turbulent mixing on the ...

R. I. Sykes; S. F. Parker; D. S. Henn; W. S. Lewellen

1994-07-01T23:59:59.000Z

315

Simulations of observed lee-waves and rotor turbulence  

Science Conference Proceedings (OSTI)

On 18 November 2008 a commercial aircraft encountered severe turbulence while flying in westerly flow along the southeastern coast of Iceland and descending from 2.500 m down to the ground for a safe landing. Numerical simulations at horizontal ...

Hálfdán Ágústsson; Haraldur Ólafsson

316

ccsd00001826, Impurity Transport in Plasma Edge Turbulence  

E-Print Network (OSTI)

,Martin Priego Wood, and Jens Juul Rasmussen Association EURATOM ­ Risø National Laboratory Optics and Plasma Research, OPL ­ 128 DK ­ 4000 Roskilde, Denmark October 14, 2004 The turbulent transport of minority

317

Turbulence Kinetic Energy Budget Profiles Derived from Doppler Sodar Measurements  

Science Conference Proceedings (OSTI)

Doppler sodar wind measurements made in light wind conditions in September 1979 near a power plant in Turbigo, Italy, are used to derive terms in the turbulence kinetic energy (TKE) budget. Measurements on five days are grouped into two classes: ...

Gary K. Greenhut; Giangiuseppe Mastrantonio

1989-02-01T23:59:59.000Z

318

Some Turbulence Characteristics in Stable Atmospheric Boundary Layer Flow  

Science Conference Proceedings (OSTI)

Atmospheric boundary layer measurements during stable and near neutral condition from seven sites in different kinds of terrain have been analyzed in order to find relationships among turbulence parameters.

Ann-Sofi Smedman

1991-03-01T23:59:59.000Z

319

Spectral Energy Fluxes in Geostrophic Turbulence: Implications for Ocean Energetics  

Science Conference Proceedings (OSTI)

The energy pathways in geostrophic turbulence are explored using a two-layer, flat-bottom, f-plane, quasigeostrophic model forced by an imposed, horizontally homogenous, baroclinically unstable mean flow and damped by bottom Ekman friction. A ...

Robert B. Scott; Brian K. Arbic

2007-03-01T23:59:59.000Z

320

Study of Buoyancy-Driven Turbulent Nuclear Burning and Validation...  

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

Study of Buoyancy-Driven Turbulent Nuclear Burning and Validation of Type Ia Supernova Models PI Name: Don Lamb PI Email: lamb@oddjob.uchicago.edu Institution: ASCAlliance Flash...

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.
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to obtain the most current and comprehensive results.


321

Study of Buoyancy-Driven Turbulent Nuclear Burning and Validation...  

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

created from a simulation run on the Blue GeneP at the Argonne Leadership Computing Facility in 2009. Study of Buoyancy-Driven Turbulent Nuclear Burning and Validation of Type Ia...

322

Reducing Turbulent Transport in Toroidal Configurations via Shaping  

Science Conference Proceedings (OSTI)

Recent progress in reducing turbulent transport in stellarators and tokamaks by 3D shaping using a stellarator optimization code in conjunction with a gyrokinetic code is presented. The original applications of the method focussed on ion temperature gradient transport in a quasi-axisymmetric stellarator design. Here, an examination of both other turbulence channels and other starting configurations is initiated. It is found that the designs evolved for transport from ion temperature gradient turbulence also display reduced transport from other transport channels whose modes are also stabilized by improved curvature, such as electron temperature gradient and ballooning modes. The optimizer is also applied to evolving from a tokamak, finding appreciable turbulence reduction for these devices as well. From these studies, improved understanding is obtained of why the deformations found by the optimizer are beneficial, and these deformations are related to earlier theoretical work in both stellarators and tokamaks.

H.E. Mynick, N. Pomphrey and P. Xanthopoulos

2011-04-20T23:59:59.000Z

323

A New Moist Turbulence Parameterization in the Community Atmosphere Model  

Science Conference Proceedings (OSTI)

A new moist turbulence parameterization is presented and implemented in the Community Atmosphere Model (CAM). It is derived from Grenier and Bretherton but has been heavily modified to improve its numerical stability and efficiency with the long ...

Christopher S. Bretherton; Sungsu Park

2009-06-01T23:59:59.000Z

324

Prediction of turbulence control for arbitrary periodic spanwise wall movement  

E-Print Network (OSTI)

In order to generalize the well-known spanwise-oscillating-wall technique for drag reduction, non-sinusoidal oscillations of a solid wall are considered as a means to alter the skin-friction drag in a turbulent channel flow. A series of Direct Numerical Simulations is conducted to evaluate the control performance of nine different temporal waveforms, in addition to the usual sinusoid, systematically changing the wave amplitude and the period for each waveform. The turbulent average spanwise motion is found to coincide with the laminar Stokes solution that is constructed, for the generic waveform, through harmonic superposition. This allows us to define and compute, for each waveform, a new penetration depth of the Stokes layer which correlates with the amount of turbulent drag reduction, and eventually to predict both turbulent drag reduction and net energy saving rate for arbitrary waveforms. Among the waveforms considered, the maximum net energy saving rate is obtained by the sinusoidal wave at its optimal ...

Cimarelli, Andrea; Hasegawa, Yosuke; De Angelis, Elisabetta; Quadrio, Maurizio

2013-01-01T23:59:59.000Z

325

Turbulent Moisture Measurements aboard Instrumented Aircraft with a Capacitive Sensor  

Science Conference Proceedings (OSTI)

The authors show how a capacitive device measuring moisture can be used aboard instrumented atmospheric aircraft as an alternate sensor for turbulence measurement. Using a calibrated Lyman-? sensor as a reference, the time response of the ...

Pierre Durand; Gabriel Abadie; Aimé Druilhet

1995-08-01T23:59:59.000Z

326

Drag Anemometer Measurements of Turbulence over a Vegetated Surface  

Science Conference Proceedings (OSTI)

Turbulent fluctuations of vertical wind and fluxes of momentum, sensible heat and latent heat measured with a drag anemometer are compared to like data measured with other instruments. Means of the measured parameters agreed well with energy ...

T. Grayson Redford Jr.; Shashi B. Verma; Norman J. Rosenberg

1981-10-01T23:59:59.000Z

327

Convectively Driven Turbulent Mixing in the Upper Ocean  

Science Conference Proceedings (OSTI)

Two experiments were performed to study the characteristics of turbulence in convective mixed layers in the upper Ocean. In the first, a diurnal convective mixed layer developed in the Bahamas under the influence of the cycle of daytime solar ...

T. J. Shay; M. C. Gregg

1986-11-01T23:59:59.000Z

328

Global Variability of the Wavenumber Spectrum of Oceanic Mesoscale Turbulence  

Science Conference Proceedings (OSTI)

The wavenumber spectra of sea surface height from satellite altimeter observations have revealed complex spatial variability that cannot be explained by a universal theory of mesoscale turbulence. Near the edge of the core regions of high eddy ...

Yongsheng Xu; Lee-Lueng Fu

2011-04-01T23:59:59.000Z

329

Internal Waves and Turbulence in the Antarctic Circumpolar Current  

Science Conference Proceedings (OSTI)

This study reports on observations of turbulent dissipation and internal wave-scale flow properties in a standing meander of the Antarctic Circumpolar Current (ACC) north of the Kerguelen Plateau. The authors characterize the intensity and spatial ...

Stephanie Waterman; Alberto C. Naveira Garabato; Kurt L. Polzin

2013-02-01T23:59:59.000Z

330

Determining Turbulent Kinetic Energy Dissipation from Batchelor Curve Fitting  

Science Conference Proceedings (OSTI)

An algorithm is presented for obtaining the rate of turbulent kinetic energy dissipation by fitting the theoretical Batchelor spectrum to the temperature gradient spectrum at high wavenumbers. The algorithm is relatively robust in selecting the ...

David A. Luketina; Jörg Imberger

2001-01-01T23:59:59.000Z

331

Ion-acoustic turbulence in a nonmonochromatic pump wave  

SciTech Connect

A theoretical study is made of the development of a steady-state turbulent condition in an unbounded homogeneous plasma due to a high-frequency electric field. (AIP)

Aliev, Y.M.; Gradov, O.M.; Izmailov, G.N.

1977-05-01T23:59:59.000Z

332

Spatial Variation in Turbulent Heat Fluxes in Drake Passage  

Science Conference Proceedings (OSTI)

High-resolution underway shipboard atmospheric and oceanic observations collected in Drake Passage from 2000 to 2009 are used to examine the spatial scales of turbulent heat fluxes and flux-related state variables. The magnitude of the seasonal ...

ChuanLi Jiang; Sarah T. Gille; Janet Sprintall; Kei Yoshimura; Masao Kanamitsu

2012-03-01T23:59:59.000Z

333

Simulation of Three-Dimensional Turbulent Velocity Fields  

Science Conference Proceedings (OSTI)

New algorithms for the simulation of three-dimensional homogeneous turbulent velocity fields are compared with standard spectral domain algorithms. Results are presented for a von Kármán model of the covariance tensor. For typical atmospheric ...

Rod Frehlich; Larry Cornman; Robert Sharman

2001-02-01T23:59:59.000Z

334

Lateral Turbulence Intensity and Plume Meandering During Stable Conditions  

Science Conference Proceedings (OSTI)

There is much evidence in the literature for the presence of mesoscale lateral meanders in the stable nighttime boundary layer. These meanders result in relatively high lateral turbulence intensities and diffusion rates when averaged over an ...

Steven R. Hanna

1983-08-01T23:59:59.000Z

335

Evaluation of the Turbulent Kinetic Energy Dissipation Rate Inside ...  

Science Conference Proceedings (OSTI)

Abstract Inferring the vertical variation of the mean turbulent kinetic energy ..... the times at which a threshold-crossings occurs are defined by the indicator function .... of noise infection and noise intensity, introducing a threshold Tc significantly ...

336

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.

337

Comments on Measuring Turbulent Exchange Within and Above Forest Canopy  

Science Conference Proceedings (OSTI)

Actual problems of measuring the turbulent exchange in and above forests (e.g., site requirements of micrormeteorological observations, aerodynamic characteristics of forests, observations of the crown-produced mixing layer, flux-profile ...

Stanislaw J. Tajchman

1981-11-01T23:59:59.000Z

338

Heat Transfer and Reconnection Diffusion in Turbulent Magnetized Plasmas  

E-Print Network (OSTI)

It is well known that magnetic fields constrain motions of charged particles, impeding the diffusion of charged particles perpendicular to magnetic field direction. This modification of transport processes is of vital importance for a wide variety of astrophysical processes including cosmic ray transport, transfer of heavy elements in the interstellar medium, star formation etc. Dealing with these processes one should keep in mind that in realistic astrophysical conditions magnetized fluids are turbulent. In this review we single out a single transport process, namely, heat transfer and consider how it occurs in the presence of the magnetized turbulence. We show that the ability of magnetic field lines to constantly change topology and connectivity is at the heart of the correct description of the 3D magnetic field stochasticity in turbulent fluids. This ability is ensured by fast magnetic reconnection in turbulent fluids and puts forward the concept of reconnection diffusion at the core of the physical pictu...

Lazarian, A

2011-01-01T23:59:59.000Z

339

The Juneau Terrain-Induced Turbulence Alert System  

Science Conference Proceedings (OSTI)

The Juneau, Alaska, airport vicinity experiences frequent episodes of moderate and severe turbulence, which affect arriving and departing air traffic. The Federal Aviation Administration funded the National Center for Atmospheric Research to ...

Marcia K. Politovich; R. Kent Goodrich; Corrinne S. Morse; Alan Yates; Robert Barron; Steven A. Cohn

2011-03-01T23:59:59.000Z

340

Energy Dissipation Rates of Turbulence in the Stable Free Atmosphere  

Science Conference Proceedings (OSTI)

For stable stratification, it is pointed out that there exists a strong correlation between the intensity of atmospheric turbulence and the energy dissipation rate ?. It is given in terms of the variance of vertical velocity ?w2 and the Brunt-...

J. Weinstock

1981-04-01T23:59:59.000Z

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.


341

A Climatology of Turbulent Dispersion in the Troposphere  

Science Conference Proceedings (OSTI)

The authors present properties of turbulent, meridional mixing along isentropic surfaces within the troposphere. Twice-daily wind fields analyses from the European Centre for Medium-Range Weather Forecasts numerical weather prediction model for ...

Matthew Huber; James C. McWilliams; Michael Ghil

2001-08-01T23:59:59.000Z

342

Statistics and Possible Sources of Aviation Turbulence over South Korea  

Science Conference Proceedings (OSTI)

The characteristics of aviation turbulence over South Korea during the recent five years (2003–08, excluding 2005) are investigated using pilot reports (PIREPs) accumulated by the Korea Aviation Meteorological Agency (KAMA). Among the total of ...

Jung-Hoon Kim; Hye-Yeong Chun

2011-02-01T23:59:59.000Z

343

Turbulence Patch Identification in Potential Density or Temperature Profiles  

Science Conference Proceedings (OSTI)

The Thorpe analysis is a recognized method used to identify and characterize turbulent regions within stably stratified fluids. By comparing an observed profile of potential temperature or potential density to a reference profile obtained by ...

Richard Wilson; Hubert Luce; Francis Dalaudier; Jacques Lefrère

2010-06-01T23:59:59.000Z

344

Cloud Droplet Growth by Condensation in Homogeneous Isotropic Turbulence  

Science Conference Proceedings (OSTI)

The growth of cloud droplets by diffusion of water vapor 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 ...

Alessandra S. Lanotte; Agnese Seminara; Federico Toschi

2009-06-01T23:59:59.000Z

345

A Simple Model of Droplet Spectral Evolution during Turbulent Mixing  

Science Conference Proceedings (OSTI)

The mixing of cloudy, saturated air with cloud-free, subsaturated air is examined with a simple one-dimensional model of the mixing process. The model incorporates (i) a one-dimensional parameterization of turbulent deformation, (ii) molecular ...

Jørgen B. Jensen; Marcia B. Baker

1989-09-01T23:59:59.000Z

346

Stratified Turbulence and the Mesoscale Variability of the Atmosphere  

Science Conference Proceedings (OSTI)

An analysis is made of Gage's proposal that the horizontal energy spectrum at mesoscale wavelengths is produced by upscale energy transfer through quasi-two-dimensional turbulence. It is suggested that principal sources of such energy can be ...

D. K. Lilly

1983-03-01T23:59:59.000Z

347

Investigation of Flow, Turbulence, and Dispersion within Built Environments  

E-Print Network (OSTI)

Properties of the wind field within the Oklahoma City ParkProperties of the wind field within the Oklahoma City Parkwinds, turbulence, and dispersion in built-up downtown areas of Oklahoma

Pan, Hansheng

2011-01-01T23:59:59.000Z

348

Chaotic Dynamos Generated by a Turbulent Flow of Liquid Sodium  

SciTech Connect

We report the observation of several dynamical regimes of the magnetic field generated by a turbulent flow of liquid sodium (VKS experiment). Stationary dynamos, transitions to relaxation cycles or to intermittent bursts, and random field reversals occur in a fairly small range of parameters. Large scale dynamics of the magnetic field result from the interactions of a few modes. The low dimensional nature of these dynamics is not smeared out by the very strong turbulent fluctuations of the flow.

Ravelet, F.; Monchaux, R.; Aumaitre, S.; Chiffaudel, A.; Daviaud, F.; Dubrulle, B. [Service de Physique de lEtat Condense, Direction des Sciences de la Matiere, CEA-Saclay, CNRS URA 2464, 91191 Gif-sur-Yvette cedex (France); Berhanu, M.; Fauve, S.; Mordant, N.; Petrelis, F. [Laboratoire de Physique Statistique de lEcole Normale Superieure, CNRS UMR 8550, 24 Rue Lhomond, 75231 Paris Cedex 05 (France); Bourgoin, M.; Odier, Ph.; Plihon, N.; Pinton, J.-F.; Volk, R. [Laboratoire de Physique de lEcole Normale Superieure de Lyon, CNRS UMR 5672, 46 allee dItalie, 69364 Lyon Cedex 07 (France)

2008-08-15T23:59:59.000Z

349

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

DOE Green Energy (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

350

Turbulence structure in a Taylor-Couette apparatus  

SciTech Connect

Turbulence measurements were made in a Taylor-Couette apparatus as a basis for future flame propagation studies. Results of the present study extend that of earlier work by more complete characterization of the featureless turbulence regime generated by the Taylor-Couette apparatus. Laser Doppler Velocimetry was used to measure Reynolds stresses, integral and micro time scales and power spectra over a wide range of turbulence intensities typically encountered by turbulent pre-mixed hydrocarbon-air flames. Measurements of radial velocity intensities are consistent with earlier axial and circumferential velocity measurements that indicated a linear relationship between turbulence intensity and the Reynolds number based on the average cylinder rotation speed and wall separation distance. Measured integral and micro time scales and approximated integral length scales were all found to decrease with the Reynolds number, possibly associated with a confinement of the largest scales (of the order of the cylinder wall separation distance). Regions of transverse isotropy were discovered in axial-radial cross correlations for average cylinder Reynolds numbers less than 6000 and are predicted to exist also for circumferential cross correlations at higher average Reynolds numbers, greater than 6000. Power spectra for the independent directions of velocity fluctuation exhibited -5/3 slopes, suggesting that the flow also has some additional isotropic characteristics and demonstrating the role of the Taylor-Couette apparatus as a novel means for generating turbulence for flame propagation studies. (author)

Fehrenbacher, Noah; Aldredge, Ralph C.; Morgan, Joshua T. [Department of Mechanical and Aeronautical Engineering, University of California, Davis, CA 95616 (United States)

2007-10-15T23:59:59.000Z

351

Dissipation and Heating in Supersonic Hydrodynamic and MHD Turbulence  

E-Print Network (OSTI)

We study energy dissipation and heating by supersonic MHD turbulence in molecular clouds using Athena, a new higher-order Godunov code. We analyze the dependence of the saturation amplitude, energy dissipation characteristics, power spectra, sonic scaling, and indicators of intermittency in the turbulence on factors such as the magnetic field strength, driving scale, energy injection rate, and numerical resolution. While convergence in the energies is reached at moderate resolutions, we find that the power spectra require much higher resolutions that are difficult to obtain. In a 1024^3 hydro run, we find a power law relationship between the velocity dispersion and the spatial scale on which it is measured, while for an MHD run at the same resolution we find no such power law. The time-variability and temperature intermittency in the turbulence both show a dependence on the driving scale, indicating that numerically driving turbulence by an arbitrary mechanism may not allow a realistic representation of these properties. We also note similar features in the power spectrum of the compressive component of velocity for supersonic MHD turbulence as in the velocity spectrum of an initially-spherical MHD blast wave, implying that the power law form does not rule out shocks, rather than a turbulent cascade, playing a significant role in the regulation of energy transfer between spatial scales.

M. Nicole Lemaster; James M. Stone

2008-09-23T23:59:59.000Z

352

The evaluation of a turbulent loads characterization system  

DOE Green Energy (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

353

Estimates of Turbulence from Numerical Weather Prediction Model Output with Applications to Turbulence Diagnosis and Data Assimilation  

Science Conference Proceedings (OSTI)

Estimates of small-scale turbulence from numerical model output are produced from local estimates of the spatial structure functions of model variables such as the velocity and temperature. The key assumptions used are the existence of a ...

Rod Frehlich; Robert Sharman

2004-10-01T23:59:59.000Z

354

Thermal soaring flight of birds and unmanned aerial vehicles  

E-Print Network (OSTI)

Thermal soaring saves much energy, but flying large distances in this form represents a great challenge for birds, people and Unmanned Aerial Vehicles (UAVs). The solution is to make use of so-called thermals, which are localized, warmer regions in the atmosphere moving upwards with a speed exceeding the descent rate of birds and planes. Saving energy by exploiting the environment more efficiently is an important possibility for autonomous UAVs as well. Successful control strategies have been developed recently for UAVs in simulations and in real applications. This paper first presents an overview of our knowledge of the soaring flight and strategy of birds, followed by a discussion of control strategies that have been developed for soaring UAVs both in simulations and applications on real platforms. To improve the accuracy of simulation of thermal exploitation strategies we propose a method to take into account the effect of turbulence. Finally we propose a new GPS independent control strategy for exploiting...

Ákos, Zsuzsa; Leven, Severin; Vicsek, Tamás; 10.1088/1748-3182/5/4/045003

2010-01-01T23:59:59.000Z

355

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

SciTech Connect

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

Caughey, David

2010-10-08T23:59:59.000Z

356

Assessment of RANS-based turbulent combustion models for prediction of gas turbine emissions: turbulence model and reaction mechanism effects  

DOE Green Energy (OSTI)

The goal of this study is to assess current, commonly applied turbulence and combustion models with respect to their performance in gas-turbine combustion (GTC). Reynolds Averaged Navier-Stokes (RANS)-based turbulence and chemistry models are two primary factors influencing the uncertainty in predicting turbulent combustion characteristics, especially for GTC. RANS-based methods are the design tools of choice in the gas turbine industry due to the high computational costs of LES (Large Eddy Simulation). In this study, lean premixed combustion of methane was simulated using two different reduced mechanisms (ARM9 and ARM19) along with the Eddy Dissipation Concept (EDC) turbulent chemistry interaction model to calculate the CO and NOx emissions. The effect of turbulence models was assessed by considering two different models. Both of the models tested performed well in the prediction of temperature and major species profiles. Predicted values of NO emission profiles showed an average difference of ±5 ppm compared to experimental values. Computed intermediate species profiles showed large qualitative and quantitative errors when compared with the experimental data. These discrepancies, especially the intermediate species hydrogen, indicate the challenges these reduced mechanisms and turbulence models can present when modeling pollutant emissions from gas turbine combustors.

Nanduri, J.R.; Celik, I.B.; Strakey, P.A.; Parsons, D.R.

2007-10-01T23:59:59.000Z

357

Random walk of magnetic field lines in dynamical turbulence: A field line tracing method. I. Slab turbulence  

SciTech Connect

To study the wandering of magnetic field lines is an important subject in theoretical physics. Results of field line random walk theories can be applied in plasma physics as well as astrophysics. Previous investigations are based on magnetostatic models. These models have been used in analytical work as well as in computer simulations to warrant mathematical and numerical tractability. To replace the magnetostatic model by a dynamical turbulence model is a difficult task. In the present article, a field line tracing method is used to describe field line wandering in dynamical magnetic turbulence. As examples different models are employed, namely, the plasma wave model, the damping model of dynamical turbulence, and the random sweeping model. It is demonstrated that the choice of the turbulence model has a very strong influence on the field line structure. It seems that if dynamical turbulence effects are included, Markovian diffusion can be found for other forms of the wave spectrum as in the magnetostatic model. Therefore, the results of the present paper are useful to specify turbulence models. As a further application we consider charged particle transport at early times.

Shalchi, A. [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada)

2010-08-15T23:59:59.000Z

358

Turbulent Velocity-Variance Profiles in the Stable Boundary Layer Generated by a Nocturnal Low-Level Jet  

Science Conference Proceedings (OSTI)

Profiles of mean winds and turbulence were measured by the High Resolution Doppler lidar in the strong-wind stable boundary layer (SBL) with continuous turbulence. The turbulence quantity measured was the variance of the streamwise wind velocity ...

Robert M. Banta; Yelena L. Pichugina; W. Alan Brewer

2006-11-01T23:59:59.000Z

359

Sirius A: turbulence or mass loss?  

E-Print Network (OSTI)

Context. Abundance anomalies observed in a fraction of A and B stars of both Pop I and II are apparently related to internal particle transport. Aims. Using available constraints from Sirius A, we wish to determine how well evolutionary models including atomic diffusion can explain observed abundance anomalies when either turbulence or mass loss is used as the main competitor to atomic diffusion. Methods. Complete stellar evolution models, including the effects of atomic diffusion and radiative accelerations, have been computed from the zero age main-sequence of 2.1M\\odot stars for metallicities of Z0 = 0.01 \\pm 0.001 and shown to agree with the observed parameters of Sirius A. Surface abundances were predicted for three values of the mass loss rate and for four values of the mixed surface zone. Results. A mixed mass of ~ 10^-6 M\\odot or a mass loss rate of 10^-13 M\\odot/yr were determined through comparison with observations. Of the 17 abundances determined observationally which are included in our calculati...

Michaud, G; Vick, M

2011-01-01T23:59:59.000Z

360

Nonlocal Phenomenology for anisotropic MHD turbulence  

E-Print Network (OSTI)

A non-local cascade model for anisotropic MHD turbulence in the presence of a guiding magnetic field is proposed. The model takes into account that (a) energy cascades in an anisotropic manner and as a result a different estimate for the cascade rate in the direction parallel and perpendicular to the guiding field is made. (b) the interactions that result in the cascade are between different scales. Eddies with wave numbers $k_\\|$ and $k_\\perp$ interact with eddies with wave numbers $q_\\|,q_\\perp$ such that a resonance condition between the wave numbers $q_\\|,q_\\perp$ and $k_\\|,k_\\perp$ holds. As a consequence energy from the eddy with wave numbers $k_\\|$ and $k_\\perp$ cascades due to interactions with eddies located in the resonant manifold whose wavenumbers are determined by: $q_\\|\\simeq \\epsilon^{{1}/{3}}k_\\perp^{2/3}/B$, $q_\\perp=k_\\perp$ and energy will cascade along the lines $k_\\|\\sim C+k_\\perp^{2/3} \\epsilon^{1/3}/B_0$. For a uniform energy injection rate in the parallel direction the resulting energy...

Alexakis, Alexandros

2007-01-01T23:59:59.000Z

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361

Fluctuating pressure correlations in wall turbulence  

E-Print Network (OSTI)

The purpose of the present paper is to study the influence of wall-echo on pressure fluctuations $p'$, and on statistical correlations containing $p'$, {\\em viz} redistribution $\\phi_{ij}$ and pressure diffusion $d_{ij}^{(p)}$. We extend the usual analysis of turbulent correlations containing pressure fluctuations in wall-bounded \\tsc{dns} computations [Kim J.: {\\em J. Fluid Mech.} {\\bf 205} (1989) 421--451], separating $p'$ not only into rapid $p_{(\\mathrm{r})}'$ and slow $p_{(\\mathrm{s})}'$ parts [Chou P.Y.: {\\em Quart. Appl. Math.} {\\bf 3} (1945) 38--54], but further into volume (weakly inhomogeneous; $p'_{(\\mathrm{r};\\mathfrak{V})}$ and $p'_{(\\mathrm{s};\\mathfrak{V})}$) and surface (strongly inhomogeneous wall-echo; $p'_{(\\mathrm{r};w)}$ and $p'_{(\\mathrm{s};w)}$) terms. An algorithm, based on a Green's function approach, is developed to compute the above splittings for various correlations containing pressure fluctuations (redistribution, pressure diffusion, velocity/pressure-gradient), in fully develope...

Gerolymos, G A; Senechal, D; Vallet, I

2013-01-01T23:59:59.000Z

362

Simulation of lean premixed turbulent combustion  

DOE Green Energy (OSTI)

There is considerable technological interest in developingnew fuel-flexible combustion systems that can burn fuels such ashydrogenor syngas. Lean premixed systems have the potential to burn thesetypes of fuels with high efficiency and low NOx emissions due to reducedburnt gas temperatures. Although traditional scientific approaches basedon theory and laboratory experiment have played essential roles indeveloping our current understanding of premixed combustion, they areunable to meet the challenges of designing fuel-flexible lean premixedcombustion devices. Computation, with itsability to deal with complexityand its unlimited access to data, hasthe potential for addressing thesechallenges. Realizing this potential requires the ability to perform highfidelity simulations of turbulent lean premixed flames under realisticconditions. In this paper, we examine the specialized mathematicalstructure of these combustion problems and discuss simulation approachesthat exploit this structure. Using these ideas we can dramatically reducecomputational cost, making it possible to perform high-fidelitysimulations of realistic flames. We illustrate this methodology byconsidering ultra-lean hydrogen flames and discuss how this type ofsimulation is changing the way researchers study combustion.

Bell, John B.; Day, Marcus S.; Almgren, Ann S.; Lijewski, MichaelJ.; Rendleman, Charles A.; Cheng, Robert K.; Shepherd, Ian G.

2006-06-25T23:59:59.000Z

363

Multiscalar measurements of turbulence-chemistry interactions in nonpremixed flames  

DOE Green Energy (OSTI)

Selected results from experiments conducted over the past several years involving simultaneous multiscalar point measurements in turbulent nonpremixed flames are reviewed in this paper. In these experiments, spontaneous Raman scattering and Rayleigh scattering measurements of the major species and temperature were combined with laser-induced fluorescence measurements of minor species. The most important feature of these experiments is that they provide detailed data on the instantaneous relationships among species concentration, temperature, and derived scalar quantities that reflect the state of mixing or the progress of reaction. The data allow quantitative comparisons of the thermochemical states in turbulent flames with those in idealized representations, such as steady strained laminar flames, perfectly stirred reactors, or adiabatic equilibrium. The data may also be compared with results (measured or calculated) from unsteady laminar flames and from direct numerical simulations (DNS) of turbulent reacting flows. such comparisons provide insights into the fundamental nature of turbulence-chemistry interactions, and they allow one to examine the validity of some of the basic assumptions that turbulent combustion models are built upon. Furthermore, these data allow quantitative evaluations of the predictive accuracy, strengths, and limitations of a wide variety of combustions models.

Barlow, R.S.

1995-12-01T23:59:59.000Z

364

GRAVITATIONALLY UNSTABLE FLAMES: RAYLEIGH-TAYLOR STRETCHING VERSUS TURBULENT WRINKLING  

SciTech Connect

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

365

Measurement of turbulent wind velocities using a rotating boom apparatus  

DOE Green Energy (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

366

A spray-suppression model for turbulent combustion  

SciTech Connect

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

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

2000-02-14T23:59:59.000Z

367

Active Control for Statistically Stationary Turbulent PremixedFlame Simulations  

Science Conference Proceedings (OSTI)

The speed of propagation of a premixed turbulent flame correlates with the intensity of the turbulence encountered by the flame. One consequence of this property is that premixed flames in both laboratory experiments and practical combustors require some type of stabilization mechanism to prevent blow-off and flashback. The stabilization devices often introduce a level of geometric complexity that is prohibitive for detailed computational studies of turbulent flame dynamics. Furthermore, the stabilization introduces additional fluid mechanical complexity into the overall combustion process that can complicate the analysis of fundamental flame properties. To circumvent these difficulties we introduce a feedback control algorithm that allows us to computationally stabilize a turbulent premixed flame in a simple geometric configuration. For the simulations, we specify turbulent inflow conditions and dynamically adjust the integrated fueling rate to control the mean location of the flame in the domain. We outline the numerical procedure, and illustrate the behavior of the control algorithm on methane flames at various equivalence ratios in two dimensions. The simulation data are used to study the local variation in the speed of propagation due to flame surface curvature.

Bell, J.B.; Day, M.S.; Grcar, J.F.; Lijewski, M.J.

2005-08-30T23:59:59.000Z

368

A spray-suppression model for turbulent combustion  

DOE Green Energy (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

369

A Model for the Turbulent Structure of the Stratocumulus–Topped Atmospheric Boundary Layer  

Science Conference Proceedings (OSTI)

A multilevel ensemble-averaged model has been developed to study the cloud-topped atmospheric boundary layer (ABL). Turbulence closure is formulated by using an equation for the turbulent kinetic energy and either a diagnostic formulation of the ...

P. G. Duynkerke; A. G. M. Driedonks

1987-01-01T23:59:59.000Z

370

A Surface Flux Parameterization Based on the Vertically Averaged Turbulence Kinetic Energy  

Science Conference Proceedings (OSTI)

A new bulk transfer formulation for the surface turbulent fluxes of momentum, heat, and moisture has been developed by using the square root of the vertically averaged turbulent kinetic energy (TKE) in the atmospheric boundary layer as a velocity ...

Changan Zhang; David A. Randall; Chin-Hoh Moeng; Mark Branson; Kerry A. Moyer; Qing Wang

1996-11-01T23:59:59.000Z

371

An Integrated Approach to Mid- and Upper-Level Turbulence Forecasting  

Science Conference Proceedings (OSTI)

An automated procedure for forecasting mid- and upper-level turbulence that affects aircraft is described. This procedure, termed the Graphical Turbulence Guidance system, uses output from numerical weather prediction model forecasts to derive ...

R. Sharman; C. Tebaldi; G. Wiener; J. Wolff

2006-06-01T23:59:59.000Z

372

On the Combined Effects of Turbulence and Gravity on Droplet Collisions in Clouds: A Numerical Study  

Science Conference Proceedings (OSTI)

This paper examines the combined influences of turbulence and gravity on droplet collision statistics in turbulent clouds by means of direct numerical simulation (DNS). The essential microphysical mechanisms that determine the geometric collision ...

Eric J. P. Woittiez; Harm J. J. Jonker; Luís M. Portela

2009-07-01T23:59:59.000Z

373

Observations of Turbulence Mixing and Vorticity in a Littoral Surface Boundary Layer  

Science Conference Proceedings (OSTI)

Measurements of small-scale vorticity, turbulence velocity, and dissipation rates of turbulence kinetic energy ? were taken in a littoral fetch-limited surface wave boundary layer. Drifters deployed on the surface formed convergence streaks with ...

R-C. Lien; B. Sanford; W-T. Tsai

2008-03-01T23:59:59.000Z

374

Parameterization of Orography-Induced Turbulence in a Mesobeta--Scale Model  

Science Conference Proceedings (OSTI)

The possibility of extending existing techniques for turbulence parameterization in the planetary boundary layer to attitude, orography-induced turbulence events is examined. Starting from a well-tested scheme, we show that it is possible to ...

P. Bougeault; P. Lacarrere

1989-08-01T23:59:59.000Z

375

Turbulent Kinetic Energy and Its Dissipation Rate in the Equatorial Mixed Layer  

Science Conference Proceedings (OSTI)

The authors apply a one-dimensional mixed layer model, based on second moment closure of turbulence, to study the characteristics of turbulence in the equatorial mixed layer. In particular, they focus on characteristics such as the TKE and the ...

Carol Anne Clayson; Lakshmi H. Kantha

1999-09-01T23:59:59.000Z

376

Turbulence Dynamics at the Shoal–Channel Interface in a Partially Stratified Estuary  

Science Conference Proceedings (OSTI)

Turbulence observations at the shoal–channel interface in South San Francisco Bay are described and analyzed in this work. Profiles of turbulent kinetic energy (TKE) shear production and dissipation rate are estimated from ADCP beam velocities ...

Audric G. Collignon; Mark T. Stacey

2013-05-01T23:59:59.000Z

377

Control of Chemical Reactions by Convective Turbulence in the Boundary Layer  

Science Conference Proceedings (OSTI)

The influence of convective turbulence on chemical reactions in the atmospheric boundary layer is studied by means of direct numerical simulation (DNS). An archetype of turbulent reacting flows is used to study the reaction zones and to obtain a ...

M. Jeroen Molemaker; Jordi Vilà-Guerau de Arellano

1998-02-01T23:59:59.000Z

378

Effects of Micro- and Macroscale Turbulent Mixing on the Chemical Processes in Engine Exhaust Plumes  

Science Conference Proceedings (OSTI)

Turbulent mixing and chemical reactions in the near field of an engine exhaust jet plume have been investigated using a mixing model that explicitly incorporates both large- and small-scale turbulent mixing and the molecular diffusion effects. A ...

S. Menon; J. Wu

1998-06-01T23:59:59.000Z

379

Evaluation of Modeled Stratocumulus-Capped Boundary Layer Turbulence with Ship-Borne Data  

Science Conference Proceedings (OSTI)

Numerically modeled turbulence simulated by the Advanced Research WRF model is evaluated with turbulence measurements from NOAA’s high resolution Doppler lidar on the NOAA Research Vessel Ronald H. Brown during the VOCALS-REx field program. A non-...

Takanobu Yamaguchi; W. Alan Brewer; Graham Feingold

380

Stably Stratified Shear Turbulence: A New Model for the Energy Dissipation Length Scale  

Science Conference Proceedings (OSTI)

A model is presented to compute the turbulent kinetic energy dissipation length scale l? in a stably stratified shear flow. The expression for l? is derived from solving the spectral balance equation for the turbulent kinetic energy. The buoyancy ...

Y. Cheng; V. M. Canuto

1994-08-01T23:59:59.000Z

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.
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to obtain the most current and comprehensive results.


381

Low-Resolution Numerical Simulation of Decaying Two-Dimensional Turbulence  

Science Conference Proceedings (OSTI)

Numerical simulations of two-dimensional turbulence show that O(??1) and O(??4) energy spectra—described by Fox and Orszag (1973a) as enstrophy-equipartitioning and strongly dissipating turbulence, respectively—occur independently of the type of ...

Andrew F. Bennett; Dale B. Haidvogel

1983-03-01T23:59:59.000Z

382

Influence of Shallow Cumuli on Subcloud Turbulence Fluxes Analyzed from Aircraft Data  

Science Conference Proceedings (OSTI)

The purpose of this study is to improve understanding of shallow cumuli in the planetary boundary layer (PBL) by quantitatively analysing subcloud turbulence variables. Aircraft turbulence data for three flights from the 1986 Hydrologic–...

Zekai Otles; John A. Young

1996-03-01T23:59:59.000Z

383

Collisions of Small Drops in a Turbulent Flow. Part III: Relative Droplet Fluxes and Swept Volumes  

Science Conference Proceedings (OSTI)

Swept volumes of cloud droplets with radii below 20 ?m are calculated under conditions typical of atmospheric cloud turbulence characterized by enormous values of Reynolds numbers, high turbulent intermittency, and characteristic values of the ...

M. B. Pinsky; A. P. Khain; B. Grits; M. Shapiro

2006-08-01T23:59:59.000Z

384

Numerical Simulations of Observed Arctic Stratus Clouds Using a Second-Order Turbulence Closure Model  

Science Conference Proceedings (OSTI)

A high-resolution one-dimensional version of a second-order turbulence closure radiative-convective model, developed at Los Alamos National Laboratory, is used to simulate the interactions among turbulence, radiation, and bulk cloud parameters in ...

W. S. Smith; C-Y. J. Kao

1996-01-01T23:59:59.000Z

385

Emergence of Jets from Turbulence in the Shallow-Water Equations on an Equatorial Beta Plane  

Science Conference Proceedings (OSTI)

Coherent jets, such as the Jovian banded winds, are a prominent feature of rotating turbulence. Shallow-water turbulence models capture the essential mechanism of jet formation, which is systematic eddy momentum flux directed up the mean velocity ...

Brian F. Farrell; Petros J. Ioannou

2009-10-01T23:59:59.000Z

386

Microstructure Estimates of Turbulent Salinity Flux and the Dissipation Spectrum of Salinity  

Science Conference Proceedings (OSTI)

Direct determination of the irreversible turbulent flux of salinity in the ocean has not been possible because of the complexity of measuring salinity on the smallest scales over which it mixes. Presented is an analysis of turbulent salinity ...

Jonathan D. Nash; James N. Moum

2002-08-01T23:59:59.000Z

387

A Near-Surface Microstructure Sensor System Used during TOGA COARE. Part II: Turbulence Measurements  

Science Conference Proceedings (OSTI)

New techniques developed for near-surface turbulence measurements during the Tropical Ocean Global Atmosphere (TOGA) Coupled Ocean–Atmosphere Response Experiment (COARE) employ a difference in spatial scales of turbulence and surface waves. ...

A. Soloviev; R. Lukas; P. Hacker; H. Schoeberlein; M. Baker; A. Arjannikov

1999-11-01T23:59:59.000Z

388

Application of the E – ? Turbulence Closure Model to the Neutral and Stable Atmospheric Boundary Layer  

Science Conference Proceedings (OSTI)

In the E – ? turbulence model an eddy-exchange coefficient is evaluated from the turbulent kinetic energy E and viscous dissipation ?. In this study we will apply the E – ? model to the stable and neutral atmospheric boundary layer. A discussion ...

P. G. Duynkerke

1988-03-01T23:59:59.000Z

389

Probability Distribution Characteristics for Surface Air–Sea Turbulent Heat Fluxes over the Global Ocean  

Science Conference Proceedings (OSTI)

To analyze the probability density distributions of surface turbulent heat fluxes, the authors apply the two-parametric modified Fisher–Tippett (MFT) distribution to the sensible and latent turbulent heat fluxes recomputed from 6-hourly NCEP–NCAR ...

Sergey K. Gulev; Konstantin Belyaev

2012-01-01T23:59:59.000Z

390

Evaluation of the Kinetic Energy Approach for Modeling Turbulent Fluxesin Stratocumulus  

Science Conference Proceedings (OSTI)

The modeling of vertical mixing by a turbulence scheme on the basis of prognostic turbulent kinetic energy (E) and a diagnostic length scale (l) is investigated with particular emphasis on the representation of entrainment. The behavior of this E–...

G. Lenderink; A. A. M. Holtslag

2000-01-01T23:59:59.000Z

391

The Structure of Turbulence in the Near-neutral Atmospheric Boundary Layer  

Science Conference Proceedings (OSTI)

In this paper, the idea of local similarity, previously used to study turbulence in the stably stratified boundary layer, is used to investigate the structure of turbulence in the neutral atmospheric boundary layer and to relate this structure to ...

A. L. M. Grant

1992-02-01T23:59:59.000Z

392

Statistics of Shear and Turbulent Dissipation Profiles in Random Internal Wave Fields  

Science Conference Proceedings (OSTI)

Because breaking internal waves produces most of the turbulence in the thermocline, the statistics of ?, the rate of turbulent dissipation, cannot be understood apart from the statistics of internal wave shear. The statistics of ? and shear are ...

M. C. Gregg; H. E. Seim; D. B. Percival

1993-08-01T23:59:59.000Z

393

Turbulence, Condensation, and Liquid Water Transport in Numerically Simulated Nonprecipitating Stratocumulus Clouds  

Science Conference Proceedings (OSTI)

Condensation and turbulent liquid water transport in stratocumulus clouds involve complicated interactions between turbulence dynamics and cloud microphysical processes, and play essential roles in defining the cloud structure. This work aims at ...

Shouping Wang; Qing Wang; Graham Feingold

2003-01-01T23:59:59.000Z

394

Measurements of Turbulent Fluxes of Momentum and Sensible Heat over the Labrador Sea  

Science Conference Proceedings (OSTI)

Turbulent fluxes of momentum and sensible heat were estimated from sonic anemometer measurements gathered over the Labrador Sea during a winter cruise of the R/V Knorr. The inertial dissipation method was used to calculate turbulent fluxes of ...

Karl Bumke; U. Karger; K. Uhlig

2002-02-01T23:59:59.000Z

395

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

Science Conference Proceedings (OSTI)

The terms of the steady-state, homogeneous turbulent kinetic energy budgets are obtained from measurements of turbulence and fine structure from the small autonomous underwater vehicle (AUV) Remote Environmental Measuring Units (REMUS). The ...

Louis Goodman; Edward R. Levine; Rolf G. Lueck

2006-07-01T23:59:59.000Z

396

12.820 / 12.822 Turbulence in Geophysical Systems, Spring 2004  

E-Print Network (OSTI)

This course presents the phenomena, theory, and modeling of turbulence in the Earth's oceans and atmosphere. The scope ranges from the fine structure to planetary scale motions. The regimes of turbulence include homogeneous ...

Legg, Sonya

397

12.820 / 12.822 Turbulence in Geophysical Systems, Spring 2005  

E-Print Network (OSTI)

This course presents the phenomena, theory, and modeling of turbulence in the Earth's oceans and atmosphere. The scope ranges from the fine structure to planetary scale motions. The regimes of turbulence include homogeneous ...

Ferrari, Raffaele

398

Numerical Simulation of ANATEX Tracer Data Using a Turbulence Closure Model for Long-Range Dispersion  

Science Conference Proceedings (OSTI)

A long-range transport model based on turbulence closure concepts is described. The model extends the description of planetary boundary layer turbulent diffusion to the larger scales and uses statistical wind information to predict contaminant ...

R. I. Sykes; S. F. Parker; D. S. Henn; W. S. Lewellen

1993-05-01T23:59:59.000Z

399

An Estimation of Buoyancy Flux for a Mixture of Turbulence and Double Diffusion  

Science Conference Proceedings (OSTI)

Microstructure measurements were made in the Mixed Water Region of the Oyashio/Kuroshio/Tsugaru currents system where both turbulence and double diffusion are involved in mixing. While intense turbulence is observed near the front between the ...

Ryuichiro Inoue; Hidekatsu Yamazaki; Fabian Wolk; Tokihiro Kono; Jiro Yoshida

2007-03-01T23:59:59.000Z

400

Direct Numerical Simulation of Differential Scalar Diffusion in Three-Dimensional Stratified Turbulence  

Science Conference Proceedings (OSTI)

The potential for differential turbulent transport of oceanic temperature (T) and salinity () is explored using three-dimensional direct numerical simulations of decaying stratified turbulence. The simulations employ a realistic molecular ...

Ann E. Gargett; William J. Merryfield; Greg Holloway

2003-08-01T23:59:59.000Z

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.


401

The Quest for K?—Preliminary Results from Direct Measurements of Turbulent Fluxes in the Ocean  

Science Conference Proceedings (OSTI)

Simultaneous measurements of vertical velocity fluctuations, w?, and temperature fluctuations, T?, on scales of three-dimensional turbulence yield a direct measure of the turbulent heat flux, Jq. The scales contributing most significantly to Jq ...

J. N. Moum

1990-12-01T23:59:59.000Z

402

Direct Numerical Simulation of Differential Scalar Diffusion in Three-Dimensional Stratified Turbulence  

Science Conference Proceedings (OSTI)

The potential for differential turbulent transport of oceanic temperature (T) and salinity (S) is explored using three-dimensional direct numerical simulations of decaying stratified turbulence. The simulations employ a realistic molecular ...

Ann E. Gargett; William J. Merryfield; Greg Holloway

2003-08-01T23:59:59.000Z

403

The Direct Estimation of Near-Bottom Turbulent Fluxes in the Presence of Energetic Wave Motions  

Science Conference Proceedings (OSTI)

Velocities produced by energetic waves can contaminate direct covariance estimates of near-bottom turbulent shear stress and turbulent heat flux. A new adaptive filtering technique is introduced to minimize the contribution of wave-induced ...

W. J. Shaw; J. H. Trowbridge

2001-09-01T23:59:59.000Z

404

An Estimate of Tidal Energy Lost to Turbulence at the Hawaiian Ridge  

Science Conference Proceedings (OSTI)

An integrated analysis of turbulence observations from four unique instrument platforms obtained over the Hawaiian Ridge leads to an assessment of the vertical, cross-ridge, and along-ridge structure of turbulence dissipation rate and ...

Jody M. Klymak; James N. Moum; Jonathan D. Nash; Eric Kunze; James B. Girton; Glenn S. Carter; Craig M. Lee; Thomas B. Sanford; Michael C. Gregg

2006-06-01T23:59:59.000Z

405

meeting summary: Future Directions for Research on Meter- and Submeter-Scale Atmospheric Turbulence  

Science Conference Proceedings (OSTI)

In the 1970s, tremendous progress was made in the physics of atmospheric finescale turbulence. In subsequent decades, effort in this field has languished. Although many scientific and technological problems associated with finescale turbulence ...

Andreas Muschinski; Donald H. Lenschow

2001-12-01T23:59:59.000Z

406

Influences of Moist Convection on a Cold-Season Outbreak of Clear-Air Turbulence (CAT)  

Science Conference Proceedings (OSTI)

The 9–10 March 2006 aviation turbulence outbreak over the central United States is examined using observations and numerical simulations. Though the turbulence occurs within a deep synoptic cyclone with widespread precipitation, comparison of ...

Stanley B. Trier; Robert D. Sharman; Todd P. Lane

2012-08-01T23:59:59.000Z

407

Gravity Wave Instability Dynamics at High Reynolds Numbers. Part II: Turbulence Evolution, Structure, and Anisotropy  

Science Conference Proceedings (OSTI)

This paper examines the character, intermittency, and anisotropy of turbulence accompanying wave instability, breaking, and turbulence evolution and decay for gravity waves (GW) having a high intrinsic frequency, amplitudes above and below ...

David C. Fritts; Ling Wang; Joe Werne; Tom Lund; Kam Wan

2009-05-01T23:59:59.000Z

408

Sampling Turbulence in the Stratified Ocean: Statistical Consequences of Strong Intermittency  

Science Conference Proceedings (OSTI)

Turbulence and turbulent mixing in the ocean are strongly intermittent in amplitude, space and time. The degree of intermittency is measured by the “intermittency factor” ?2, defined as either ?2ln?, the variance of the logarithm of the viscous ...

Mark A. Baker; Carl H. Gibson

1987-10-01T23:59:59.000Z

409

Turbulence Structure of the Hurricane Boundary Layer between the Outer Rainbands  

Science Conference Proceedings (OSTI)

As part of the Coupled Boundary Layers Air–Sea Transfer (CBLAST)-Hurricane program, flights were conducted to directly measure turbulent fluxes and turbulence properties in the high-wind boundary layer of hurricanes between the outer rainbands. ...

Jun A. Zhang; William M. Drennan; Peter G. Black; Jeffrey R. French

2009-08-01T23:59:59.000Z

410

Quality Controlling Surf Zone Acoustic Doppler Velocimeter Observations to Estimate the Turbulent Dissipation Rate  

Science Conference Proceedings (OSTI)

High-quality measurements of the turbulent dissipation rate ? are required to diagnose field surf-zone turbulence budgets. Quality control (QC) methods are presented for estimating surf zone ? with acoustic Doppler velocimeter (ADV) data. Bad ADV ...

Falk Feddersen

2010-12-01T23:59:59.000Z

411

Turbulent Transport and Heating of Trace Heavy Ions in Hot Magnetized Plasmas  

E-Print Network (OSTI)

Scaling laws for the transport and heating of trace heavy ions in low-frequency magnetized plasma turbulence are derived and compared with direct numerical simulations. The predicted dependences of turbulent fluxes and ...

Barnes, Michael

412

Stress on the Mediterranean Outflow Plume: Part II. Turbulent Dissipation and Shear Measurements  

Science Conference Proceedings (OSTI)

Bottom and interfacial stresses on the Mediterranean outflow plume are estimated using vertical profiles of turbulent dissipation and velocity collected in the Gulf of Cadiz. Turbulent dissipation is high throughout the plume, with a local ...

Gregory C. Johnson; Rolf G. Lueck; Thomas B. Sanford

1994-10-01T23:59:59.000Z

413

A New Second-Order Turbulence Closure Scheme for the Planetary Boundary Layer  

Science Conference Proceedings (OSTI)

A new turbulence formulation for the planetary boundary layer (PBL) is presented and compared with large-eddy simulations (LES) for the dry PBL. The new scheme contains a prognostic equation for the turbulent kinetic energy. Other second-order ...

K. Abdella; N. McFarlane

1997-07-01T23:59:59.000Z

414

Calculation of Surface Fluxes under Convective Conditions by Turbulence Closure Models  

Science Conference Proceedings (OSTI)

A method of deriving new relationships between near-surface turbulent fluxes and vertical differences of wind speed and potential temperature between two levels in the atmospheric surface layer from simplified second-order turbulence closure ...

Lech ?obocki

2001-03-01T23:59:59.000Z

415

A Pressure-Sphere Anemometer for Measuring Turbulence and Fluxes in Hurricanes  

Science Conference Proceedings (OSTI)

Turbulence and air-surface exchange are important factors throughout the life cycle of a tropical cyclone. Conventional turbulence instruments are not designed to function in the extreme environment encountered in such storms. A new instrument ...

Richard M. Eckman; Ronald J. Dobosy; David L. Auble; Thomas W. Strong; Timothy L. Crawford

2007-06-01T23:59:59.000Z

416

Observation of a localized transition from edge to core density turbulence in the TFTR tokamak  

Science Conference Proceedings (OSTI)

A localized transition zone is observed between turbulent, long-wavelength density fluctuations ([ital k][sub [perpendicular

Durst, R.D.; Fonck, R.J.; Kim, J.S.; Paul, S.F.; Bretz, N.; Bush, C.; Chang, Z.; Hulse, R. (Department of Nuclear Engineering and Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States) Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States))

1993-11-08T23:59:59.000Z

417

Convective cell generation by kinetic Alfven wave turbulence in the auroral ionosphere  

Science Conference Proceedings (OSTI)

Modulation of convective cells by kinetic Alfven wave (KAW) turbulence is investigated. The interaction is governed by a nonlinear dispersion relation for the convective cells. It is shown that KAW turbulence is disrupted by excitation of the large-scale convective motion through a resonant instability. Application of the results to the auroral ionosphere shows that cross-scale coupling of the KAW turbulence and convective cells plays an important role in the evolution of ionospheric plasma turbulence.

Zhao, J. S.; Wu, D. J. [Purple Mountain Observatory, Chinese Academy of Sciences 210008, Nanjing (China); Yu, M. Y. [Department of Physics, Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China); Institute for Theoretical Physics I, Ruhr University, D-44780 Bochum (Germany); Lu, J. Y. [National Center for Space Weather, China Meteorology Administration 100081, Beijing (China)

2012-06-15T23:59:59.000Z

418

TURBULENT HEAT TRANSPORT IN TWO-AND THREE-DIMENSIONAL TEMPERATURE FIELDS  

E-Print Network (OSTI)

Most fluid flows and heat transfer processes of practicalfor turbulent heat and mass transfer processes. The study

Samaraweera, D.S.A.

2011-01-01T23:59:59.000Z

419

HEATS: Thermal Energy Storage  

SciTech Connect

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

420

Los Alamos scientists propose new theory for development of turbulent  

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

Turbulent magnetic reconnection Turbulent magnetic reconnection Los Alamos scientists propose new theory for development of turbulent magnetic reconnection This new theory was developed to better explain recent large-scale three-dimensional kinetic simulations that describe the physics of this process. April 15, 2011 New LANL 3-D model shows the formation of "flux ropes" in a thin boundary layer of a magnetic field New LANL 3-D model shows the formation of "flux ropes" in a thin boundary layer of a magnetic field. This research seeks to uncover the most fundamental physics of magnetic reconnection, key to a better understanding of Earth's magnetosphere. Contact Kevin Roark Communicatons Office (505) 665-9202 Email LOS ALAMOS, New Mexico, April 15, 2011-In this week's Nature Physics,

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

Multiple mapping conditioning of velocity in turbulent jet flames  

Science Conference Proceedings (OSTI)

Multiple mapping conditioning (MMC) has emerged as a new approach to model turbulent reacting flows. This study revises the standard MMC closure for velocity in turbulent jet flows from linearity in the reference space to linearity in the composition space. This modeling amendment ensures that the standard velocity model in conditional moment closure studies can now be used for MMC computation as well. A simplified model for the velocity-dependence of MMC drift coefficients is derived without loss of generality and is implemented for the revised velocity closure. Modeling results have been corroborated against the Direct Numerical Simulation database of a spatially evolving, planar turbulent jet flame. The revised model shows marked improvement over standard MMC closure in predicting velocity statistics close to the nozzle. (author)

Vaishnavi, P. [Mechanical Engineering Department, Imperial College, London SW7 2AZ (United Kingdom); Kronenburg, A. [Institut fuer Technische Verbrennung, Universitaet Stuttgart, 70174 Stuttgart (Germany)

2010-10-15T23:59:59.000Z

422

Parallel Electric Field Spectrum of Solar Wind Turbulence  

E-Print Network (OSTI)

By searching through more than 10 satellite-years of THEMIS and Cluster data, three reliable examples of parallel electric field turbulence in the undisturbed solar wind have been found. The perpendicular and parallel electric field spectra in these examples have similar shapes and amplitudes, even at large scales (frequencies below the ion gyroscale) where Alfvenic turbulence with no parallel electric field component is thought to dominate. The spectra of the parallel electric field fluctuations are power laws with exponents near -5/3 below the ion scales (~ 0.1 Hz), and with a flattening of the spectrum in the vicinity of this frequency. At small scales (above a few Hz), the spectra are steeper than -5/3 with values in the range of -2.1 to -2.8. These steeper slopes are consistent with expectations for kinetic Alfven turbulence, although their amplitude relative to the perpendicular fluctuations is larger than expected.

Mozer, F S

2013-01-01T23:59:59.000Z

423

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

424

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

DOE Data Explorer (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.

None

425

Search for conformal invariance in compressible two-dimensional turbulence  

E-Print Network (OSTI)

We present a search for conformal invariance in vorticity isolines of two-dimensional compressible turbulence. The vorticity is measured by tracking the motion of particles that float at the surface of a turbulent tank of water. The three-dimensional turbulence in the tank has a Taylor microscale $Re_\\lambda \\simeq 160$. The conformal invariance theory being tested here is related to the behavior of equilibrium systems near a critical point. This theory is associated with the work of L\\"owner, Schramm and others and is usually referred to as Schramm-L\\"owner Evolution (SLE). The system was exposed to several tests of SLE. The results of these tests suggest that zero-vorticity isolines exhibit noticeable departures from this type of conformal invariance.

S. Stefanus; J. Larkin; W. I. Goldburg

2011-06-10T23:59:59.000Z

426

A New Second-Order Turbulence Closure Scheme for Modeling the Oceanic Mixed Layer  

Science Conference Proceedings (OSTI)

A new second-order turbulence closure scheme is proposed for the oceanic mixed layer. The scheme is similar in complexity to a Mellor–Yamada level 2.5 scheme in that the turbulent kinetic energy is the only turbulence quantity treated ...

S. J. D. D’Alessio; K. Abdella; N. A. McFarlane

1998-08-01T23:59:59.000Z

427

Shock-unsteadiness model applied to oblique shock wave/turbulent boundary-layer interaction  

Science Conference Proceedings (OSTI)

Reynolds-averaged Navier-Stokes prediction of shock wave/turbulent boundary layer interactions can yield significant error in terms of the size of the separation bubble. In many applications, this can alter the shock structure and the resulting surface ... Keywords: high-speed flows, separation bubble, shock-unsteadiness, turbulence modelling, turbulent boundary layer

Amjad Ali Pasha; Krishnendu Sinha

2008-09-01T23:59:59.000Z

428

Review of the shear-stress transport turbulence model experience from an industrial perspective  

Science Conference Proceedings (OSTI)

The present author was asked to provide an update on the status and the more recent developments around the shear-stress transport (SST) turbulence model for this special issue of the journal. The article is therefore not intended as a comprehensive ... Keywords: SAS, SST turbulence model, engineering flows, laminar-turbulent transition, scale-adaptive simulation, unsteady flows

Florian R. Menter

2009-04-01T23:59:59.000Z

429

Thermal and Electrical Transport in Oxide Heterostructures  

E-Print Network (OSTI)

of thermal conductivity . . . . . . . . . . . . . . . .4.4 Thermal transport in2.3.2 Thermal transport . . . . . . . . . . . . . . . .

Ravichandran, Jayakanth

2011-01-01T23:59:59.000Z

430

Electron Thermal Transport and Multi-scale Turbulence in Low Collisionality H-mode Plasmas  

E-Print Network (OSTI)

Bull. Am. Phys. Soc. 55, 346 (2010)52nd American Physical Society Annual Meeting of Division of Plasma Physics Chicago Illinois, US, 2010999618515

Schmitz, L.

2010-08-24T23:59:59.000Z

431

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

Science Conference Proceedings (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

432

MEASUREMENTS AND COMPUTATIONS OF FUEL DROPLET TRANSPORT IN TURBULENT FLOWS  

SciTech Connect

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

Joseph Katz and Omar Knio

2007-01-10T23:59:59.000Z

433

Variable energy flux in quasi-static magnetohydrodynamic turbulence  

E-Print Network (OSTI)

Experiments and numerical simulations show that the energy spectrum of the magnetohydrodynamic turbulence in the quasi-static limit deviates from Kolmogorov's $k^{-5/3}$ spectrum as the external magnetic field, or equivalently the interaction parameter, is increased. To explain this phenomena, we construct an analytical turbulence model with variable energy flux that arises due to the Lorentz-force induced dissipation. The energy spectra computed using our model for various interaction parameters are in qualitative agreement with earlier experimental and numerical results.

Mahendra K. Verma

2013-04-25T23:59:59.000Z

434

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 is in agreement 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

2013-05-29T23:59:59.000Z

435

Electron geodesic acoustic modes in electron temperature gradient mode turbulence  

Science Conference Proceedings (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

436

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

437

Short wavelength ion temperature gradient turbulence  

Science Conference Proceedings (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

438

Thermal Management of Solar Cells  

E-Print Network (OSTI)

phonon transmission and interface thermal conductance acrossF. Miao, et al. , "Superior Thermal Conductivity of Single-Advanced Materials for Thermal Management of Electronic

Saadah, Mohammed Ahmed

2013-01-01T23:59:59.000Z

439

Thermal Spray Coatings  

Science Conference Proceedings (OSTI)

Table 35   Thermal spray coatings used for hardfacing applications...piston ring (internal combustion);

440

Plasma-Thermal Synthesis  

INL’s Plasma-Thermal Synthesis process improves the conversion process for natural gas into liquid hydrocarbon fuels.

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

Ocean Thermal Energy Conversion  

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

A process called ocean thermal energy conversion (OTEC) uses the heat energy stored in the Earth's oceans to generate electricity.

442

Nanocomposite Thermal Spray Coatings.  

Science Conference Proceedings (OSTI)

Long-Term Surface Restoration Effect Introduced by Advanced Lubricant Additive · Nanocomposite Thermal Spray Coatings. New Hardfacing Overlay Claddings ...

443

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

444

H I POWER SPECTRA AND THE TURBULENT INTERSTELLAR MEDIUM OF DWARF IRREGULAR GALAXIES  

SciTech Connect

H I spatial power spectra were determined for a sample of 24 nearby dwarf irregular galaxies selected from the Local Irregulars That Trace Luminosity Extremes-The H I Nearby Galaxy Survey sample. The two-dimensional power spectral indices asymptotically become a constant for each galaxy when a significant part of the line profile is integrated. For narrow channel maps, the power spectra become shallower as the channel width decreases, and this shallowing trend continues to our single channel maps. This implies that even the highest velocity resolution of 1.8 km s{sup -1} is not smaller than the thermal dispersion of the coolest, widespread H I component. The one-dimensional power spectra of azimuthal profiles at different radii suggest that the shallower power spectra for narrower channel width is mainly contributed by the inner disks, which indicates that the inner disks have proportionally more cooler H I than the outer disks. Galaxies with lower luminosity (M{sub B} > -14.5 mag) and star formation rate (SFR, log(SFR (M{sub Sun} yr{sup -1})) < -2.1) tend to have steeper power spectra, which implies that the H I line-of-sight depths can be comparable with the radial length scales in low-mass galaxies. A lack of a correlation between the inertial-range spectral indices and SFR surface density implies that either non-stellar power sources are playing a fundamental role in driving the interstellar medium turbulent structure or the nonlinear development of turbulent structures has little to do with the driving sources.

Zhang Hongxin [Purple Mountain Observatory/Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, 2 West Beijing Road, Nanjing 210008 (China); Hunter, Deidre A. [Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States); Elmegreen, Bruce G., E-mail: hxzhang@pmo.ac.cn, E-mail: hxzhang@lowell.edu, E-mail: dah@lowell.edu, E-mail: bge@us.ibm.com [IBM T. J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, NY 10598 (United States)

2012-07-20T23:59:59.000Z

445

Building Energy Software Tools Directory: Thermal Comfort  

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

Thermal Comfort Thermal Comfort logo. Provides a user-friendly interface for calculating thermal comfort parameters and making thermal comfort predictions using several thermal...

446

Reynolds Stress and Turbulent Energy Production in a Tidal Channel  

Science Conference Proceedings (OSTI)

A high-frequency (1.2 MHz) acoustic Doppler current profiler (ADCP) moored on the seabed has been used to observe the mean and turbulent flow components in a narrow tidally energetic channel over six tidal cycles at neap and spring tides. The ...

Tom P. Rippeth; Eirwen Williams; John H. Simpson

2002-04-01T23:59:59.000Z

447

An Analysis of Low-Frequency Maritime Atmospheric Turbulence  

Science Conference Proceedings (OSTI)

New data are presented for the spectrum of turbulent wind energy under maritime conditions in the frequency region 1.0–0.03 mHz. The corresponding measurements were made at five levels on a mast 46 m high on a small islet off the coast of central ...

Johannes Gjerstad; Svein Erik Aasen; Helge I. Andersson; Iver Brevik; Jørgen Løvseth

1995-08-01T23:59:59.000Z

448

Charecterization of inertial and pressure effects in homogeneous turbulence  

E-Print Network (OSTI)

The objective of the thesis is to characterize the linear and nonlinear aspects of inertial and pressure effects in turbulent flows. In the first part of the study, computations of Navier-Stokes and 3D Burgers equations are performed in the rapid distortion (RD) limit to analyze the inviscid linear processes in homogeneous turbulence. By contrasting the results of Navier- Stokes RD equations and Burgers RD equations, the effect of pressure can be isolated. The evolution of turbulent kinetic energy and anisotropy components and invariants are examined. In the second part of the thesis, the velocity gradient dynamics in turbulent flows are studied with the help of inviscid 3D Burgers equations and restricted Euler equations. The analytical asymptotic solutions of velocity gradient tensor are obtained for both Burgers and restricted Euler equations. Numerical computations are also performed to identify the stable solutions. The results are compared and contrasted to identify the effect of pressure on nonlinear velocity gradient dynamics. Of particular interest are the sign of the intermediate principle strain-rate and tendency of vorticity to align with the intermediate principle strain-rate. These aspects of velocity gradients provide valuable insight into the role of pressure in the energy cascade process.

Bikkani, Ravi Kiran

2005-08-01T23:59:59.000Z

449

Kinematics of Turbulence Convected by a Random Wave Field  

Science Conference Proceedings (OSTI)

Turbulent velocity spectra measured beneath wind waves show a large enhancement about the central wave frequency. A “5/3" frequency dependence can be seen both above and below the central peak, but with an apparent increase in spectral density at ...

J. L. Lumley; E. A. Terray

1983-11-01T23:59:59.000Z

450

Turbulent heating of the corona and solar wind: the heliospheric  

E-Print Network (OSTI)

of telegraph services - Once per 500 years (ice cores) - Solar-terrestrial connection - Interplanetary space of radiators - Dust environment - Cp/Cg problems - Solar panels and power #12;Solar Probe Plus 2018 launch 35Turbulent heating of the corona and solar wind: the heliospheric dark energy problem Stuart D. Bale

451

Viscous Dissipation of Turbulence Kinetic Energy in Storms  

Science Conference Proceedings (OSTI)

In this note the magnitude of the viscous dissipation of turbulence kinetic energy in the surface layer of storms is investigated. It is shown that the layer-integrated dissipative heating is a cubic function of the wind speed. The magnitude of ...

Steven Businger; Joost A. Businger

2001-12-01T23:59:59.000Z

452

Small-Scale Moist Turbulence in Numerically Generated Convective Clouds  

Science Conference Proceedings (OSTI)

The authors present simulations of cloud-free and cloudy, nonprecipitating, convective turbulence at spatial resolutions down to ?x = 2.6 m for a domain size of (1 km)3. The runs are analyzed with attention focused on the dynamical differences ...

K. Spyksma; P. Bartello

2008-06-01T23:59:59.000Z

453

Early Measurements of Turbulence in the Ocean: Motives and Techniques  

Science Conference Proceedings (OSTI)

In the summer of 1950, the authors joined the staff of the Pacific Naval Laboratory (PNL) of the Defense Research Board of Canada. A research program was undertaken to see if the turbulent wake of a submarine could be detected for a useful ...

R. W. Stewart; H. L. Grant

1999-11-01T23:59:59.000Z

454

Structure and Spacing of Jets in Barotropic Turbulence  

Science Conference Proceedings (OSTI)

Turbulent flows are often observed to be organized into large-spatial-scale jets such as the familiar zonal jets in the upper levels of the Jovian atmosphere. These relatively steady large-scale jets are not forced coherently but are maintained ...

Brian F. Farrell; Petros J. Ioannou

2007-10-01T23:59:59.000Z

455

A Minimalist Organization Functioning in a Turbulent Environment  

E-Print Network (OSTI)

organizational structure, prompted by internal opinion as well as by concerns expressed by the Healthorganizational growth and development. Finally, we thank our School of Public Healthorganizational population of public sector minimalist organizations that have been set in the turbulent HIV/AIDS- related health

Kieler, Bruce; Rundall, Thomas G.

1993-01-01T23:59:59.000Z

456

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

2006-10-08T23:59:59.000Z

457

Gravity Surface Wave Bifurcation in a Highly Turbulent Swirling Flow  

E-Print Network (OSTI)

Gravity Surface Wave Bifurcation in a Highly Turbulent Swirling Flow Michael Baumer University Gravity Wave 2 3 Measurements 3 4 Mechanical Hardware: Problems and Solutions 5 5 Results 7 6 Conclusions investigated a free-surface gravity wave bifurcation in the large-separation regime, that is, where

Witten, Thomas A.

458

A Quasi-equilibrium Turbulent Energy Model for Geophysical Flows  

Science Conference Proceedings (OSTI)

The Mellor-Yamada hierarchy of turbulent closure models is reexamined to show that the elimination of a slight inconsistency in their analysis leads to a quasi-equilibrium model that is somewhat simpler than their level 2½ model. Also the need to ...

B. Galperin; L. H. Kantha; S. Hassid; A. Rosati

1988-01-01T23:59:59.000Z

459

Anomalous Transport Processes in Turbulent non-Abelian Plasmas  

E-Print Network (OSTI)

Turbulent color fields, which can arise in the early and late stages of relativistic heavy ion collisions, may contribute significantly to the transport processes in the matter created in these collisions. We review the theory of these anomalous transport processes and discuss their possible phenomenology in the glasma and quasistationary expanding quark-gluon plasma.

Masayuki Asakawa; Steffen A. Bass; Berndt Müller

2010-08-20T23:59:59.000Z

460

A Similarity Theory of the Tropospheric Turbulence Energy Spectrum  

Science Conference Proceedings (OSTI)

A three-range model is proposed for the energy spectrum of tropospheric turbulence in which the range-I spectrum is governed by the cascade of eddy enstrophy, that of range-II by the cascade of eddy kinetic energy, and that of range-III by ...

F. A. Gifford

1988-04-01T23:59:59.000Z

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.


461

Parameterizing Turbulent Exchange over Sea Ice in Winter  

Science Conference Proceedings (OSTI)

The Surface Heat Budget of the Arctic Ocean (SHEBA) experiment produced 18 000 h of turbulence data from the atmospheric surface layer over sea ice while the ice camp drifted for a year in the Beaufort Gyre. Multiple sites instrumented during ...

Edgar L. Andreas; P. Ola G. Persson; Andrey A. Grachev; Rachel E. Jordan; Thomas W. Horst; Peter S. Guest; Christopher W. Fairall

2010-02-01T23:59:59.000Z

462

The Stellar IMF as a Property of Turbulence  

E-Print Network (OSTI)

We propose to interpret the stellar IMF as a property of the turbulence in the star--forming gas. Gravitationally unstable density enhancements in the turbulent flow collapse and form stars. Their mass distribution can be derived analytically from the power spectrum of the turbulent flow and the isothermal shock jump conditions in the magnetized gas. For a power spectrum index \\beta=1.74, consistent with Larson's velocity dispersion--size relation as well as with new numerical and analytic results on supersonic turbulence, we obtain a power law mass distribution of dense cores with a slope equal to 3/(4-\\beta)=1.33, consistent with the slope of Salpeter's stellar IMF. Below one solar mass, the mass distribution flattens and turns around at a fraction of a solar mass, as observed for the stellar IMF in a number of stellar clusters, because only the densest cores are gravitationally unstable. The mass distribution at low masses is determined by the Log--Normal distribution of the gas density. The intermittent nature of this distribution is responsible for the generation of a significant number of collapsing cores of brown dwarf mass.

Paolo Padoan; Ake Nordlund

2004-11-16T23:59:59.000Z

463

Atmospheric Lagrangian coherent structures considering unresolved turbulence and forecast uncertainty  

E-Print Network (OSTI)

Atmospheric Lagrangian coherent structures considering unresolved turbulence and forecast, the uncertainty of the forecast FTLE fields is analyzed using ensemble forecasting. Unavoidable errors of the forecast velocity data due to the chaotic dynamics of the atmosphere is the salient reason for errors

Ross, Shane

464

Freely propagating open premixed turbulent flames stabilized by swirl  

DOE Green Energy (OSTI)

A novel means has been developed for using weak swirl to stabilize freely propagating open premixed turbulent flames (swirl numbers between 0.05 to 0.3). By injecting a small amount of air tangentially into the co-flow of a concentric burner, stationary flames can be maintained above the burner exit for a large range of mixture, turbulence and flow conditions. The absence of physical surfaces in the vicinity of the flame provides free access to laser diagnostics. Laser Doppler anemometry and laser Mie scattering measurements of four flames with and without incident turbulence show that their features are typical of wrinkled laminar flames. The most distinct characteristics is that flame stabilization does not rely on flow recirculation. Centrifugal force induced by swirl causes flow divergence, and the flame is maintained at where the local mass flux balances the burning rate. The flame speeds can be estimated based on the centerline velocity vector, which is locally normal to the flame brush. This flame geometry is the closest approximation to the 1-D planar flame for determining fundamental properties to advance turbulent combustion theories. 18 refs.

Chan, C.K.; Lau, K.S.; Chin, W.K. (Hong Kong Polytechnic, Kowloon (Hong Kong)); Cheng, R.K. (Lawrence Berkeley Lab., CA (United States))

1991-12-01T23:59:59.000Z

465

Near-Surface Turbulence in the Presence of Breaking Waves  

Science Conference Proceedings (OSTI)

Observations with a three-axis pulse-to-pulse coherent acoustic Doppler profiler and acoustic resonators reveal the turbulence and bubble field beneath breaking waves in the open ocean at wind speeds up to 14 m s?1. About 55%–80% of velocity ...

Johannes R. Gemmrich; David M. Farmer

2004-05-01T23:59:59.000Z

466

Theory of Equilibrium Temperatures in Radiative-Turbulent Atmospheres  

Science Conference Proceedings (OSTI)

We have developed a thermodynamic model for the determination of the temperature profile based on the balance of radiative and turbulent fluxes. In the context of a one-dimensional case, we show that the temperature field is governed by a first-...

Kuo-Nan Liou; Szu-Cheng S. Ou

1983-01-01T23:59:59.000Z

467

A Radio-Controlled Aircraft to Investigate Atmospheric Turbulence  

Science Conference Proceedings (OSTI)

A radio-controlled aircraft model to investigate atmospheric turbulence is described. The model with an airspeed of 20–40 m s?1 in the height range between 5 and 550 m and the flight time up to 30 min was equipped to carry a useful load weighing ...

Vitaly P. Kukharets; L. R. Tsvang

1998-02-01T23:59:59.000Z

468

A Gas-Kinetic Scheme For The Simulation Of Compressible Turbulent Flows  

E-Print Network (OSTI)

A gas-kinetic scheme for the continuum regime is applied to the simulation of turbu- lent compressible flow, by replacing the molecular relaxation time with a turbulent relaxation time in the BGK model. The turbulence dynamics is modelled on the basis of a standard, linear two-equation turbulence model. The hydrodynamic limit of the resulting turbulence model is linear in smooth flow and non-linear in the presence of stronger flow gradients. The non-linear correction terms in the numerical flux are weighed as a function of "rarefaction" - referred to turbulence dynamics and not to molecular dynamics, i.e. measured by the ratio of turbulence to mean flow scales of motion. Even though no assumptions on the nature of the turbulence have been made and a linear two-equation turbulence model is used, the turbulence gas-kinetic scheme seems able to correct the turbulent stress tensor in an effective way; on the basis of a number of turbulence modelling benchmark flow cases, characterized by strong shock - boundary l...

Righi, Marcello

2013-01-01T23:59:59.000Z

469

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 are developed. Simulations of initially non-premixed mixtures yield scalar probability distribution functions that are in good agreement with numerical data obtained from Navier-Stokes (NS) equation based computation. One-dimensional chemically-reacting flow simulation of a premixed mixture yields a flame speed that is consistent with experimentally determined value. The second study involves direct numerical simulation (DNS) and large-eddy simulation (LES) of decaying homogenous isotropic turbulence (HIT) with and without frame rotation. Three categories of simulations are performed: (i) LBE-DNS in both inertial and rotating frames; (ii) LBE-LES in inertial frame; (iii) Comparison of the LBE-LES vs. NS-LES. The LBE-DNS results of the decay exponents for kinetic energy k and dissipation rate ?, and the low wave-number scaling of the energy spectrum agree well with established classical results. The LBE-DNS also captures rotating turbulence physics. The LBE-LES accurately captures low-wave number scaling, energy decay and large scale structures. The comparisons indicate that the LBE-LES simulations preserve flow structures somewhat more accurately than the NS-LES counterpart. In the third study, we numerically investigate the near-field mixing features in low aspect-ratio (AR) rectangular turbulent jets (RTJ) using the LBE method. We use D3Q19 multiple-relaxation-time (MRT) LBE incorporating a subgrid Smagorinsky model for LES. Simulations of four jets which characterized by AR, exit velocity, and Reynolds number are performed. The investigated near-field behaviors include: (1) Decay of mean streamwise velocity (MSV) and inverse MSV; (2) Spanwise and lateral profiles of MSV; (3) Half-velocity width development and MSV contours; and (4) Streamwise turbulence intensity distribution and spanwise profiles of streamwise turbulence intensity. The computations are compared against experimental data and the agreement is good. We capture both unique features of RTJ: the saddle-back spanwise profile of MSV and axis-switching of long axis from spanwise to lateral direction. Overall, this work serves to establish the feasibility of the LBE method as a viable tool for computing mixing, combustion, and turbulence.

Yu, Huidan

2004-12-01T23:59:59.000Z

470

Prediction of the Proton-to-Total Turbulent Heating in the Solar Wind  

E-Print Network (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 >~ 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 ~ 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

2011-01-01T23:59:59.000Z

471

Magnetic turbulence suppression by a helical mode in a cylindrical geometry  

Science Conference Proceedings (OSTI)

To study processes involved in a helical structure formation in reversed field pinch devices, the scaling of a turbulent boundary layer width associated with a vortex structure having large shears of magnetic field and flow is obtained for reduced magnetohydrodynamics. The coherent vortex, with its flow and magnetic shears, interacts with Alfven turbulence, forming a turbulent boundary layer at the edge of the vortex. The layer arises from the balance between turbulence diffusion rates and shearing rates and suppresses the turbulence in the structure. The suppression of turbulence impedes relaxation of the coherent vortex profiles, leading to long coherence times. The scaling of the boundary layer width reveals that both magnetic shear and flow shear can effectively suppress magnetic turbulence.

Kim, J.-H.; Terry, P. W. [Department of Physics and Center for Momentum Transport and Flow Organization, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

2012-12-15T23:59:59.000Z

472

Measurements of Turbulence at Two Tidal Energy Sites in Puget Sound, WA  

SciTech Connect

Field measurements of turbulence are pre- sented from two sites in Puget Sound, WA (USA) that are proposed for electrical power generation using tidal current turbines. Rapidly sampled data from multiple acoustic Doppler instruments are analyzed to obtain statistical mea- sures of fluctuations in both the magnitude and direction of the tidal currents. The resulting turbulence intensities (i.e., the turbulent velocity fluctuations normalized by the harmonic tidal currents) are typically 10% at the hub- heights (i.e., the relevant depth bin) of the proposed turbines. Length and time scales of the turbulence are also analyzed. Large-scale, anisotropic eddies dominate the energy spectra, which may be the result of proximity to headlands at each site. At small scales, an isotropic turbulent cascade is observed and used to estimate the dissipation rate of turbulent kinetic energy. Data quality and sampling parameters are discussed, with an emphasis on the removal of Doppler noise from turbulence statistics.

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

2012-06-05T23:59:59.000Z

473

Three-dimensional Fast Flux Test Facility plenum model turbulent flow prediction and data comparison  

Science Conference Proceedings (OSTI)

Two- and three-dimensional numerical simulations of turbulent flow in a scaled Fast Flux Test Facility (FFTF) upper plenum model were performed using the TEMPEST hydrothermal code. A standard k-element of model was used to describe turbulence through an effective viscosity. Comparisons with previously reported mean velocity and turbulence field data measured in the plenum model and two-dimensional numerical simulations using the TEACH code were made. Predicted horizontal and vertical mean velocities and turbulent kinetic energy are shown to be in good agreement with available experimental data when inlet conditions of the dissipation of turbulent kinetic energy are appropriately prescribed. The three-dimensional quarter-symmetry simulation predicts the turbulent kinetic energy field significantly better than the two-dimensional centerplane simulations. These results lead to conclusions concerning deficiencies in the experimental data and the turbulence model.

Eyler, L.L.; Sawdye, R.W.

1981-01-01T23:59:59.000Z

474

Magnetohydrodynamic lattice Boltzmann simulations of turbulence and rectangular jet flow  

E-Print Network (OSTI)

Magnetohydrodynamic (MHD) investigations of decaying isotropic turbulence and rectangular jets (RJ) are carried out. A novel MHD lattice Boltzmann scheme that combines multiple relaxation time (MRT) parameters for the velocity field with a single 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-rate tensor are evaluated to assess the key physical MHD turbulence mechanisms. The magnetic and kinetic energies interact and exchange through the influence of the Lorentz force work. An initial random fluctuating magnetic field increases the vortex stretching and forward cascade mechanisms. A strong uniform mean magnetic field increases the anisotropy of the turbulent flow field and causes inverse cascading. In the RJ studies, an investigation into the MHD effects on velocity, instability, and the axis-switching phenomena is performed at various magnetic field strengths and Magnetic Reynolds Numbers. The magnetic field is found to decelerate the jet core, inhibit instability, and prevent axis-switching. The key physical mechanisms are: (i) the exchange of energy between kinetic and magnetic modes and (ii) the magnetic field effect on the vorticity evolution. From these studies, it is found that magnetic field influences momentum, vorticity, and energy evolution and the degree of modification depends on the field strength. This interaction changes vortex evolution, and alters turbulence processes and rectangular jet flow characteristics. Overall, this study provides more insight into the physics of MHD flows, which suggests possible applications of MHD Flow Control.

Riley, Benjamin Matthew

2007-05-01T23:59:59.000Z

475

Lewis number effects on turbulent premixed flame structure  

DOE Green Energy (OSTI)

The influence of the Lewis number on turbulent flame front geometry is investigated in a premixed turbulent stagnation point flame. A laser tomography technique is used to obtain the flame shape, a fractal analysis of the multiscale flame edges is performed and the distribution of local flame front curvature is determined. Lean H[sub 2]/Air and C[sub 3]H[sub 8]/Air mixtures with similar burning rates were investigated with Lewis numbers of 0.33 and 1.85 respectively. At the conditions studied the laminar H[sub 2]/Air mixture is unstable and a cellular structure is observed. Turbulence in the reactant is generated by a perforated plate and the turbulent length scale (3mm) and intensity (7%) at the nozzle exit are fixed. The equivalence ratio is set so that the burning velocity is the same for all the cases. Results show clearly that the turbulent flame surface area is dependent on the Lewis number. For a Lewis number less than unity surface area production is observed. The shape of the flame front curvature distribution is not found to be very sensitive to the Lewis number. For the H[sub 2]/Air mixture the distribution is skewed toward the positive values indicating the presence of cusps while for the C[sub 3]H[sub 8]/Air mixture the distribution is more symmetrical. In both cases the average curvature is found to be zero, and if the local burning speed varies linearly with curvature, the local positive and negative burning velocity variations due to curvature will balance.

Goix, P.J. (Centre National de la Recherche Scientifique (CNRS), 230 - Mont-Saint-Aignan (France). URA CORIA); Shepherd, I.G. (Lawrence Berkeley Lab., CA (United States))

1992-09-01T23:59:59.000Z

476

Lewis number effects on turbulent premixed flame structure  

DOE Green Energy (OSTI)

The influence of the Lewis number on turbulent flame front geometry is investigated in a premixed turbulent stagnation point flame. A laser tomography technique is used to obtain the flame shape, a fractal analysis of the multiscale flame edges is performed and the distribution of local flame front curvature is determined. Lean H{sub 2}/Air and C{sub 3}H{sub 8}/Air mixtures with similar burning rates were investigated with Lewis numbers of 0.33 and 1.85 respectively. At the conditions studied the laminar H{sub 2}/Air mixture is unstable and a cellular structure is observed. Turbulence in the reactant is generated by a perforated plate and the turbulent length scale (3mm) and intensity (7%) at the nozzle exit are fixed. The equivalence ratio is set so that the burning velocity is the same for all the cases. Results show clearly that the turbulent flame surface area is dependent on the Lewis number. For a Lewis number less than unity surface area production is observed. The shape of the flame front curvature distribution is not found to be very sensitive to the Lewis number. For the H{sub 2}/Air mixture the distribution is skewed toward the positive values indicating the presence of cusps while for the C{sub 3}H{sub 8}/Air mixture the distribution is more symmetrical. In both cases the average curvature is found to be zero, and if the local burning speed varies linearly with curvature, the local positive and negative burning velocity variations due to curvature will balance.

Goix, P.J. [Centre National de la Recherche Scientifique (CNRS), 230 - Mont-Saint-Aignan (France). URA CORIA; Shepherd, I.G. [Lawrence Berkeley Lab., CA (United States)

1992-09-01T23:59:59.000Z

477

Near-Neutral Surface Layer Turbulence at the Boulder Atmospheric Observatory Tower: Evidence of Increasing Vertical Turbulence with Height  

Science Conference Proceedings (OSTI)

Wind and turbulence profiles were analyzed during breezy, near-neutral conditions at the Boulder Atmospheric Observatory tower to quantify the effects of an abrupt 20- to 30-m increase in terrain located 3–5 km west of the tower. Results indicate ...

Brent M. Bowen

2000-05-01T23:59:59.000Z

478

Section 1: Interfacial Turbulence and AirWater Scalar Transfer Turbulence and wave dynamics across gasliquid interfaces 1  

E-Print Network (OSTI)

The calculation of the gas transfer between the ocean and atmosphere13 S.A. Kitaigorodskii The influence of wind relationship to airwater gas transfer rates51 D. Turney, S. Banerjee Turbulent gas flux measurements near the airwater interface in an oscillating-grid tank 65 J.G. Janzen, H.E. Schulz, G.H. Jirka Sensible and latent

Takada, Shoji

479

Catalytic thermal barrier coatings  

Science Conference Proceedings (OSTI)

A catalyst element (30) for high temperature applications such as a gas turbine engine. The catalyst element includes a metal substrate such as a tube (32) having a layer of ceramic thermal barrier coating material (34) disposed on the substrate for thermally insulating the metal substrate from a high temperature fuel/air mixture. The ceramic thermal barrier coating material is formed of a crystal structure populated with base elements but with selected sites of the crystal structure being populated by substitute ions selected to allow the ceramic thermal barrier coating material to catalytically react the fuel-air mixture at a higher rate than would the base compound without the ionic substitutions. Precious metal crystallites may be disposed within the crystal structure to allow the ceramic thermal barrier coating material to catalytically react the fuel-air mixture at a lower light-off temperature than would the ceramic thermal barrier coating material without the precious metal crystallites.

Kulkarni, Anand A. (Orlando, FL); Campbell, Christian X. (Orlando, FL); Subramanian, Ramesh (Oviedo, FL)

2009-06-02T23:59:59.000Z

480

Evaluations of Upper-Level Turbulence Diagnostics Performance Using the Graphical Turbulence Guidance (GTG) System and Pilot Reports (PIREPs) over East Asia  

Science Conference Proceedings (OSTI)

The forecast skill of upper-level turbulence diagnostics is evaluated using available turbulence observations [viz., pilot reports (PIREPs)] over East Asia. The six years (2003–08) of PIREPs used in this study include null, light, and moderate-or-...

Jung-Hoon Kim; Hye-Yeong Chun; Robert D. Sharman; Teddie L. Keller

2011-09-01T23:59:59.000Z

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