While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

1

Kinematics of Turbulence Convected by a Random Wave Field

Science Journals Connector (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

2

Wave Packets and Turbulent Peter Jordan1

Wave Packets and Turbulent Jet Noise Peter Jordan1 and Tim Colonius2 1 DÂ´epartement Fluides, California 91125; email: peter.jordan@univ-poitiers.fr, colonius@caltech.edu Annu. Rev. Fluid Mech. 2013. 45

Dabiri, John O.

3

Turbulent round jet under gravity waves

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

Ryu, Yong Uk

2002-01-01T23:59:59.000Z

4

Discrete wave turbulence of rotational capillary water waves

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

Adrian Constantin; Elena Kartashova; Erik Wahlén

2010-05-12T23:59:59.000Z

5

Wave turbulence in quantum fluids

Science Journals Connector (OSTI)

...range, as shown by the inset bifurcation diagram. Fig. 2. Second sound turbulence...metastable state. (Inset) Bifurcation diagram showing regions of stability (unshaded) and...159 . 9 Ryutova M Tarbell T ( 2003 ) MHD shocks and the origin of the solar transition...

German V. Kolmakov; Peter Vaughan Elsmere McClintock; Sergey V. Nazarenko

2014-01-01T23:59:59.000Z

6

Neoclassical generation of toroidal zonal flow by drift wave turbulence

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

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

2006-03-15T23:59:59.000Z

7

Residual turbulence from velocity shear stabilized interchange instabilities

The stabilizing effect of velocity shear on the macroscopic, broad bandwidth, ideal interchange instability is studied in linear and nonlinear regimes. A 2D dissipative magnetohydrodynamic (MHD) code is employed to simulate the system. For a given flow shear, V Prime , linear growth rates are shown to be suppressed to below the shear-free level at both the small and large wavelengths. With increasing V Prime , the unstable band in wavenumber-space shrinks so that the peak growth results for modes that correspond to relatively high wavenumbers, on the scale of the density gradient. In the nonlinear turbulent steady state, a similar turbulent spectrum obtains, and the convection cells are roughly circular. In addition, the density fluctuation level and the degree of flattening of the initial inverted density profile are found to decrease as V Prime increases; in fact, unstable modes are almost completely stabilized and the density profile reverts to laminar when V Prime is a few times the classic interchange growth rate. Moreover, the turbulent particle flux diminishes with increasing velocity shear such that all the flux is carried by the classical diffusive flux in the asymptotic limit. The simulations are compared with measurements of magnetic fluctuations from the Maryland Centrifugal Experiment, MCX, which investigated interchange modes in the presence of velocity shear. The experimental spectral data, taken in the plasma edge, are in general agreement with the numerical data obtained in higher viscosity simulations for which the level of viscosity is chosen consistent with MCX Reynolds numbers at the edge. In particular, the residual turbulence in both cases is dominated by elongated convection cells. Finally, concomitant Kelvin-Helmholtz instabilities in the system are also examined. Complete stability to interchanges is obtained only in the parameter space wherein the generalized Rayleigh inflexion theorem is satisfied.

Hung, C. P.; Hassam, A. B. [University of Maryland at College Park, College Park, Maryland 20742 (United States)

2013-01-15T23:59:59.000Z

8

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

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

Fominov, Yakov

9

DNS of Detonation Wave and Isotropic Turbulence Interaction

DNS of Detonation Wave and Isotropic Turbulence Interaction Hari Narayanan Nagarajan , Luca Massa A direct numerical simulation of detonation wave with compressible homogeneous isotropic turbulence is carried out with three different detonation Mach numbers to study the effect of detonation wave

Texas at Arlington, University of

10

Compressible Turbulence and Interactions with Shock Waves and Material

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

11

Fluctuations of energy flux in wave turbulence Eric Falcon,1

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

Falcon, Eric

12

Toward a wave turbulence formulation of statistical nonlinear optics

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

Garnier, Josselin

13

Wave turbulence revisited: Where does the energy flow?

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

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

2014-04-03T23:59:59.000Z

14

Confirmation of the effective coefficient for scattering by turbulent velocity fluctuations

Science Journals Connector (OSTI)

The effective structure?function parameter for scattering by atmospheric turbulent velocity fluctuations has normally been assumed to be C eff 2=4C 2 V /c 2 0 However a new derivation by V. E. Ostashev [Waves Random Media4 403–428 (1994)] which takes into account the vectorial nature of the wind velocity field suggests that C eff 2=22C 2 V /3c 2 0. An experiment was designed to determine the correct value of the coefficient. Amplitude variances were monitored for several discrete frequencies between 380 and 3500 Hz at distances up to 675 m. Cup and hot?wire anemometers were used to determine C 2 V . A theory for scattering by inertial?subrange turbulence was then used to calculate the C eff 2 coefficient from the amplitude variance and C 2 V . Although there is some tendency in favor of the 22/3 coefficient the results cannot be considered conclusive. The main difficulty appears to be obtaining a sufficiently accurate measurement of C 2 V .

Makeda J. Smith; D. Keith Wilson; Michael Heyd; David I. Havelock; Harry J. Auvermann; John M. Noble

1997-01-01T23:59:59.000Z

15

Interaction of turbulent plasma flow with a hypersonic shock wave

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

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

1997-02-01T23:59:59.000Z

16

P And S Wave Velocity Determination

There are three general methods that can be used to determine formation velocities from full waveform logs. The first approach is to make use of the data from the entire waveform. This type of velocity analysis is performed ...

Willis, M. E.

1983-01-01T23:59:59.000Z

17

We analytically consider how velocity shear in the corona and solar wind can cause an initial Alfven wave to drive up other propagating signals. The process is similar to the familiar coupling into other modes induced by non-WKB refraction in an inhomogeneous plasma, except here the refraction is a consequence of velocity shear. We limit our discussion to a low-beta plasma, and ignore couplings into signals resembling the slow mode. If the initial Alfven wave is propagating nearly parallel to the background magnetic field, then the induced signals are mainly a forward-going (i.e., propagating in the same sense as the original Alfven wave) fast mode, and a driven signal propagating like a forward-going Alfven wave but polarized like the fast mode; both signals are compressive and subject to damping by the Landau resonance. For an initial Alfven wave propagating obliquely with respect to the magnetic field, the induced signals are mainly forward- and backward-going fast modes, and a driven signal propagating like a forward-going Alfven wave but polarized like the fast mode; these signals are all compressive and subject to damping by the Landau resonance. A backward-going Alfven wave, thought to be important in the development of MHD turbulence, is also produced, but it is very weak. However, we suggest that for oblique propagation of the initial Alfven wave the induced fast-polarized signal propagating like a forward-going Alfven wave may interact coherently with the initial Alfven wave and distort it at a strong-turbulence-like rate.

Hollweg, Joseph V.; Chandran, Benjamin D. G. [Space Science Center, Morse Hall, University of New Hampshire, Durham, NH 03824 (United States); Kaghashvili, Edisher Kh., E-mail: joe.hollweg@unh.edu, E-mail: ekaghash@aer.com, E-mail: benjamin.chandran@unh.edu [Atmospheric and Environmental Research, A Verisk Analytics Company, 131 Hartwell Avenue, Lexington, MA 02421 (United States)

2013-06-01T23:59:59.000Z

18

ARM - PI Product - Cloud-Scale Vertical Velocity and Turbulent Dissipation

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

ProductsCloud-Scale Vertical Velocity and Turbulent ProductsCloud-Scale Vertical Velocity and Turbulent Dissipation Rate Retrievals Comments? We would love to hear from you! Send us a note below or call us at 1-888-ARM-DATA. Send PI Product : Cloud-Scale Vertical Velocity and Turbulent Dissipation Rate Retrievals Site(s) NSA General Description Time-height fields of retrieved in-cloud vertical wind velocity and turbulent dissipation rate, both retrieved primarily from vertically-pointing, Ka-band cloud radar measurements. Files are available for manually-selected, stratiform, mixed-phase cloud cases observed at the North Slope of Alaska (NSA) site during periods covering the Mixed-Phase Arctic Cloud Experiment (MPACE, late September through early November 2004) and the Indirect and Semi-Direct Aerosol Campaign (ISDAC, April-early May

19

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

20

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

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

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

21

Measurement of velocity field in parametrically excited solitary waves

Paramerically excited solitary waves emerge as localized structures in high-aspect-ratio free surfaces subject to vertical vibrations. Herein, we provide the first experimental characterization of the hydrodynamics of thess waves using Particle Image Velocimetry. We show that the underlying velocity field of parametrically excited solitary waves is mainly composed by an oscillatory velocity field. Our results confirm the accuracy of Hamiltonian models with added dissipation in describing this field. Remarkably, our measurements also uncover the onset of a streaming velocity field which is shown to be as important as other crucial nonlinear terms in the current theory. The observed streaming pattern is particularly interesting due to the presence of oscillatory meniscii.

Gordillo, Leonardo

2014-01-01T23:59:59.000Z

22

. . . . . . . . , . . . ~ . ~ INTRODUCTION BACKGROUND TO THE PROBLEM Theory of Mountain Waves Mountain Waves and Clear Air Turbulence (CAT). Page iv v vi viii The Vertical Propagation and Transfer of Energy of Mountain Waves into the Stratosphere The Influence of Wind... and wave energy under the influence of wind shear (Booker and Bretherton, 1967). A critical level, if it exists, is the level at which the horizontal phase velocity of the wave equals the mean wind speed. If a wave passes through a criti- cal level...

Incrocci, Thomas Paul

2012-06-07T23:59:59.000Z

23

Scaling turbulent atmospheric stratification: a turbulence/wave wind model

, it displays no wave-like phenomenol- ogy. We show how to extend the FIF model to account for more realistic

Lovejoy, Shaun

24

THE EFFECTS OF WAVE ESCAPE ON FAST MAGNETOSONIC WAVE TURBULENCE IN SOLAR FLARES

One of the leading models for electron acceleration in solar flares is stochastic acceleration by weakly turbulent fast magnetosonic waves ({sup f}ast waves{sup )}. In this model, large-scale flows triggered by magnetic reconnection excite large-wavelength fast waves, and fast-wave energy then cascades from large wavelengths to small wavelengths. Electron acceleration by large-wavelength fast waves is weak, and so the model relies on the small-wavelength waves produced by the turbulent cascade. In order for the model to work, the energy cascade time for large-wavelength fast waves must be shorter than the time required for the waves to propagate out of the solar-flare acceleration region. To investigate the effects of wave escape, we solve the wave kinetic equation for fast waves in weak turbulence theory, supplemented with a homogeneous wave-loss term. We find that the amplitude of large-wavelength fast waves must exceed a minimum threshold in order for a significant fraction of the wave energy to cascade to small wavelengths before the waves leave the acceleration region. We evaluate this threshold as a function of the dominant wavelength of the fast waves that are initially excited by reconnection outflows.

Pongkitiwanichakul, Peera; Chandran, Benjamin D. G. [Space Science Center and Department of Physics, University of New Hampshire, Durham, NH 03824 (United States); Karpen, Judith T. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); DeVore, C. Richard, E-mail: pbu3@unh.edu, E-mail: benjamin.chandran@unh.edu, E-mail: judy.karpen@nasa.gov, E-mail: devore@nrl.navy.mil [Naval Research Laboratory, Washington, DC 20375 (United States)

2012-09-20T23:59:59.000Z

25

Numerical evidence of turbulence generated by non-breaking surface waves

Science Journals Connector (OSTI)

Numerical simulation of monochromatic surface waves propagating over a turbulent field is conducted to reveal the mechanism of turbulence production by non-breaking waves. The numerical model solves the primitive equations subject to the fully ...

Wu-ting Tsai; Shi-ming Chen; Guan-hung Lu

26

Excitation of Langmuir wave turbulence in high-frequency (HF) pump waves over Gakona, Alaska

(cont.) Investigated in this thesis are the excitation and observation of Langmuir wave turbulence caused by the parametric decay instability (PDI) in high-frequency space plasma heating experiments conducted at the NSF/DoD ...

Rokusek, Daniel L

2007-01-01T23:59:59.000Z

27

Alfven Wave Turbulence and Perpendicular Ion Temperatures in Coronal Holes

Low-frequency Alfven-wave turbulence causes ion trajectories to become chaotic, or "stochastic," when the turbulence amplitude is sufficiently large. Stochastic orbits enable ions to absorb energy from the turbulence, increasing the perpendicular ion temperature even when the fluctuation frequencies are too small for a cyclotron resonance to occur. In this paper, an analytic expression for the stochastic heating rate is used in conjunction with an observationally constrained turbulence model to obtain an analytic formula for the perpendicular ion temperature as a function of heliocentric distance r, ion mass, and ion charge in coronal holes for values of r between 2 and 15 solar radii (Rs). The resulting temperature profiles provide a good fit to observations of protons and OVI ions at 2Rs heating also offers a natural explanation for several detailed features of the UVCS observations, including the preferential and anisotropic h...

Chandran, Benjamin D G

2010-01-01T23:59:59.000Z

28

Theoretical and observational studies on the turbulence of the interstellar medium developed fast in the past decades. The theory of supersonic magnetized turbulence, as well as the understanding of projection effects of observed quantities, are still in progress. In this work we explore the characterization of the turbulent cascade and its damping from observational spectral line profiles. We address the difference of ion and neutral velocities by clarifying the nature of the turbulence damping in the partially ionized. We provide theoretical arguments in favor of the explanation of the larger Doppler broadening of lines arising from neutral species compared to ions as arising from the turbulence damping of ions at larger scales. Also, we compute a number of MHD numerical simulations for different turbulent regimes and explicit turbulent damping, and compare both the 3-dimensional distributions of velocity and the synthetic line profile distributions. From the numerical simulations, we place constraints on t...

Falceta-Goncalves, D; Houde, M

2010-01-01T23:59:59.000Z

29

Resonant wave-particle interactions modified by intrinsic Alfvenic turbulence

The concept of wave-particle interactions via resonance is well discussed in plasma physics. This paper shows that intrinsic Alfven waves can qualitatively modify the physics discussed in conventional linear plasma kinetic theories. It turns out that preexisting Alfven waves can affect particle motion along the ambient magnetic field and, moreover, the ensuing force field is periodic in time. As a result, the meaning of the usual Landau and cyclotron resonance conditions becomes questionable. It turns out that this effect leads us to find a new electromagnetic instability. In such a process intrinsic Alfven waves not only modify the unperturbed distribution function but also result in a different type of cyclotron resonance which is affected by the level of turbulence. This instability might enable us to better our understanding of the observed radio emission processes in the solar atmosphere.

Wu, C. S.; Lee, K. H. [Institute of Space Science, National Central University, Zhongli, Taiwan (China); Wang, C. B. [CAS Key Laboratory of Geospace Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei (China); Wu, D. J. [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing (China)

2012-08-15T23:59:59.000Z

30

Measurements of parallel electron velocity distributions using whistler wave absorption

We describe a diagnostic to measure the parallel electron velocity distribution in a magnetized plasma that is overdense ({omega}{sub pe} > {omega}{sub ce}). This technique utilizes resonant absorption of whistler waves by electrons with velocities parallel to a background magnetic field. The whistler waves were launched and received by a pair of dipole antennas immersed in a cylindrical discharge plasma at two positions along an axial background magnetic field. The whistler wave frequency was swept from somewhat below and up to the electron cyclotron frequency {omega}{sub ce}. As the frequency was swept, the wave was resonantly absorbed by the part of the electron phase space density which was Doppler shifted into resonance according to the relation {omega}-k{sub ||v||} = {omega}{sub ce}. The measured absorption is directly related to the reduced parallel electron distribution function integrated along the wave trajectory. The background theory and initial results from this diagnostic are presented here. Though this diagnostic is best suited to detect tail populations of the parallel electron distribution function, these first results show that this diagnostic is also rather successful in measuring the bulk plasma density and temperature both during the plasma discharge and into the afterglow.

Thuecks, D. J.; Skiff, F.; Kletzing, C. A. [Department of Physics and Astronomy, University of Iowa, 203 Van Allen Hall, Iowa City, Iowa 52242 (United States)

2012-08-15T23:59:59.000Z

31

Plasma turbulence driven by transversely large-scale standing shear Alfven waves

Using two-dimensional particle-in-cell simulations, we study generation of turbulence consisting of transversely small-scale dispersive Alfven and electrostatic waves when plasma is driven by a large-scale standing shear Alfven wave (LS-SAW). The standing wave is set up by reflecting a propagating LS-SAW. The ponderomotive force of the standing wave generates transversely large-scale density modifications consisting of density cavities and enhancements. The drifts of the charged particles driven by the ponderomotive force and those directly caused by the fields of the standing LS-SAW generate non-thermal features in the plasma. Parametric instabilities driven by the inherent plasma nonlinearities associated with the LS-SAW in combination with the non-thermal features generate small-scale electromagnetic and electrostatic waves, yielding a broad frequency spectrum ranging from below the source frequency of the LS-SAW to ion cyclotron and lower hybrid frequencies and beyond. The power spectrum of the turbulence has peaks at distinct perpendicular wave numbers (k{sub Up-Tack }) lying in the range d{sub e}{sup -1}-6d{sub e}{sup -1}, d{sub e} being the electron inertial length, suggesting non-local parametric decay from small to large k{sub Up-Tack }. The turbulence spectrum encompassing both electromagnetic and electrostatic fluctuations is also broadband in parallel wave number (k{sub ||}). In a standing-wave supported density cavity, the ratio of the perpendicular electric to magnetic field amplitude is R(k{sub Up-Tack }) = |E{sub Up-Tack }(k{sub Up-Tack })/|B{sub Up-Tack }(k{sub Up-Tack })| Much-Less-Than V{sub A} for k{sub Up-Tack }d{sub e} < 0.5, where V{sub A} is the Alfven velocity. The characteristic features of the broadband plasma turbulence are compared with those available from satellite observations in space plasmas.

Singh, Nagendra; Rao, Sathyanarayan [Electrical and Computer Engineering, University of Alabama, Huntsville, Alabama 35899 (United States)

2012-12-15T23:59:59.000Z

32

The Prevalence of Similarity of the Turbulent Wall-bounded Velocity Profile

In a now very influential paper, Luciano Castillo and William George used a flow governing equation approach for the outer boundary layer region to seek similarity solutions for the mean velocity and Reynolds shear stress profiles. The development led to a less-constrained version of Clauser's pressure gradient constraint parameter. Using their new pressure gradient constraint parameter equal to a constant as a search criterion, Castillo and George claim to have found many turbulent boundary layer experimental datasets that exhibited velocity profile similarity. In fact Castillo, George, and coworkers examined an extensive set of experimental datasets and claim that most turbulent boundary layers appear to be equilibrium similarity boundary layers. This is in direct contradiction to the classical belief that equilibrium similarity flows are special flows and are difficult to achieve in experiments, a contradiction that Castillo and George themselves acknowledge. The importance of this observation cannot be ov...

Weyburne, David

2014-01-01T23:59:59.000Z

33

Statistics of pressure and of pressure-velocity correlations in isotropic turbulence

Some pressure and pressure-velocity correlation in a direct numerical simulations of a three-dimensional turbulent flow at moderate Reynolds numbers have been analyzed. We have identified a set of pressure-velocity correlations which posseses a good scaling behaviour. Such a class of pressure-velocity correlations are determined by looking at the energy-balance across any sub-volume of the flow. According to our analysis, pressure scaling is determined by the dimensional assumption that pressure behaves as a ``velocity squared'', unless finite-Reynolds effects are overwhelming. The SO(3) decompositions of pressure structure functions has also been applied in order to investigate anisotropic effects on the pressure scaling.

L. Biferale; P. Gualtieri; F. Toschi

2000-01-17T23:59:59.000Z

34

E-Print Network 3.0 - alfven wave turbulence Sample Search Results

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

Union 2003 Magnetic field turbulence, electron heating, magnetic holes, proton cyclotron waves... the heating events. We propose a scenario which can link the above ......

35

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

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

Rehme, K.

1982-10-01T23:59:59.000Z

36

In-service inspection of Sodium-Cooled Fast Reactors (SFR) requires the development of non-destructive techniques adapted to the harsh environment conditions and the examination complexity. From past experiences, ultrasonic techniques are considered as suitable candidates. The ultrasonic telemetry is a technique used to constantly insure the safe functioning of reactor inner components by determining their exact position: it consists in measuring the time of flight of the ultrasonic response obtained after propagation of a pulse emitted by a transducer and its interaction with the targets. While in-service the sodium flow creates turbulences that lead to temperature inhomogeneities, which translates into ultrasonic velocity inhomogeneities. These velocity variations could directly impact the accuracy of the target locating by introducing time of flight variations. A stochastic simulation model has been developed to calculate the propagation of ultrasonic waves in such an inhomogeneous medium. Using this approach, the travel time is randomly generated by a stochastic process whose inputs are the statistical moments of travel times known analytically. The stochastic model predicts beam deviations due to velocity inhomogeneities, which are similar to those provided by a determinist method, such as the ray method.

Lu, B.; Darmon, M.; Leymarie, N.; Chatillon, S.; Potel, C. [CEA, LIST, F-91191 Gif-sur-Yvette (France); Laboratoire d'Acoustique de l'Universite du Maine (LAUM), UMR CNRS 6613, 72085 Le Mans Cedex 9 (France)

2012-05-17T23:59:59.000Z

37

Superfluid Turbulence from Quantum Kelvin Wave to Classical Kolmogorov Cascades

The main topological feature of a superfluid is a quantum vortex with an identifiable inner and outer radius. A novel unitary quantum lattice gas algorithm is used to simulate quantum turbulence of a Bose-Einstein condensate superfluid described by the Gross-Pitaevskii equation on grids up to 5760{sup 3}. For the first time, an accurate power-law scaling for the quantum Kelvin wave cascade is determined: k{sup -3}. The incompressible kinetic energy spectrum exhibits very distinct power-law spectra in 3 ranges of k space: a classical Kolmogorov k{sup -(5/3)} spectrum at scales greater than the outer radius of individual quantum vortex cores and a quantum Kelvin wave cascade spectrum k{sup -3} on scales smaller than the inner radius of the quantum vortex core. The k{sup -3} quantum Kelvin wave spectrum due to phonon radiation is robust, while the k{sup -(5/3)} classical Kolmogorov spectrum becomes robust on large grids.

Yepez, Jeffrey [Air Force Research Laboratory, Hanscom Air Force Base, Massachusetts 01731 (United States); Vahala, George [Department of Physics, William and Mary, Williamsburg, Virginia 23185 (United States); Vahala, Linda [Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, Virginia 23529 (United States); Soe, Min [Department of Mathematics and Physical Sciences, Rogers State University, Claremore, Oklahoma 74017 (United States)

2009-08-21T23:59:59.000Z

38

Acoustically forced lean premixed turbulent bluff-body stabilized flames are investigated using turbulent combustion CFD. The calculations simulate aspects of the experimental investigation by Balachandran et al. [R. Balachandran, B. Ayoola, C. Kaminski, A. Dowling, E. Mastorakos, Combust. Flame 143 (2005) 37-55] and focus on the amplitude dependence of the flame response. For the frequencies of interest in this investigation an unsteady Reynolds-averaged Navier-Stokes (URANS) approach is appropriate. The combustion is represented using a modified laminar flamelet approach with an algebraic representation of the flame surface density. The predictions are compared with flame surface density (FSD) and OH* chemiluminescence measurements. In the experiments the response of the flame has been quantified by means of a number of single-frequency, amplitude-dependent transfer functions. The predicted flame shape and position are in good agreement with the experiment. The dynamic response of the flame to inlet velocity forcing is also well captured by the calculations. At moderate frequencies nonlinear behavior of the transfer functions is observed as the forcing amplitude is increased. In the experiments this nonlinearity was attributed in part to the rollup of the reacting shear layer into vortices and in part to the collision of the inner and outer flame sheets. This transition to nonlinearity is also observed in the transfer functions obtained from the predictions. Furthermore, the vortex shedding and flame-sheet collapse may be seen in snapshots of the predicted flow field taken throughout the forcing cycle. The URANS methodology successfully predicts the behavior of the forced premixed turbulent flames and captures the effects of saturation in the transfer function of the response of the heat release to velocity fluctuations. (author)

Armitage, C.A.; Mastorakos, E.; Cant, R.S. [Department of Engineering, Trumpington Street, University of Cambridge, Cambridge, CB2 1PZ (United Kingdom); Balachandran, R. [Department of Mechanical Engineering, University College London, Torrington Place, London, WC1E 7JE (United Kingdom)

2006-08-15T23:59:59.000Z

39

The fluctuating magnetic helicity is considered an important parameter in diagnosing the characteristic modes of solar wind turbulence. Among them is the Alfven-cyclotron wave, which is probably responsible for the solar wind plasma heating, but has not yet been identified from the magnetic helicity of solar wind turbulence. Here, we present the possible signatures of Alfven-cyclotron waves in the distribution of magnetic helicity as a function of {theta}{sub VB}, which is the angle between the solar wind velocity and local mean magnetic field. We use magnetic field data from the STEREO spacecraft to calculate the {theta}{sub VB} distribution of the normalized reduced fluctuating magnetic helicity {sigma}{sub m}. We find a dominant negative {sigma}{sub m} for 1 s < p < 4 s (p is time period) and for {theta}{sub VB} < 30 deg. in the solar wind outward magnetic sector, and a dominant positive {sigma}{sub m} for 0.4 s < p < 4 s and for {theta}{sub VB}>150 deg. in the solar wind inward magnetic sector. These features of {sigma}{sub m} appearing around the Doppler-shifted ion-cyclotron frequencies may be consistent with the existence of Alfven-cyclotron waves among the outward propagating fluctuations. Moreover, right-handed polarized waves at larger propagation angles, which might be kinetic Alfven waves or whistler waves, have also been identified on the basis of the {sigma}{sub m} features in the angular range 40 deg. < {theta}{sub VB} < 140 deg. Our findings suggest that Alfven-cyclotron waves (together with other wave modes) play a prominent role in turbulence cascading and plasma heating of the solar wind.

He Jiansen; Tu Chuanyi; Yao Shuo; Tian Hui [Department of Geophysics, Peking University, Beijing 100871 (China); Marsch, Eckart, E-mail: jshept@gmail.com [Max-Planck-Institut fuer Sonnensystemforschung, 37191 Katlenburg-Lindau (Germany)

2011-04-20T23:59:59.000Z

40

Wave Breaking Dissipation Observed with “SWIFT” Drifters

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Energy dissipation rates during ocean wave breaking are estimated from high-resolution profiles of turbulent velocities collected within 1 m of the surface. The velocity profiles are obtained from a pulse-coherent acoustic Doppler sonar on a wave-...

Jim Thomson

2012-12-01T23:59:59.000Z

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

41

TURBULENCE-INDUCED RELATIVE VELOCITY OF DUST PARTICLES. I. IDENTICAL PARTICLES

We study the relative velocity of inertial particles suspended in turbulent flows and discuss implications for dust particle collisions in protoplanetary disks. We simulate a weakly compressible turbulent flow, evolving 14 particle species with friction timescale, ?{sub p}, covering the entire range of scales in the flow. The particle Stokes numbers, St, measuring the ratio of ?{sub p} to the Kolmogorov timescale, are in the range 0.1 ?< St ?< 800. Using simulation results, we show that the model by Pan and Padoan gives satisfactory predictions for the rms relative velocity between identical particles. The probability distribution function (PDF) of the relative velocity is found to be highly non-Gaussian. The PDF tails are well described by a 4/3 stretched exponential function for particles with ?{sub p} ? 1-2 T{sub L}, where T{sub L} is the Lagrangian correlation timescale, consistent with a prediction based on PP10. The PDF approaches Gaussian only for very large particles with ?{sub p} ?> 54 T{sub L}. We split particle pairs at given distances into two types with low and high relative speeds, referred to as continuous and caustic types, respectively, and compute their contributions to the collision kernel. Although amplified by the effect of clustering, the continuous contribution vanishes in the limit of infinitesimal particle distance, where the caustic contribution dominates. The caustic kernel per unit cross section rises rapidly as St increases toward ? 1, reaches a maximum at ?{sub p} ? 2 T{sub L}, and decreases as ?{sub p}{sup -1/2} for ?{sub p} >> T{sub L}.

Pan, Liubin [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Padoan, Paolo, E-mail: lpan@cfa.harvard.edu, E-mail: ppadoan@icc.ub.edu [ICREA and ICC, University of Barcelona, Marti i Franqučs 1, E-08028 Barcelona (Spain)

2013-10-10T23:59:59.000Z

42

An Exact Finite-Amplitude Wave on a Helmholtz Velocity Profile in an Infinite Boussinesq Fluid

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For the Helmholtz velocity profile shown in Fig. 1, it is shown that the interface can support an exact steady finite-amplitude wave which radiates internal gravity waves away from the interface.

R. Grimshaw

1980-12-01T23:59:59.000Z

43

energy flux are in good agreement with wave turbulence theory. The Kolmogorov-Zakharov constant waves interact with each other, they can develop a regime of wave turbulence where the wave energyPHYSICAL REVIEW E 89, 023003 (2014) Energy flux measurement from the dissipated energy in capillary

Falcon, Eric

44

It is shown that the quasi-linear evolution of ion and electron distribution functions as result of wave-particle interaction of Kinetic Alfven Waves in the turbulent solar wind plasma leads to instability of long wavelength electromagnetic cyclotron waves and to an increase of the ion temperature perpendicular to the magnetic field.

Rudakov, L; Ganguli, G; Mithaiwala, M

2010-01-01T23:59:59.000Z

45

Turbulence is a phenomenon found throughout space and astrophysical plasmas. It plays an important role in solar coronal heating, acceleration of the solar wind, and heating of the interstellar medium. Turbulence in these regimes is dominated by Alfvén waves. Most turbulence theories have been established using ideal plasma models, such as incompressible MHD. However, there has been no experimental evidence to support the use of such models for weakly to moderately collisional plasmas which are relevant to various space and astrophysical plasma environments. We present the first experiment to measure the nonlinear interaction between two counterpropagating Alfvén waves, which is the building block for astrophysical turbulence theories. We present here four distinct tests that demonstrate conclusively that we have indeed measured the daughter Alfvén wave generated nonlinearly by a collision between counterpropagating Alfvén waves.

Drake, D. J. [Department of Physics, Astronomy, and Geosciences, Valdosta State University, Valdosta, Georgia 31698 (United States)] [Department of Physics, Astronomy, and Geosciences, Valdosta State University, Valdosta, Georgia 31698 (United States); Schroeder, J. W. R.; Howes, G. G.; Kletzing, C. A.; Skiff, F. [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242 (United States)] [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242 (United States); Carter, T. A.; Auerbach, D. W. [Department of Physics and Astronomy, University of California, Los Angeles, California 90095 (United States)] [Department of Physics and Astronomy, University of California, Los Angeles, California 90095 (United States)

2013-07-15T23:59:59.000Z

46

Robust energy transfer mechanism via precession resonance in nonlinear turbulent wave systems

A robust energy transfer mechanism is found in nonlinear wave systems, which favours transfers towards modes interacting via triads with nonzero frequency mismatch, applicable in meteorology, nonlinear optics and plasma wave turbulence. We introduce the concepts of truly dynamical degrees of freedom and triad precession. Transfer efficiency is maximal when the triads' precession frequencies resonate with the system's nonlinear frequencies, leading to a collective state of synchronised triads with strong turbulent cascades at intermediate nonlinearity. Numerical simulations confirm analytical predictions.

Miguel D. Bustamante; Brenda Quinn; Dan Lucas

2014-04-30T23:59:59.000Z

47

Generation of large-scale vorticity in a homogeneous turbulence with a mean velocity shear Tov by the gradient of the Reynolds stresses is studied. Generation of a mean vorticity in a homogeneous-induced'' deflection of equilibrium mean vorticity and ``Reynolds stress-induced'' generation of perturbations of mean

Elperin, Tov

48

Velocity width of the resonant domain in wave-particle interaction

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Wave-particle interaction is a ubiquitous physical mechanism exhibiting locality in velocity space. A single-wave Hamiltonian provides a rich model by which to study the self-consistent interaction between one electrostatic wave and N quasiresonant particles. For the simplest nonintegrable Hamiltonian coupling two particles to one wave, we analytically derive the particle velocity borders separating quasi-integrable motions from chaotic ones. These estimates are fully retrieved through computation of the largest Lyapunov exponent. For the large-N particle self-consistent case, we numerically investigate the localization of stochasticity in velocity space and test a qualitative estimate of the borders of chaos.

Marie-Christine Firpo and Fabrice Doveil

2001-12-19T23:59:59.000Z

49

Energy flux measurement from the dissipated energy in capillary wave turbulence Luc Deike, Michael the dissipation is increased. The energy dissipated by capillary waves is also measured and found to increase with the frequency and the newly defined mean energy flux are in good agreement with wave turbulence theory

Paris-Sud XI, UniversitĂ© de

50

Turbulence in space and astrophysical plasmas is governed by the nonlinear interactions between counterpropagating Alfvén waves. Here, we present the theoretical considerations behind the design of the first laboratory measurement of an Alfvén wave collision, the fundamental interaction underlying Alfvénic turbulence. By interacting a relatively large-amplitude, low-frequency Alfvén wave with a counterpropagating, smaller-amplitude, higher-frequency Alfvén wave, the experiment accomplishes the secular nonlinear transfer of energy to a propagating daughter Alfvén wave. The predicted properties of the nonlinearly generated daughter Alfvén wave are outlined, providing a suite of tests that can be used to confirm the successful measurement of the nonlinear interaction between counterpropagating Alfvén waves in the laboratory.

Howes, G. G.; Nielson, K. D.; Schroeder, J. W. R.; Skiff, F.; Kletzing, C. A. [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242 (United States)] [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242 (United States); Drake, D. J. [Department of Physics, Astronomy, and Geosciences, Valdosta State University, Valdosta, Georgia 31698 (United States)] [Department of Physics, Astronomy, and Geosciences, Valdosta State University, Valdosta, Georgia 31698 (United States); Carter, T. A. [Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States)] [Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States)

2013-07-15T23:59:59.000Z

51

P wave velocity variations in the Coso region, California, derived from

P wave velocity variations in the Coso region, California, derived from P wave velocity variations in the Coso region, California, derived from local earthquake travel times Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Journal Article: P wave velocity variations in the Coso region, California, derived from local earthquake travel times Details Activities (1) Areas (1) Regions (0) Abstract: Inversion of 4036 P wave travel time residuals from 429 local earthquakes using a tomographic scheme provides information about three-dimensional upper crustal velocity variations in the Indian Wells Valley-Coso region of southeastern California. The residuals are calculated relative to a Coso-specific velocity model, corrected for station elevation, weighted, and back-projected along their ray paths through models defined with layers of blocks. Slowness variations in the surface

52

Characterization of the effect of Froude number on surface waves and heat transfer in inclined describes wave/heat transfer phenomena in inclined turbulent open surface water flows. The experiments were. These changes lead to a heat transfer improvement, enough to double the heat transfer coefficient

Abdou, Mohamed

53

Flows in which shock waves and turbulence are present and interact dynamically occur in a wide range of applications, including inertial confinement fusion, supernovae explosion, and scramjet propulsion. Accurate simulations of such problems are challenging because of the contradictory requirements of numerical methods used to simulate turbulence, which must minimize any numerical dissipation that would otherwise overwhelm the small scales, and shock-capturing schemes, which introduce numerical dissipation to stabilize the solution. The objective of the present work is to evaluate the performance of several numerical methods capable of simultaneously handling turbulence and shock waves. A comprehensive range of high-resolution methods (WENO, hybrid WENO/central difference, artificial diffusivity, adaptive characteristic-based filter, and shock fitting) and suite of test cases (Taylor-Green vortex, Shu-Osher problem, shock-vorticity/entropy wave interaction, Noh problem, compressible isotropic turbulence) relevant to problems with shocks and turbulence are considered. The results indicate that the WENO methods provide sharp shock profiles, but overwhelm the physical dissipation. The hybrid method is minimally dissipative and leads to sharp shocks and well-resolved broadband turbulence, but relies on an appropriate shock sensor. Artificial diffusivity methods in which the artificial bulk viscosity is based on the magnitude of the strain-rate tensor resolve vortical structures well but damp dilatational modes in compressible turbulence; dilatation-based artificial bulk viscosity methods significantly improve this behavior. For well-defined shocks, the shock fitting approach yields good results.

Johnsen, Eric [Center for Turbulence Research, Stanford University, Stanford, CA 94305 (United States)], E-mail: johnsen@stanford.edu; Larsson, Johan [Center for Turbulence Research, Stanford University, Stanford, CA 94305 (United States)], E-mail: jola@stanford.edu; Bhagatwala, Ankit V. [Department of Aeronautics and Astronautics, Stanford University, Stanford, CA 94305 (United States); Cabot, William H. [Lawrence Livermore National Laboratory, Livermore, CA 94551 (United States); Moin, Parviz [Center for Turbulence Research, Stanford University, Stanford, CA 94305 (United States); Olson, Britton J. [Department of Aeronautics and Astronautics, Stanford University, Stanford, CA 94305 (United States); Rawat, Pradeep S. [Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, CA 90095 (United States); Shankar, Santhosh K. [Department of Aeronautics and Astronautics, Stanford University, Stanford, CA 94305 (United States); Sjoegreen, Bjoern [Lawrence Livermore National Laboratory, Livermore, CA 94551 (United States); Yee, H.C. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Zhong Xiaolin [Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, CA 90095 (United States); Lele, Sanjiva K. [Department of Aeronautics and Astronautics, Stanford University, Stanford, CA 94305 (United States)

2010-02-20T23:59:59.000Z

54

Shear wave seismic velocity profiling and depth to water table earthquake site

..................................................................................................... 6 Summary of seismic refraction/reflection methodsShear wave seismic velocity profiling and depth to water table Â earthquake site response measurements for Valley County, Idaho Lee M. Liberty and Gabriel M. Gribler, Boise State University Center

Barrash, Warren

55

Three-dimensional P and S waves velocity structures of the Coso geothermal

P and S waves velocity structures of the Coso geothermal P and S waves velocity structures of the Coso geothermal area, California, from microseismic travel time data Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Journal Article: Three-dimensional P and S waves velocity structures of the Coso geothermal area, California, from microseismic travel time data Details Activities (1) Areas (1) Regions (0) Abstract: High precision P and S wave travel times for 2104 microearthquakes with focus <6 km are used in a non-linear inversion to derive high-resolution three-dimensional compressional and shear velocity structures at the Coso Geothermal Area in eastern California. Block size for the inversion is 0.2 km horizontally and 0.5 km vertically and inversions are investigated in the upper 5 km of the geothermal area.

56

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

Science Journals Connector (OSTI)

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

G. G. Craddock and P. H. Diamond

1991-09-16T23:59:59.000Z

57

Compressible Turbulence and Interactions with Shock Waves and...

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

in various disciplines, including supernova explosions, inertial confinement fusion, hypersonic flight and propulsion, and shock wave lithotripsy. Accomplishments: A novel...

58

Internal wave energy radiated from a turbulent mixed layer James R. Munroe1, a)

on the surface or the barotropic tide acting on bottom topography, transport their energy to the ocean interiorInternal wave energy radiated from a turbulent mixed layer James R. Munroe1, a) and Bruce R in the shear layer is characterized using particle image velocimetry to measure the kinetic energy den- sity

Sutherland, Bruce

59

Saturation levels of heat-flux- and fast-electron-driven ion-acoustic-wave turbulence

Science Journals Connector (OSTI)

Saturation levels of ion-acoustic-wave turbulence driven by a heat-flux and a suprathermal electron current have been calculated on the basis of perturbed-orbit theory. The levels are found to be lower than those commonly estimated from simple trapping arguments and too low to explain the thermal-flux inhibition observed in many laser-plasma experiments.

H. C. Barr and T. J. M. Boyd

1981-10-01T23:59:59.000Z

60

Excitation of solitons by an external resonant wave with a slowly varying phase velocity

A novel mechanism is proposed for the excitation of solitons in nonlinear dispersive media. The mechanism employs an external pumping wave with a varying phase velocity, which provides a continuous resonant excitation of a nonlinear wave in the medium. Two different schemes of a continuous resonant growth (continuous phase-locking) of the induced nonlinear wave are suggested. The first of them requires a definite time dependence of the pumping wave phase velocity and is relatively sensitive to the initial wave phase. The second employs the dynamic autoresonance effect and is insensitive to the exact time dependence of the pumping wave phase velocity. It is demonstrated analytically and numerically, for a particular example of a driven Korteweg-de Vries (KdV) equation with periodic boundary conditions, that as the nonlinear wave grows, it transforms into a soliton, which continues growing and accelerating adiabatically. A fully nonlinear perturbation theory is developed for the driven KdV equation to follow the growing wave into the strongly nonlinear regime and describe the soliton formation.

Aranson, I.; Meerson, B. [Hebrew Univ., Jerusalem (Israel). Racah Inst. of Physics; Tajima, Toshiki [Texas Univ., Austin, TX (United States)

1992-02-01T23:59:59.000Z

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

61

Kinetic Alfvén wave turbulence and formation of localized structures

This work presents non-linear interaction of magnetosonic wave with kinetic Alfvén wave for intermediate ?-plasma (m{sub e}/m{sub i}???1). A set of dimensionless equations have been developed for analysis by considering ponderomotive force due to pump kinetic Alfvén wave in the dynamics of magnetosonic wave. Stability analysis has been done to study modulational instability or linear growth rate. Further, numerical simulation has been carried out to study the nonlinear stage of instability and resulting power spectrum applicable to solar wind around 1 AU. Due to the nonlinearity, background density of magnetosonic wave gets modified which results in localization of kinetic Alfvén wave. From the obtained results, we observed that spectral index follows k{sup ?3.0}, consistent with observation received by Cluster spacecraft for the solar wind around 1 AU. The result shows the steepening of power spectrum which may be responsible for heating and acceleration of plasma particles in solar wind.

Sharma, R. P. [Centre for Energy Studies, Indian Institute of Technology Delhi, Delhi 110016 (India)] [Centre for Energy Studies, Indian Institute of Technology Delhi, Delhi 110016 (India); Modi, K. V. [Centre for Energy Studies, Indian Institute of Technology Delhi, Delhi 110016 (India) [Centre for Energy Studies, Indian Institute of Technology Delhi, Delhi 110016 (India); Mechanical Engineering Department, Government Engineering College Valsad, Gujarat 396001 (India)

2013-08-15T23:59:59.000Z

62

Measurement of shear wave velocity of heavy oil De-hua Han, Jiajin Liu, University of Houston

for measurement of fluid velocity is to measure the travel time of the transmission wave and then the velocity can water, has been used and is good for P-wave measurement for a lot of fluid samples. But the transmission the principle of this method. The shear wave transducer is coupled with a buffer made of some kind of plastic

63

Filamentation of magnetosonic wave and generation of magnetic turbulence in laser plasma interaction

This paper presents a theoretical model for the magnetic turbulence in laser plasma interaction due to the nonlinear coupling of magnetosonic wave with ion acoustic wave in overdense plasma. For this study, dynamical equations of magnetosonic waves and the ion acoustic waves have been developed in the presence of ponderomotive force due to the pump magnetosonic wave. Slowly converging and diverging behavior has been studied semi-analytically, this results in the formation of filaments of the magnetosonic wave. Numerical simulation has also been carried out to study nonlinear stage. From the results, it has been found that the localized structures become quite complex in nature. Further, power spectrum has been studied. Results show that the spectral index follows (?k{sup ?2.0}) scaling at smaller scale. Relevance of the present investigation has been shown with the experimental observation.

Modi, K. V., E-mail: kvmodi.iitd@gmail.com [Centre for Energy Studies, Indian Institute of Technology Delhi, Delhi 110016 (India); Mechanical Engineering Department, Government Engineering College Valsad, Gujarat 396001 (India); Tiwary, Prem Pyari, E-mail: prempyari@gmail.com [Centre for Energy Studies, Indian Institute of Technology Delhi, Delhi 110016 (India); Department of Physics and Computer Science, Dayal Bagh Educational Institute (Deemed University), Dayal Bagh, Agra 282005 (India); Singh, Ram Kishor, E-mail: ram007kishor@gmail.com; Sharma, R. P., E-mail: rpsharma@ces.iitd.ac.in [Centre for Energy Studies, Indian Institute of Technology Delhi, Delhi 110016 (India); Satsangi, V. R. [Department of Physics and Computer Science, Dayal Bagh Educational Institute (Deemed University), Dayal Bagh, Agra 282005 (India)

2014-10-15T23:59:59.000Z

64

Energy flux measurement from the dissipated energy in capillary wave turbulence

We study experimentally the influence of dissipation on stationary capillary wave turbulence on the surface of a fluid by changing its viscosity. We observe that the frequency power law scaling of the capillary spectrum departs significantly from its theoretical value when the dissipation is increased. The energy dissipated by capillary waves is also measured and found to increase nonlinearly with the mean power injected within the fluid. Here, we propose an experimental estimation of the energy flux at every scale of the capillary cascade. The latter is found to be non constant through the scales. For fluids of low enough viscosity, we found that both capillary spectrum scalings with the frequency and the newly defined mean energy flux are in good agreement with wave turbulence theory. The Kolmogorov-Zakharov constant is then experimentally estimated and compared to its theoretical value.

Luc Deike; Michaël Berhanu; Eric Falcon

2013-09-26T23:59:59.000Z

65

Shift in the longitudinal sound velocity due to sliding charge-density waves

Science Journals Connector (OSTI)

The nonlinear conductivity observed for moderate electric fields in NbSe3, TaS3, (TaS4)2I, and K0.3MoO3 below the charge-density-wave-transition is believed to be due to the sliding of the charge-density waves. The sliding motion leads to a Doppler shift of the x-ray diffraction peaks, but this effect has not yet been resolved. We show here that besides the Doppler shift, a sliding incommensurate charge-density wave causes a change in the longitudinal sound velocity of the crystal that is linear in the charge-density-wave velocity. The resulting anisotropic shift is estimated in a mean-field approximation and found to be experimentally observable.

S. N. Coppersmith and C. M. Varma

1984-09-15T23:59:59.000Z

66

Parametric Instabilities in Turbulent, Inhomogeneous Plasma

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It is known that parametric instabilities involving two coupled modes, with oppositely directed group velocities, saturate convectively if the medium is inhomogeneous. This work considers the modification of that result when weak long-wave turbulence is present, in addition to the background inhomogeneity. We find that the convective saturation disappears when the turbulence exceeds a certain level, absolute growth occurring instead.

Dwight R. Nicholson and Allan N. Kaufman

1974-11-11T23:59:59.000Z

67

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

Pidaparthi, Sahitya

2011-01-01T23:59:59.000Z

68

A New Global Rayleigh and Love Wave Group Velocity Dataset For Constraining Lithosphere Properties

A New Global Rayleigh and Love Wave Group Velocity Dataset For Constraining Lithosphere Properties features and fit our data very well. This dataset will be used to constrain lithospheric structure globally the global datasets used in Ritzwoller et al. (2002) already consist of more than 100,000 paths, the nature

Laske, Gabi

69

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

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

Shepherd, Theodore Gordon

1984-01-01T23:59:59.000Z

70

The slow-mode nature of compressible wave power in solar wind turbulence

We use a large, statistical set of measurements from the Wind spacecraft at 1 AU, and supporting synthetic spacecraft data based on kinetic plasma theory, to show that the compressible component of inertial range solar wind turbulence is primarily in the kinetic slow mode. The zero-lag cross correlation C(delta n, delta B_parallel) between proton density fluctuations delta n and the field-aligned (compressible) component of the magnetic field delta B_parallel is negative and close to -1. The typical dependence of C(delta n,delta B_parallel) on the ion plasma beta_i is consistent with a spectrum of compressible wave energy that is almost entirely in the kinetic slow mode. This has important implications for both the nature of the density fluctuation spectrum and for the cascade of kinetic turbulence to short wavelengths, favoring evolution to the kinetic Alfven wave mode rather than the (fast) whistler mode.

Howes, G G; Klein, K G; Chen, C H K; Salem, C S; TenBarge, J M

2011-01-01T23:59:59.000Z

71

Electron Fluid Description of Wave-Particle Interactions in Strong Buneman Turbulence

To understand the nature of anomalous resistivity in magnetic reconnection, we investigate turbulence-induced momentum transport and energy dissipation during Buneman instability in force-free current sheets. Using 3D particle-in-cell simulations, we find that the macroscopic effects generated by wave-particle interactions in Buneman instability can be approximately described by a set of electron fluid equations. These equations show that the energy dissipation and momentum transports along current sheets are locally quasi-static but globally non-static and irreversible. Turbulence drag dissipates both the streaming energy of current sheets and the associated magnetic energy. The decrease of magnetic field maintains an inductive electric field that re-accelerates electrons. The net loss of streaming energy is converted into the heat of electrons moving along the magnetic field and increases the electron Boltzmann entropy. The growth of self-sustained Buneman waves satisfies a Bernoulli-like equation that rela...

Che, H

2014-01-01T23:59:59.000Z

72

A robust energy transfer mechanism is found in nonlinear wave systems, which favours transfers towards modes interacting via non-resonant triads, applicable in meteorology, nonlinear optics and plasma wave turbulence. Transfer efficiency is maximal when the frequency mismatch of the non-resonant triad balances the system's nonlinear frequency: at intermediate levels of oscillation amplitudes an instability is triggered that explores unstable manifolds of periodic orbits, so turbulent cascades are most efficient at intermediate nonlinearity. Numerical simulations confirm analytical predictions.

Miguel D. Bustamante; Brenda Quinn

2013-09-02T23:59:59.000Z

73

Effects of neutral interactions on velocity-shear-driven plasma waves

In a laboratory experiment, we demonstrate the substantial effects that collisions between charged and neutral particles have on low-frequency (?{sub i}????????{sub e}) shear-driven electrostatic lower hybrid waves in a plasma. We establish a strong (up to 2.5?kV/m) highly localized electric field with a length scale shorter than the ion gyroradius, so that the ions in the plasma, unlike the electrons, do not develop the full E?×?B drift velocity. The resulting shear in the particle velocities initiates the electron-ion hybrid (EIH) instability, and we observe the formation of strong waves in the vicinity of the shear with variations in plasma densities of 10% or greater. Our experimental configuration allows us to vary the neutral background density by more than a factor of two while holding the charged particle density effectively constant. Not surprisingly, increasing the neutral density decreases the growth rate/saturation amplitude of the waves and increases the threshold electric field necessary for wave formation, but the presence of neutrals affects the dominant wave frequency as well. We show that a 50% increase in the neutral density decreases the wave frequency by 20% while also suppressing the electric field dependence of the frequency that is observed when fewer neutrals are present. The majority of these effects, as well as the values of the frequencies we observe, closely match the predictions of previously developed linear EIH instability theory, for which we present the results of a numerical solution.

Enloe, C. L. [Physics Department, US Air Force Academy, Colorado Springs, Colorado 80840 (United States); Tejero, E. M.; Amatucci, W. E.; Crabtree, C.; Ganguli, G. [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (United States); Sotnikov, V. [Sensors Directorate, Air Force Research Laboratory, Dayton, Ohio 45433 (United States)

2014-06-15T23:59:59.000Z

74

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

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

Connaughton, Colm; Quinn, Brenda

2014-01-01T23:59:59.000Z

75

1.1 This practice covers a procedure for measuring the ultrasonic velocities in the outer wall of polyethylene storage tanks. An angle beam lateral longitudinal (LCR) wave is excited with wedges along a circumferential chord of the tank wall. A digital ultrasonic flaw detector is used with sending-receiving search units in through transmission mode. The observed velocity is temperature corrected and compared to the expected velocity for a new, unexposed sample of material which is the same as the material being evaluated. The difference between the observed and temperature corrected velocities determines the degree of UV exposure of the tank. 1.2 The practice is intended for application to the outer surfaces of the wall of polyethylene tanks. Degradation typically occurs in an outer layer approximately 3.2-mm (0.125-in.) thick. Since the technique does not interrogate the inside wall of the tank, wall thickness is not a consideration other than to be aware of possible guided (Lamb) wave effects or reflection...

American Society for Testing and Materials. Philadelphia

2011-01-01T23:59:59.000Z

76

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

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

Colm Connaughton; Sergey Nazarenko; Brenda Quinn

2014-07-07T23:59:59.000Z

77

Generation of lower hybrid and whistler waves by an ion velocity ring distribution

Using fully kinetic simulations in two and three spatial dimensions, we consider the generation and nonlinear evolution of lower hybrid waves produced by a cold ion ring velocity distribution in a low beta plasma. We show that the initial development of the instability is very similar in two and three dimensions and not significantly modified by electromagnetic effects, consistent with linear theory. At saturation, the level of electric field fluctuations is a small fraction of the background thermal energy; the electric field and corresponding density fluctuations consist of long, field-aligned striations. Energy extracted from the ring goes primarily into heating the background ions and the electrons at comparable rates. The initial growth and saturation of the magnetic components of the lower hybrid waves are related to the electric field components, consistent with linear theory. As the growing electric field fluctuations saturate, parallel propagating whistler waves develop by the interaction of two lower hybrid waves. At later times, these whistlers are replaced by longer wavelength, parallel propagating whistlers that grow through the decay of the lower hybrid fluctuations. Wave matching conditions demonstrate these conversion processes of lower hybrid waves to whistler waves. The conversion efficiency (=ratio of the whistler wave energy to the energy in the saturated lower hybrid waves) is computed and found to be significant ({approx}15%) for the parameters of the three-dimensional simulation (and even larger in the two-dimensional simulation), although when normalized in terms of the initial kinetic energy in the ring ions the overall efficiency is very small (<10{sup -4}). The results are compared with relevant linear and nonlinear theory.

Winske, D.; Daughton, W. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2012-07-15T23:59:59.000Z

78

Results are presented for lead free primers based on diazodinitrophenol (DDNP)compared with tests on lead styphnate based primers. First, barrel friction measurements in 5.56 mm NATO are presented. Second, shot to shot variations in blast waves are presented as determined by detonating primers in a 7.62x51mm rifle chamber with a firing pin, but without any powder or bullet loaded and measuring the blast wave at the muzzle with a high speed pressure transducer. Third, variations in primer blast waves, muzzle velocities, and ignition delay are presented after environmental conditioning (150 days) for two lead based and two DDNP based primers under cold and dry (-25 deg C,0% relative humidity), ambient (20 deg C, 50% relative humidity), and hot & humid (50 deg C, 100% relative humidity) conditions in 5.56 mm NATO. Taken together, these results indicate that DDNP based primers are not sufficiently reliable for service use.

Courtney, Elya; Summer, Peter David; Courtney, Michael

2014-01-01T23:59:59.000Z

79

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

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

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

2014-06-15T23:59:59.000Z

80

The Velocity of Propagation of Longitudinal Waves in Liquids at Audio-Frequencies

Science Journals Connector (OSTI)

A method for measuring the velocity of propagation of longitudinal waves in liquids is described which is at the same time precise and convenient of application. A column of liquid contained in a cylindrical vertical steel tube was brought into resonance vibration at audio frequency by an electromagnetically excited diaphragm at the bottom. From the solution of the equation of propagation it is shown that when the resonance frequency of the system is the same as that of the diaphragm the reaction of the latter on the system is very small. The height of the column of liquid in the tube was adjusted until its natural frequency nearly corresponded with the predetermined resonance frequency of the diaphragm. The height was then varied slightly and the frequency adjusted until resonance occurred. From several observations of this type the appropriate height corresponding to the resonance frequency of the diaphragm was obtained by interpolation. The velocity of propagation of the longitudinal waves was then calculated from the relation V=f0, where f0 is the natural frequency of the diaphragm when clamped in the holder and ? is the wavelength.Correction for the elasticity of the walls of the tube.—The correction formulas of Korteweg, Lamb and Gronwall were tested experimentally on tubes of different dimensions. The latter was found to give the most satisfactory agreement, the two former being unsuitable for precision measurements.Measurements.—The velocity of sound was measured in air-free distilled water at 25°C. The average of 52 observations gave for this velocity 1485.4±2.3 m/sec. From this value the bulk modulus, G, and the adiabatic compressibility, ?, were calculated. Curves were plotted illustrating the variation of the velocity of sound with temperature for the range 25°-70°C and with concentration for solutions of NaCl and KCl of different normalities. Curves for the corresponding variations of G and ? are also given.

Louis Gordon Pooler

1930-04-01T23:59:59.000Z

While these samples are representative of the content of NLE

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We encourage you to perform a real-time search of NLE

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81

1 Green's Functions for Surface Waves in a Generic Velocity Structure 1 and Green's functions have been well established 14 for many decades. However, or Green's function surface displacement. We address this gap in the 19 literature

82

Nonlinear interaction of proton whistler with kinetic Alfvén wave to study solar wind turbulence

This paper presents the nonlinear interaction between small but finite amplitude kinetic Alfvén wave (KAW) and proton whistler wave using two-fluid model in intermediate beta plasma, applicable to solar wind. The nonlinearity is introduced by modification in the background density. This change in density is attributed to the nonlinear ponderomotive force due to KAW. The solutions of the model equations, governing the nonlinear interaction (and its effect on the formation of localized structures), have been obtained using semi-analytical method in solar wind at 1AU. It is concluded that the KAW properties significantly affect the threshold field required for the filament formation and their critical size (for proton whistler). The magnetic and electric field power spectra have been obtained and their relevance with the recent observations of solar wind turbulence by Cluster spacecraft has been pointed out.

Goyal, R.; Sharma, R. P. [Centre for Energy Studies, Indian Institute of Technology, Delhi-110016 (India)] [Centre for Energy Studies, Indian Institute of Technology, Delhi-110016 (India); Goldstein, M. L. [NASA Goddard Space Flight Centre, Code 673, Greenbelt, Maryland 20771 (United States)] [NASA Goddard Space Flight Centre, Code 673, Greenbelt, Maryland 20771 (United States); Dwivedi, N. K. [Austrian Academy of Sciences, Space Research Institute, Schmiedlstrasse 6, 8042 Graz (Austria)] [Austrian Academy of Sciences, Space Research Institute, Schmiedlstrasse 6, 8042 Graz (Austria)

2013-12-15T23:59:59.000Z

83

Broader source: All U.S. Department of Energy (DOE) Office Webpages (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 fÂ¨ ur Plasmaphysik, EURATOM Association, Greifswald, Germany At certain values of the edge rotational transform, Îą a = 1/q a , the confinement time of plasmas in the Wendelstein 7-AS (W7-AS) stellarator was found to

84

Upper mantle structure of South America from joint inversion of waveforms and fundamental mode tomographic S wave velocity model for the upper mantle beneath South America is presented. We developed three-dimensional (3-D) upper mantle S velocity model and a Moho depth model for South America, which

van der Lee, Suzan

85

Optical pin apparatus for measuring the arrival time and velocity of shock waves and particles

An apparatus for the detection of the arrival and for the determination of the velocity of disturbances such as shock-wave fronts and/or projectiles. Optical pins using fluid-filled microballoons as the light source and an optical fiber as a link to a photodetector have been used to investigate shock-waves and projectiles. A microballoon filled with a noble gas is affixed to one end of a fiber-optic cable, and the other end of the cable is attached to a high-speed streak camera. As the shock-front or projectile compresses the microballoon, the gas inside is heated and compressed producing a bright flash of light. The flash of light is transmitted via the optic cable to the streak camera where it is recorded. One image-converter streak camera is capable of recording information from more than 100 microballoon-cable combinations simultaneously.

Benjamin, R.F.

1983-10-18T23:59:59.000Z

86

Optical pin apparatus for measuring the arrival time and velocity of shock waves and particles

An apparatus for the detection of the arrival and for the determination of the velocity of disturbances such as shock-wave fronts and/or projectiles. Optical pins using fluid-filled microballoons as the light source and an optical fiber as a link to a photodetector have been used to investigate shock-waves and projectiles. A microballoon filled with a noble gas is affixed to one end of a fiber-optic cable, and the other end of the cable is attached to a high-speed streak camera. As the shock-front or projectile compresses the microballoon, the gas inside is heated and compressed producing a bright flash of light. The flash of light is transmitted via the optic cable to the streak camera where it is recorded. One image-converter streak camera is capable of recording information from more than 100 microballoon-cable combinations simultaneously.

Benjamin, Robert F. (315 Rover Blvd., Los Alamos, NM 87544)

1987-01-01T23:59:59.000Z

87

Optical pin apparatus for measuring the arrival time and velocity of shock waves and particles

An apparatus is disclosed for the detection of the arrival and for the determination of the velocity of disturbances such as shock-wave fronts and/or projectiles. Optical pins using fluid-filled microballoons as the light source and an optical fiber as a link to a photodetector have been used to investigate shock-waves and projectiles. A microballoon filled with a noble gas is affixed to one end of a fiber-optic cable, and the other end of the cable is attached to a high-speed streak camera. As the shock-front or projectile compresses the microballoon, the gas inside is heated and compressed producing a bright flash of light. The flash of light is transmitted via the optic cable to the streak camera where it is recorded. One image-converter streak camera is capable of recording information from more than 100 microballoon-cable combinations simultaneously. 3 figs.

Benjamin, R.F.

1987-03-10T23:59:59.000Z

88

Ion Bernstein waves in a plasma with a kappa velocity distribution

Using a Vlasov-Poisson model, a numerical investigation of the dispersion relation for ion Bernstein waves in a kappa-distributed plasma has been carried out. The dispersion relation is found to depend significantly on the spectral index of the ions, ?{sub i}, the parameter whose smallness is a measure of the departure from thermal equilibrium of the distribution function. Over all cyclotron harmonics, the typical Bernstein wave curves are shifted to higher wavenumbers (k) if ?{sub i} is reduced. For waves whose frequency lies above the lower hybrid frequency, ?{sub LH}, an increasing excess of superthermal particles (decreasing ?{sub i}) reduces the frequency, ?{sub peak}, of the characteristic peak at which the group velocity vanishes, while the associated k{sub peak} is increased. As the ratio of ion plasma to cyclotron frequency (?{sub pi}/?{sub ci}) is increased, the fall-off of ? at large k is smaller for lower ?{sub i} and curves are shifted towards larger wavenumbers. In the lower hybrid frequency band and harmonic bands above it, the frequency in a low-?{sub i} plasma spans only a part of the intraharmonic space, unlike the Maxwellian case, thus exhibiting considerably less coupling between adjacent bands for low ?{sub i}. It is suggested that the presence of the ensuing stopbands may be a useful diagnostic for the velocity distribution characteristics. The model is applied to the Earth's plasma sheet boundary layer in which waves propagating perpendicularly to the ambient magnetic field at frequencies between harmonics of the ion cyclotron frequency are frequently observed.

Nsengiyumva, F.; Mace, R. L.; Hellberg, M. A. [School of Chemistry and Physics, University of KwaZulu-Natal, Durban 4000 (South Africa)] [School of Chemistry and Physics, University of KwaZulu-Natal, Durban 4000 (South Africa)

2013-10-15T23:59:59.000Z

89

, refraction, breaking, and turbulence, to name a few. Beginning offshore where the water depth is sufficiently deep and constant, waves are found to be symmetric with respect to the wave crest (Hsiao et al., 2008) before they began to deform due... to measure the free surface elevation, allowing the evolution of the solitary wave over the shallow water shelf and up the planar beach to be documented. To do this, two types of wave gauges were required due to the depth of water offshore and onshore...

Swigler, David Townley

2010-10-12T23:59:59.000Z

90

Measurement of the Injected Power . . . . . . . . . . . . . . . . . . . 60 2.4 Fluctuations of the Energy Flux that involve a finite mean energy flux per unit surface and density across the scales. In the case of a n Fluctuations of the Energy Flux in Wave Turbulence S. Auma^itre , E. Falcon,Â§ and S. Fauve SPEC, DSM, CEA

Falcon, Eric

91

Science Journals Connector (OSTI)

A single-wave-number representation of a nonlinear energy spectrum, i.e., a stretching-energy spectrum, is found in elastic-wave turbulence governed by the Föppl–von Kármán (FvK) equation. The representation enables energy decomposition analysis in the wave-number space and analytical expressions of detailed energy budgets in the nonlinear interactions. We numerically solved the FvK equation and observed the following facts. Kinetic energy and bending energy are comparable with each other at large wave numbers as the weak turbulence theory suggests. On the other hand, stretching energy is larger than the bending energy at small wave numbers, i.e., the nonlinearity is relatively strong. The strong correlation between a mode ak and its companion mode a?k is observed at the small wave numbers. The energy is input into the wave field through stretching-energy transfer at the small wave numbers, and dissipated through the quartic part of kinetic-energy transfer at the large wave numbers. Total-energy flux consistent with energy conservation is calculated directly by using the analytical expression of the total-energy transfer, and the forward energy cascade is observed clearly.

Naoto Yokoyama and Masanori Takaoka

2014-12-08T23:59:59.000Z

92

By means of the offered analytical method the determinant relation for a phase velocities of elastic waves for an arbitrary propagation directions in a piezoelectric crystal are received. The phase velocities of three normal elastic waves for the crystal of LiNbO3 are calculated. Results of this calculation for each of waves are presented graphically in the form of the cards allowing easily to define phase velocities in any given direction in crystal.

A. A. Golubeva

2010-07-26T23:59:59.000Z

93

Free-space communication allows one to use spatial mode encoding, which is susceptible to the effects of diffraction and turbulence. Here, we discuss the optimum communication modes of a system while taking such effects into account. We construct a free-space communication system that encodes information onto the plane-wave (PW) modes of light. We study the performance of this system in the presence of atmospheric turbulence, and compare it with previous results for a system employing orbital-angular-momentum (OAM) encoding. We are able to show that the PW basis is the preferred basis set for communication through atmospheric turbulence for a large Fresnel number system. This study has important implications for high-dimensional quantum key distribution systems.

Mohammad Mirhosseini; Brandon Rodenburg; Mehul Malik; Robert W. Boyd

2013-04-02T23:59:59.000Z

94

Short Note Green's Functions for Surface Waves in a Generic Velocity Structure by Victor C. Tsai displacement/stress eigenfunctions and Green's functions have been well established for many decades. However on frequency, or Green's function surface displacement. We address this gap in the liter- ature and here

95

In this study, hydraulic and seismic tomographic measurements were used to derive a site-specific relationship between the geophysical parameter p-wave velocity and the hydraulic parameters, diffusivity and specific storage. Our field study includes diffusivity tomograms derived from hydraulic travel time tomography, specific storage tomograms, derived from hydraulic attenuation tomography, and p-wave velocity tomograms, derived from seismic tomography. The tomographic inversion was performed in all three cases with the SIRT (Simultaneous Iterative Reconstruction Technique) algorithm, using a ray tracing technique with curved trajectories. The experimental set-up was designed such that the p-wave velocity tomogram overlaps the hydraulic tomograms by half. The experiments were performed at a wellcharacterized sand and gravel aquifer, located in the Leine River valley near Göttingen, Germany. Access to the shallow subsurface was provided by direct-push technology. The high spatial resolution of hydraulic and seismic tomography was exploited to derive representative site-specific relationships between the hydraulic and geophysical parameters, based on the area where geophysical and hydraulic tests were performed. The transformation of the p-wave velocities into hydraulic properties was undertaken using a k-means cluster analysis. Results demonstrate that the combination of hydraulic and geophysical tomographic data is a promising approach to improve hydrogeophysical site characterization.

Brauchler, R.; Doetsch, J.; Dietrich, P.; Sauter, M.

2012-01-10T23:59:59.000Z

96

Validating a Time-Dependent Wave-Turbulence-Driven Model of the Solar Wind

Although the mechanisms responsible for heating the Sun's corona and accelerating the solar wind are still being actively investigated, it is largely accepted that photospheric motions provide the energy source and that the magnetic field must play a key role in the process. \\citet{2010ApJ...708L.116V} presented a model for heating and accelerating the solar wind based on the turbulent dissipation of Alfv\\'en waves. We first use a time-dependent model of the solar wind to reproduce one of \\citeauthor{2010ApJ...708L.116V}'s solutions; then we extend its application to the case when the energy equation includes thermal conduction and radiation losses, and the upper chromosphere is part of the computational domain. Using this model, we explore parameter space and describe the characteristics of a fast-solar-wind solution. We discuss how this formulation may be applied to a 3D MHD model of the coron a and solar wind \\citep{2009ApJ...690..902L}.

Lionello, Roberto; Downs, Cooper; Linker, Jon A; Miki?, Zoran; Verdini, Andrea

2014-01-01T23:59:59.000Z

97

Anomalous electron-ion energy coupling in electron drift wave turbulence

annulus arises due to a wave energy flux differential acrossprincipal collisionless wave energy dissipation channel inOn the other hand, wave energy can be dissipated by ion

Zhao, Lei

98

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

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

99

Science Journals Connector (OSTI)

A continuum pumped full of waveenergy at an amplitude sufficiently large so that reversible nonlinearities dominate irreversible linear response becomes waveturbulent. In the limit of high nonlinearity acoustic turbulence and wind waveturbulence accumulate at 1/f and 1/f 5 power spectra respectively. A waveturbulent system can support new propagating energy modes analogous to second sound in superfluid He4. This hyperbolic (nondiffusive) transport could account for the anomalous diffusivity observed in plasma devices and for the difficulties faced in achieving confinement. The key to the understanding of these phenomena is the nonlinearity in the continuum mechanics which leads to three basic effects: (1) scattering of sound by sound to produce waves with sum and difference frequencies; (2) refraction of waves by a slowly varying (inhomogeneous) background; (3) reaction of the background due to changes in the distribution of sound waves. Details of these processes are presented in the framework of the Euler equations.

Seth Putterman; A. Larraza; P. H. Roberts

1986-01-01T23:59:59.000Z

100

E-Print Network 3.0 - acoustic wave velocity Sample Search Results

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

43.30.Ft, 43... short range was deemed desirable for isolating the effects of shallow water internal waves on acoustic... internal waves are not un- usual and it was ......

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

101

The interpretation of surface altimetric signals in terms of Rossby waves is revisited. Rather than make the long-wave approximation, the horizontal scale of the waves is adjusted to optimally fit the phase speed predicted ...

Tulloch, Ross

102

Science Journals Connector (OSTI)

The transition of a system of partial differential equations which describe the stationary flow behind the shock–wave front of a detonation complex upon detonation of a cylindrical charge to a system...

A. R. Gushanov

2001-01-01T23:59:59.000Z

103

Velocity measurements in shallow sediments from ground surface to approximately 370 to 400 feet bgs were collected by Redpath Geophysics using impulsive S- and P-wave seismic sources (Redpath 2007). Measurements below this depth within basalt and sedimentary interbeds were made by UTA between October and December 2006 using the T-Rex vibratory seismic source in each of the three boreholes. Results of these measurements including seismic records, wave-arrival identifications and interpreted velocity profiles are presented in the following six volumes: I. P-Wave Measurements in Borehole C4993 II. P-Wave Measurements in Borehole C4996 III. P-Wave Measurements in Borehole C4997 IV. S-Wave Measurements in Borehole C4993 V. S-Wave Measurements in Borehole C4996 VI. S-Wave Measurements in Borehole C4997 In this volume (V), all S-wave measurements are presented that were performed in Borehole C4996 at the WTP with T-Rex as the seismic source and the Lawrence Berkeley National Laboratory (LBNL) 3-D wireline geophone as the at-depth borehole receiver.

Stokoe, Kenneth H.; Li, Song Cheng; Cox, Brady R.; Menq, Farn-Yuh

2007-06-06T23:59:59.000Z

104

Velocity measurements in shallow sediments from ground surface to approximately 370 to 400 feet bgs were collected by Redpath Geophysics using impulsive S- and P-wave seismic sources (Redpath 2007). Measurements below this depth within basalt and sedimentary interbeds were made by UTA between October and December 2006 using the T-Rex vibratory seismic source in each of the three boreholes. Results of these measurements including seismic records, wave-arrival identifications and interpreted velocity profiles are presented in the following six volumes: I. P-Wave Measurements in Borehole C4993 II. P-Wave Measurements in Borehole C4996 III. P-Wave Measurements in Borehole C4997 IV. S-Wave Measurements in Borehole C4993 V. S-Wave Measurements in Borehole C4996 VI. S-Wave Measurements in Borehole C4997 In this volume (VI), all S-wave measurements are presented that were performed in Borehole C4997 at the WTP with T-Rex as the seismic source and the Lawrence Berkeley National Laboratory (LBNL) 3-D wireline geophone as the at-depth borehole receiver.

Stokoe, Kenneth H.; Li, Song Cheng; Cox, Brady R.; Menq, Farn-Yuh

2007-06-06T23:59:59.000Z

105

Stress-wave velocity of wood-based panels: Effect of moisture,

for wood-based panel products. In the forest products industry, nondestructive evaluation (NDE) technology, Ross and Pellerin 1994). One NDE technique, which uses stress-wave propagation characteristics, has received considerable atten- tion. Stress-wave-based NDE techniques have been investi- gated extensively

106

Modelling suspended sediment in environmental turbulent fluids

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

Cao, Meng

2014-01-01T23:59:59.000Z

107

P- and SV-wave transversely isotropic phase velocities analysis from VSP data

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......Measured anisotropy in Pierre Shale, Geophys. Prosp., 31...been applied to the Pierre Shale data (White, Martineau...elastic wave propagation in anisotropic media is the fact that the...al. (1983) in the Pierre Shale where two neighbouring wells......

J. de Parscau

1991-12-01T23:59:59.000Z

108

of the interstellar medium,1 acceleration of the solar wind,2,3 solar coronal heating,4 trans- port of energy and mass, Valdosta, Georgia 31698, USA 2 Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa heating, acceleration of the solar wind, and heating of the interstellar medium. Turbulence

California at Los Angles, University of

109

Anisotropic turbulent model for solar coronal heating

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

110

Surface wave phase velocities of the Western United States from a two-station method

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......the University of Colorado at Boulder (Lin et-al. 2009), which...Cascade Ranges, Columbia Plateau flood basalts, HLP and NW BR (High...colocated with the Columbia River flood basalts to the east in Washington...observed beneath the Columbia River flood basalt province. Love wave......

Anna Foster; Göran Ekström; Meredith Nettles

2014-01-01T23:59:59.000Z

111

On breaking waves and turbulence at the air-sea interface /

instrumentation was a pair of FLIR SC6000 Long-Wave in-instantaneous Stereo LWIR cameras FLIR SC6000 640x512 pixels

Sutherland, Peter Jesse

2013-01-01T23:59:59.000Z

112

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Abstract Shear wave velocity data have been acquired at several marine gas hydrate drilling expeditions, including the India National Gas Hydrate Program Expedition 1 (NGHP-01), the Ocean Drilling Program (ODP) Leg 204, and Integrated Ocean Drilling Program (IODP) Expedition 311 (X311). In this study we use data from these marine drilling expeditions to develop an understanding of general grain-size control on the P- and S-wave properties of sediments. A clear difference in the downhole trends of P-wave (Vp) and S-wave (Vs) velocity and the Vp/Vs ratio from all three marine regions was observed: the northern Cascadia margin (IODP X311) shows the highest P-wave and S-wave velocity values overall and those from the India margin (Expedition NGHP-01) are the lowest. The southern Cascadia margin (ODP Leg 204) appears to have similar low P-wave and S-wave velocity values as seen off India. S-wave velocity values increase relative to the sites off India, but they are not as high as those seen on the northern Cascadia margin. Such regional differences can be explained by the amount of silt/sand (or lack thereof) occurring at these sites, with northern Cascadia being the region of the highest silt/sand occurrences. This grain-size control on P-wave and S-wave velocity and associated mineral composition differences is amplified when compared to the Arctic permafrost environments, where gas hydrate predominantly occurs in sand- and silt-dominated formations. Using a cross-plot of gamma ray values versus the Vp/Vs ratio, we compare the marine gas hydrate occurrences in these regions: offshore eastern India margin, offshore Cascadia margin, the Ignik-Sikumi site in Alaska, and the Mallik 5L-38 site in the Mackenzie Delta. The log-data from the Arctic permafrost regions show a strongly linear Vp–Vs relationship, similar to the previously defined empirical relationships by Greenberg and Castagna (1992). P- and S-wave velocity data from the India margin and ODP Leg 204 deviate strongly from these linear trends, whereas data from IODP X311 plot closer to the trend of the Arctic data sets and previously published relationships. Three new linear relationships for different grain size marine sediment hosts are suggested:a) mud-dominated (Mahanadi Basin, ODP Leg 204 & NGHP-01-17): Vs = 1.5854 × Vp ? 2.1649 b) silty-mud (KG Basin): Vs = 0.8105 × Vp ? 1.0223 c) silty-sand (IODP X311): Vs = 0.5316 × Vp ? 0.4916 We investigate the relationship of gas hydrate saturation determined from electrical resistivity on the Vp/Vs ratio and found that the sand-dominated Arctic hosts show a clearly decreasing trend of Vp/Vs ratio with gas hydrate saturation. Though limited due to lower overall GH saturations, a similar trend is seen for sites from IODP X311 and at the ash-dominated NGHP-01-17 sediment in the Andaman Sea. Gas hydrate that occurs predominantly in fractured clay hosts show a different trend where the Vp/Vs ratio is much higher than at sand-dominated sites and remains constant or increases slightly with increasing gas hydrate saturation. This trend may be the result of anisotropy in fracture-dominated systems, where P- and S-wave velocities appear higher and Archie-based saturations of gas hydrate are overestimated. Gas hydrate concentrations were also estimated in these three marine settings and at Arctic sites using an effective medium model, combining P- and S-wave velocities as equally weighted constraints on the calculation. The effective medium approach generally overestimates S-wave velocity in high-porosity, clay-dominated sediments, but can be accurately used in sand-rich formations.

M. Riedel; D. Goldberg; G. Guerin

2014-01-01T23:59:59.000Z

113

Optical-Fiber Gravitational Wave Detector: Dynamical 3-Space Turbulence Detected

Preliminary results from an optical-fiber gravitational wave interferometric detector are reported. The detector is very small, cheap and simple to build and operate. It is assembled from readily available opto-electronic components. A parts list is given. The detector can operate in two modes: one in which only instrument noise is detected, and data from a 24 hour period is reported for this mode, and in a 2nd mode in which the gravitational waves are detected as well, and data from a 24 hour period is analysed. Comparison shows that the instrument has a high S/N ratio. The frequency spectrum of the gravitational waves shows a pink noise spectrum, from 0 to 0.1Hz.

Reginald T Cahill

2007-07-16T23:59:59.000Z

114

The Spatial and Temporal Dependence of Coronal Heating by Alfven Wave Turbulence

The solar atmosphere may be heated by Alfven waves that propagate up from the convection zone and dissipate their energy in the chromosphere and corona. To further test this theory, we consider wave heating in an active region observed on 2012 March 7. A potential field model of the region is constructed, and 22 field lines representing observed coronal loops are traced through the model. Using a three-dimensional (3D) reduced magneto-hydrodynamics (MHD) code, we simulate the dynamics of Alfven waves in and near the observed loops. The results for different loops are combined into a single formula describing the average heating rate Q as function of position within the observed active region. We suggest this expression may be approximately valid also for other active regions, and therefore may be used to construct 3D, time-dependent models of the coronal plasma. Such models are needed to understand the role of thermal non-equilibrium in the structuring and dynamics of the Sun's corona.

Asgari-Targhi, M; Cranmer, S R; DeLuca, E E

2013-01-01T23:59:59.000Z

115

A single-wavenumber representation of nonlinear energy spectrum, i.e., stretching energy spectrum is found in elastic-wave turbulence governed by the F\\"oppl-von K\\'arm\\'an (FvK) equation. The representation enables energy decomposition analysis in the wavenumber space, and analytical expressions of detailed energy budget in the nonlinear interactions are obtained for the first time in wave turbulence systems. We numerically solved the FvK equation and observed the following facts. Kinetic and bending energies are comparable with each other at large wavenumbers as the weak turbulence theory suggests. On the other hand, the stretching energy is larger than the bending energy at small wavenumbers, i.e., the nonlinearity is relatively strong. The strong correlation between a mode $a_{\\bm{k}}$ and its companion mode $a_{-\\bm{k}}$ is observed at the small wavenumbers. Energy transfer shows that the energy is input into the wave field through stretching-energy transfer at the small wavenumbers, and dissipated through the quartic part of kinetic-energy transfer at the large wavenumbers. A total-energy flux consistent with the energy conservation is calculated directly by using the analytical expression of the total-energy transfer, and the forward energy cascade is observed clearly.

Naoto Yokoyama; Masanori Takaoka

2014-12-09T23:59:59.000Z

116

The dynamics of variable-density turbulence

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

Sandoval, D.L.

1995-11-01T23:59:59.000Z

117

Residual energy in magnetohydrodynamic turbulence and in the solar wind

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

118

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

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

1993-12-01T23:59:59.000Z

119

Science Journals Connector (OSTI)

This paper presents the anisotropic characteristics of the elastic moduli, P-wave velocities, and thermal conductivities of three types of anisotropic rocks, i.e., Asan gneiss, Boryeong shale, and Yeoncheon schist, occurring in Korea. The experiments were conducted on rock samples that show clear evidence of transverse isotropy. Cylindrical core samples with different anisotropy angles were prepared by coring at 15-degree intervals from the transversely isotropic plane using the laboratory directional coring system established for this study. Elastic moduli, P-wave velocities, and thermal conductivities were determined along the sample axis for different anisotropy angles. The anisotropy ratio is defined as the ratio of the properties parallel to the transversely isotropic plane to those perpendicular to the plane, and the anisotropy ratios for the thermal conductivities (K(90°)/K(0°)) of Asan gneiss, Boryeong shale, and Yeoncheon schist were 1.4, 2.1, and 2.5, respectively. The P-wave velocity anisotropy ratios (VP(90°)/VP(0°)) for Asan gneiss, Boryeong shale, and Yeoncheon schist were 1.2, 1.5, and 2.3, respectively. The elastic moduli, P-wave velocities, and thermal conductivities that were obtained were compared with theoretical predictions by mean prediction error (MPE). The correlations between the measured properties were evidently correlated with some minor scatter in the data. The degree of anisotropy measured in this study suggests that ignoring anisotropy in rock properties may mislead to erroneous results. The application of tensorial transformation evaluations revealed that the three types of rocks chosen for this study can be modeled effectively by a transversely isotropic model.

Hanna Kim; Jung-Woo Cho; Insun Song; Ki-Bok Min

2012-01-01T23:59:59.000Z

120

This report describes the procedures and the results of a series of downhole measurements of shear- and compression-wave velocities performed as part of the Seismic Boreholes Project at the site of the Waste Treatment Plant (WTP). The measurements were made in several stages from October 2006 through early February 2007. Although some fieldwork was carried out in conjunction with the University of Texas at Austin (UT), all data acquired by UT personnel are reported separately by that organization.

Redpath, Bruce B.

2007-04-27T23:59:59.000Z

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

121

Science Journals Connector (OSTI)

New experimental data that make it possible to explain and predict the observed variability of turbulent-energy dissipation in the upper ocean are discussed. ... For this purpose, the dependence of the energy dis...

S. A. Kitaigorodskii

2009-06-01T23:59:59.000Z

122

Turbulent transport of energetic ions

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

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

2006-11-30T23:59:59.000Z

123

Selected problems in turbulence theory and modeling

Three different topics of turbulence research that cover modeling, theory and model computation categories are selected and studied in depth. In the first topic, "velocity gradient dynamics in turbulence" (modeling), the Lagrangian linear diffusion...

Jeong, Eun-Hwan

2004-09-30T23:59:59.000Z

124

Science Journals Connector (OSTI)

Measurements are presented of time-synchronized axial ion velocities at three positions in the discharge channel and plume of a diverging cusped field thruster operating on xenon. Xenon axial ion velocities for the thruster are derived from laser-induced fluorescence measurements of the 5d[4]7/2–6p[3]5/2 xenon ion excited state transition centred at ? = 834.72 nm. The thruster is operated in a high-current mode, where the anode discharge current is shown to oscillate quasi-periodically. A sample-hold scheme is implemented to correlate ion velocities to phases along the current cycle. These time-synchronized measurements show that median axial ion velocities decrease as discharge current increases, and that the widths of ion velocity distributions increase with increases in discharge current for positions at the exit plane and outside the thruster channel.

N A MacDonald; M A Cappelli; W A Hargus Jr

2014-01-01T23:59:59.000Z

125

Generation of electromagnetic structures via modulational instability of drift waves

Generation mechanism for large scale electromagnetic structures (blobs) is considered by employing the technique of four-wave interactions (modulational instability). It is shown that primary electrostatic turbulence may generate elongated electromagnetic structures with poloidal modulations. Such structures are principally related to drift-Alfven waves. The analysis fully takes into account finite ion temperature effects and associated diamagnetic contributions to Reynolds stress. The turbulent generation of blobs has instability growth rates which scale similar to the zonal flow instabilities, {gamma}{approx}

Smolyakov, A. I. [Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2 (Canada); Nuclear Fusion Institute, Russian Research Center 'Kurchatov Institute', 1 Kurchatov Square, 123182, Moscow (Russian Federation); Krasheninnikov, S. I. [University of California at San Diego, 9500 Gilman Dr., La Jolla, California 92093 (United States)

2008-07-15T23:59:59.000Z

126

Holographic Vortex Liquids and Superfluid Turbulence

Science Journals Connector (OSTI)

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

Paul M. Chesler; Hong Liu; Allan Adams

2013-07-26T23:59:59.000Z

127

3-ft Wave Flume Facility | Open Energy Information

3-ft Wave Flume Facility 3-ft Wave Flume Facility Overseeing Organization United States Army Corp of Engineers (ERDC) Hydrodynamic Testing Facility Type Flume Length(m) 45.1 Beam(m) 0.9 Depth(m) 0.9 Water Type Freshwater Cost(per day) Contact POC Towing Capabilities Towing Capabilities None Wavemaking Capabilities Wavemaking Capabilities Yes Maximum Wave Height(m) 0.2 Maximum Wave Height(m) at Wave Period(s) 10.0 Wave Period Range(s) 10.0 Current Velocity Range(m/s) 0.0 Programmable Wavemaking Yes Simulated Beach No Channel/Tunnel/Flume Channel/Tunnel/Flume None Wind Capabilities Wind Capabilities None Control and Data Acquisition Description Automated data acquisition and control system Cameras None Available Sensors Flow, Pressure Range(psi), Turbulence, Velocity, Wave Probe

128

5-ft Wave Flume Facility | Open Energy Information

5-ft Wave Flume Facility 5-ft Wave Flume Facility Overseeing Organization United States Army Corp of Engineers (ERDC) Hydrodynamic Testing Facility Type Flume Length(m) 63.4 Beam(m) 1.5 Depth(m) 1.5 Water Type Freshwater Cost(per day) Contact POC Towing Capabilities Towing Capabilities None Wavemaking Capabilities Wavemaking Capabilities Yes Maximum Wave Height(m) 0.5 Maximum Wave Height(m) at Wave Period(s) 10.0 Wave Period Range(s) 10.0 Current Velocity Range(m/s) 0.0 Programmable Wavemaking Yes Simulated Beach No Channel/Tunnel/Flume Channel/Tunnel/Flume Yes Recirculating No Wind Capabilities Wind Capabilities None Control and Data Acquisition Description Automated data acquisition and control system Cameras None Available Sensors Flow, Pressure Range(psi), Turbulence, Velocity, Wave Probe

129

The dynamics of variable-density turbulence

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

Sandoval, D.L.

1995-11-01T23:59:59.000Z

130

PERPENDICULAR ION HEATING BY REDUCED MAGNETOHYDRODYNAMIC TURBULENCE

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

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

2013-10-20T23:59:59.000Z

131

Perpendicular ion acceleration in whistler turbulence

Whistler turbulence is an important contributor to solar wind turbulence dissipation. This turbulence contains obliquely propagating whistler waves at electron scales, and these waves have electrostatic components perpendicular to the mean magnetic field. In this paper, a full kinetic, two-dimensional particle-in-cell simulation shows that whistler turbulence can accelerate ions in the direction perpendicular to the mean magnetic field. When the ions pass through wave-particle resonances region in the phase space during their cyclotron motion, the ions are effectively accelerated in the perpendicular direction. The simulation results suggest that whistler turbulence contributes to the perpendicular heating of ions observed in the solar wind.

Saito, S. [Graduate School of Science, Nagoya University, Furocho, Chikusa, Nagoya 464-8601 (Japan)] [Graduate School of Science, Nagoya University, Furocho, Chikusa, Nagoya 464-8601 (Japan); Nariyuki, Y. [Faculty of Human Development, University of Toyama, 3190, Toyama 930-8555 (Japan)] [Faculty of Human Development, University of Toyama, 3190, Toyama 930-8555 (Japan)

2014-04-15T23:59:59.000Z

132

Omega?to?the?one?third term in dispersion relation for acoustic pulse propagation through turbulence

Science Journals Connector (OSTI)

The author’s earlier formulation of pulse propagation through turbulence required a somewhat ad hoc separation of the effects of large scale and small scale turbulence with the selection of a cut?off turbulentwave number k c that separates the two regimes. A neater?cleaner formulation proceeds with the premise that the frequency dispersion of pulses is caused by that part of the turbulence spectrum which lies in the inertial range originally predicted by Kolmogoroff. The acoustic propagating wave’s dispersion relation has the acoustic wave number being of the form k=(?/c)+F(?) where c is a spatially averaged sound speed and where for mechanical turbulence the extra term F(?) must depend on only the angular frequency ? the sound speedc and the turbulent energy dissipation ? per unit fluid mass and per unit time. If the turbulence is weak then the quantity F(?) has to be of second order in the portions of the turbulent fluid velocity in the intertial range so following Kolmogoroff’s reasoning it must vary with ? as ?2/3. Simple dimensional analysis then reveals that F(?) is K?2/3 c ?7/3?1/3 the latter factor being as announced in the title of this abstract and K being a universal dimensionless complex constant. A similar result holds for thermal turbulence. The analysis showing that the separating?out of the effects of turbulence in the inertial regime is in fact possible yields K=?0.37e i?/3. The dispersion is typically small but has an accumulative effect that leads to a sizable pulse distortion over large propagation distances. [Work supported by NASA Langley Research Center.

Allan D. Pierce

1995-01-01T23:59:59.000Z

133

A framework for studying the effect of compliant surfaces on wall turbulence

This paper extends the resolvent formulation proposed by McKeon & Sharma (2010) to consider turbulence-compliant wall interactions. Under this formulation, the turbulent velocity field is expressed as a linear superposition of propagating modes, identified via a gain-based decomposition of the Navier-Stokes equations. Compliant surfaces, modeled as a complex wall-admittance linking pressure and velocity, affect the gain and structure of these modes. With minimal computation, this framework accurately predicts the emergence of the quasi-2D propagating waves observed in recent direct numerical simulations. Further, the analysis also enables the rational design of compliant surfaces, with properties optimized to suppress flow structures energetic in wall turbulence. It is shown that walls with unphysical negative damping are required to interact favorably with modes resembling the energetic near-wall cycle, which could explain why previous studies have met with limited success. Positive-damping walls are eff...

Luhar, M; McKeon, B J

2014-01-01T23:59:59.000Z

134

Science Journals Connector (OSTI)

detonation velocity, detonation rate, velocity of detonation, V.O.D., detonating velocity, rate of detonation, detonating rate, detonation speed, detonating speed, speed of detonation ? Detonationsge...

2014-08-01T23:59:59.000Z

135

Information theoretical characterization of turbulence

Science Journals Connector (OSTI)

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

K. Ikeda and K. Matsumoto

1989-05-08T23:59:59.000Z

136

Rogue waves for a long wave-short wave resonance model with multiple short waves

1 Rogue waves for a long wave-short wave resonance model with multiple short waves Hiu Ning Chan (1 waves; Long-short resonance PACS Classification: 02.30.Jr; 05.45.Yv; 47.35.Fg #12;2 ABSTRACT A resonance between long and short waves will occur if the phase velocity of the long wave matches the group velocity

137

ARM - Measurement - Atmospheric turbulence

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

138

Information Content of Turbulence

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

Rory Cerbus; Walter Goldburg

2013-07-03T23:59:59.000Z

139

-multiple of the wavelength: n 2 L ,n 1,2,... . A vibrating string is an example of a transverse wave: its oscillation2011 Waves - 1 STANDING WAVES ON A STRING The objectives of the experiment are: Â· To show that standing waves can be set up on a string. Â· To determine the velocity of a standing wave. Â· To understand

Glashausser, Charles

140

Active skin for turbulent drag reduction

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

Mani, Raghavendran

2002-01-01T23:59:59.000Z

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

141

Transition to turbulence in ferrofluids

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

Altmeyer, Sebastian; Lai, Ying-Cheng

2015-01-01T23:59:59.000Z

142

Modulation of homogeneous turbulence seeded with finite size ...

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

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

2010-01-30T23:59:59.000Z

143

Waves is the supporting document to the Master of Fine Arts thesis exhibition of the same title. Exhibited March 7-12 2010 in the Art and Design Gallery at the University of Kansas, Waves was comprised of a series of mixed media drawings...

LaCure, Mari Mae

2010-04-29T23:59:59.000Z

144

The role of damped Alfven waves on magnetospheric accretion models of young stars

We examine the role of Alfven wave damping in heating the plasma in the magnetic funnels of magnetospheric accretion models of young stars. We study four different damping mechanisms of the Alfven waves: nonlinear, turbulent, viscous-resistive and collisional. Two different possible origins for the Alfven waves are discussed: 1) Alfven waves generated at the surface of the star by the shock produced by the infalling matter; and 2) Alfven waves generated locally in the funnel by the Kelvin-Helmholtz instability. We find that, in general, the damping lengths are smaller than the tube length. Since thermal conduction in the tube is not efficient, Alfven waves generated only at the star's surface cannot heat the tube to the temperatures necessary to fit the observations. Only for very low frequency Alfven waves ~10^{-5} the ion cyclotron frequency, is the viscous-resistive damping length greater than the tube length. In this case, the Alfven waves produced at the surface of the star are able to heat the whole tube. Otherwise, local production of Alfven waves is required to explain the observations. The turbulence level is calculated for different frequencies for optically thin and thick media. We find that turbulent velocities varies greatly for different damping mechanisms, reaching \\~100 km s^{-1} for the collisional damping of small frequency waves.

M. J. Vasconcelos; V. Jatenco-Pereira; R. Opher

2002-04-03T23:59:59.000Z

145

In this volume (II), all P-wave measurements are presented that were performed in Borehole C4996 at the Waste Treatment Plant (WTP) with T-Rex as the seismic source and the Lawrence Berkeley National Laboratory (LBNL) 3-D wireline geophone as the at-depth borehole receiver. P-wave measurements were performed over the depth range of 360 to 1400 ft, typically in 10-ft intervals. However, in some interbeds, 5-ft depth intervals were used, while below about 1180 ft, depth intervals of 20 ft were used. Compression (P) waves were generated by moving the base plate of T-Rex for a given number of cycles at a fixed frequency as discussed in Section 2. This process was repeated so that signal averaging in the time domain was performed using 3 to about 15 averages, with 5 averages typically used. In addition to the LBNL 3-D geophone, called the lower receiver herein, a 3-D geophone from Redpath Geophysics was fixed at a depth of 22 ft in Borehole C4996, and a 3-D geophone from the University of Texas was embedded near the borehole at about 1.5 ft below the ground surface. This volume is organized into 12 sections as follows: Section 1: Introduction, Section 2: Explanation of Terminology, Section 3: Vp Profile at Borehole C4996, Sections 4 to 6: Unfiltered P-wave records of lower vertical receiver, reaction mass, and reference receiver, Sections 7 to 9: Filtered P-wave signals of lower vertical receiver, reaction mass and reference receiver, Section 10: Expanded and filtered P-wave signals of lower vertical receiver, and Sections 11 and 12: Waterfall plots of unfiltered and filtered lower vertical receiver signals.

Stokoe, Kenneth H.; Li, Song Cheng; Cox, Brady R.; Menq, Farn-Yuh

2007-07-06T23:59:59.000Z

146

In this volume (I), all P-wave measurements are presented that were performed in Borehole C4993 at the Waste Treatment Plant (WTP) with T-Rex as the seismic source and the Lawrence Berkeley National Laboratory (LBNL) 3-D wireline geophone as the at-depth borehole receiver. P-wave measurements were performed over the depth range of 370 to 1400 ft, typically in 10-ft intervals. However, in some interbeds, 5-ft depth intervals were used, while below about 1200 ft, depth intervals of 20 ft were used. Compression (P) waves were generated by moving the base plate of T-Rex for a given number of cycles at a fixed frequency as discussed in Section 2. This process was repeated so that signal averaging in the time domain was performed using 3 to about 15 averages, with 5 averages typically used. In addition to the LBNL 3-D geophone, called the lower receiver herein, a 3-D geophone from Redpath Geophysics was fixed at a depth of 22 ft in Borehole C4993, and a 3-D geophone from the University of Texas was embedded near the borehole at about 1.5 ft below the ground surface. This volume is organized into 12 sections as follows: Section 1: Introduction, Section 2: Explanation of Terminology, Section 3: Vp Profile at Borehole C4993, Sections 4 to 6: Unfiltered P-wave records of lower vertical receiver, reaction mass, and reference receiver, Sections 7 to 9: Filtered P-wave signals of lower vertical receiver, reaction mass and reference receiver, Section 10: Expanded and filtered P-wave signals of lower vertical receiver, and Sections 11 and 12: Waterfall plots of unfiltered and filtered lower vertical receiver signals.

Stokoe, Kenneth H.; Li, Song Cheng; Cox, Brady R.; Menq, Farn-Yuh

2007-07-06T23:59:59.000Z

147

In this volume (III), all P-wave measurements are presented that were performed in Borehole C4997 at the Waste Treatment Plant (WTP) with T-Rex as the seismic source and the Lawrence Berkeley National Laboratory (LBNL) 3-D wireline geophone as the at-depth borehole receiver. P-wave measurements were performed over the depth range of 390 to 1220 ft, typically in 10-ft intervals. However, in some interbeds, 5-ft depth intervals were used. Compression (P) waves were generated by moving the base plate of T-Rex for a given number of cycles at a fixed frequency as discussed in Section 2. This process was repeated so that signal averaging in the time domain was performed using 3 to about 15 averages, with 5 averages typically used. In addition to the LBNL 3-D geophone, called the lower receiver herein, a 3-D geophone from Redpath Geophysics was fixed at a depth of 40 ft (later relocated to 27.5 ft due to visibility in borehole after rain) in Borehole C4997, and a 3-D geophone from the University of Texas was embedded near the borehole at about 1.5 ft below the ground surface. This volume is organized into 12 sections as follows: Section 1: Introduction, Section 2: Explanation of Terminology, Section 3: Vp Profile at Borehole C4997, Sections 4 to 6: Unfiltered P-wave records of lower vertical receiver, reaction mass, and reference receiver, Sections 7 to 9: Filtered P-wave signals of lower vertical receiver, reaction mass and reference receiver, Section 10: Expanded and filtered P-wave signals of lower vertical receiver, and Sections 11 and 12: Waterfall plots of unfiltered and filtered lower vertical receiver signals.

Stokoe, Kenneth H.; Li, Song Cheng; Cox, Brady R.; Menq, Farn-Yuh

2007-06-06T23:59:59.000Z

148

In this volume (IV), all S-wave measurements are presented that were performed in Borehole C4993 at the Waste Treatment Plant (WTP) with T-Rex as the seismic source and the Lawrence Berkeley National Laboratory (LBNL) 3-D wireline geophone as the at-depth borehole receiver. S-wave measurements were performed over the depth range of 370 to 1300 ft, typically in 10-ft intervals. However, in some interbeds, 5-ft depth intervals were used, while below about 1200 ft, depth intervals of 20 ft were used. Shear (S) waves were generated by moving the base plate of T-Rex for a given number of cycles at a fixed frequency as discussed in Section 2. This process was repeated so that signal averaging in the time domain was performed using 3 to about 15 averages, with 5 averages typically used. In addition, a second average shear wave record was recorded by reversing the polarity of the motion of the T-Rex base plate. In this sense, all the signals recorded in the field were averaged signals. In all cases, the base plate was moving perpendicular to a radial line between the base plate and the borehole which is in and out of the plane of the figure shown in Figure 1.1. The definition of “in-line”, “cross-line”, “forward”, and “reversed” directions in items 2 and 3 of Section 2 was based on the moving direction of the base plate. In addition to the LBNL 3-D geophone, called the lower receiver herein, a 3-D geophone from Redpath Geophysics was fixed at a depth of 22 ft in Borehole C4993, and a 3-D geophone from the University of Texas (UT) was embedded near the borehole at about 1.5 ft below the ground surface. The Redpath geophone and the UT geophone were properly aligned so that one of the horizontal components in each geophone was aligned with the direction of horizontal shaking of the T-Rex base plate. This volume is organized into 12 sections as follows. Section 1: Introduction, Section 2: Explanation of Terminology, Section 3: Vs Profile at Borehole C4993, Sections 4 to 6: Unfiltered S-wave records of lower horizontal receiver, reaction mass, and reference receiver, respectively, Sections 7 to 9: Filtered S-wave signals of lower horizontal receiver, reaction mass and reference receiver, respectively, Section 10: Expanded and filtered S-wave signals of lower horizontal receiver, and Sections 11 and 12: Waterfall plots of unfiltered and filtered lower horizontal receiver signals, respectively.

Stokoe, Kenneth H.; Li, Song Cheng; Cox, Brady R.; Menq, Farn-Yuh

2007-06-06T23:59:59.000Z

149

Electromagnetic weak turbulence theory revisited

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

150

Advances in compressible turbulent mixing

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

151

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

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

1998-07-01T23:59:59.000Z

152

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

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

Goodman, Louis

153

Velocity determination from velocity spectra

. Lithologic and structural information can bc inferred from the interval velocities and thicknesses. Actual seismic exploration data (which are twelvefold sub- surface coverage data taken at Niller County, Arkansas) were used to make the actual velocity...) with decreasing increment of normal incidence time and rms velocity, 2) with in- creasing interval between the initial and final values of time and TRACE NO. & SHOT-GEOPHONE DISTANCE l 2 3 4 3 6 X, X X 4 Xs X~ RMS VELOCITY V ca Jo M A tD M NNO = J o) y...

Yang, Sung Jin

2012-06-07T23:59:59.000Z

154

GeophysicsDivision, SandiaNational Laboratories,Albuquerque,New Mexico ROBERT W. CLAYTON Seismological velocity variations in the Indian Wells Valley-Coso region of southeasternCalifornia. The residuals layer reflect local geology, including slow velocities for the sedimentary basins of Indian Wells

Clayton, Robert W.

155

Turbulent Dynamics in the Solar Convection Zone

Science Journals Connector (OSTI)

...nonisotropic, ra-diative, inhomogeneous MHD turbulence. Considering the effort that...helioseismic methods based on such ring diagram and phase analyses (24) may provide...Ser. 76, 208 (1995). 24. Ring diagram methods applied to local wave fields are...

Nicholas Brummell; Juri Toomre; Fausto Cattaneo

1995-09-08T23:59:59.000Z

156

Estimating Oceanic Turbulence Dissipation from Seismic Images

Science Journals Connector (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

2013-08-01T23:59:59.000Z

157

MHD Waves in Astrophysical Plasma

Science Journals Connector (OSTI)

The dependence of the wave velocities on the angle ? between the undisturbed field B 0 and the wave vector k is clearly demonstrated in a polar diagram—the phase velocity diagram. In Fig.?15.2, th...

Boris V. Somov

2012-01-01T23:59:59.000Z

158

Two-field theory of incompressible-fluid turbulence

Science Journals Connector (OSTI)

The turbulent velocity field in wave-number space is decomposed into two distinct fields. One is a purely chaotic field; while the other is a correction field, and carries all the phase information. Application of this decomposition to a thin shell of wave numbers in the dissipation range allows the elimination of modes in that shell, with the usual mode-coupling problems being circumvented by the use of a conditional average. The (conditional) mean effect of the eliminated modes appears as an increment to the viscosity, with terms of order ?2 being neglected, where ? is a dimensionless measure of bandwidth thickness, such that 0???1. An iteration (with appropriate rescaling) to successively lower shells reaches a fixed point, corresponding to a renormalized turbulent viscosity. As previously reported [W. D. McComb and A. G. Watt, Phys. Rev. Lett. 65, 3281 (1990)], the spectrum of the purely chaotic field is found to take the Kolmogorov -5/3 power-law form, with a value for the Kolmogorov spectral constant of ?=1.6, independent of ? over the range of bandwidths for which the theory is valid.

W. D. McComb and A. G. Watt

1992-10-15T23:59:59.000Z

159

Lunar Laser-Ranging Detection of Light-Speed Anisotropy and Gravitational Waves

The Apache Point Lunar Laser-ranging Operation (APOLLO), in NM, can detect photon bounces from retro-reflectors on the moon surface to 0.1ns timing resolution. This facility enables not only the detection of light speed anisotropy, which defines a local preferred frame of reference - only in that frame is the speed of light isotropic, but also fluctuations/turbulence (gravitational waves) in the flow of the dynamical 3-space relative to local systems/observers. So the APOLLO facility can act as an effective "gravitational wave" detector. A recently published small data set from November 5, 2007, is analysed to characterise both the average anisotropy velocity and the wave/turbulence effects. The results are consistent with some 13 previous detections, with the last and most accurate being from the spacecraft earth-flyby Doppler-shift NASA data.

Reginald T Cahill

2010-01-14T23:59:59.000Z

160

Effect of Adhesive Tape on the Velocity Profile of Water

Science Journals Connector (OSTI)

... fully developed turbulent flow in order to discover the effect on the velocity profile of roughening the channel bed by sticking sand grains of various known dimensions to it by means ...

ALAN E. COSSAR

1970-09-05T23:59:59.000Z

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

161

Science Journals Connector (OSTI)

......the upper 5 km of the crust is anisotropic. The range of anisotropy for...the rock samples, limestone-anisotropic shale. Since the ray path is velocity-dependent...equation (1986) for limestone-anisotropic shale using the following data (Levin......

E. A. Boztepe; L. W. Braile

1994-11-01T23:59:59.000Z

162

A Dynamical Model of Plasma Turbulence in the Solar Wind

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

Howes, G G

2015-01-01T23:59:59.000Z

163

Effect of turbulence on electron cyclotron current drive and heating in ITER

Non-linear local electromagnetic gyrokinetic turbulence simulations of the ITER standard scenario H-mode are presented for the q=3/2 and q=2 surfaces. The turbulent transport is examined in regions of velocity space characteristic of electrons heated by electron cyclotron waves. Electromagnetic fluctuations and sub-dominant micro-tearing modes are found to contribute significantly to the transport of the accelerated electrons, even though they have only a small impact on the transport of the bulk species. The particle diffusivity for resonant passing electrons is found to be less than 0.15 m^2/s, and their heat conductivity is found to be less than 2 m^2/s. Implications for the broadening of the current drive and energy deposition in ITER are discussed.

Casson, F J; Angioni, C; Buchholz, R; Peeters, A G

2014-01-01T23:59:59.000Z

164

Alfvenic Turbulence in the Extended Solar Corona: Kinetic Effects and Proton Heating

We present a model of magnetohydrodynamic (MHD) turbulence in the extended solar corona that contains the effects of collisionless dissipation and anisotropic particle heating. Measurements made by UVCS/SOHO have revived interest in the idea that ions are energized by the dissipation of ion cyclotron resonant waves, but such high-frequency (i.e., small wavelength) fluctuations have not been observed. A turbulent cascade is one possible way of generating small-scale fluctuations from a pre-existing population of low-frequency MHD waves. We model this cascade as a combination of advection and diffusion in wavenumber space. The dominant spectral transfer occurs in the direction perpendicular to the background magnetic field. As expected from earlier models, this leads to a highly anisotropic fluctuation spectrum with a rapidly decaying tail in parallel wavenumber. The wave power that decays to high enough frequencies to become ion cyclotron resonant depends on the relative strengths of advection and diffusion in the cascade. For the most realistic values of these parameters, though, there is insufficient power to heat protons and heavy ions. The dominant oblique fluctuations (with dispersion properties of kinetic Alfven waves) undergo Landau damping, which implies strong parallel electron heating. We discuss the probable nonlinear evolution of the electron velocity distributions into parallel beams and discrete phase-space holes (similar to those seen in the terrestrial magnetosphere) which can possibly heat protons via stochastic interactions.

S. R. Cranmer; A. A. van Ballegooijen

2003-05-08T23:59:59.000Z

165

Enhancement and suppression of heat transfer by MHD turbulence

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

166

Buoyancy-generated variable-density turbulence

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

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

1996-07-01T23:59:59.000Z

167

Determination of Non-thermal Velocity Distributions from SERTS Linewidth Observations

Science Journals Connector (OSTI)

Non-thermal velocities obtained from the measurement of coronal Extreme Ultraviolet (EUV) linewidths have been consistently observed in solar EUV spectral observations and have been theorized to result from many plausible scenarios including wave motions, turbulence, or magnetic reconnection. Constraining these velocities can provide a physical limit for the available energy resulting from unresolved motions in the corona. We statistically determine a series of non-thermal velocity distributions from linewidth measurements of 390 emission lines from a wide array of elements and ionization states observed during the Solar Extreme Ultraviolet Research Telescope and Spectrograph 1991-1997 flights covering the spectral range 174-418 Ĺ and a temperature range from 80,000 K to 12.6 MK. This sample includes 248 lines from active regions, 101 lines from quiet-Sun regions, and 41 lines were observed from plasma off the solar limb. We find a strongly peaked distribution corresponding to a non-thermal velocity of 19-22 km s–1 in all three of the quiet-Sun, active region, and off-limb distributions. For the possibility of Alfvén wave resonance heating, we find that velocities in the core of these distributions do not provide sufficient energy, given typical densities and magnetic field strengths for the coronal plasma, to overcome the estimated coronal energy losses required to maintain the corona at the typical temperatures working as the sole mechanism. We find that at perfect efficiency 50%-60% of the needed energy flux can be produced from the non-thermal velocities measured.

Aaron J. Coyner; Joseph M. Davila

2011-01-01T23:59:59.000Z

168

DETERMINATION OF NON-THERMAL VELOCITY DISTRIBUTIONS FROM SERTS LINEWIDTH OBSERVATIONS

Non-thermal velocities obtained from the measurement of coronal Extreme Ultraviolet (EUV) linewidths have been consistently observed in solar EUV spectral observations and have been theorized to result from many plausible scenarios including wave motions, turbulence, or magnetic reconnection. Constraining these velocities can provide a physical limit for the available energy resulting from unresolved motions in the corona. We statistically determine a series of non-thermal velocity distributions from linewidth measurements of 390 emission lines from a wide array of elements and ionization states observed during the Solar Extreme Ultraviolet Research Telescope and Spectrograph 1991-1997 flights covering the spectral range 174-418 A and a temperature range from 80,000 K to 12.6 MK. This sample includes 248 lines from active regions, 101 lines from quiet-Sun regions, and 41 lines were observed from plasma off the solar limb. We find a strongly peaked distribution corresponding to a non-thermal velocity of 19-22 km s{sup -1} in all three of the quiet-Sun, active region, and off-limb distributions. For the possibility of Alfven wave resonance heating, we find that velocities in the core of these distributions do not provide sufficient energy, given typical densities and magnetic field strengths for the coronal plasma, to overcome the estimated coronal energy losses required to maintain the corona at the typical temperatures working as the sole mechanism. We find that at perfect efficiency 50%-60% of the needed energy flux can be produced from the non-thermal velocities measured.

Coyner, Aaron J. [Department of Physics, Catholic University of America, 620 Michigan Avenue, Washington, DC 20064 (United States); Davila, Joseph M., E-mail: aaron.j.coyner@nasa.gov [Code 671, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2011-12-01T23:59:59.000Z

169

SPECTRAL AND INTERMITTENCY PROPERTIES OF RELATIVISTIC TURBULENCE

High-resolution numerical simulations are utilized to examine isotropic turbulence in a compressible fluid when long-wavelength velocity fluctuations approach light speed. Spectral analysis reveals an inertial sub-range of relativistic motions with a broadly 5/3 index. The use of generalized Lorentz covariant structure functions based on the four-velocity is proposed. These structure functions extend the She-Leveque model for intermittency into the relativistic regime.

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

2013-01-20T23:59:59.000Z

170

Scaling, Intermittency and Decay of MHD Turbulence

We discuss a few recent developments that are important for understanding of MHD turbulence. First, MHD turbulence is not so messy as it is usually believed. In fact, the notion of strong non-linear coupling of compressible and incompressible motions along MHD cascade is not tenable. Alfven, slow and fast modes of MHD turbulence follow their own cascades and exhibit degrees of anisotropy consistent with theoretical expectations. Second, the fast decay of turbulence is not related to the compressibility of fluid. Rates of decay of compressible and incompressible motions are very similar. Third, viscosity by neutrals does not suppress MHD turbulence in a partially ionized gas. Instead, MHD turbulence develops magnetic cascade at scales below the scale at which neutrals damp ordinary hydrodynamic motions. Forth, density statistics does not exhibit the universality that the velocity and magnetic field do. For instance, at small Mach numbers the density is anisotropic, but it gets isotropic at high Mach numbers. Fifth, the intermittency of magnetic field and velocity are different. Both depend on whether the measurements are done in local system of reference oriented along the local magnetic field or in the global system of reference related to the mean magnetic field.

A. Lazarian; J. Cho

2004-08-10T23:59:59.000Z

171

Detonation Turbulence Interaction L. Massa, M. Chauhan and F. Lu

Detonation Turbulence Interaction L. Massa, M. Chauhan and F. Lu This paper reports a numerical study on the effect of turbulence on the detonation wave properties. The analysis is based-mechanics equations in three dimensions to determine the fine-scale evolution. I. Introduction The detonation

Texas at Arlington, University of

172

Tidally Generated Turbulence over the Knight Inlet Sill

Science Journals Connector (OSTI)

Very high turbulent dissipation rates (above ? = 10?4 W kg?1) were observed in the nonlinear internal lee waves that form each tide over a sill in Knight Inlet, British Columbia. This turbulence was due to both shear instabilities and the ...

Jody M. Klymak; Michael C. Gregg

2004-05-01T23:59:59.000Z

173

Inhomogeneous distribution of droplets in cloud turbulence

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

Itzhak Fouxon; Yongnam Park; Roei Harduf; Changhoon Lee

2014-10-30T23:59:59.000Z

174

Fractional and fractal derivatives modeling of turbulence

This study makes the first attempt to use the 2/3-order fractional Laplacian modeling of enhanced diffusing movements of random turbulent particle resulting from nonlinear inertial interactions. A combined effect of the inertial interactions and the molecule Brownian diffusivities is found to be the bi-fractal mechanism behind multifractal scaling in the inertial range of scales of moderate Reynolds number turbulence. Accordingly, a stochastic equation is proposed to describe turbulence intermittency. The 2/3-order fractional Laplacian representation is also used to construct a fractional Reynolds equation for nonlinear interactions of fluctuating velocity components, underlying turbulence spacetime fractal structures of Levy 2/3 stable distribution. The new perspective of this study is that the fractional calculus is an effective approach modeling of chaotic fractal phenomena induced by nonlinear interactions.

Wen Chen

2005-11-30T23:59:59.000Z

175

Petascale Simulations of Inhomogeneous Alfven Turbulence in the Solar Wind

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

176

Planar Richtmyer-Meshkov instabilities and transition to turbulence

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

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

2011-01-21T23:59:59.000Z

177

Detonation velocity deficit and curvature radius of flexible detonation fuses

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The detonation velocity deficit in bending flexible detonating fuses is studied, based on the detonation wave’s corner effects and delay time ... model and a theoretical mathematical equation of the detonation ve...

Y. -Q. Wen; Ya. -K. Ye; N. Yan

2012-03-01T23:59:59.000Z

178

Turbulent structures and budgets behind permeable ribs

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

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

2008-02-15T23:59:59.000Z

179

DIRECT NUMERICAL SIMULATION OF INTERACTION OF DETONATION WAVE WITH HOMOGENEOUS

DIRECT NUMERICAL SIMULATION OF INTERACTION OF DETONATION WAVE WITH HOMOGENEOUS ISOTROPIC TURBULENCE SIMULATION OF INTERACTION OF DETONATION WAVE WITH HOMOGENEOUS ISOTROPIC TURBULENCE HARI NARAYANAN NAGARAJAN The propagation of a shock or detonation wave through a reactive mixture has been the subject of research for over

Texas at Arlington, University of

180

Lattice Boltzmann simulations of decaying homogeneous isotropic turbulence

Science Journals Connector (OSTI)

Decaying homogeneous isotropic turbulence in inertial and rotating reference frames is investigated to evaluate the capability of the lattice Boltzmann method in turbulence. In the inertial frame case, the decay exponents of kinetic energy and dissipation and the low wave-number scaling of the spectrum are studied. The results are in agreement with classical ones. In the frame-rotation case, simulations show that the energy decay rate decreases with decreasing Rossby number as the energy cascade is inhibited by rotation, again in agreement with turbulence physics. These results clearly indicate that the lattice Boltzmann method captures important features of decaying turbulence.

Huidan Yu; Sharath S. Girimaji; Li-Shi Luo

2005-01-25T23:59:59.000Z

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181

NUMERICAL SIMULATIONS OF DRIVEN RELATIVISTIC MAGNETOHYDRODYNAMIC TURBULENCE

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

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

2012-01-01T23:59:59.000Z

182

Can Wind Lidars Measure Turbulence?

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Modeling of the systematic errors in the second-order moments of wind speeds measured by continuous-wave (ZephIR) and pulsed (WindCube) lidars is presented. These lidars use the conical scanning technique to measure the velocity field. The model ...

A. Sathe; J. Mann; J. Gottschall; M. S. Courtney

2011-07-01T23:59:59.000Z

183

Wave-wave interactions in solar type III radio bursts

The high time resolution observations from the STEREO/WAVES experiment show that in type III radio bursts, the Langmuir waves often occur as localized magnetic field aligned coherent wave packets with durations of a few ms and with peak intensities well exceeding the strong turbulence thresholds. Some of these wave packets show spectral signatures of beam-resonant Langmuir waves, down- and up-shifted sidebands, and ion sound waves, with frequencies, wave numbers, and tricoherences satisfying the resonance conditions of the oscillating two stream instability (four wave interaction). The spectra of a few of these wave packets also contain peaks at f{sub pe}, 2f{sub pe} and 3 f{sub pe} (f{sub pe} is the electron plasma frequency), with frequencies, wave numbers and bicoherences (computed using the wavelet based bispectral analysis techniques) satisfying the resonance conditions of three wave interactions: (1) excitation of second harmonic electromagnetic waves as a result of coalescence of two oppositely propagating Langmuir waves, and (2) excitation of third harmonic electromagnetic waves as a result of coalescence of Langmuir waves with second harmonic electromagnetic waves. The implication of these findings is that the strong turbulence processes play major roles in beam stabilization as well as conversion of Langmuir waves into escaping radiation in type III radio bursts.

Thejappa, G. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); MacDowall, R. J. [NASA/Goddard Space Flight Center, Greenbelt MD 20771 (United States)

2014-02-11T23:59:59.000Z

184

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

185

Phenomenology of Wall Bounded Newtonian Turbulence

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

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

2005-06-28T23:59:59.000Z

186

The Temperature of Interstellar Clouds from Turbulent Heating

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

Liubin Pan; Paolo Padoan

2008-06-30T23:59:59.000Z

187

Velocities of Wave-Transmission in Rocks

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...excep- tion the fundamental requirement that...interior- wall of boiler-room. This...the buildings safe for operation and providing...amperes for normal operation. A Laon tube...0.1, the fundamental REPORTS AND PAPERS...

L. H. Adams

188

Penetration and scattering of lower hybrid waves by density fluctuations

Lower Hybrid [LH] ray propagation in toroidal plasma is controlled by a combination of the azimuthal spectrum launched from the antenna, the poloidal variation of the magnetic field, and the scattering of the waves by the density fluctuations. The width of the poloidal and radial RF wave spectrum increases rapidly as the rays penetrate into higher density and scatter from the turbulence. The electron temperature gradient [ETG] spectrum is particularly effective in scattering the LH waves due to its comparable wavelengths and parallel phase velocities. ETG turbulence is also driven by the radial gradient of the electron current density giving rise to an anomalous viscosity spreading the LH-driven plasma currents. The scattered LH spectrum is derived from a Fokker-Planck equation for the distribution of the ray trajectories with a diffusivity proportional to the fluctuations. The LH ray diffusivity is large giving transport in the poloidal and radial wavenumber spectrum in one - or a few passes - of the rays through the core plasma.

Horton, W. [Institute for Fusion Studies, University of Texas at Austin (United States); Goniche, M.; Peysson, Y.; Decker, J.; Ekedahl, A.; Litaudon, X. [CEA, IRFM, F-13108 St-Paul-Lez-Durance (France)

2014-02-12T23:59:59.000Z

189

Feedback control of edge turbulence in a tokamak

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An experiment on feedback control of edge turbulence has been undertaken on the KT-5C tokamak. The results indicate that the edge turbulence could be suppressed or enhanced depending on the phase shift of the feedback network. In a typical case of 90° phase shift feedback, the turbulence amplitudes of both T-tildee and ńe were reduced by about 25% when the gain of the feedback network was 15. Correspondingly the radial particle flux decreased to about 75% level of the background. Through bispectral analysis it is found that there exists a substantial nonlinear coupling between various modes comprised in edge turbulence, especially in the frequency range from about 10 kHz to 100 kHz, which contains the large part of the edge turbulence energy in KT-5C tokamak. In particular, by actively controlling the turbulence amplitude using feedback, a direct experimental evidence of the link between the nonlinear wave-wave coupling over the whole spectrum in turbulence, the saturated turbulence amplitude, and the radial particle flux was provided.

Zhai Kan; Wen Yi-zhi; Yu Chang-xuan; Liu Wan-dong; Wang Chao; Zhuang Ge; Xu Zhi-zhan

1997-03-01T23:59:59.000Z

190

Effective traveling-wave excitation below the speed of light

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We demonstrate that effective traveling-wave excitation of high-gain amplifiers requires velocities that are remarkably slower than the velocity of light. Experiments with a...

Tommasini, Riccardo; Fill, Ernst E

2001-01-01T23:59:59.000Z

191

Mass dependency of turbulent parameters in stationary glow discharge plasmas

A direct current glow discharge tube is used to determine how mass changes the effects of certain turbulence characteristics in a weakly ionized gas. Helium, neon, argon, and krypton plasmas were created, and an axial magnetic field, varied from 0.0 to 550.0 Gauss, was used to enhance mass dependent properties of turbulence. From the power spectra of light emission variations associated with velocity fluctuations, determination of mass dependency on turbulent characteristic unstable modes, energy associated with turbulence, and the rate at which energy is transferred from scale to scale are measured. The magnetic field strength is found to be too weak to overcome particle diffusion to the walls to affect the turbulence in all four types of plasmas, though mass dependency is still detected. Though the total energy and the rate at which the energy moves between scales are mass invariant, the amplitude of the instability modes that characterize each plasma are dependent on mass.

Titus, J. B.; Alexander, A. B. [Florida A and M University, Tallahassee, Florida 32310 (United States)] [Florida A and M University, Tallahassee, Florida 32310 (United States); Wiggins, D. L. [Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53703 (United States)] [Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53703 (United States); Johnson, J. A. III [Pyramid Plasmas LLC, Lawrenceville, Georgia 30043 (United States)] [Pyramid Plasmas LLC, Lawrenceville, Georgia 30043 (United States)

2013-05-15T23:59:59.000Z

192

Turbulent drag reduction through oscillating discs

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

Wise, Daniel J

2014-01-01T23:59:59.000Z

193

NONIDEAL MAGNETOHYDRODYNAMIC TURBULENT DECAY IN MOLECULAR CLOUDS

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

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

2009-08-20T23:59:59.000Z

194

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

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

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

2012-03-15T23:59:59.000Z

195

The formation of the observed core-halo feature in the solar wind electron velocity distribution function is a long-time puzzle. In this letter based on the current knowledge of nanoflares we show that the nanoflare-accelerated electron beams are likely to trigger a strong electron two-stream instability that generates kinetic Alfv\\'en wave and whistler wave turbulence, as we demonstrated in a previous paper. We further show that the core-halo feature produced during the origin of kinetic turbulence is likely to originate in the inner corona and can be preserved as the solar wind escapes to space along open field lines. We formulate a set of equations to describe the heating processes observed in the simulation and show that the core-halo temperature ratio of the solar wind is insensitive to the initial conditions in the corona and is related to the core-halo density ratio of the solar wind and to the quasi-saturation property of the two-stream instability at the time when the exponential decay ends. This rel...

Che, H

2014-01-01T23:59:59.000Z

196

Coastal Microstructure: From Active Overturn to Fossil Turbulence

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

Leung, Pak Tao

2012-02-14T23:59:59.000Z

197

A study on the effect of inlet turbulence on gas mixing for single point aerosol sampling

not be effective for achieving a uniform velocity profile. Numerical computations are performed with commercially available computational fluid dynamics (CFD) software (FLUENT[], Version 5.4), and the performance of the turbulence and particle tracking models...

Mohan, Anand

2012-06-07T23:59:59.000Z

198

Large-eddy simulation of a wind turbine wake in turbulent

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

Firestone, Jeremy

199

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

,7Â10 . The Rhines definition involves, however, the undeter- mined energy content of the flow, which depends and dissipation. Clearly, turbulent flows stabilized by the friction have their energy content, hence rms velocity the jet number and the energy peak of the -plane turbulence for strong . The intermediate cases show

Gurarie, David

200

Basic Properties of Compressible MHD Turbulence: Implications for Molecular Clouds

Recent advances in understanding of the basic properties of compressible Magnetohydrodynamic (MHD) turbulence call for revisions of some of the generally accepted concepts. First, MHD turbulence is not so messy as it is usually believed. In fact, the notion of strong non-linear coupling of compressible and incompressible motions is not tenable. Alfven, slow and fast modes of MHD turbulence follow their own cascades and exhibit degrees of anisotropy consistent with theoretical expectations. Second, the fast decay of turbulence is not related to the compressibility of fluid. Rates of decay of compressible and incompressible motions are very similar. Third, viscosity by neutrals does not suppress MHD turbulence in a partially ionized gas. Instead, MHD turbulence develops magnetic cascade at scales below the scale at which neutrals damp ordinary hydrodynamic motions. The implications of those changes of MHD turbulence paradigm for molecular clouds require further studies. Those studies can benefit from testing of theoretical predictions using new statistical techniques that utilize spectroscopic data. We briefly discuss advances in development of tools using which the statistics of turbulent velocity can be recovered from observations.

A. Lazarian; J. Cho

2003-11-17T23:59:59.000Z

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

201

Observable consequences of Langmuir turbulence in active galactic nuclei

The authors discuss in detail the observable consequences of non-linear microscopic plasma processes in active galactic nuclei. The combination of several elementary momentum gain (shock acceleration and stochastic acceleration) and loss processes (synchroton radiation, inverse Compton scattering) produces an almost monoenergetic distribution function of relativistic electrons - the pile-up - which excites Langmuir waves. Turbulent wave-wave and wave-particle interactions lead to nonlinear stabilization of the pile-up. The temporal and spatial evolution of the Langmuir waves and the relativistic electrons determine the shape and time scale of the spectral variations. The model is applied to extragalactic nuclei and to the galactic center as well.

Lesch, H.

1989-04-01T23:59:59.000Z

202

Tidal Flow Turbulence Measurements

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

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

203

COLLISIONLESS DAMPING AT ELECTRON SCALES IN SOLAR WIND TURBULENCE

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

204

Studies of the velocity fields near a submerged rectangular object

of the time periodic waves past a submerged rectangular object. For sotne wave conditions, large energy dissipation occurred at the submerged object due to vortex generation. The amount of energy dissipation was examined by comparing incident wave energy... object. A two component laser-Doppler anemometer (LDA) was used to obtain detailed measurements of the instantaneous velocity field and flow visualization was conducted to study the vortex structure around the submerged object. The measured wave...

Kim, Young-Ki

2012-06-07T23:59:59.000Z

205

Localized velocity anomalies in the lower mantle

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......projection centred on the Argentina source region. The location...approximately 80" from the Argentina source region. S-waves...Bolivia are dominated by SV energy, and large Sp precursors...closer to the stations than Argentina. Lower mantle velocity anomalies......

Thorne Lay

1983-02-01T23:59:59.000Z

206

IWA : an analysis program for isentropic wave measurements.

IWA (Isentropic Wave Analysis) is a program for analyzing velocity profiles of isentropic compression experiments. IWA applies incremental impedance matching correction to measured velocity profiles to obtain in-situ particle velocity profiles for Lagrangian wave analysis. From the in-situ velocity profiles, material properties such as wave velocities, stress, strain, strain rate, and strength are calculated. The program can be run in any current version of MATLAB (2008a or later) or as a Windows XP executable.

Ao, Tommy

2009-02-01T23:59:59.000Z

207

IMPLODING IGNITION WAVES. I. ONE-DIMENSIONAL ANALYSIS

We show that converging spherical and cylindrical shock waves may ignite a detonation wave in a combustible medium, provided the radius at which the shocks become strong exceeds a critical radius, R{sub crit}. An approximate analytic expression for R{sub crit} is derived for an ideal gas equation of state and a simple (power-law-Arrhenius) reaction law, and shown to reproduce the results of numerical solutions. For typical acetylene-air experiments we find R{sub crit} {approx} 100 {mu}m (spherical) and R{sub crit} {approx} 1 mm (cylindrical). We suggest that the deflagration to detonation transition (DDT) observed in these systems may be due to converging shocks produced by the turbulent deflagration flow, which reaches sub- (but near) sonic velocities on scales >>R{sub crit}. Our suggested mechanism differs from that proposed by Zel'dovich et al., in which a fine-tuned spatial gradient in the chemical induction time is required to be maintained within the turbulent deflagration flow. Our analysis may be readily extended to more complicated equations of state and reaction laws. An order of magnitude estimate of R{sub crit} within a white dwarf at the pre-detonation conditions believed to lead to Type Ia supernova explosions is 0.1 km, suggesting that our proposed mechanism may be relevant for DDT initiation in these systems. The relevance of our proposed ignition mechanism to DDT initiation may be tested by both experiments and numerical simulations.

Kushnir, Doron; Waxman, Eli [Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100 (Israel); Livne, Eli [Racah Institute of Physics, Hebrew University, Jerusalem (Israel)

2012-06-20T23:59:59.000Z

208

Experimental investigation of burning velocities of ultra-wet methane-air-steam mixtures

Experimental investigation of burning velocities of ultra-wet methane-air-steam mixtures Eric Abstract Global burning velocities of methane-air-steam mixtures are measured on prismatic laminar Bunsen flames and lifted turbulent V-flames for various preheating temperatures, equivalence ratios and steam

Paris-Sud XI, UniversitĂ© de

209

Science Journals Connector (OSTI)

......is essential for mass estimates based on...motions in the gas velocity field within galaxy...et-al. 2012) maps, obtained with X-ray...on the turbulent velocities in a set of galaxy...the large atomic mass of the Fe-xxv ion...supernova (SN) driven winds (Springel Hernquist......

V. Biffi; K. Dolag; H. Böhringer

2013-01-01T23:59:59.000Z

210

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

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

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

1995-08-01T23:59:59.000Z

211

PROPAGATING WAVES ALONG SPICULES

Alfvenic waves are thought to play an important role in coronal heating and acceleration of solar wind. Here we investigate the statistical properties of Alfvenic waves along spicules (jets that protrude into the corona) in a polar coronal hole using high-cadence observations of the Solar Optical Telescope on board Hinode. We developed a technique for the automated detection of spicules and high-frequency waves. We detected 89 spicules and found (1) a mix of upward propagating, downward propagating, as well as standing waves (occurrence rates of 59%, 21%, and 20%, respectively); (2) the phase speed gradually increases with height; (3) upward waves dominant at lower altitudes, standing waves at higher altitudes; (4) standing waves dominant in the early and late phases of each spicule, while upward waves were dominant in the middle phase; (5) in some spicules, we find waves propagating upward (from the bottom) and downward (from the top) to form a standing wave in the middle of the spicule; and (6) the medians of the amplitude, period, and velocity amplitude were 55 km, 45 s, and 7.4 km s{sup -1}, respectively. We speculate that upward propagating waves are produced near the solar surface (below the spicule) and downward propagating waves are caused by reflection of (initially) upward propagating waves off the transition region at the spicule top. The mix of upward and downward propagating waves implies that exploiting these waves to perform seismology of the spicular environment requires careful analysis and may be problematic.

Okamoto, Takenori J. [National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); De Pontieu, Bart, E-mail: joten.okamoto@nao.ac.jp [Lockheed Martin Solar and Astrophysics Laboratory, B/252, 3251 Hanover Street, Palo Alto, CA 94304 (United States)

2011-08-01T23:59:59.000Z

212

Mean- Field Approximation and a Small Parameter in Turbulence Theory

Numerical and physical experiments on two-dimensional (2d) turbulence show that the differences of transverse components of velocity field are well described by a gaussian statistics and Kolmogorov scaling exponents. In this case the dissipation fluctuations are irrelevant in the limit of small viscosity. In general, one can assume existence of critical space-dimensionality $d=d_{c}$, at which the energy flux and all odd-order moments of velocity difference change sign and the dissipation fluctuations become dynamically unimportant. At $d', leading to the observed gaussian statistics and Kolmogorov scaling of transverse velocity differences. It is shown that in the vicinity of $d=d_{c}$ the ratio of the relaxation and translation characteristic times decreases to zero, thus giving rise to a small parameter of the theory. The expressions for pressure and dissipation contributions to the exact equation for the generating function of transverse velocity differences are derived in the vicinity of $d=d_{c}$. The resulting equation describes experimental data on two-dimensional turbulence and demonstrate onset of intermittency as $d-d_{c}>0$ and $r/L\\to 0$ in three-dimensional flows in close agreement with experimental data. In addition, some new exact relations between correlation functions of velocity differences are derived. It is also predicted that the single-point pdf of transverse velocity difference in developing as well as in the large-scale stabilized two-dimensional turbulence is a gaussian.

Victor Yakhot

2000-01-13T23:59:59.000Z

213

Elastic constants and velocity surfaces of indurated anisotropic shales

Science Journals Connector (OSTI)

The velocities of two Devonian-Mississippian shales have been measured to confining pressures of 200 MPa in a laboratory study of anisotropy and wave propagation. Both samples were found to be transversely iso...

Joel E. Johnston; Nikolas I. Christensen

1994-09-01T23:59:59.000Z

214

Nonextensive statistical dynamics applied to wall turbulence

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

Simen Ĺ Ellingsen; Per-Ĺge Krogstad

2014-02-10T23:59:59.000Z

215

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

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

Abdou, Mohamed

216

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

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

California at Los Angeles, University of

217

Extreme wave impinging and overtopping

This investigates the velocity fields of a plunging breaking wave impinging on a structure through measurements in a two-dimensional wave tank. As the wave breaks and overtops the structure, so-called green water is generated. The flow becomes multi...

Ryu, Yong Uk

2009-06-02T23:59:59.000Z

218

Global invariants in ideal magnetohydrodynamic turbulence

Magnetohydrodynamic (MHD) turbulence is an important though incompletely understood factor affecting the dynamics of many astrophysical, geophysical, and technological plasmas. As an approximation, viscosity and resistivity may be ignored, and ideal MHD turbulence may be investigated by statistical methods. Incompressibility is also assumed and finite Fourier series are used to represent the turbulent velocity and magnetic field. The resulting model dynamical system consists of a set of independent Fourier coefficients that form a canonical ensemble described by a Gaussian probability density function (PDF). This PDF is similar in form to that of Boltzmann, except that its argument may contain not just the energy multiplied by an inverse temperature, but also two other invariant integrals, the cross helicity and magnetic helicity, each multiplied by its own inverse temperature. However, the cross and magnetic helicities, as usually defined, are not invariant in the presence of overall rotation or a mean magnetic field, respectively. Although the generalized form of the magnetic helicity is known, a generalized cross helicity may also be found, by adding terms that are linear in the mean magnetic field and angular rotation vectors, respectively. These general forms are invariant even in the presence of overall rotation and a mean magnetic field. We derive these general forms, explore their properties, examine how they extend the statistical theory of ideal MHD turbulence, and discuss how our results may be affected by dissipation and forcing.

Shebalin, John V. [Astromaterials Research Office, NASA Johnson Space Center, Houston, Texas 77058-3696 (United States)] [Astromaterials Research Office, NASA Johnson Space Center, Houston, Texas 77058-3696 (United States)

2013-10-15T23:59:59.000Z

219

(6) The above calculations ignore the effect of air resistance on the object. We assume that resistance is proportional to velocity and decreases with increasing

2007-02-02T23:59:59.000Z

220

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

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

Jackson, Aaron P; Calder, Alan C

2014-01-01T23:59:59.000Z

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

221

Petascale Simulations of Inhomogeneous AlfvĂ©n Turbulence in the Solar Wind

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

222

Large-Eddy Simulation of Langmuir Turbulence in Pure Wind Seas

Science Journals Connector (OSTI)

The scaling of turbulent kinetic energy (TKE) and its vertical component (VKE) in the upper ocean boundary layer, forced by realistic wind stress and surface waves including the effects of Langmuir circulations, is investigated using large-eddy ...

Ramsey R. Harcourt; Eric A. D’Asaro

2008-07-01T23:59:59.000Z

223

The Influence of Turbulence and Vertical Wind Profile in Wind Turbine Power Curve

Science Journals Connector (OSTI)

To identify the influence of turbulence and vertical wind profile in wind turbine performance, wind speed measurements at different heights have been ... equipment, specifically a pulsed wave one. The wind profil...

A. Honrubia; A. Vigueras-Rodríguez…

2012-01-01T23:59:59.000Z

224

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

Science Journals Connector (OSTI)

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

Chia-Ren Chu; Pei-Hung Chiang

2014-01-01T23:59:59.000Z

225

This paper presents a theoretical framework for understanding plasma turbulence in astrophysical plasmas. It is motivated by observations of electromagnetic and density fluctuations in the solar wind, interstellar medium and galaxy clusters, as well as by models of particle heating in accretion disks. All of these plasmas and many others have turbulentmotions at weakly collisional and collisionless scales. The paper focuses on turbulence in a strong mean magnetic field. The key assumptions are that the turbulent fluctuations are small compared to the mean field, spatially anisotropic with respect to it and that their frequency is low compared to the ion cyclotron frequency. The turbulence is assumed to be forced at some system-specific outer scale. The energy injected at this scale has to be dissipated into heat, which ultimately cannot be accomplished without collisions. A kinetic cascade develops that brings the energy to collisional scales both in space and velocity. The nature of the kinetic cascade in various scale ranges depends on the physics of plasma fluctuations that exist there. There are four special scales that separate physically distinct regimes: the electron and ion gyroscales, the mean free path and the electron diffusion scale. In each of the scale ranges separated by these scales, the fully kinetic problem is systematically reduced to a more physically transparent and computationally tractable system of equations, which are derived in a rigorous way. In the "inertial range" above the ion gyroscale, the kinetic cascade separates into two parts: a cascade of Alfvenic fluctuations and a passive cascade of density and magnetic-fieldstrength fluctuations. The former are governed by the Reduced Magnetohydrodynamic (RMHD) equations at both the collisional and collisionless scales; the latter obey a linear kinetic equation along the (moving) field lines associated with the Alfvenic component (in the collisional limit, these compressive fluctuations become the slow and entropy modes of the conventional MHD). In the "dissipation range" below ion gyroscale, there are again two cascades: the kinetic-Alfven-wave (KAW) cascade governed by two fluid-like Electron Reduced Magnetohydrodynamic (ERMHD) equations and a passive cascade of ion entropy fluctuations both in space and velocity. The latter cascade brings the energy of the inertial-range fluctuations that was Landau-damped at the ion gyroscale to collisional scales in the phase space and leads to ion heating. The KAWenergy is similarly damped at the electron gyroscale and converted into electron heat. Kolmogorov-style scaling relations are derived for all of these cascades. The relationship between the theoretical models proposed in this paper and astrophysical applications and observations is discussed in detail.

A.A. Schekochihin, S.C. Cowley, W. Dorland, G.W. Hammett, G.G. Howes, E. Quataert, and T. Tatsuno

2009-04-23T23:59:59.000Z

226

A KINETIC MODEL OF SOLAR WIND GENERATION BY OBLIQUE ION-CYCLOTRON WAVES

The fast solar wind is generated by extended perpendicular ion heating in coronal holes, but the kinetic mechanism responsible for this heating has not been determined. One long-standing possibility is the resonant-cyclotron dissipation of ion-cyclotron waves, replenished from a turbulent cascade of interacting counter-propagating Alfven waves. We present results of a kinetic model for proton heating by the quasilinear resonant-cyclotron wave-particle interaction in a coronal hole. The resonant wave spectrum is taken as a power law in wavenumber, uniformly distributed in propagation direction between 0 deg. and 60 deg. with respect to the large-scale radial magnetic field. We obtain the steady-state solution of the kinetic guiding-center equation for the proton distribution in an expanding coronal hole, including the effects of large-scale forces of gravity, charge-separation electric field, Alfven wave ponderomotive force, and mirror force, along with the small-scale scattering from the wave dissipation. We find that plausible wave intensities can yield reasonable flow speeds and temperatures in the heliocentric radial range between 2 and 6 solar radii. We address the claim in earlier work that dissipation of parallel-propagating ion-cyclotron waves cannot provide enough acceleration and show that claim to be incorrect. We find that the combined action of the large-scale forces and the resonant-cyclotron scattering produces proton distribution functions with a characteristic structure: compressed in the sunward half of velocity space with a high-density shell separate from the origin, and relatively expanded in the anti-sunward half of velocity space. We suggest that qualitatively similar proton distributions would result from the kinetic evolution of any sufficiently effective perpendicular heating mechanism operating in an expanding coronal hole.

Isenberg, Philip A.; Vasquez, Bernard J. [Institute for the Study of Earth, Oceans and Space and Department of Physics, University of New Hampshire, Durham, NH 03824 (United States)

2011-04-20T23:59:59.000Z

227

Simulation Strategies for Shock-Turbulence Interactions

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

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

2008-02-20T23:59:59.000Z

228

Electron distributions observed with Langmuir waves in the plasma sheet boundary layer

The present paper investigates the Langmuir turbulence driven by counter-streaming electron beams and its plausible association with observed features in the Earth's plasma sheet boundary layer region. A one-dimensional electrostatic particle-in-cell simulation code is employed in order to simulate broadband electrostatic waves with characteristic frequency in the vicinity of the electron plasma frequency ?/?{sub pe}?1.0. The present simulation confirms that the broadband electrostatic waves may indeed be generated by the counter-streaming electron beams. It is also found that the observed feature associated with low energy electrons, namely quasi-symmetric velocity space plateaus, are replicated according to the present simulation. However, the present investigation only partially succeeds in generating the suprathermal tails such that the origin of observed quasi power-law energetic population formation remains outstanding.

Hwang, Junga [Solar and Space Weather Research Group, Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of); Department of Astronomy and Space Science, University of Science and Technology, Daejeon (Korea, Republic of); Rha, Kicheol [Department of Physics, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Seough, Jungjoon [Solar and Space Weather Research Group, Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of); Yoon, Peter H. [School of Space Research, Kyung Hee University, Yongin-Si, Gyeonggi-Do 446-701 (Korea, Republic of); Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742 (United States)

2014-09-15T23:59:59.000Z

229

Observations of Edge Turbulence

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

230

Properties of vortices in the self-similar turbulent jet A. Agrawal, A.K. Prasad

to the fundamental importance of their flow physics. Consequently, their time-averaged velocity profiles, spread rate turbulent axisymmetric jet. The velocity fields were high-pass filtered to expose the vortical structures, the strongest eddies in the high-pass fil- tered field occur near the jet axis. The average circulation

Prasad, Ajay K.

231

The dynamics of interacting nonlinearities governing long wavelength driftwave turbulence

Because of the ubiquitous nature of turbulence and the vast array of different systems which have turbulent solutions, the study of turbulence is an area of active research. Much present day understanding of turbulence is rooted in the well established properties of homogeneous Navier-Stokes turbulence, which, due to its relative simplicity, allows for approximate analytic solutions. This work examines a group of turbulent systems with marked differences from Navier-Stokes turbulence, and attempts to quantify some of their properties. This group of systems represents a variety of drift wave fluctuations believed to be of fundamental importance in laboratory fusion devices. From extensive simulation of simple local fluid models of long wavelength drift wave turbulence in tokamaks, a reasonably complete picture of the basic properties of spectral transfer and saturation has emerged. These studies indicate that many conventional notions concerning directions of cascades, locality and isotropy of transfer, frequencies of fluctuations, and stationarity of saturation are not valid for moderate to long wavelengths. In particular, spectral energy transfer at long wavelengths is dominated by the E {times} B nonlinearity, which carries energy to short scale in a manner that is highly nonlocal and anisotropic. In marked contrast to the canonical self-similar cascade dynamics of Kolmogorov, energy is efficiently passed between modes separated by the entire spectrum range in a correlation time. At short wavelengths, transfer is dominated by the polarization drift nonlinearity. While the standard dual cascade applies in this subrange, it is found that finite spectrum size can produce cascades that are reverse directed and are nonconservative in enstrophy and energy similarity ranges. In regions where both nonlinearities are important, cross-coupling between the nolinearities gives rise to large no frequency shifts as well as changes in the spectral dynamics.

Newman, D.E.

1993-09-01T23:59:59.000Z

232

Nathan Holmberg Modeling of Turbulent Water over Natural Terrain

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

Goodman, James R.

233

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

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

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

2015-01-01T23:59:59.000Z

234

Science Journals Connector (OSTI)

A novel drifter platform was used to measure floc properties, turbulence, suspended sediment concentration (SSC), velocity and salinity in both Lagrangian and Eulerian frames of reference. In Lagrangian mode the system performed well in a heavily ...

Iain T. MacDonald; Julia C. Mullarney

235

We present a theoretical framework for plasma turbulence in astrophysical plasmas (solar wind, interstellar medium, galaxy clusters, accretion disks). The key assumptions are that the turbulence is anisotropic with respect to the mean magnetic field and frequencies are low compared to the ion cyclotron frequency. The energy injected at the outer scale scale has to be converted into heat, which ultimately cannot be done without collisions. A KINETIC CASCADE develops that brings the energy to collisional scales both in space and velocity. Its nature depends on the physics of plasma fluctuations. In each of the physically distinct scale ranges, the kinetic problem is systematically reduced to a more tractable set of equations. In the "inertial range" above the ion gyroscale, the kinetic cascade splits into a cascade of Alfvenic fluctuations, which are governed by the RMHD equations at both the collisional and collisionless scales, and a passive cascade of compressive fluctuations, which obey a linear kinetic equation along the moving field lines associated with the Alfvenic component. In the "dissipation range" between the ion and electron gyroscales, there are again two cascades: the kinetic-Alfven-wave (KAW) cascade governed by two fluid-like Electron RMHD equations and a passive phase-space cascade of ion entropy fluctuations. The latter cascade brings the energy of the inertial-range fluctuations that was damped by collisionless wave-particle interaction at the ion gyroscale to collisional scales in the phase space and leads to ion heating. The KAW energy is similarly damped at the electron gyroscale and converted into electron heat. Kolmogorov-style scaling relations are derived for these cascades. Astrophysical and space-physical applications are discussed in detail.

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

2007-03-31T23:59:59.000Z

236

ARM - Measurement - Vertical velocity

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

govMeasurementsVertical velocity govMeasurementsVertical velocity 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 : Vertical velocity The component of the velocity vector, along the local vertical. Categories Atmospheric State 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 KAZR : Ka ARM Zenith Radar MMCR : Millimeter Wavelength Cloud Radar SODAR : Mini Sound Detection and Ranging

237

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

Velocity Focus Group Velocity Focus Group ARM 2008 Science Team Meeting Norfolk, VA March 10-14 Background Vertical velocity measurements have been at the top of the priority list of the cloud modeling community for some time. Doppler measurements from ARM profiling radars operating at 915-MHz, 35-GHz and 94-GHz have been largely unexploited. The purpose of this new focus group is to develop vertical velocity ARM products suitable for modelers. ARM response to their request has been slow. Most ARM instruments are suitable for cloud observations and have limited capabilities in precipitation Using ARM datasets for evaluating and improving cloud parameterization in global climate models (GCMs) is not straightforward, due to gigantic scale mismatches. Consider this... Looking only vertically drastically limits opportunities

238

Turbulent Vertical Kinetic Energy in the Ocean Mixed Layer

Science Journals Connector (OSTI)

Vertical velocities in the ocean boundary layer were measured for two weeks at an open ocean, wintertime site using neutrally buoyant floats. Simultaneous measurements of the surface meteorology and surface waves showed a large variability in ...

Eric A. D'Asaro

2001-12-01T23:59:59.000Z

239

We present our progress toward setting initial conditions in variable density turbulence models. In particular, we concentrate our efforts on the BHR turbulence model for turbulent Rayleigh-Taylor instability. Our approach is to predict profiles of relevant parameters before the fully turbulent regime and use them as initial conditions for the turbulence model. We use an idealized model of the mixing between two interpenetrating fluids to define the initial profiles for the turbulence model parameters. Velocities and volume fractions used in the idealized mixing model are obtained respectively from a set of ordinary differential equations modeling the growth of the Rayleigh-Taylor instability and from an idealization of the density profile in the mixing layer. A comparison between predicted initial profiles for the turbulence model parameters and initial profiles of the parameters obtained from low Atwood number three dimensional simulations show reasonable agreement.

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

2010-01-01T23:59:59.000Z

240

Sheets Wave Basin | Open Energy Information

Sheets Wave Basin Sheets Wave Basin Jump to: navigation, search Basic Specifications Facility Name Sheets Wave Basin Overseeing Organization University of Rhode Island Hydrodynamic Testing Facility Type Wave Basin Length(m) 30.0 Beam(m) 3.6 Depth(m) 1.8 Cost(per day) $750(+ Labor/Materials) Towing Capabilities Towing Capabilities Yes Maximum Velocity(m/s) 2.0 Length of Effective Tow(m) 25.0 Wavemaking Capabilities Wavemaking Capabilities Yes Maximum Wave Height(m) 0.3 Maximum Wave Height(m) at Wave Period(s) 3.0 Maximum Wave Length(m) 10 Wave Period Range(s) 3.0 Current Velocity Range(m/s) 0.0 Programmable Wavemaking Yes Wavemaking Description Pre-programmed for regular and irregular waves, but wavemaker is capable of any input motion. Wave Direction Uni-Directional

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

241

Turbulence Structure and Wall Signature in Hypersonic Turbulent Boundary Layer

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

MartĂn, Pino

242

We present direct numerical simulations of inhomogeneous reduced magnetohydrodynamic (RMHD) turbulence between the Sun and the Alfvén critical point. These are the first such simulations that take into account the solar-wind outflow velocity and the radial inhomogeneity of the background solar wind without approximating the nonlinear terms in the governing equations. RMHD turbulence is driven by outward-propagating Alfvén waves (z {sup +} fluctuations) launched from the Sun, which undergo partial non-WKB reflection to produce sunward-propagating Alfvén waves (z {sup –} fluctuations). We present 10 simulations with different values of the correlation time ?{sub c{sub sun}{sup +}} and perpendicular correlation length L{sub ?} of outward-propagating Alfvén waves at the coronal base. We find that between 15% and 33% of the z {sup +} energy launched into the corona dissipates between the coronal base and Alfvén critical point. Between 33% and 40% of this input energy goes into work on the solar-wind outflow, and between 22% and 36% escapes as z {sup +} fluctuations through the simulation boundary at r = r{sub A}. The z {sup ±} power spectra scale like k{sub perpendicular}{sup -?{sup ±}}, where k is the wavenumber in the plane perpendicular to B{sub 0}. In our simulation with the smallest value of ?{sub c{sub sun}{sup +}} (?2 minutes) and largest value of L{sub ?} (2 × 10{sup 4} km), we find that ?{sup +} decreases approximately linearly with increasing ln (r), reaching a value of 1.3 at r = 11.1 R{sub ?}. Our simulations with larger values of ?{sub c{sub sun}{sup +}} exhibit alignment between the contours of constant ?{sup +}, ?{sup –}, ?{sub 0}{sup +}, and ?{sub 0}{sup -}, where ?{sup ±} are the Elsässer potentials and ?{sub 0}{sup ±} are the outer-scale parallel Elsässer vorticities.

Perez, Jean Carlos; Chandran, Benjamin D. G. [Space Science Center, University of New Hampshire, Durham, NH 03824 (United States)

2013-10-20T23:59:59.000Z

243

A One-Dimensional Propagation of Shock Wave Supported by Atmospheric Millimeter-Wave Plasma

Science Journals Connector (OSTI)

A shock wave supported by an atmospheric breakdown plasma caused by a high-power millimeter-wave ... was detached from the ionization front of the plasma whenever the propagation velocity of the ionization ... . ...

Yasuhisa Oda; Toshikazu Yamaguchi…

2011-06-01T23:59:59.000Z

244

The traveling-wave photodetector of the present invention combines an absorptive optical waveguide and an electrical transmission line, in which optical absorption in the waveguide results in a photocurrent at the electrodes of the electrical transmission line. The optical waveguide and electrical transmission line of the electrically distributed traveling-wave photodetector are designed to achieve matched velocities between the light in the optical waveguide and electrical signal generated on the transmission line. This velocity synchronization provides the traveling-wave photodetector with a large electrical bandwidth and a high quantum efficiency, because of the effective extended volume for optical absorption. The traveling-wave photodetector also provides large power dissipation, because of its large physical size.

Hietala, V.M.; Vawter, G.A.

1992-12-31T23:59:59.000Z

245

Acceleration of low energy charged particles by gravitational waves

The acceleration of charged particles in the presence of a magnetic field and gravitational waves is under consideration. It is shown that the weak gravitational waves can cause the acceleration of low energy particles under appropriate conditions. Such conditions may be satisfied close to the source of the gravitational waves if the magnetized plasma is in a turbulent state.

G. Voyatzis; L. Vlahos; S. Ichtiaroglou; D. Papadopoulos

2005-12-07T23:59:59.000Z

246

Condensation of classical nonlinear waves Colm Connaughton1

Condensation of classical nonlinear waves Colm Connaughton1 , Christophe Josserand2 , Antonio of a large-scale coherent structure (a condensate) in classical wave equa- tions by considering description of the condensation process by using a wave turbulence the- ory with ultraviolet cut-off. In 3

247

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

248

Coherent structures in ion temperature gradient turbulence-zonal flow

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

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

2014-10-15T23:59:59.000Z

249

Neutrino oscillations in a turbulent plasma

A new model for the joint neutrino flavor and plasma oscillations is introduced, in terms of the dynamics of the neutrino flavor polarization vector in a plasma background. Fundamental solutions are found for both time-invariant and time-dependent media, considering slow and fast variations of the electron plasma density. The model is shown to be described by a generalized Hamiltonian formalism. In the case of a broad spectrum of electron plasma waves, a statistical approach indicates the shift of both equilibrium value and frequency oscillation of flavor coherence, due to the existence of a turbulent plasma background.

Mendonça, J. T. [Instituto de Física, Universidade de Săo Paulo, Săo Paulo, SP, CEP 05508-090 Brazil and IPFN, Instituto Superior Técnico, 1049-001 Lisboa (Portugal)] [Instituto de Física, Universidade de Săo Paulo, Săo Paulo, SP, CEP 05508-090 Brazil and IPFN, Instituto Superior Técnico, 1049-001 Lisboa (Portugal); Haas, F. [Departamento de Física, Universidade Federal do Paraná, Curitiba PR, CEP 81531-990 (Brazil)] [Departamento de Física, Universidade Federal do Paraná, Curitiba PR, CEP 81531-990 (Brazil)

2013-07-15T23:59:59.000Z

250

Single particle resuspension experiments in turbulent channel flows

Science Journals Connector (OSTI)

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

T. Barth; J. Preuß; G. Müller; U. Hampel

2014-01-01T23:59:59.000Z

251

Perspectives on Deposition Velocity

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

Deposition Deposition Velocity ... Going down the rabbit hole to explain that sinking feeling Brian DiNunno, Ph.D. Project Enhancement Corporation June 6 th , 2012 Discussion Framework ď‚— Development of the HSS Deposition Velocity Safety Bulletin ď‚— Broader discussion of appropriate conservatism within dispersion modeling and DOE-STD-3009 DOE-STD-3009 Dose Comparison "General discussion is provided for source term calculation and dose estimation, as well as prescriptive guidance for the latter. The intent is that calculations be based on reasonably conservative estimates of the various input parameters." - DOE-STD-3009, Appendix A.3 DOE-STD-3009 Dispersion

252

Velocity pump reaction turbine

An expanding hydraulic/two-phase velocity pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This velocity pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.

House, Palmer A. (Walnut Creek, CA)

1982-01-01T23:59:59.000Z

253

Velocity pump reaction turbine

An expanding hydraulic/two-phase velocity pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This velocity pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.

House, Palmer A. (Walnut Creek, CA)

1984-01-01T23:59:59.000Z

254

Particle Heating by Alfvenic Turbulence in Hot Accretion Flows

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

Eliot Quataert

1997-10-13T23:59:59.000Z

255

Computational analysis of incompressible turbulent flow in an idealised swirl combustor

Science Journals Connector (OSTI)

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

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

2011-01-01T23:59:59.000Z

256

-surface materials. For both trends, the resistivity (r) and p-wave velocity (Vp) are related in the form Log10 r = m resistivity and seismic velocity in heterogeneous near-surface materials, Geophys. Res. Lett., 30(7), 1373Evidence for correlation of electrical resistivity and seismic velocity in heterogeneous near

Meju, Max

257

An explosive plane-wave air lens which enables a spherical wave form to be converted to a planar wave without the need to specially machine or shape explosive materials is described. A disc-shaped impactor having a greater thickness at its center than around its periphery is used to convert the spherical wave into a plane wave. When the wave reaches the impactor, the center of the impactor moves first because the spherical wave reaches the center of the impactor first. The wave strikes the impactor later in time as one moves radially along the impactor. Because the impactor is thinner as one moves radially outward, the velocity of the impactor is greater at the periphery than at the center. An acceptor explosive is positioned so that the impactor strikes the acceptor simultaneously. Consequently, a plane detonation wave is propagated through the acceptor explosive. 4 figs.

Marsh, S.P.

1988-03-08T23:59:59.000Z

258

An explosive plane-wave air lens which enables a spherical wave form to be converted to a planar wave without the need to specially machine or shape explosive materials is described. A disc-shaped impactor having a greater thickness at its center than around its periphery is used to convert the spherical wave into a plane wave. When the wave reaches the impactor, the center of the impactor moves first because the spherical wave reaches the center of the impactor first. The wave strikes the impactor later in time as one moves radially along the impactor. Because the impactor is thinner as one moves radially outward, the velocity of the impactor is greater at the periphery than at the center. An acceptor explosive is positioned so that the impactor strikes the acceptor simultaneously. Consequently, a plane detonation wave is propagated through the acceptor explosive. 3 figs., 3 tabs.

Marsh, S.P.

1987-03-12T23:59:59.000Z

259

An explosive plane-wave air lens which enables a spherical wave form to be converted to a planar wave without the need to specially machine or shape explosive materials is described. A disc-shaped impactor having a greater thickness at its center than around its periphery is used to convert the spherical wave into a plane wave. When the wave reaches the impactor, the center of the impactor moves first because the spherical wave reaches the center of the impactor first. The wave strikes the impactor later in time as one moves radially along the impactor. Because the impactor is thinner as one moves radially outward, the velocity of the impactor is greater at the periphery than at the center. An acceptor explosive is positioned so that the impactor strikes the acceptor simultaneously. Consequently, a plane detonation wave is propagated through the acceptor explosive.

Marsh, Stanley P. (Los Alamos, NM)

1988-01-01T23:59:59.000Z

260

Characterization of Relativistic MHD Turbulence

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

Garrison, David

2015-01-01T23:59:59.000Z

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

261

Generalized Flows, Intrinsic Stochasticity, and Turbulent Transport

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

Weinan E; Eric Vanden Eijnden

2000-03-10T23:59:59.000Z

262

Boussinesq-equation and rans hybrid wave model.

??This dissertation presents the development of a novel hybrid wave model, comprised of the irrotational, 1-D horizontal Boussinesq and 2-D vertical turbulence-closed Reynolds Averaged Navier-Stokes… (more)

Sitanggang, Khairil Irfan

2009-01-01T23:59:59.000Z

263

Cap Bubble Drift Velocity in a Confined Test Section

In the two-group interfacial area transport equation, bubbles are categorized into two groups, i.e., spherical/distorted bubbles as group 1 and cap/slug/churn-turbulent bubbles as group 2. The bubble rise velocities for both groups of bubbles may be estimated by the drift flux model by applying different distribution parameters and drift velocities for both groups. However, the drift velocity for group 2 bubbles is not always applicable (when the wall effect becomes important) as in the current test loop of interest where the flow channel is confined by two parallel flat walls, with a dimension of 200-mm in width and 10-mm in gap. The previous experiments indicated that no stable slug flow existed in this test section, which was designed to permit visualization of the flow patterns and bubble characteristics without the distortion associated with curved surfaces. In fact, distorted cap bubbly and churn-turbulent flow was observed. Therefore, it is essential to developed a correlation for cap bubble drift velocity in this confined flow channel. Since the rise velocity of a cap bubble depends on its size, a high-speed movie camera is used to capture images of cap bubbles to obtain the bubble size information. Meanwhile, the rise velocity of cap and elongated bubbles (called cap bubbles hereafter) is investigated by examining the captured images frame by frame. As a result, the conventional correlation of drift velocity for slug bubbles is modified and acceptable agreements between the measurements and correlation estimation are achieved.

Xiaodong Sun; Seungjin Kim; Mamoru Ishii; Frank W. Lincoln; Stephen G. Beus

2002-10-09T23:59:59.000Z

264

EVOLUTION OF SHOCKS AND TURBULENCE IN MAJOR CLUSTER MERGERS

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

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

2011-01-01T23:59:59.000Z

265

Science Journals Connector (OSTI)

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

Benjamin A. Carreras

1997-01-23T23:59:59.000Z

266

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

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

1990-01-01T23:59:59.000Z

267

Multiphase turbulent interstellar medium: some recent results from radio astronomy

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

Roy, Nirupam

2015-01-01T23:59:59.000Z

268

Turbulent flame speed for syngas at gas turbine relevant conditions

Science Journals Connector (OSTI)

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

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

2011-01-01T23:59:59.000Z

269

Seismic velocity estimation from time migration

Seismic images . . . . . . . . . . . . . . . . .Algorithms producing the seismic velocities from thethe Dix velocities and the true seismic velocities in 2D . .

Cameron, Maria Kourkina

2007-01-01T23:59:59.000Z

270

Are "EIT Waves" Fast-Mode MHD Waves?

We examine the nature of large-scale, coronal, propagating wave fronts (``EIT waves'') and find they are incongruous with solutions using fast-mode MHD plane-wave theory. Specifically, we consider the following properties: non-dispersive single pulse manifestions, observed velocities below the local Alfven speed, and different pulses which travel at any number of constant velocities, rather than at the ``predicted'' fast-mode speed. We discuss the possibility of a soliton-like explanation for these phenomena, and show how it is consistent with the above-mentioned aspects.

M. J. Wills-Davey; C. E. DeForest; J. O. Stenflo

2007-04-23T23:59:59.000Z

271

Advances in three-dimensional turbulence measurement capability

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

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

1988-11-01T23:59:59.000Z

272

In this thesis, we investigate the potential role played by large-scale anomalous heat sources (e.g. prolonged heat wave events) in generating acoustic-gravity waves (AGWs) that might trigger widespread plasma turbulence ...

Pradipta, Rezy

2012-01-01T23:59:59.000Z

273

versus the deep water wave height for the two wave lengths and for the 15' and 90' walls. For a particular wave length scour increased with increase in wave height, because of the greater energies and velocities associated with higher waves... were identical, Because the wave lengths differed, the deep water wave heights differed. For longer waves the scour increased at all points where the wall was installed. The greater weve length resulted in greater energy and particle velocities and...

Chesnutt, Charles Burgess

2012-06-07T23:59:59.000Z

274

Density scaling and anisotropy in supersonic MHD turbulence

We study the statistics of density for supersonic turbulence in a medium with magnetic pressure larger than the gaseous pressure. This study is motivated by molecular cloud research. Our simulations exhibit clumpy density structures, which contrast increases with the Mach number. At 10 Machs densities of some clumps are three orders of magnitude higher than the mean density. These clumps give rise to flat and approximately isotropic density spectrum corresponding to the random distribution of clumps in space. We claim that the clumps originate from our random, isotropic turbulence driving. When the contribution from those clumps is suppressed by studying logarithm of density, the density statistics exhibit scale-dependent anisotropy consistent with the models where density structures arise from shearing by Alfv\\'en waves. It is noteworthy that originally such models were advocated for the case of low-Mach, nearly incompressible turbulence.

A. Beresnyak; A. Lazarian; J. Cho

2005-02-25T23:59:59.000Z

275

Hinsdale Wave Basin 1 | Open Energy Information

Hinsdale Wave Basin 1 Hinsdale Wave Basin 1 Jump to: navigation, search Basic Specifications Facility Name Hinsdale Wave Basin 1 Overseeing Organization Oregon State University Hydrodynamics Hydrodynamic Testing Facility Type Wave Basin Length(m) 104.0 Beam(m) 3.7 Depth(m) 4.6 Cost(per day) $3500 Towing Capabilities Towing Capabilities None Wavemaking Capabilities Wavemaking Capabilities Yes Maximum Wave Height(m) 1.8 Maximum Wave Height(m) at Wave Period(s) 10.0 Wave Period Range(s) 10.0 Current Velocity Range(m/s) 0.0 Programmable Wavemaking Yes Wavemaking Description Monochromatic waves (cnoidal, Stokes, Airy), solitary waves, user-defined free surface timeseries or board displacement timeseries for random waves Wave Direction Uni-Directional Simulated Beach Yes Description of Beach 12' by 12' concrete slabs anchored to flume walls

276

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

Science Journals Connector (OSTI)

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

Amit Kr. Chattopadhyay and Jayanta K. Bhattacharjee

2000-12-21T23:59:59.000Z

277

Cyprinid swimming behaviour in response to turbulent flow

Science Journals Connector (OSTI)

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

Ana T. Silva; Christos Katopodis; José M. Santos; Maria T. Ferreira; António N. Pinheiro

2012-01-01T23:59:59.000Z

278

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

279

Energy Flux and Wavelet Diagnostics of Secondary Mountain Waves

Science Journals Connector (OSTI)

In recent years, aircraft data from mountain waves have been primarily analyzed using velocity and temperature power spectrum and momentum flux estimation. Herein it is argued that energy flux wavelets (i.e., pressure–velocity wavelet cross-...

Bryan K. Woods; Ronald B. Smith

2010-11-01T23:59:59.000Z

280

Quantum ghost imaging through turbulence

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

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

2011-05-15T23:59:59.000Z

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

281

HIGH-RESOLUTION OBSERVATIONS AND THE PHYSICS OF HIGH-VELOCITY CLOUD A0

The neutral hydrogen structure of high-velocity cloud A0 (at about -180 km s{sup -1}) has been mapped with a 9.'1 resolution. Gaussian decomposition of the profiles is used to separately map families of components defined by similarities in center velocities and line widths. About 70% of the H I gas is in the form of a narrow, twisted filament whose typical line widths are of the order of 24 km s{sup -1}. Many bright features with narrow line widths of the order of 6 km s{sup -1}, clouds, are located in and near the filament. A third category with properties between those of the filament and clouds appears in the data. The clouds are not always co-located with the broader line width filament emission as seen projected on the sky. Under the assumption that magnetic fields underlie the presence of the filament, a theorem is developed for its stability in terms of a toroidal magnetic field generated by the flow of gas along field lines. It is suggested that the axial magnetic field strength may be derived from the excess line width of the H I emission over and above that due to kinetic temperature by invoking the role of Alfven waves that create what is in essence a form of magnetic turbulence. At a distance of 200 pc the axial and the derived toroidal magnetic field strengths in the filament are then about 6 {mu}G while for the clouds they are about 4 {mu}G. The dependence of the derived field strength on distance is discussed.

Verschuur, Gerrit L., E-mail: verschuur@aol.com [Physics Department, University of Memphis, Memphis, TN 38152 (United States)

2013-04-01T23:59:59.000Z

282

Propagation Distance Required to Reach Steady-State Detonation Velocity in Finite-Sized Charges

The decay of a detonation wave from its initial CJ velocity to its final, steady state velocity upon encountering a finite thickness or diameter charge is investigated numerically and theoretically. The numerical simulations use an ideal gas equation of state and pressure dependent reaction rate in order to ensure a stable wave structure. The confinement is also treated as an ideal gas with variable impedance. The velocity decay along the centerline is extracted from the simulations and compared to predictions base on a front evolution equation that uses the steady state detonation velocity-front curvature relation ($D_n-\\kappa$). This model fails to capture the finite signaling speed of the leading rarefaction resulting from the interaction with the yielding confinement. This signaling speed is verified to be the maximum signal velocity occurring in the ideal ZND wave structure of the initial CJ velocity. A simple heuristic model based on the rarefaction generated by a one-dimensional interaction between the...

Li, Jianling; Higgins, Andrew J

2014-01-01T23:59:59.000Z

283

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

Science Journals Connector (OSTI)

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

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

2015-01-01T23:59:59.000Z

284

Asymptotic expansion and statistical description of turbulent systems

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

Hagan, W.K. III

1986-01-01T23:59:59.000Z

285

Asymptotic expansion and statistical description of turbulent systems

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

Hagan, W.K. III

1986-01-01T23:59:59.000Z

286

Filtering Turbulent Sparsely Observed Geophysical Flows

Science Journals Connector (OSTI)

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

John Harlim; Andrew J. Majda

2010-04-01T23:59:59.000Z

287

Discrimination of porosity and fluid saturation using seismic velocity analysis

The method of the invention is employed for determining the state of saturation in a subterranean formation using only seismic velocity measurements (e.g., shear and compressional wave velocity data). Seismic velocity data collected from a region of the formation of like solid material properties can provide relatively accurate partial saturation data derived from a well-defined triangle plotted in a (.rho./.mu., .lambda./.mu.)-plane. When the seismic velocity data are collected over a large region of a formation having both like and unlike materials, the method first distinguishes the like materials by initially plotting the seismic velocity data in a (.rho./.lambda., .mu./.lambda.)-plane to determine regions of the formation having like solid material properties and porosity.

Berryman, James G. (Danville, CA)

2001-01-01T23:59:59.000Z

288

Stress anisotropy and velocity anisotropy in low porosity shale

Science Journals Connector (OSTI)

Shales are known for often marked intrinsic anisotropy of many of their properties, including strength, permeability and velocity for example. In addition, it is well known that anisotropic stress fields can also have a significant impact on anisotropy of velocity, even in an isotropic medium. This paper sets out to investigate the ultrasonic velocity response of well-characterised low porosity shales from the Officer Basin in Western Australia to both isotropic and anisotropic stress fields and to evaluate the velocity response to the changing stress field. During consolidated undrained multi-stage triaxial tests on core plugs cut normal to bedding, Vpv increases monotonically with increasing effective stress and Vs1 behaves similarly although with some scatter. Vph and Vsh remain constant initially but then decrease within each stage of the multi-stage test, although velocity from stage to stage at any given differential stress increases. This has the impact of decreasing both P-wave (?) and S-wave anisotropy (?) through application of differential stress within each loading stage. However, increasing the magnitude of an isotropic stress field has little effect on the velocity anisotropies. The intrinsic anisotropy of the shale remains reasonably high at the highest confining pressures. The results indicate the magnitude and orientation of the stress anisotropy with respect to the shale microfabric has a significant impact on the velocity response to changing stress fields.

U. Kuila; D.N. Dewhurst; A.F. Siggins; M.D. Raven

2011-01-01T23:59:59.000Z

289

Slow waves in fractures filled with viscous fluid Valeri Korneev1

Slow waves in fractures filled with viscous fluid Valeri Korneev1 ABSTRACT Stoneley guided waves in a fluid-filled fracture generally have larger amplitudes than other waves; therefore, their properties, a simple dispersion equa- tion for wave-propagation velocity is obtained. This velocity is much smaller

Korneev, Valeri A.

290

SURFACE ALFVEN WAVES IN SOLAR FLUX TUBES

Magnetohydrodynamic (MHD) waves are ubiquitous in the solar atmosphere. Alfven waves and magneto-sonic waves are particular classes of MHD waves. These wave modes are clearly different and have pure properties in uniform plasmas of infinite extent only. Due to plasma non-uniformity, MHD waves have mixed properties and cannot be classified as pure Alfven or magneto-sonic waves. However, vorticity is a quantity unequivocally related to Alfven waves as compression is for magneto-sonic waves. Here, we investigate MHD waves superimposed on a one-dimensional non-uniform straight cylinder with constant magnetic field. For a piecewise constant density profile, we find that the fundamental radial modes of the non-axisymmetric waves have the same properties as surface Alfven waves at a true discontinuity in density. Contrary to the classic Alfven waves in a uniform plasma of infinite extent, vorticity is zero everywhere except at the cylinder boundary. If the discontinuity in density is replaced with a continuous variation of density, vorticity is spread out over the whole interval with non-uniform density. The fundamental radial modes of the non-axisymmetric waves do not need compression to exist unlike the radial overtones. In thin magnetic cylinders, the fundamental radial modes of the non-axisymmetric waves with phase velocities between the internal and the external Alfven velocities can be considered as surface Alfven waves. On the contrary, the radial overtones can be related to fast-like magneto-sonic modes.

Goossens, M.; Andries, J.; Soler, R.; Van Doorsselaere, T. [Centre for Plasma Astrophysics, Department of Mathematics, Katholieke Universiteit Leuven, Celestijnenlaan 200B, 3001 Leuven (Belgium); Arregui, I.; Terradas, J., E-mail: marcel.goossens@wis.kuleuven.be [Solar Physics Group, Departament de Fisica, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain)

2012-07-10T23:59:59.000Z

291

Excitation of kinetic geodesic acoustic modes by drift waves in nonuniform plasmas

Effects of system nonuniformities and kinetic dispersiveness on the spontaneous excitation of Geodesic Acoustic Mode (GAM) by Drift Wave (DW) turbulence are investigated based on nonlinear gyrokinetic theory. The coupled nonlinear equations describing parametric decay of DW into GAM and DW lower sideband are derived and then solved both analytically and numerically to investigate the effects on the parametric decay process due to system nonuniformities, such as nonuniform diamagnetic frequency, finite radial envelope of DW pump, and kinetic dispersiveness. It is found that the parametric decay process is a convective instability for typical tokamak parameters when finite group velocities of DW and GAM associated with kinetic dispersiveness and finite radial envelope are taken into account. When, however, nonuniformity of diamagnetic frequency is taken into account, the parametric decay process becomes, time asymptotically, a quasi-exponentially growing absolute instability.

Qiu, Z. [Inst. Fusion Theory and Simulation, Zhejiang Univ., Hangzhou 310027 (China)] [Inst. Fusion Theory and Simulation, Zhejiang Univ., Hangzhou 310027 (China); Chen, L. [Inst. Fusion Theory and Simulation, Zhejiang Univ., Hangzhou 310027 (China) [Inst. Fusion Theory and Simulation, Zhejiang Univ., Hangzhou 310027 (China); Dept. Physics and Astronomy, Univ. of California, Irvine, California 92697-4575 (United States); Zonca, F. [Inst. Fusion Theory and Simulation, Zhejiang Univ., Hangzhou 310027 (China) [Inst. Fusion Theory and Simulation, Zhejiang Univ., Hangzhou 310027 (China); Associazione Euratom-ENEA sulla Fusione, C.P. 65 - I-00044 - Frascati (Italy)

2014-02-15T23:59:59.000Z

292

2D full wave modeling for a synthetic Doppler backscattering diagnostic

Doppler backscattering (DBS) is a plasma diagnostic used in tokamaks and other magnetic confinement devices to measure the fluctuation level of intermediate wavenumber (k{sub {theta}}{rho}{sub s}{approx} 1) density fluctuations and the lab frame propagation velocity of turbulence. Here, a synthetic DBS diagnostic is described, which has been used for comparisons between measurements in the DIII-D tokamak and predictions from nonlinear gyrokinetic simulations. To estimate the wavenumber range to which a Gaussian beam would be sensitive, a ray tracing code and a 2D finite difference, time domain full wave code are used. Experimental density profiles and magnetic geometry are used along with the experimental antenna and beam characteristics. An example of the effect of the synthetic diagnostic on the output of a nonlinear gyrokinetic simulation is presented.

Hillesheim, J. C.; Schmitz, L.; Kubota, S.; Rhodes, T. L.; Carter, T. A. [Department of Physics and Astronomy, University of California, Los Angeles, California 90095 (United States); Holland, C. [University of California, San Diego, La Jolla, California 92093 (United States)

2012-10-15T23:59:59.000Z

293

Experimental evidence of accelerated energy transfer in turbulence

Science Journals Connector (OSTI)

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

R. Labbé; C. Baudet; G. Bustamante

2007-01-19T23:59:59.000Z

294

Global simulations of magnetorotational turbulence – II. Turbulent energetics

Science Journals Connector (OSTI)

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

E. R. Parkin

2014-01-01T23:59:59.000Z

295

Supercomputers Capture Turbulence in the Solar Wind

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

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

296

Hinsdale Wave Basin 2 | Open Energy Information

Wave Basin 2 Wave Basin 2 Jump to: navigation, search Basic Specifications Facility Name Hinsdale Wave Basin 2 Overseeing Organization Oregon State University Hydrodynamics Length(m) 48.8 Beam(m) 26.5 Depth(m) 2.1 Water Type Freshwater Cost(per day) $3500 Towing Capabilities Towing Capabilities None Wavemaking Capabilities Wavemaking Capabilities Yes Maximum Wave Height(m) 0.8 Maximum Wave Height(m) at Wave Period(s) 10.0 Wave Period Range(s) 10.0 Current Velocity Range(m/s) 0.0 Programmable Wavemaking Yes Wavemaking Description Monochromatic waves (cnoidal, Stokes, Airy), solitary waves, user-defined free surface timeseries or board displacement timeseries for random waves Wave Direction Both Simulated Beach Yes Description of Beach Built to client specifications, currently rigid concrete over gravel fill

297

Haynes Wave Basin | Open Energy Information

Wave Basin Wave Basin Jump to: navigation, search Basic Specifications Facility Name Haynes Wave Basin Overseeing Organization Texas A&M (Haynes) Hydrodynamic Testing Facility Type Wave Basin Length(m) 38.1 Beam(m) 22.9 Depth(m) 1.5 Water Type Freshwater Cost(per day) $150/hour (excluding labor) Towing Capabilities Towing Capabilities None Wavemaking Capabilities Wavemaking Capabilities Yes Maximum Wave Height(m) 0.6 Maximum Wave Height(m) at Wave Period(s) 3.3 Maximum Wave Length(m) 10.7 Wave Period Range(s) 3.3 Current Velocity Range(m/s) 0.2 Programmable Wavemaking Yes Wavemaking Description Directional, irregular, any spectrum, cnoidal or solitary wave Wave Direction Both Simulated Beach Yes Description of Beach Stone Channel/Tunnel/Flume Channel/Tunnel/Flume None

298

White light velocity interferometer

The invention is a technique that allows the use of broadband and incoherent illumination. Although denoted white light velocimetry, this principle can be applied to any wave phenomenon. For the first time, powerful, compact or inexpensive sources can be used for remote target velocimetry. These include flash and arc lamps, light from detonations, pulsed lasers, chirped frequency lasers, and lasers operating simultaneously in several wavelengths. The technique is demonstrated with white light from an incandescent source to measure a target moving at 16 m/s.

Erskine, David J. (Oakland, CA)

1997-01-01T23:59:59.000Z

299

White light velocity interferometer

The invention is a technique that allows the use of broadband and incoherent illumination. Although denoted white light velocimetry, this principle can be applied to any wave phenomenon. For the first time, powerful, compact or inexpensive sources can be used for remote target velocimetry. These include flash and arc lamps, light from detonations, pulsed lasers, chirped frequency lasers, and lasers operating simultaneously in several wavelengths. The technique is demonstrated with white light from an incandescent source to measure a target moving at 16 m/s. 41 figs.

Erskine, D.J.

1997-06-24T23:59:59.000Z

300

White light velocity interferometer

The invention is a technique that allows the use of broadband and incoherent illumination. Although denoted white light velocimetry, this principle can be applied to any wave phenomenon. For the first time, powerful, compact or inexpensive sources can be used for remote target velocimetry. These include flash and arc lamps, light from detonations, pulsed lasers, chirped frequency lasers, and lasers operating simultaneously in several wavelengths. The technique is demonstrated with white light from an incandescent source to measure a target moving at 16 m/s.

Erskine, David J. (Oakland, CA)

1999-01-01T23:59:59.000Z

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

301

White light velocity interferometer

The invention is a technique that allows the use of broadband and incoherent illumination. Although denoted white light velocimetry, this principle can be applied to any wave phenomenon. For the first time, powerful, compact or inexpensive sources can be used for remote target velocimetry. These include flash and arc lamps, light from detonations, pulsed lasers, chirped frequency lasers, and lasers operating simultaneously in several wavelengths. The technique is demonstrated with white light from an incandescent source to measure a target moving at 16 m/s. 41 figs.

Erskine, D.J.

1999-06-08T23:59:59.000Z

302

A comparison of weak-turbulence and PIC simulations of weak electron-beam plasma interaction

Quasilinear theory has long been used to treat the problem of a weak electron beam interacting with plasma and generating Langmuir waves. Its extension to weak-turbulence theory treats resonant interactions of these Langmuir waves with other plasma wave modes, in particular ion-sound waves. These are strongly damped in plasma of equal ion and electron temperatures, as sometimes seen in, for example, the solar corona and wind. Weak turbulence theory is derived in the weak damping limit, with a term describing ion-sound wave damping then added. In this paper we use the EPOCH particle-in-cell code to numerically test weak turbulence theory for a range of electron-ion temperature ratios. We find that in the cold ion limit the results agree well, but increasing ion temperature the three-wave resonance becomes broadened in proportion to the ion-sound wave damping rate. This may be important in, for example, the theory of solar radio bursts, where the spectrum of Langmuir waves is critical. Additionally we establish...

Ratcliffe, Heather; Rozenan, Mohammed B Che; Nakariakov, Valery

2014-01-01T23:59:59.000Z

303

Unitaxial constant velocity microactuator

A uniaxial drive system or microactuator capable of operating in an ultra-high vacuum environment is disclosed. The mechanism includes a flexible coupling having a bore therethrough, and two clamp/pusher assemblies mounted in axial ends of the coupling. The clamp/pusher assemblies are energized by voltage-operated piezoelectrics therewithin to operatively engage the shaft and coupling causing the shaft to move along its rotational axis through the bore. The microactuator is capable of repeatably positioning to sub-nanometer accuracy while affording a scan range in excess of 5 centimeters. Moreover, the microactuator generates smooth, constant velocity motion profiles while producing a drive thrust of greater than 10 pounds. The system is remotely controlled and piezoelectrically driven, hence minimal thermal loading, vibrational excitation, or outgassing is introduced to the operating environment. 10 figs.

McIntyre, T.J.

1994-06-07T23:59:59.000Z

304

Turbulent Magnetic Reconnection Near a

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

Ng, Chung-Sang

305

Experimental determination of the effective structure-function parameter for atmospheric turbulence

Science Journals Connector (OSTI)

The effective structure-function parameter for scattering by atmospheric turbulentvelocityfluctuations has normally been assumed to be C eff 2 =4C V 2 /c 0 2 where C V 2 is the velocitystructure-function parameter and c 0 the sound speed. However a new derivation by Ostashev [WavesRandom Media4 403–428 (1994)] which takes into account the vectorial nature of the wind velocity field suggests that C eff 2 =22C V 2 /3c 0 2 . An experiment was designed to determine the correct value of the coefficient. Sound-pressure amplitude variances were monitored for several discrete frequencies between 380 and 3800 Hz at distances up to 250 m. Cup and hot-wire anemometers were used to determine C V 2 . A theory for scattering by inertial-subrange turbulence was then used to calculate the C eff 2 coefficient from the amplitude variance and C V 2 . Datasets recorded under different atmospheric conditions yielded different relationships between the coefficients and failed to verify either the 4 or 22/3 value. Some possible explanations for this behavior are discussed including the need for more realistic meteorological modeling.

D. K. Wilson; D. I. Havelock; M. Heyd; M. J. Smith; J. M. Noble; H. J. Auvermann

1999-01-01T23:59:59.000Z

306

Experimental Study on Kinematics and Dynamics of Breaking Waves in Deep Water

aerated region were obtained from the BIV measurements. In addition, the modified PIV technique is capable of measuring the velocities in the entire flow field including the aerated region. Mean and turbulent properties were obtained by the ensemble...

Lim, Ho Joon

2011-10-21T23:59:59.000Z

307

Temporal Velocity Variations beneath the Coso Geothermal Field Observed

Velocity Variations beneath the Coso Geothermal Field Observed Velocity Variations beneath the Coso Geothermal Field Observed using Seismic Double Difference Tomography of Compressional and Shear Wave Arrival Times Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Conference Proceedings: Temporal Velocity Variations beneath the Coso Geothermal Field Observed using Seismic Double Difference Tomography of Compressional and Shear Wave Arrival Times Details Activities (1) Areas (1) Regions (0) Abstract: Microseismic imaging can be an important tool for characterizing geothermal reservoirs. Since microseismic sources occur more or less continuously both due to the operations of a geothermal field and the naturally occurring background seismicity, passive seismic monitoring is well suited to quantify the temporal variations in the vicinity of a

308

Wave-current interaction in water of finite depth

In this thesis, the nonlinear interaction of waves and current in water of finite depth is studied. Wind is not included. In the first part, a 2D theory for the wave effect on a turbulent current over rough or smooth bottom ...

Huang, Zhenhua, 1967-

2004-01-01T23:59:59.000Z

309

Uncertainty quantification for turbulent mixing simulations

We have achieved validation in the form of simulation-experiment agreement for Rayleigh-Taylor turbulent mixing rates (known as {alpha}) over the past decade. The problem was first posed sixty years ago. Recent improvements in our simulation technology allow sufficient precision to distinguish between mixing rates for different experiments. We explain the sensitivity and non-universality of the mixing rate. These playa role in the difficulties experienced by many others in efforts to compare experiment with simulation. We analyze the role of initial conditions, which were not recorded for the classical experiments of Youngs et al. Reconstructed initial conditions with error bars are given. The time evolution of the long and short wave length portions of the instability are analyzed. We show that long wave length perturbations are strong at t = 0, but are quickly overcome by the rapidly growing short wave length perturbations. These conclusions, based solely on experimental data analysis, are in agreement with results from theoretical bubble merger models and numerical simulation studies but disagree with models based on superposition of modes.

Sharp, David Howland [Los Alamos National Laboratory; Glimm, James G [STONEY BROOK UNIV.; Kaman, Tulin [STONEY BROOK UNIV.

2011-01-20T23:59:59.000Z

310

A new method for simulating the three-dimensional dynamics of charged energetic particles in very broadband noncompressive magnetic turbulence is introduced. All scales within the primary inertial range of the turbulence observed in the solar wind near 1 AU are now included for the independent computations of both the particle dynamics and the turbulent magnetic field lines (MFLs). While previous theories of resonant particle pitch-angle (PA) scattering and transport in interplanetary magnetic fields had favored interpreting the observed depletions in the electron PA distributions (PADs) around 90 Degree-Sign PA as evidence of poor scattering at low PA cosines, the computed particle dynamics reveal a very different reality. The MFL directions now vary on many scales, and the PADs are depleted around 90 Degree-Sign PA due to nonresonant filtering of the particles that propagate at too large an angle to the local magnetic field. Rather than being too weak, the scattering through 90 Degree-Sign PA is actually so strong that the particles (electrons and protons/ions) are reflected and trapped in the turbulent magnetic fields. While the low-frequency nonresonant turbulence produces ubiquitous magnetic traps that only let through particles with the most field-aligned velocities, higher-frequency near-gyroscale turbulence, when present, enhances particle transport by allowing the particles to navigate between magnetic traps. Finally, visualizing both particle trajectories and MFLs in the very same turbulence reveals a powerful tool for understanding the effects of the turbulent fields on the particle dynamics and cross-field transport. Some cross-field-line scattering, strongly amplified by MFL dispersal, results in a strong cross-field scattering of the particles. From this visualization, it also appears that near-gyroscale turbulence, previously known as gyroresonant turbulence, does not resonantly interact with the particles. The interaction between particles and fields at or near the gyroscale, though potentially strong, does not actually involve the periodic driving of a true resonance.

Ragot, B. R. [Helio Research, P.O. Box 1414, Nashua, NH 03061 (United States)

2012-10-20T23:59:59.000Z

311

The Standing Wave on a String as an Oscillator

Science Journals Connector (OSTI)

In the usual treatment of waves in introductory courses one begins with traveling waves and the frequency/wavelength relationship f??=?v where v is the wave velocity. One then makes the point about superposition and shows that two waves traveling in opposite directions can add up to a standing wave; Eq. (1) still applies. This approach is problematic in two ways: (1) The motion being described standing waves has no apparent “velocity ” and so it seems unnecessarily complex—perhaps unreasonably complex—to construct it out of moving waves; (2) It is not easy to derive the formula for the velocity of waves especially for an audience without calculus or without multi-variate calculus (the wave equation).

Michael Sobel

2007-01-01T23:59:59.000Z

312

Ion temperature in plasmas with intrinsic Alfven waves

This Brief Communication clarifies the physics of non-resonant heating of protons by low-frequency Alfvenic turbulence. On the basis of general definition for wave energy density in plasmas, it is shown that the wave magnetic field energy is equivalent to the kinetic energy density of the ions, whose motion is induced by the wave magnetic field, thus providing a self-consistent description of the non-resonant heating by Alfvenic turbulence. Although the study is motivated by the research on the solar corona, the present discussion is only concerned with the plasma physics of the heating process.

Wu, C. S. [CAS Key Laboratory of Geospace Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei (China); Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742 (United States); Yoon, P. H. [Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742 (United States); School of Space Research, Kyung Hee University, Yongin, Gyeonggi 446-701 (Korea, Republic of); Wang, C. B. [CAS Key Laboratory of Geospace Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei (China)

2014-10-15T23:59:59.000Z

313

Internal Tides and Turbulence along the 3000-m Isobath of the Hawaiian Ridge

Science Journals Connector (OSTI)

Full-depth velocity and density profiles taken along the 3000-m isobath characterize the semidiurnal internal tide and bottom-intensified turbulence along the Hawaiian Ridge. Observations reveal baroclinic energy fluxes of 21 ± 5 kW m?1 radiating ...

Craig M. Lee; Thomas B. Sanford; Eric Kunze; Jonathan D. Nash; Mark A. Merrifield; Peter E. Holloway

2006-06-01T23:59:59.000Z

314

PHYSICS OF FLUIDS 24, 103306 (2012) Numerical simulation of turbulent sediment transport,

PHYSICS OF FLUIDS 24, 103306 (2012) Numerical simulation of turbulent sediment transport, from bed October 2012) Sediment transport is studied as a function of the grain to fluid density ratio using two), vertical velocities are so small that sediment transport occurs in a thin layer at the surface

Claudin, Philippe

315

Experimental study of turbulent unconfined groundwater flow in a single fracture

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

Zhan, Hongbin

316

Available online 9 February 2011 Keywords: Syngas Hydrogen Global consumption speeds Turbulent flame speed since they are the primary constitu- ents of syngas fuels. Data are reported at mean flow velocities than SL,0. Ă? 2011 The Combustion Institute. Published by Elsevier Inc. All rights reserved. 1

Lieuwen, Timothy C.

317

A Reconsideration of Matter Waves

Matter waves were discovered in the early 20th century from their wavelength, predicted by DeBroglie, Planck's constant divided by the particle's momentum, that is, lmw = h/mv. But, the failure to obtain a reasonable theory for the matter wave frequency resulted somewhat in loss of further interest. It was expected that the frequency of the matter wave should correspond to the particle kinetic energy, that is, fmw = 1/2mv^2/h but the resulting velocity of the matter of the particle, v = fmw x lmw, is that the matter wave moves at one half the speed of the particle, obviously absurd as the particle and its wave must move together. If relativistic mass is used (as it should in any case) the problem remains, the same mass appearing in numerator and denominator and canceling. It is no help to hypothesize that the total energy, not just the kinetic energy, yields the matter wave. That attributes a matter wave to a particle at rest. It also gives the resulting velocity as c^2/v, the wave racing ahead of its particle. A reinterpretation of Einstein's derivation of relativistic kinetic energy (which produced his famous E = mc^2) leads to a valid matter wave frequency and a new understanding of particle kinetics and of the atom's stable orbits.

Roger Ellman

2005-05-16T23:59:59.000Z

318

Alden Wave Basin | Open Energy Information

Wave Basin Wave Basin Jump to: navigation, search Basic Specifications Facility Name Alden Wave Basin Overseeing Organization Alden Research Laboratory, Inc Hydrodynamic Testing Facility Type Wave Basin Length(m) 33.5 Beam(m) 21.3 Depth(m) 1.2 Water Type Freshwater Cost(per day) Depends on study Towing Capabilities Towing Capabilities None Wavemaking Capabilities Wavemaking Capabilities Yes Maximum Wave Height(m) 0.3 Maximum Wave Height(m) at Wave Period(s) 1.0 Maximum Wave Length(m) 1.8 Wave Period Range(s) 1.0 Current Velocity Range(m/s) 0.0 Programmable Wavemaking Yes Wavemaking Description Period adjustable electronically, height adjustable mechanically Wave Direction Both Simulated Beach Yes Description of Beach Designed as needed using commercially available sand/sediment

319

Interfaces and inhomogeneous turbulence

Science Journals Connector (OSTI)

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

2011-01-01T23:59:59.000Z

320

Memory effects in turbulent transport

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

Alexander Hubbard; Axel Brandenburg

2008-11-17T23:59:59.000Z

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We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

321

Compound cooling flow turbulator for turbine component

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

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

2014-11-25T23:59:59.000Z

322

Energy Dispersion in African Easterly Waves

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The existence of an upstream (eastward) group velocity for African easterly waves (AEWs) is shown based on single-point lag regressions using gridded reanalysis data from 1990 to 2010. The eastward energy dispersion is consistent with the ...

Michael Diaz; Anantha Aiyyer

2013-01-01T23:59:59.000Z

323

Science Journals Connector (OSTI)

Waves receive their energy from the wind by means of a ... whose yield is not yet clearly understood. Energy in the wave is more concentrated than in the wind ... density. For this reason a motor utilizing wave p...

Ferruccio Mosetti

1982-01-01T23:59:59.000Z

324

Relation between plasma plume density and gas flow velocity in atmospheric pressure plasma

We have studied atmospheric pressure plasma generated using a quartz tube, helium gas, and copper foil electrode by applying RF high voltage. The atmospheric pressure plasma in the form of a bullet is released as a plume into the atmosphere. To study the properties of the plasma plume, the plasma plume current is estimated from the difference in currents on the circuit, and the drift velocity is measured using a photodetector. The relation of the plasma plume density n{sub plu}, which is estimated from the current and the drift velocity, and the gas flow velocity v{sub gas} is examined. It is found that the dependence of the density on the gas flow velocity has relations of n{sub plu} ? log(v{sub gas}). However, the plasma plume density in the laminar flow is higher than that in the turbulent flow. Consequently, in the laminar flow, the density increases with increasing the gas flow velocity.

Yambe, Kiyoyuki; Taka, Shogo; Ogura, Kazuo [Graduate School of Science and Technology, Niigata University, Niigata 950-2181 (Japan)] [Graduate School of Science and Technology, Niigata University, Niigata 950-2181 (Japan)

2014-04-15T23:59:59.000Z

325

Seismic Velocity And Attenuation Structure Of The Geysers Geothermal Field,

Velocity And Attenuation Structure Of The Geysers Geothermal Field, Velocity And Attenuation Structure Of The Geysers Geothermal Field, California Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Journal Article: Seismic Velocity And Attenuation Structure Of The Geysers Geothermal Field, California Details Activities (1) Areas (1) Regions (0) Abstract: The Geysers geothermal field is located in northern California and is one of the world's largest producers of electricity from geothermal energy. A key resource management issue at this field is the distribution of fluid in the matrix of the reservoir rock. In this paper, we interpret seismic compressional-wave velocity and quality quotient (Q) data at The Geysers in terms of the geologic structure and fluid saturation in the reservoir. Our data consist of waveforms from approximately 300

326

Nonlinear closures for scale separation in supersonic magnetohydrodynamic turbulence

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

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

2015-01-01T23:59:59.000Z

327

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

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

Gerbi, Gregory Peter

2008-01-01T23:59:59.000Z

328

Magnetic energy production by turbulence in binary neutron star mergers

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

Zrake, Jonathan

2013-01-01T23:59:59.000Z

329

Alfv'en Wave Solitons and Solar Intermediate Drift Bursts

propagate at velocities of the order of the Alfv'en velocÂ ity in a direction inclined to the magnetic field, the solar wind, and possibly accretion disks, and extraÂ galactic jets. In such magnetized plasmas Alfv'en waves are easily excited by various processes. Linear waves propagate at the Alfv'en speed v

Guedel, Manuel

330

A Novel Statistical Channel Model for Turbulence-Induced Fading in Free-Space Optical Systems

In this paper, we propose a new probability distribution function which accurately describes turbulence-induced fading under a wide range of turbulence conditions. The proposed model, termed Double Generalized Gamma (Double GG), is based on a doubly stochastic theory of scintillation and developed via the product of two Generalized Gamma (GG) distributions. The proposed Double GG distribution generalizes many existing turbulence channel models and provides an excellent fit to the published plane and spherical waves simulation data. Using this new statistical channel model, we derive closed form expressions for the outage probability and the average bit error as well as corresponding asymptotic expressions of free-space optical communication systems over turbulence channels. We demonstrate that our derived expressions cover many existing results in the literature earlier reported for Gamma-Gamma, Double-Weibull and K channels as special cases.

Aminikashani, Mohammadreza; Kavehrad, Mohsen

2015-01-01T23:59:59.000Z

331

Numerical simulation of buoyant turbulent flow. Final report

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

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

1985-08-01T23:59:59.000Z

332

The Earth's hum: the excitation of Earth normal modes by ocean waves

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......air to the density of water. I will assume (at...suggest the forcing of atmospheric microbaroms (the equivalent...waves follow the deep water dispersion curve. At...turbulence an inefficient generator of sound at low Mach...suggests low Mach number atmospheric turbulence on the Earth......

Spahr C. Webb

2008-08-01T23:59:59.000Z

333

Bubble entrainment by breaking waves and their influence on optical scattering in the upper ocean

Bubble entrainment by breaking waves and their influence on optical scattering in the upper ocean's surface inject bubbles and turbulence into the water column. During periods of rough weather the scales and the turbulent transport of bubbles to depth. Depending on their concentrations and size distribution

Stramski, Dariusz

334

Seismic waves in stratified anisotropic media

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......structure response as a function of frequency and radial...group, and energy velocities...structure response as a function of frequency and radial...group, and energy velocities...plane-wave response. This method...for each frequency, data for...amounts of storage required......

Gerard J. Fryer; L. Neil Frazer

1984-09-01T23:59:59.000Z

335

The impact of pedestal turbulence and electron inertia on edge-localized-mode crashes

We demonstrate that the occurrence of Edge-Localized-Modes (ELM) crashes does not depend only on the linear peeling-ballooning threshold, but also relies on nonlinear processes. Wave-wave interaction constrains the growth time of a mode, thus inducing a shift in the criterion for triggering an ELM crash. An ELM crash requires the P-B growth rate to exceed a critical value ?>?{sub c}, where ?{sub c} is set by 1/?{sup Ż}{sub c}, and ?{sup Ż}{sub c} is the averaged mode phase coherence time. For 0turbulence develops but drives enhanced turbulent transport. We also show that electron inertia dramatically changes the instability threshold when density is low. However, P-B turbulence alone cannot generate enough current transport to allow fast reconnection during an ELM crash.

Xi, P. W. [FSC and State Key Lab of Nuclear Physics and Technology, Department of Physics, Peking University, Beijing 100871 (China) [FSC and State Key Lab of Nuclear Physics and Technology, Department of Physics, Peking University, Beijing 100871 (China); Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Xu, X. Q. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)] [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Diamond, P. H. [WCI Center for Fusion Theory, National Fusion Research Institute, Daejeon (Korea, Republic of) [WCI Center for Fusion Theory, National Fusion Research Institute, Daejeon (Korea, Republic of); Center for Astrophysics and Space Sciences and Department of Physics, University of California San Diego, La Jolla, California 92093-0429 (United States)

2014-05-15T23:59:59.000Z

336

Estimation of boundary layer transition noise from velocity measurements

Science Journals Connector (OSTI)

Velocity measurements of artificially generatedflow structures in the transition region of an incompressible boundary layer with zero pressure gradient are described. These measurements made in a laminar flow water channel allow calculation of the velocity normal to the wall in a turbulent spot. This velocity specifies the linearized boundary condition for the acoustic equation at the wall. The approach relates the radiated noise to fluctuations in the normal velocity at the plate through fluctuations in the displacement thickness. Although this approach has been previously proposed [H. W. Liepmann unpublished (1954) J. Laufer J. E. Ffowcs?Williams and S. Childress AGARDograph 90 39–42 (1964) G. C. Lauchle J. Acoust. Soc. Am. 69 665–671 (1981) G. C. Lauchle ASME NCA 5 31–38 (1989)] it has never been applied. The results of these experiments will be compared to concurrent experiments run in an anechoic wind tunnel. Ultimately this work will be extended to naturally occurring structures in the transition region. [Work supported by ONR under Grant ?N00014?90?J?1365.

Michael H. Krane; Wayne R. Pauley

1991-01-01T23:59:59.000Z

337

In the parts of the solar corona and solar wind that experience the fewest Coulomb collisions, the component proton, electron, and heavy ion populations are not in thermal equilibrium with one another. Observed differences in temperatures, outflow speeds, and velocity distribution anisotropies are useful constraints on proposed explanations for how the plasma is heated and accelerated. This paper presents new predictions of the rates of collisionless heating for each particle species, in which the energy input is assumed to come from magnetohydrodynamic (MHD) turbulence. We first created an empirical description of the radial evolution of Alfven, fast-mode, and slow-mode MHD waves. This model provides the total wave power in each mode as a function of distance along an expanding flux tube in the high-speed solar wind. Next, we solved a set of cascade advection-diffusion equations that give the time-steady wavenumber spectra at each distance. An approximate term for nonlinear coupling between the Alfven and fast-mode fluctuations is included. For reasonable choices of the parameters, our model contains enough energy transfer from the fast mode to the Alfven mode to excite the high-frequency ion cyclotron resonance. This resonance is efficient at heating protons and other ions in the direction perpendicular to the background magnetic field, and our model predicts heating rates for these species that agree well with both spectroscopic and in situ measurements. Nonetheless, the high-frequency waves comprise only a small part of the total Alfvenic fluctuation spectrum, which remains highly two dimensional as is observed in interplanetary space.

Cranmer, Steven R.; Van Ballegooijen, Adriaan A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2012-08-01T23:59:59.000Z

338

Liu UCD Phy9B 07 1 Ch15. Mechanical Waves

Liu UCD Phy9B 07 1 Ch15. Mechanical Waves #12;Liu UCD Phy9B 07 2 15-1. Introduction Source: disturbance + cohesive force between adjacent pieces A wave is a disturbance that propagates through space Mechanical wave: needs a medium to propagate Wave pulse #12;Liu UCD Phy9B 07 3 Distinctions Wave velocity vs

Yoo, S. J. Ben

339

Kinematics measurements of regular, irregular, and rogue waves by PIV/LDV

waves. A series of experiments were conducted in a 2-D wave tank at Texas A&M University to measure wave velocities and accelerations using LDV and PIV systems. The wave crests of regular and rogue waves are the focus of this study. With the measured...

Choi, Hae-Jin

2007-04-25T23:59:59.000Z

340

Velocity of Elastic Waves in Granite and Norite

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...excep- tion the fundamental requirement that...interior- wall of boiler-room. This...the buildings safe for operation and providing...amperes for normal operation. A Laon tube...0.1, the fundamental REPORTS AND PAPERS...

L. Don Leet

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

341

Crust and Upper Mantle P Wave Velocity Structure Beneath Valles...

Structure Beneath Valles Caldera, New Mexico- Results from the Jemez Teleseismic Tomography Experiment Jump to: navigation, search OpenEI Reference LibraryAdd to library...

342

Large-Eddy Simulation of Marine Atmospheric Boundary Layers above a Spectrum of Moving Waves

Science Journals Connector (OSTI)

Momentum and scalar transport in the marine atmospheric boundary layer (MABL) is driven by a turbulent mix of winds, buoyancy, and surface gravity waves. To investigate the interaction between these processes, a large-eddy simulation (LES) model ...

Peter P. Sullivan; James C. McWilliams; Edward G. Patton

2014-11-01T23:59:59.000Z

343

The Impact of Finite-Amplitude Bottom Topography on Internal Wave Generation in the Southern Ocean

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Direct observations in the Southern Ocean report enhanced internal wave activity and turbulence in a kilometer-thick layer above rough bottom topography collocated with the deep-reaching fronts of the Antarctic Circumpolar Current. Linear theory, ...

Maxim Nikurashin; Raffaele Ferrari; Nicolas Grisouard; Kurt Polzin

2014-11-01T23:59:59.000Z

344

Fluid-bubble interaction and dissipation mechanisms under unsteady breaking waves

Fluid-bubble interaction and dissipation mechanisms under unsteady breaking waves of air in bubbles that are believed to suppress liquid phase turbulence to incorporate entrained bubble populations using an Eulerian-Eulerian formulation

Kirby, James T.

345

DeFrees Large Wave Basin | Open Energy Information

Large Wave Basin Large Wave Basin Jump to: navigation, search Basic Specifications Facility Name DeFrees Large Wave Basin Overseeing Organization Cornell University Hydrodynamics Hydrodynamic Testing Facility Type Wave Basin Length(m) 32.0 Beam(m) 0.6 Depth(m) 0.9 Water Type Freshwater Towing Capabilities Towing Capabilities None Wavemaking Capabilities Wavemaking Capabilities Yes Maximum Wave Height(m) 0.5 Maximum Wave Height(m) at Wave Period(s) 3.0 Maximum Wave Length(m) 64 Wave Period Range(s) 3.0 Current Velocity Range(m/s) 0.0 Programmable Wavemaking Yes Wavemaking Description Computer controlled 4m hydraulic wave paddle stroke allows a series of solitary waves to be generated; arbitrary wave shape possible Wave Direction Uni-Directional Simulated Beach Yes

346

Science Journals Connector (OSTI)

The nature of solar windturbulence in the dissipation range at scales much smaller than the large magnetohydrodynamic (MHD) scales remains under debate. Here a two-dimensional model based on the hybrid code abbreviated as A.I.K.E.F. is presented which treats massive ions as particles obeying the kinetic Vlasov equation and massless electrons as a neutralizing fluid. Up to a certain wavenumber in the MHD regime the numerical system is initialized by assuming a superposition of isotropic Alfvén waves with amplitudes that follow the empirically confirmed spectral law of Kolmogorov. Then turbulence develops and energy cascades into the dispersive spectral range where also dissipative effects occur. Under typical solar wind conditions weak turbulence develops as a superposition of normal modes in the kinetic regime. Spectral analysis in the direction parallel to the background magnetic field reveals a cascade of left-handed Alfvén/ion-cyclotron waves up to wave vectors where their resonant absorption sets in as well as a continuing cascade of right-handed fast-mode and whistler waves. Perpendicular to the background field a broad turbulent spectrum is found to be built up of fluctuations having a strong compressive component. Ion-Bernstein waves seem to be possible normal modes in this propagation direction for lower driving amplitudes. Also signatures of short-scale pressure-balanced structures (very oblique slow-mode waves) are found.

D. Verscharen; E. Marsch; U. Motschmann; J. Müller

2012-01-01T23:59:59.000Z

347

The quenching of star formation in accretion-driven clumpy turbulent tori of active galactic nuclei

Galactic gas-gas collisions involving a turbulent multiphase ISM share common ISM properties: dense extraplanar gas visible in CO, large linewidths (>= 50 km/s), strong mid-infrared H_2 line emission, low star formation activity, and strong radio continuum emission. Gas-gas collisions can occur in the form of ICM ram pressure stripping, galaxy head-on collisions, compression of the intragroup gas and/or galaxy ISM by an intruder galaxy which flies through the galaxy group at a high velocity, or external gas accretion on an existing gas torus in a galactic center. We suggest that the common theme of all these gas-gas interactions is adiabatic compression of the ISM leading to an increase of the turbulent velocity dispersion of the gas. The turbulent gas clouds are then overpressured and star formation is quenched. Within this scenario we developed a model for turbulent clumpy gas disks where the energy to drive turbulence is supplied by external infall or the gain of potential energy by radial gas accretion wi...

Vollmer, B

2013-01-01T23:59:59.000Z

348

Fermi velocity renormalization and dynamical gap generation in graphene

We study the renormalization of the Fermi velocity by the long-range Coulomb interactions between the charge carriers in the Dirac-cone approximation for the effective low-energy description of the electronic excitations in graphene at half filling. Solving the coupled system of Dyson-Schwinger equations for the dressing functions in the corresponding fermion propagator with various approximations for the particle-hole polarization we observe that Fermi velocity renormalization effects generally lead to a considerable increase of the critical coupling for dynamical gap generation and charge-density wave formation at the semimetal-insulator transition.

C. Popovici; C. S. Fischer; L. von Smekal

2015-01-12T23:59:59.000Z

349

Comparison of P-wave and S-wave data in a fractured reservoir

-wave and S-wave stations . Table 2 The depths, times, and RMS velocities of the seismic reflectors (Tertiary and Cretaceous systems) at locations 45, 0 and 65. 0 on the P-wave section . 32 Table 3 The RMS velocities, depths of the seismic reflectors...-wave seismic lines were shot, parallel to each other, in Burleson County, Texas. The circles indicate ~ oil-producing wells. The two lines trend northwest-southeast and are appmximately thee and a half miles long (Fig. 2) The contours represent cumulative...

Al-Mustafa, Husam Mustafa

2012-06-07T23:59:59.000Z

350

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

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

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

2009-04-01T23:59:59.000Z

351

A climatic dataset of ocean vertical turbulent mixing coefficient based on real energy sources

Science Journals Connector (OSTI)

Using data on wind stress, significant height of combined wind waves and swell, potential temperature, salinity and seawater velocity, as well as objectively-analyzed in situ temperature and salinity, we establis...

Yu Zhang; YiHua Lin; RuiXin Huang

2014-10-01T23:59:59.000Z

352

Fast Computation Algorithm for Discrete Resonances among Gravity Waves

Traditionally resonant interactions among short waves, with large real wave-numbers, were described statistically and only a small domain in spectral space with integer wave-numbers, discrete resonances, had to be studied separately in resonators. Numerical simulations of the last few years showed unambiguously the existence of some discrete effects in the short-waves part of the wave spectrum. Newly presented model of laminated turbulence explains theoretically appearance of these effects thus putting a novel problem - construction of fast algorithms for computation of solutions of resonance conditions with integer wave-numbers of order $10^3$ and more. Example of such an algorithm for 4-waves interactions of gravity waves is given. Its generalization on the different types of waves is briefly discussed.

Elena Kartashova

2006-05-25T23:59:59.000Z

353

Quantitative imaging of turbulent and reacting flows

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

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

1993-12-01T23:59:59.000Z

354

The various manifestations of collisionless dissipation in wave propagation

The propagation of an electrostatic wave packet inside a collisionless and initially Maxwellian plasma is always dissipative because of the irreversible acceleration of the electrons by the wave. Then, in the linear regime, the wave packet is Landau damped, so that in the reference frame moving at the group velocity, the wave amplitude decays exponentially with time. In the nonlinear regime, once phase mixing has occurred and when the electron motion is nearly adiabatic, the damping rate is strongly reduced compared to the Landau one, so that the wave amplitude remains nearly constant along the characteristics. Yet, we show here that the electrons are still globally accelerated by the wave packet, and in one dimension, this leads to a non local amplitude dependence of the group velocity. As a result, a freely propagating wave packet would shrink, and therefore, so would its total energy. In more than one dimension, not only does the magnitude of the group velocity nonlinearly vary, but also its direction. In the weakly nonlinear regime, when the collisionless damping rate is still significant compared to its linear value, the group velocity is directed towards the outside of the wave packet and tends to increase its transverse extent, while the opposite is true once the wave is essentially undamped. The impact of the nonlinear variation of the group velocity on the transverse size of the wave packet is quantified, and compared to that induced by the self-focussing due to wave front bowing.

Benisti, Didier; Morice, Olivier; Gremillet, Laurent [CEA, DAM, DIF, F-91297 Arpajon (France)

2012-06-15T23:59:59.000Z

355

ARM - Measurement - Hydrometeor fall velocity

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

fall velocity fall velocity 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 : Hydrometeor fall velocity Fall velocity of hydrometeors (e.g. rain, snow, graupel, hail). Categories Cloud 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 DISDROMETER : Impact Disdrometer LDIS : Laser Disdrometer WSACR : Scanning ARM Cloud Radar, tuned to W-Band (95GHz) Field Campaign Instruments DISDROMETER : Impact Disdrometer PDI : Phase Doppler Interferometer

356

Fundamental Statistical Descriptions of Plasma Turbulence in Magnetic Fields

A pedagogical review of the historical development and current status (as of early 2000) of systematic statistical theories of plasma turbulence is undertaken. Emphasis is on conceptual foundations and methodology, not practical applications. Particular attention is paid to equations and formalism appropriate to strongly magnetized, fully ionized plasmas. Extensive reference to the literature on neutral-fluid turbulence is made, but the unique properties and problems of plasmas are emphasized throughout. Discussions are given of quasilinear theory, weak-turbulence theory, resonance-broadening theory, and the clump algorithm. Those are developed independently, then shown to be special cases of the direct-interaction approximation (DIA), which provides a central focus for the article. Various methods of renormalized perturbation theory are described, then unified with the aid of the generating-functional formalism of Martin, Siggia, and Rose. A general expression for the renormalized dielectric function is deduced and discussed in detail. Modern approaches such as decimation and PDF methods are described. Derivations of DIA-based Markovian closures are discussed. The eddy-damped quasinormal Markovian closure is shown to be nonrealizable in the presence of waves, and a new realizable Markovian closure is presented. The test-field model and a realizable modification thereof are also summarized. Numerical solutions of various closures for some plasma-physics paradigms are reviewed. The variational approach to bounds on transport is developed. Miscellaneous topics include Onsager symmetries for turbulence, the interpretation of entropy balances for both kinetic and fluid descriptions, self-organized criticality, statistical interactions between disparate scales, and the roles of both mean and random shear. Appendices are provided on Fourier transform conventions, dimensional and scaling analysis, the derivations of nonlinear gyrokinetic and gyrofluid equations, stochasticity criteria for quasilinear theory, formal aspects of resonance-broadening theory, Novikov's theorem, the treatment of weak inhomogeneity, the derivation of the Vlasov weak-turbulence wave kinetic equation from a fully renormalized description, some features of a code for solving the direct-interaction approximation and related Markovian closures, the details of the solution of the EDQNM closure for a solvable three-wave model, and the notation used in the article.

John A. Krommes

2001-02-16T23:59:59.000Z

357

Accepted, Nuclear Fusion, 1999 Turbulent Transport and Turbulence in Radiative I-Mode Plasmas in

Accepted, Nuclear Fusion, 1999 Turbulent Transport and Turbulence in Radiative I-Mode Plasmas of Physics University of Alberta Edmonton, Alberta Canada, T6G 2J1 1/4/00 17:25 PM #12;Accepted, Nuclear Fusion, 1999 1 Abstract First measurements of turbulence levels and turbulence-induced transport

California at San Diego, University of

358

Assessment of TurbulenceChemistry Interaction in Hypersonic Turbulent Boundary Layers

Assessment of TurbulenceÂChemistry Interaction in Hypersonic Turbulent Boundary Layers L. Duan of the turbulenceÂchemistry interaction are performed in hypersonic turbulent boundary layers using direct numerical simulation flowfields under typical hypersonic conditions representative of blunt-body and slender- body

MartĂn, Pino

359

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

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

MartĂn, Pino

360

Usage of turbulence for superresolved imaging

Science Journals Connector (OSTI)

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

Zalevsky, Zeev; Rozental, Shay; Meller, Moshe

2007-01-01T23:59:59.000Z

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

361

Flight–crash events in turbulence

Science Journals Connector (OSTI)

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

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

2014-01-01T23:59:59.000Z

362

Effects of Atmospheric Turbulence on Ballistic Testing

Science Journals Connector (OSTI)

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

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

2008-05-01T23:59:59.000Z

363

Property:Current Velocity Range(m/s) | Open Energy Information

Velocity Range(m/s) Velocity Range(m/s) Jump to: navigation, search Property Name Current Velocity Range(m/s) Property Type String Pages using the property "Current Velocity Range(m/s)" Showing 25 pages using this property. (previous 25) (next 25) 1 1.5-ft Wave Flume Facility + 0.0 + 10-ft Wave Flume Facility + 0.0 + 11-ft Wave Flume Facility + 0.0 + 2 2-ft Flume Facility + 0.0 + 3 3-ft Wave Flume Facility + 0.0 + 5 5-ft Wave Flume Facility + 0.0 + 6 6-ft Wave Flume Facility + 0.0 + A Alden Large Flume + 3.2 + Alden Small Flume + 0.0 + Alden Wave Basin + 0.0 + B Breakwater Research Facility + 0.0 + C Carderock Maneuvering & Seakeeping Basin + 0.0 + Carderock Tow Tank 2 + 0.0 + Carderock Tow Tank 3 + 0.0 + Chase Tow Tank + 0.0 + Coastal Harbors Modeling Facility + 0.0 +

364

Trapping and Frequency Variability in Electron Acoustic Waves

Trapping and Frequency Variability in Electron Acoustic Waves C.F. Driscoll, F. Anderegg, D 92093 USA Abstract. Electron Acoustic Waves (EAWs) with a phase velocity less than twice the plasma Langmuir waves, and at large excitations resonance is observed over a broad range. Laser Induced

California at San Diego, University of

365

Stimulated Neutrino Transformation Through Turbulence

We derive an analytical solution for the flavor evolution of a neutrino through a turbulent density profile which is found to accurately predict the amplitude and transition wavelength of numerical solutions on a case-by-case basis. The evolution is seen to strongly depend upon those Fourier modes in the turbulence which are approximately the same as the splitting between neutrino eigenvalues. Transitions are strongly enhanced by those Fourier modes in the turbulence which are approximately the same as the splitting between neutrino eigenvalues. We also find a suppression of transitions due to the long wavelength modes when the ratio of their amplitude and the wavenumber is of order, or greater than, the first root of the Bessel function $J_0$.

Kelly M. Patton; James P. Kneller; Gail C. McLaughlin

2014-04-15T23:59:59.000Z

366

Particle Velocity Distributions and Ionization Processes in a Gas-Puff Z Pinch

Science Journals Connector (OSTI)

We have measured the time-dependent radial velocity distributions of singly to five times ionized ions in an imploding plasma shell by observing the spectral shapes and intensities of emission lines in various directions. An ionization wave propagating much faster than the local radial ion velocities is observed. The ionization front velocity is found to be consistent with estimates of electron heat conduction into the plasma-neutral layer. The ionization and velocity histories of the particles are experimentally determined. The mechanisms of momentum transfer to the particles are also determined and compared with existing models.

M. E. Foord; Y. Maron; G. Davara; L. Gregorian; A. Fisher

1994-06-13T23:59:59.000Z

367

Stability Regimes of Turbulent Nitrogen-Diluted Hydrogen Jet Flames

One option for combustion in zero-emission Integrated Gasification Combined Cycle (IGCC) power plants is non-premixed combustion of nitrogen-diluted hydrogen in air. An important aspect to non-premixed combustion is flame stability or anchoring, though only a few fundamental stability studies of these flames have taken place to date. The following paper presents the results of experiments investigating the effects of nitrogen diluent fraction, jet diameter, and exit velocity on the static stability limits of a turbulent hydrogen jet flame issuing from a thin-lipped tube into a quiescent atmosphere. Four different stability limits are observed: detachment from the burner lip, reattachment to the burner lip, transition from a laminar lifted flame base to blowout or to a turbulent lifted flame, and transition from a turbulent lifted flame to blowout. The applicability of existing theories and correlations to the stability results is discussed. These results are an important step in assessing the viability of a non-premixed combustion approach using hydrogen diluted with nitrogen as a fuel.

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

2007-03-01T23:59:59.000Z

368

turbulent heat International Journal of Numerical

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

Lin, Wen-Wei

369

TURBULENCE IN SUPERSONIC AND HYPERSONIC BOUNDARY LAYERS

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

MartĂn, Pino

370

Protostellar Outflow Evolution in Turbulent Environments

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

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

2008-04-11T23:59:59.000Z

371

OTRC Wave Basin | Open Energy Information

OTRC Wave Basin OTRC Wave Basin Jump to: navigation, search Basic Specifications Facility Name OTRC Wave Basin Overseeing Organization Texas A&M (OTRC) Hydrodynamic Testing Facility Type Wave Basin Length(m) 45.7 Beam(m) 30.5 Depth(m) 5.8 Water Type Freshwater Cost(per day) $300/hour (excluding labor) Special Physical Features 4.6m wide x 9.1m long x 16.8m deep pit with adjustable depth floor in test area Towing Capabilities Towing Capabilities Yes Maximum Velocity(m/s) 0.6 Length of Effective Tow(m) 27.4 Wavemaking Capabilities Wavemaking Capabilities Yes Maximum Wave Height(m) 0.9 Maximum Wave Height(m) at Wave Period(s) 4.0 Maximum Wave Length(m) 25 Wave Period Range(s) 4.0 Current Velocity Range(m/s) 0.6 Programmable Wavemaking Yes Wavemaking Description GEDAP 3D wave generation software, 48 hinged flap wave generator

372

Anomalous electron heat transport driven by low frequency electromagnetic turbulence

We consider the anomalous electron and heat transport in a tokamak plasma. The electrons are described by the nonlinear drift-kinetic equation. We analyze transport through the averaged response function in the presence of drift-Alfven wave turbulence. In contrast to recent findings by Terry, Diamond, and Hahm, we conclude that magnetic fluctuations lead to a substantial transport of both parallel and perpendicular energies. The latter, previously neglected, is found to be significant and of the order of the test-particle diffusion.

Thoul, A.A.; Similon, P.L.; Sudan, R.N.

1987-09-28T23:59:59.000Z

373

This paper studies the turbulent cascade of magnetic energy in weakly collisional magnetized plasmas. A cascade model is presented, based on the assumptions of local nonlinear energy transfer in wavenumber space, critical balance between linear propagation and nonlinear interaction times, and the applicability of linear dissipation rates for the nonlinearly turbulent plasma. The model follows the nonlinear cascade of energy from the driving scale in the MHD regime, through the transition at the ion Larmor radius into the kinetic Alfven wave regime, in which the turbulence is dissipated by kinetic processes. The turbulent fluctuations remain at frequencies below the ion cyclotron frequency due to the strong anisotropy of the turbulent fluctuations, k_parallel cyclotron damping. The conditions under which the gyrokinetic cascade reaches the ion cyclotron frequency are established. Cascade model solutions imply that collisionless damping provides a natural explanation for the observed range of spectral indices in the dissipation range of the solar wind. The dissipation range spectrum is predicted to be an exponential fall off; the power-law behavior apparent in observations may be an artifact of limited instrumental sensitivity. The cascade model is motivated by a programme of gyrokinetic simulations of turbulence and particle heating in the solar wind.

Gregory G. Howes; Steven C. Cowley; William Dorland; Gregory W. Hammett; Eliot Quataert; Alexander A. Schekochihin

2007-07-20T23:59:59.000Z

374

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

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

375

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

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

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

2002-07-01T23:59:59.000Z

376

Saturation of radiation-induced parametric instabilities by excitation of Langmuir turbulence

Progress made in the last few years in the calculation of the saturation spectra of parametric instabilities which involve Langmuir daughter waves will be reviewed. These instabilities include the ion acoustic decay instability, the two plasmon decay instability (TPDI), and stimulated Raman scattering (SRS). In particular I will emphasize spectral signatures which can be directly compared with experiment. The calculations are based on reduced models of driven Laugmuir turbulence. Thomson scattering from hf-induced Langmuir turbulence in the unpreconditioned ionosphere has resulted in detailed agreement between theory and experiment at early times. Strong turbulence signatures dominate in this regime where the weak turbulence approximation fails completely. Recent experimental studies of the TPDI have measured the Fourier spectra of Langmuir waves as well as the angular and frequency, spectra of light emitted near 3/2 of the pump frequency again permitting some detailed comparisons with theory. The experiments on SRS are less detailed but by Thomson scattering the secondary decay of the daughter Langmuir wave has been observed. Scaling laws derived from a local model of SRS saturation are compared with full simulations and recent Nova experiments.

Dubois, D.F.; Rose, H.A. [Los Alamos National Lab., NM (United States); Russell, D. [Lodestar Research Inc., Boulder, CO (United States)

1995-12-01T23:59:59.000Z

377

Âmediated turbulence is caused by the Doppler effect on the traveling waves. The observations are in good accord mechaÂ nisms do not account for cardiac fibrillation [13], while the Doppler effect we have observed to DefectÂMediated Turbulence Driven by a Doppler Instability Qi Ouyang, 1, * Harry L. Swinney, 2,+ and Ge

Texas at Austin. University of

378

Magnetic helicity signature produced by cross-field 2D turbulence

Hybrid numerical simulations of freely decaying 2D turbulence are presented. The background magnetic field is perpendicular to the simulation plane, which eliminates linear kinetic Alfven waves from the system. The normalized magnetic helicity of the initial large-scale fluctuations is zero, while the normalized cross-helicity is not. As the turbulence evolves, it develops nonzero magnetic helicity at smaller scales, in the proton kinetic range. In the quasi-steady state of evolution, the magnetic helicity spectrum has a peak consistent with the solar wind observations.

Markovskii, S. A.; Vasquez, Bernard J. [Space Science Center, Institute for the Study of Earth, Oceans, and Space, and Department of Physics, University of New Hampshire, Durham, NH 03824 (United States)

2013-06-13T23:59:59.000Z

379

Magnetic-field-line random walk in turbulence: A two-point correlation function description

Science Journals Connector (OSTI)

The standard theory of field-line random walk is based on the description of turbulence in the wave number space. The latter description takes into account the details of turbulence at small scales. Such details, however, are not important in the theory of random walking magnetic field lines. In the present paper we therefore use simple decorrelation models to estimate the field-line diffusion coefficient. Previous results are recovered as special limits. It is shown that a full analytical description is possible and that the only parameter controlling the field-line diffusion coefficient is the Kubo number.

A. Shalchi; A. Dosch; J. A. le Roux; G. M. Webb; G. P. Zank

2012-02-28T23:59:59.000Z

380

Magnetic helicity signature produced by cross-field 2D turbulence

Science Journals Connector (OSTI)

Hybrid numerical simulations of freely decaying 2D turbulence are presented. The background magnetic field is perpendicular to the simulation plane which eliminates linear kinetic Alfvén waves from the system. The normalized magnetic helicity of the initial large-scale fluctuations is zero while the normalized cross-helicity is not. As the turbulence evolves it develops nonzero magnetic helicity at smaller scales in the proton kinetic range. In the quasi-steady state of evolution the magnetic helicity spectrum has a peak consistent with the solar wind observations.

2013-01-01T23:59:59.000Z

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

381

simulation of turbulent sediment transport O. DurĂˇn (1,2) , B. Andreotti (1) , P. Claudin (1) 1. Laboratoire Carolina 27515, USA Abstract Sediment transport is studied by means of two phase numerical simulations to empirical transport laws. The vertical velocities of the grains are small and sediment transport occurs

Claudin, Philippe

382

, the velocity and concentration field measurements using the developed two-phase PIV and LIF methods are applied for a bubble plume in a density-stratified ambient. The turbulent flow characteristics induced by a bubble plume in a stratified ambient water...

Seol, Dong Guan

2009-05-15T23:59:59.000Z

383

Particle pinch and collisionality in gyrokinetic simulations of tokamak plasma turbulence

The generic problem of how, in a turbulent plasma, the experimentally relevant conditions of a particle flux very close to the null are achieved, despite the presence of strong heat fluxes, is addressed. Nonlinear gyrokinetic simulations of plasma turbulence in tokamaks reveal a complex dependence of the particle flux as a function of the turbulent spatial scale and of the velocity space as collisionality is increased. At experimental values of collisionality, the particle flux is found close to the null, in agreement with the experiment, due to the balance between inward and outward contributions at small and large scales, respectively. These simulations provide full theoretical support to the prediction of a peaked density profile in a future nuclear fusion reactor.

Angioni, C. [IPP-EURATOM Association, Max-Planck-Institut fuer Plasmaphysik, D-85748 Garching (Germany); Candy, J.; Waltz, R. E. [General Atomics, San Diego, California 92121 (United States); Fable, E.; Maslov, M.; Weisen, H. [Centre de Recherches en Physique des Plasmas, Association Euratom-Confederation Suisse, EPFL, 1015 Lausanne (Switzerland); Peeters, A. G. [Department of Physics, Center for Fusion, Space and Astrophysics, University of Warwick, CV4 7AL Coventry (United Kingdom)

2009-06-15T23:59:59.000Z

384

Collision-dependent power law scalings in 2D gyrokinetic turbulence

Nonlinear gyrokinetics provides a suitable framework to describe short-wavelength turbulence in magnetized laboratory and astrophysical plasmas. In the electrostatic limit, this system is known to exhibit a free energy cascade towards small scales in (perpendicular) real and/or velocity space. The dissipation of free energy is always due to collisions (no matter how weak the collisionality), but may be spread out across a wide range of scales. Here, we focus on freely-decaying 2D electrostatic turbulence on sub-ion-gyroradius scales. An existing scaling theory for the turbulent cascade in the weakly collisional limit is generalized to the moderately collisional regime. In this context, non-universal power law scalings due to multiscale dissipation are predicted, and this prediction is confirmed by means of direct numerical simulations.

Cerri, S S; Jenko, F; Told, D

2014-01-01T23:59:59.000Z

385

Collision-dependent power law scalings in two dimensional gyrokinetic turbulence

Nonlinear gyrokinetics provides a suitable framework to describe short-wavelength turbulence in magnetized laboratory and astrophysical plasmas. In the electrostatic limit, this system is known to exhibit a free energy cascade towards small scales in (perpendicular) real and/or velocity space. The dissipation of free energy is always due to collisions (no matter how weak the collisionality), but may be spread out across a wide range of scales. Here, we focus on freely decaying two dimensional electrostatic turbulence on sub-ion-gyroradius scales. An existing scaling theory for the turbulent cascade in the weakly collisional limit is generalized to the moderately collisional regime. In this context, non-universal power law scalings due to multiscale dissipation are predicted, and this prediction is confirmed by means of direct numerical simulations.

Cerri, S. S., E-mail: silvio.sergio.cerri@ipp.mpg.de; Bańón Navarro, A.; Told, D. [Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Jenko, F. [Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Max-Planck/Princeton Center for Plasma Physics (Germany)

2014-08-15T23:59:59.000Z

386

Direct numerical investigation of detonation waves using a Monte Carlo method.

??A detonation wave describes a shock that propagates at supersonic velocity through a chemically unstable gas medium and is driven by the energy released by… (more)

O'Connor, Patrick

2008-01-01T23:59:59.000Z

387

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

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

Lin, Zhihong

2014-03-13T23:59:59.000Z

388

An observational study of turbulence in the SPBL

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

Kurzeja, R.

1997-09-01T23:59:59.000Z

389

Spectral Cascade and Energy Dissipation in Kinetic Alfven Wave Turbulence

zhihongl@uci.edu Department of Physics and Astronomy, University of California, Irvine, California 92697 magnetic field (Bieber, J. W. et al 1996; Podesta, J. J. 2009). Consistent with observations in the solar

Lin, Zhihong

390

Turbulence and internal waves in tidal flow over topography

water, so as to avoid an unnecessary increase in computational grid points. Simulations at subcritical

Gayen, Bishakhdatta

2012-01-01T23:59:59.000Z

391

Turbulence and internal waves in tidal flow over topography

Haren, H. 2007 Internal tides and energy fluxes over greatInternal tides are susceptible to dissipation and energysemidiurnal tide, suggesting direct energy transfer from the

Gayen, Bishakhdatta

2012-01-01T23:59:59.000Z

392

Turbulent Flow and Transport Modeling by Long Waves and Currents

mixing simulation is developed based on the ?-coordinate grid system. In Chapter VI, the conclusions of this study are presented. Also included are suggestions for the future and further studies. 7 CHAPTER II BOUSSINESQ EQUATIONS FOR WEAKLY... mixing simulation is developed based on the ?-coordinate grid system. In Chapter VI, the conclusions of this study are presented. Also included are suggestions for the future and further studies. 7 CHAPTER II BOUSSINESQ EQUATIONS FOR WEAKLY...

Kim, Dae Hong

2010-10-12T23:59:59.000Z

393

Ultrasonic guided waves in eccentric annular pipes

This paper studies the feasibility of using ultrasonic guided waves to rapidly inspect tubes and pipes for possible eccentricity. While guided waves are well established in the long range inspection of structures such as pipes and plates, studies for more complex cross sections are limited and analytical solutions are often difficult to obtain. Recent developments have made the Semi Analytical Finite Element (SAFE) method widely accessible for researchers to study guided wave properties in complex structures. Here the SAFE method is used to study the effect of eccentricity on the modal structures and velocities of lower order guided wave modes in thin pipes of diameters typically of interest to the industry. Results are validated using experiments. The paper demonstrates that even a small eccentricity in the pipe can strongly affect guided wave mode structures and velocities and hence shows potential for pipe eccentricity inspection.

Pattanayak, Roson Kumar; Balasubramaniam, Krishnan; Rajagopal, Prabhu [Centre for NDE, Indian Institute of Technology - Madras Chennai 600036, T. N. (India)

2014-02-18T23:59:59.000Z

394

Proton heating by parallel Alfven wave cascade

In a recent series of papers, the present authors developed a kinetic theory for low-frequency turbulence propagating parallel to the ambient magnetic field. Making use of this theory, it was shown that low-frequency Alfvenic turbulence may cascade to ion-cyclotron frequency range and beyond by nonlinear three-wave decay processes. The significance of such a finding is that it may lead to the proton heating by cyclotron resonance. However, the actual proton heating process was not demonstrated. The present paper complements the previous works by including the proton heating in the discussion. It is found that the left-hand circularly polarized Alfven-cyclotron turbulence leads to a moderate heating of the protons in the perpendicular direction and cooling in the parallel direction. It is also found that ion-acoustic turbulence is generated by the decay instability process. Finally, the heating rate is shown to increase in inverse proportion to the time scale of the wave source.

Yoon, P. H.; Fang, T.-M. [Massachusetts Technological Laboratory, Inc., 330 Pleasant Street, Belmont, Massachusetts 02478 (United States)

2009-06-15T23:59:59.000Z

395

Seismic Shear Waves in Deep Seismic Reflection Surveys: Some Notes on Problems and Profits

Science Journals Connector (OSTI)

—Shear (S) waves differ from compressional (P) waves because of their lower propagation velocities, their lower frequencies and due to the different character of their particle motion. The move-out of travel-time...

E. Lüschen

1999-09-01T23:59:59.000Z

396

The Response of an Open Stratospheric Balloon to the Presence of Inertio-Gravity Waves

Science Journals Connector (OSTI)

Analytic solutions for the vertical response of an open stratospheric balloon to the presence of inertio-gravity waves during its descent are obtained. Monochromatic waves with simultaneous variations in density, velocity, and temperature are ...

P. Alexander; J. Cornejo; A. De la Torre

1996-01-01T23:59:59.000Z

397

Quantitative imaging of the air-water flow fields formed by unsteady breaking waves

An experimental method for simultaneously measuring the velocity fields on the air and water side of unsteady breaking waves is presented. The method is applied to breaking waves to investigate the physics of the air and ...

Belden, Jesse (Jesse Levi)

2009-01-01T23:59:59.000Z

398

Guided Wave Propagation in Tubular Section with Multi-Layered Viscoelastic Coating

. The dispersion of phase velocity and wave attenuation for coated pipes are evaluated against a baseline model which is the bare, uncoated tubing to establish the propagation characteristics of the guided shear and longitudinal waves in the presence of multiple...

Kuo, Chi-Wei 1982-

2012-11-16T23:59:59.000Z

399

Just as the transversely isotropic model with a vertical symmetry axis (VTI media) is typical for describing horizontally layered sediments, transverse isotropy with a tilted symmetry axis (TTI) describes dipping TI layers (such as tilted shale beds near salt domes) or crack systems. P-wave kinematic signatures in TTI media are controlled by the velocity V{sub PO} in the symmetry direction, Thomsen's anisotropic coefficients {xi} and {delta}, and the orientation (tilt {nu} and azimuth {beta}) of the symmetry axis. Here, the authors show that all five parameters can be obtained from azimuthally varying P-wave NMO velocities measured for two reflectors with different dips and/or azimuths (one of the reflectors can be horizontal). The shear-wave velocity V{sub SO} in the symmetry direction, which has negligible influence on P-wave kinematic signatures, can be found only from the moveout of shear waves. Using the exact NMO equation, the authors examine the propagation of errors in observed moveout velocities into estimated values of the anisotropic parameters and establish the necessary conditions for a stable inversion procedure. Since the azimuthal variation of the NMO velocity is elliptical, each reflection event provides them with up to three constraints on the model parameters. Generally, the five parameters responsible for P-wave velocity can be obtained from two P-wave ellipses, but the feasibility of the moveout inversion strongly depends on the tilt {nu}. While most of the analysis is carried out for a single layer, the authors also extend the inversion algorithm to vertically heterogeneous TTI media above a dipping reflector using the generalized Dix equation. A synthetic example for a strongly anisotropic, stratified TTI medium demonstrates a high accuracy of the inversion.

Grechka, V.; Tsvankin, I.

2000-02-01T23:59:59.000Z

400

DeFrees Small Wave Basin | Open Energy Information

Wave Basin Wave Basin Jump to: navigation, search Basic Specifications Facility Name DeFrees Small Wave Basin Overseeing Organization Cornell University Hydrodynamics Hydrodynamic Testing Facility Type Wave Basin Length(m) 15.0 Beam(m) 0.8 Depth(m) 0.9 Water Type Freshwater Towing Capabilities Towing Capabilities None Wavemaking Capabilities Wavemaking Capabilities Yes Maximum Wave Height(m) 0.3 Maximum Wave Height(m) at Wave Period(s) 3.0 Maximum Wave Length(m) 30 Wave Period Range(s) 3.0 Current Velocity Range(m/s) 0.0 Programmable Wavemaking Yes Wavemaking Description Computer controlled hydraulic paddle, arbitrary wave shape possible Wave Direction Uni-Directional Simulated Beach Yes Description of Beach 1:10 sloping glass with dissipative horsehair covering if needed

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

401

Turbulent phenomena in protein folding

Science Journals Connector (OSTI)

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

Igor V. Kalgin and Sergei F. Chekmarev

2011-01-31T23:59:59.000Z

402

Lithospheric Velocity Structure of the Anatolain plateau-Caucasus-Caspian Regions

Anatolian Plateau-Caucasus-Caspian region is an area of complex structure accompanied by large variations in seismic wave velocities. Despite the complexity of the region little is known about the detailed lithospheric structure. Using data from 29 new broadband seismic stations in the region, a unified velocity structure is developed using teleseismic receiver functions and surface waves. Love and Rayleigh surface waves dispersion curves have been derived from event-based analysis and ambient-noise correlation. We jointly inverted the receiver functions with the surface wave dispersion curves to determine absolute shear wave velocity and important discontinuities such as sedimentary layer, Moho, lithospheric-asthenospheric boundary. We combined these new station results with Eastern Turkey Seismic Experiment results (29 stations). Caspian Sea and Kura basin underlained by one of the thickest sediments in the world. Therefore, short-period surface waves are observed to be very slow. The strong crustal multiples in receiver functions and the slow velocities in upper crust indicate the presence of thick sedimentary unit (up to 20 km). Crustal thickness varies from 34 to 52 km in the region. The thickest crust is in Lesser Caucasus and the thinnest is in the Arabian Plate. The lithospheric mantle in the Greater Caucasus and the Kura depression is faster than the Anatolian Plateau and Lesser Caucasus. This possibly indicates the presence of cold lithosphere. The lower crust is slowest in the northeastern part of the Anatolian Plateau where Holocene volcanoes are located.

Gok, R; Mellors, R J; Sandvol, E; Pasyanos, M; Hauk, T; Yetirmishli, G; Teoman, U; Turkelli, N; Godoladze, T; Javakishvirli, Z

2009-04-15T23:59:59.000Z

403

Teleseismic evidence for a low-velocity body under the Coso geothermal area

Teleseismic evidence for a low-velocity body under the Coso geothermal area Teleseismic evidence for a low-velocity body under the Coso geothermal area Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Journal Article: Teleseismic evidence for a low-velocity body under the Coso geothermal area Details Activities (1) Areas (1) Regions (0) Abstract: Teleseismic P wave arrivals were recorded by a dense array of seismograph stations located in the Coso geothermal area, California. The resulting pattern of relative residuals an area showing approximately 0.2-s excess travel time that migrates with changing source azimuth, suggesting that the area is the 'delay shadow' produced by a deep, low-velocity body. Inversion of the relative residual data for three-dimensional velocity structure determines the lateral variations in velocity to a depth of 22.5

404

Original articles: Intelligent multichannel sensors for pulse wave analysis

Science Journals Connector (OSTI)

Aortic pulse wave velocity is an independent predictive indicator for all cause mortality and cardiovascular morbidity. Unfortunately it is only invasively accessible and thus the A. carotis-A. femoralis pulse wave velocity (cfPWV) is recommended as ... Keywords: Arterial stiffness, BP, Cardiovascular risk, ECG, Electrocardiography, FIR, ICA, INA, Idxao, Idxo, Idxs, LED, PTT, PW, PWV, Pulse transit time, Pulse wave velocity, SD, cfPWV, dBP, p'(Idxo), p'(Idxs), p(Idxo), p(Idxs), sBP

S. Rosenkranz; C. Mayer; J. Kropf; S. Wassertheurer

2011-11-01T23:59:59.000Z

405

Velocity Distributions from Nonextensive Thermodynamics

There is no accepted mechanism that explains the equilibrium structures that form in collisionless cosmological N-body simulations. Recent work has identified nonextensive thermodynamics as an innovative approach to the problem. The distribution function that results from adopting this framework has the same form as for polytropes, but the polytropic index is now related to the degree of nonextensiveness. In particular, the nonextensive approach can mimic the equilibrium structure of dark matter density profiles found in simulations. We extend the investigation of this approach to the velocity structures expected from nonextensive thermodynamics. We find that the nonextensive and simulated N-body rms-velocity distributions do not match one another. The nonextensive rms-velocity profile is either monotonically decreasing or displays little radial variation, each of which disagrees with the rms-velocity distributions seen in simulations. We conclude that the currently discussed nonextensive models require further modifications in order to corroborate dark matter halo simulations. (adapted from TeX)

Eric I. Barnes; Liliya L. R. Williams; Arif Babul; Julianne J. Dalcanton

2006-10-05T23:59:59.000Z

406

Small-scale Interaction of Turbulence with Thermonuclear Flames in Type Ia Supernovae

Microscopic turbulence-flame interactions of thermonuclear fusion flames occuring in Type Ia Supernovae were studied by means of incompressible direct numerical simulations with a highly simplified flame description. The flame is treated as a single diffusive scalar field with a nonlinear source term. It is characterized by its Prandtl number, Pr << 1, and laminar flame speed, S_L. We find that if S_L ~ u', where u' is the rms amplitude of turbulent velocity fluctuations, the local flame propagation speed does not significantly deviate from S_L even in the presence of velocity fluctuations on scales below the laminar flame thickness. This result is interpreted in the context of subgrid-scale modeling of supernova explosions and the mechanism for deflagration-detonation-transitions.

J. C. Niemeyer; W. K. Bushe; G. R. Ruetsch

1999-05-07T23:59:59.000Z

407

APRIL 2006 MOUM ET. AL. 1 Energy Transport by Nonlinear Internal Waves

APRIL 2006 MOUM ET. AL. 1 Energy Transport by Nonlinear Internal Waves J. N. MOUM1 , J. M. KLYMAK2. The energy transported by these waves includes a nonlinear advection term uE that is negligible in linear internal waves. Unlike linear internal waves, the pressure-velocity energy flux up includes important

408

SEPTEMBER 2006 MOUM ET. AL. 1 Energy Transport by Nonlinear Internal Waves

SEPTEMBER 2006 MOUM ET. AL. 1 Energy Transport by Nonlinear Internal Waves J. N. MOUM1 , J. M of coastline. The energy transported by these waves includes a nonlinear advection term uE that is negligible in linear internal waves. Unlike linear internal waves, the pressure-velocity energy flux up includes

409

Gas Density Fluctuations in the Perseus Cluster: Clumping Factor and Velocity Power Spectrum

X-ray surface brightness fluctuations in the core of the Perseus Cluster are analyzed, using deep observations with the Chandra observatory. The amplitude of gas density fluctuations on different scales is measured in a set of radial annuli. It varies from 8 to 12 per cent on scales of ~10-30 kpc within radii of 30-160 kpc from the cluster center and from 9 to 7 per cent on scales of ~20-30 kpc in an outer, 60-220 kpc annulus. Using a statistical linear relation between the observed amplitude of density fluctuations and predicted velocity, the characteristic velocity of gas motions on each scale is calculated. The typical amplitudes of the velocity outside the central 30 kpc region are 90-140 km/s on ~20-30 kpc scales and 70-100 km/s on smaller scales ~7-10 kpc. The velocity power spectrum is consistent with cascade of turbulence and its slope is in a broad agreement with the slope for canonical Kolmogorov turbulence. The gas clumping factor estimated from the power spectrum of the density fluctuations is low...

Zhuravleva, I; Arevalo, P; Schekochihin, A A; Allen, S W; Fabian, A C; Forman, W R; Sanders, J S; Simionescu, A; Sunyaev, R; Vikhlinin, A; Werner, N

2015-01-01T23:59:59.000Z

410

Statistically Steady Turbulence in Soap Films: Direct Numerical Simulations with Ekman Friction

We present a detailed direct numerical simulation (DNS) designed to investigate the combined effects of walls and Ekman friction on turbulence in forced soap films. We concentrate on the forward-cascade regime and show how to extract the isotropic parts of velocity and vorticity structure functions and thence the ratios of multiscaling exponents. We find that velocity structure functions display simple scaling whereas their vorticity counterparts show multiscaling; and the probability distribution function of the Weiss parameter $\\Lambda$, which distinguishes between regions with centers and saddles, is in quantitative agreement with experiments.

Prasad Perlekar; Rahul Pandit

2008-11-09T23:59:59.000Z

411

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

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

Gutierrez Torres, Claudia del Carmen

2005-11-01T23:59:59.000Z

412

An anisotropic-Alfvenic-turbulence-based solar wind model with proton temperature anisotropy

How the solar wind is accelerated to its supersonic speed is intimately related to how it is heated. Mechanisms based on ion-cyclotron resonance have been successful in explaining a large number of observations, those concerning the significant ion temperature anisotropy above coronal holes in particular. However, they suffer from the inconsistency with turbulence theory which says that the turbulent cascade in a low-beta medium like the solar corona should proceed in the perpendicular rather than the parallel direction, meaning that there is little energy in the ion gyro-frequency range for ions to absorb via ion-cyclotron resonance. Recently a mechanism based on the interaction between the solar wind particles and the anisotropic turbulence has been proposed, where the perpendicular proton energy addition is via the stochastic heating (Chandran et al. 2011). We extend this promising mechanism by properly accounting for the effect of proton temperature anisotropy on the propagation of Alfven waves, for the r...

Li, Bo

2012-01-01T23:59:59.000Z

413

The Bandt-Pompe permutation entropy and the Jensen-Shannon statistical complexity are used to analyze fluctuating time series of three different plasmas: the magnetohydrodynamic (MHD) turbulence in the plasma wind tunnel of the Swarthmore Spheromak Experiment (SSX), drift-wave turbulence of ion saturation current fluctuations in the edge of the Large Plasma Device (LAPD) and fully-developed turbulent magnetic fluctuations of the solar wind taken from the WIND spacecraft. The entropy and complexity values are presented as coordinates on the CH plane for comparison among the different plasma environments and other fluctuation models. The solar wind is found to have the highest permutation entropy and lowest statistical complexity of the three data sets analyzed. Both laboratory data sets have larger values of statistical complexity, suggesting these systems have fewer degrees of freedom in their fluctuations, with SSX magnetic fluctuations having slightly less complexity than the LAPD edge fluctuations. The CH ...

Weck, Peter J; Brown, Michael R; Wicks, Robert T

2014-01-01T23:59:59.000Z

414

Turbulent equipartitions in two dimensional drift convection

Unlike the thermodynamic equipartition of energy in conservative systems, turbulent equipartitions (TEP) describe strongly non-equilibrium systems such as turbulent plasmas. In turbulent systems, energy is no longer a good invariant, but one can utilize the conservation of other quantities, such as adiabatic invariants, frozen-in magnetic flux, entropy, or combination thereof, in order to derive new, turbulent quasi-equilibria. These TEP equilibria assume various forms, but in general they sustain spatially inhomogeneous distributions of the usual thermodynamic quantities such as density or temperature. This mechanism explains the effects of particle and energy pinch in tokamaks. The analysis of the relaxed states caused by turbulent mixing is based on the existence of Lagrangian invariants (quantities constant along fluid-particle or other orbits). A turbulent equipartition corresponds to the spatially uniform distribution of relevant Lagrangian invariants. The existence of such turbulent equilibria is demonstrated in the simple model of two dimensional electrostatically turbulent plasma in an inhomogeneous magnetic field. The turbulence is prescribed, and the turbulent transport is assumed to be much stronger than the classical collisional transport. The simplicity of the model makes it possible to derive the equations describing the relaxation to the TEP state in several limits.

Isichenko, M.B.; Yankov, V.V. [Univ. of California, Santa Barbara, CA (United States). Inst. for Theoretical Physics

1995-07-25T23:59:59.000Z

415

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

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

A. Lazarian; J. Cho

2003-02-05T23:59:59.000Z

416

On Deviations from Gaussian Statistics for Surface Gravity Waves

Here we discuss some issues concerning the statistical properties of ocean surface waves. We show that, using the approach of weak turbulence theory, deviations from Gaussian statistics can be naturally included. In particular we discuss the role of bound and free modes for the determination of the statistical properties of the surface elevation. General formulas for skewness and kurtosis as a function of the spectral wave action density are here derived.

M. Onorato; A. R. Osborne; M. Serio

2005-03-31T23:59:59.000Z

417

Science Journals Connector (OSTI)

wave energy ? Wellenenergie f [Die einer Schwerewelle innewohnende potentielle und kinetische Energie. Sie ist etwa proportional dem Quadrat der Wellenhöhe. Zeichen: E we ...

2014-08-01T23:59:59.000Z

418

Site-Specific Velocity and Density Model for the Waste Treatment Plant, Hanford, Washington.

This report documents the work conducted under the SBP to develop a shear wave and compressional wave velocity and density model specific to the WTP site. Section 2 provides detailed background information on the WTP site and its underlying geology as well as on the Seismic Boreholes Project activities leading up to the Vs and Vp measurements. In Section 3, methods employed and results obtained are documented for measurements of Vs and Vp velocities in basalts and interbeds. Section 4 provides details on velocity measurements in the sediments underlying the WTP. Borehole gravity measurements of density of the subsurface basalt and sediments are described in Section 5. Section 6 describes the analysis of data presented in section 3-5, and presents the overall velocity and density model for the WTP site.

Rohay, Alan C.; Brouns, Thomas M.

2007-06-27T23:59:59.000Z

419

Reflective ghost imaging through turbulence

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

420

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

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

2013-12-15T23:59:59.000Z

While these samples are representative of the content of NLE

they are not comprehensive nor are they the most current set.

We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

421

Nonlinear wave evolution in the expanding solar wind

Science Journals Connector (OSTI)

We report here on a numerical model allowing direct numerical simulations of magnetohydrodynamic fluctuations advected by the expanding solar wind. We show that the expansion of the plasma delays and possibly freezes the turbulent evolution, but that it also triggers the nonlinear evolution of otherwise stable (Alfvén) waves, which can thus release their energy in the wind.

Roland Grappin; Marco Velli; André Mangeney

1993-04-05T23:59:59.000Z

422

BENCAP, LLC: CAPSULE VELOCITY TEST

Ben Cap, LLC, has a technology that utilizes bebtonite to plug wells. The bentonite is encapsulated in a cardboard capsule, droped down to the bottom of the well where it is allowed to hydrate, causing the bentonite to expand and plug the well. This method of plugging a well is accepted in some, but not all states. This technology can save a significant amount of money when compared to cementing methods currently used to plug and abandon wells. The test objective was to obtain the terminal velocity of the capsule delivery system as it drops through a column of water in a wellbore. Once the terminal velocity is known, the bentonite swelling action can be timed not to begin swelling until it reaches the bottom of the well bore. The results of the test showed that an average speed of 8.93 plus or minus 0.12 ft/sec was achieved by the capsule as it was falling through a column of water. Plotting the data revealed a very linear function with the capsules achieving terminal velocity shortly after being released. The interference of the capsule impacting the casing was not readily apparent in any of the runs, but a siginal sampling anomaly was present in one run. Because the anomaly was so brief and not present in any of the other runs, no solid conclusions could be drawn. Additional testing would be required to determine the effects of capsules impacting a fluid level that is not at surface.

Meidinger, Brian

2005-09-07T23:59:59.000Z

423

Quantifying Turbulence for Tidal Power Applications

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

424

Odor Landscapes in Turbulent Environments

Science Journals Connector (OSTI)

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

Antonio Celani; Emmanuel Villermaux; Massimo Vergassola

2014-10-28T23:59:59.000Z

425

As an example of the unification of gravitation and particle physics, an exact solution of the five-dimensional field equations is studied which describes waves in the classical Einstein vacuum. While the solution is essentially 5D in nature, the waves exist in ordinary 3D space, and may provide a way to test for an extra dimension.

Paul S. Wesson

2012-12-11T23:59:59.000Z

426

Two techniques for forecasting clear air turbulence

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

Arbeiter, Randolph George

2012-06-07T23:59:59.000Z

427

High-Frequency Internal Waves on the Oregon Continental Shelf

Science Journals Connector (OSTI)

Measurements of vertical velocity by isopycnal-following, neutrally buoyant floats deployed on the Oregon shelf during the summers of 2000 and 2001 were used to characterize internal gravity waves on the shelf using measurements of vertical ...

Eric A. D’Asaro; Ren-Chieh Lien; Frank Henyey

2007-07-01T23:59:59.000Z

428

Fine-Scale Zonal Flow Suppression of Electron Temperature Gradient Turbulence

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

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

2006-11-30T23:59:59.000Z

429

Effect of Turbulence Fluctuations on Surface Heating Rate in Hypersonic Turbulent

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

MartĂn, Pino

430

Study of turbulence-chemistry interaction in hypersonic turbulent boundary layers

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

MartĂn, Pino

431

Heat release effects on decaying homogeneous compressible turbulence

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

Lee, Kurn Chul

2009-05-15T23:59:59.000Z

432

COHERENT STRUCTURES IN PLASMA TURBULENCE: PERSISTENCE, INTERMITTENCY...

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

TURBULENCE: PERSISTENCE, INTERMITTENCY, AND CONNECTIONS WITH OBSERVATIONS by Kurt W. Smith A dissertation submitted in partial fulfillment of the requirements for the degree of...

433

MHL 2D Wind/Wave | Open Energy Information

MHL 2D Wind/Wave MHL 2D Wind/Wave Jump to: navigation, search Basic Specifications Facility Name MHL 2D Wind/Wave Overseeing Organization University of Michigan Hydrodynamics Hydrodynamic Testing Facility Type Tunnel Length(m) 35.1 Beam(m) 0.7 Depth(m) 1.2 Cost(per day) $2000 (+ Labor/Materials) Towing Capabilities Towing Capabilities None Wavemaking Capabilities Wavemaking Capabilities Yes Maximum Wave Height(m) 0.2 Wave Period Range(s) 0.0 Current Velocity Range(m/s) 0.0 Programmable Wavemaking Yes Wavemaking Description Regular and irregular wave spectrum Wave Direction Uni-Directional Simulated Beach Yes Description of Beach Removable beach Channel/Tunnel/Flume Channel/Tunnel/Flume Yes Recirculating No Wind Capabilities Wind Capabilities Yes Wind Velocity Range(m/s) 20.4

434

University of Iowa Wave Basin | Open Energy Information

University of Iowa Wave Basin University of Iowa Wave Basin Overseeing Organization University of Iowa Hydrodynamic Testing Facility Type Wave Basin Length(m) 40.0 Beam(m) 20.0 Depth(m) 3.0 Cost(per day) Contact POC Special Physical Features Towed 3DPIV; contactless motion tracking; free surface measurement mappingv Towing Capabilities Towing Capabilities Yes Maximum Velocity(m/s) 2.5 Length of Effective Tow(m) 25.0 Wavemaking Capabilities Wavemaking Capabilities Yes Maximum Wave Height(m) 0.6 Wave Period Range(s) 0.0 Current Velocity Range(m/s) 0.0 Programmable Wavemaking Yes Wavemaking Description Fully programmable for regular or irregular waves Wave Direction Uni-Directional Simulated Beach Yes Description of Beach Trusses overlaid with lattice and matting Channel/Tunnel/Flume

435

Predicting velocities and turbulent exchange in isolated street canyons and at a neighborhood scale

Urban planners need a fast, simple model to assess the impact of early design phase iterations of neighborhood layout on the microclimate. Specifically, this model should be able to predict the expected urban heat island ...

Hall, Terianne C

2010-01-01T23:59:59.000Z

436

Wave-particle interaction and Hamiltonian dynamics investigated in a traveling wave tube

For wave-particle interaction studies, the one-dimensional (1-D) beam-plasma system can be advantageously replaced by a Traveling Wave Tube (TWT). This led us to a detailed experimental analysis of the self-consistent interaction between unstable waves and a small either cold or warm beam. More recently, a test electron beam has been used to observe its non-self-consistent interaction with externally excited wave(s). The velocity distribution function of the electron beam is investigated with a trochoidal energy analyzer that records the beam energy distribution at the output of the TWT. An arbitrary waveform generator is used to launch a prescribed spectrum of waves along the slow wave structure (a 4 m long helix) of the TWT. The nonlinear synchronization of particles by a single wave responsible for Landau damping is observed. The resonant velocity domain associated to a single wave is also observed, as well as the transition to large-scale chaos when the resonant domains of two waves and their secondary resonances overlap leading to a typical 'devil's staircase' behavior. A new strategy for the control of chaos is tested.

Doveil, Fabrice; Macor, Alessandro [Physique des Interactions Ioniques et Moleculaires, Unite 6633 CNRS-Universite de Provence, Equipe Turbulence Plasma, Case 321, Centre de Saint-Jerome, F-13397 Marseille cedex 20 (France)

2006-05-15T23:59:59.000Z

437

Bending waves due to a moving harmonic force.

Science Journals Connector (OSTI)

In many structurally induced and flow?induced vibration problems the harmonic forcing function is not stationary but moves with a velocity V 0. The effect of the forcing function velocity V 0 upon the free vibrational wave?number characteristics of a membrane and a plate is analyzed. The Mach numberM is defined to be the ratio of the velocity V 0 to the wave speed of the bending waves. For the membrane the effect of the Mach number is to increase the wave number (shorter wavelength) ahead of the forcing function and to decrease the wave number (longer wavelength) behind it. At supersonic speeds no disturbances travel ahead of the forcing function and both wave numbers lead to trailing waves. These results are equivalent to the classical Doppler?shifted results. The results of the plate are more complex. The right and left traveling waves retain their basic properties with the magnitude of the wave number changing monotomically as a function of the Mach numberM. The near?field decaying disturbances also retain their basic properties but immediately obtain components that induce the decaying disturbances to become left traveling waves with decaying components. At Mach numbers greater than 2 these disturbances become pure waves trailing without any decaying factor. The importance of each of these components as a function of the Mach number is discussed.

Mauro Pierucci

1992-01-01T23:59:59.000Z

438

Compressional-wave and shear-wave velocities from long-spaced sonic waveforms

-SPACED SONIC TOOL UT LTF R L TNR 3' Lr TN R LrTFR LT 10' C FR NR 8' D I FRI (( 'I ll NrR ) ( rt I ll ))8. I ) 8 I I I I ) I I I l I I I-I Ii& I ? ? +) ? +l ?? I I~ I lk ) I LT I ? I I 10' A LT Figure 2. Configuration... REFERENCES 56 VITA 58 LIST OF TABLES TABLE Page I Input parameters for synthetic sonic waveforms. 23 2 Synthetic waveform computed slowness error ? 9"-diameter borehole. . . . 25 3 Synthetic waveform computed slowness error ? 4"-diameter borehole...

Lake, Leonard Cornelius

2012-06-07T23:59:59.000Z

439

Measuring In-Situ Mdf Velocity Of Detonation

A system for determining the velocity of detonation of a mild detonation fuse mounted on the surface of a device includes placing the device in a predetermined position with respect to an apparatus that carries a couple of sensors that sense the passage of a detonation wave at first and second spaced locations along the fuse. The sensors operate a timer and the time and distance between the locations is used to determine the velocity of detonation. The sensors are preferably electrical contacts that are held spaced from but close to the fuse such that expansion of the fuse caused by detonation causes the fuse to touch the contact, causing an electrical signal to actuate the timer.

Horine, Frank M. (Albuquerque, NM); James, Jr., Forrest B. (Albuquerque, NM)

2005-10-25T23:59:59.000Z

440

We use a suite of cosmological hydrodynamical simulations, run by two fixed grid codes, to investigate the properties of solenoidal and dilatational motions of the intergalactic medium (IGM) and the impact of numerical viscosity on turbulence in an ?CDM universe. The codes differ only in the spatial difference discretization. We find that (1) The vortical motion grows rapidly since z = 2 and reaches ?10 km s{sup –1}-90 km s{sup –1} at z = 0. Meanwhile, the small-scale compressive ratio r{sub CS} drops from 0.84 to 0.47, indicating comparable vortical and compressive motions at z = 0. (2) Power spectra of the solenoidal velocity possess two regimes, ?k {sup –0.89} and ?k {sup –2.02}, while the total and dilatational velocity follow the scaling k {sup –1.88} and k {sup –2.20}, respectively, in the turbulent range. The IGM turbulence may contain two distinct phases, the supersonic and post-supersonic phases. (3) The non-thermal pressure support, measured by the vortical kinetic energy, is comparable with the thermal pressure for ?{sub b} ? 10-100, or T < 10{sup 5.5} K at z = 0.0. The deviation of the baryon fraction from the cosmic mean shows a preliminary positive correlation with the turbulence pressure support. (4) A relatively higher numerical viscosity would dissipate both the compressive and vortical motions of the IGM into thermal energy more effectively, resulting in less developed vorticity, remarkably shortened inertial range, and leading to a non-negligible uncertainty in the thermal history of gas accretion. Shocks in regions outside of clusters are significantly suppressed by numerical viscosity since z = 2, which may directly cause the different levels of turbulence between the two codes.

Zhu, Weishan; Gu, Qiusheng [School of Astronomy and Space Science, Nanjing University, Nanjing, 210092 (China); Feng, Long-long [Purple Mountain Observatory, Nanjing, 210008 (China); Xia, Yinhua [School of Mathematical Sciences, University of Science and Technology of China, Hefei, Anhui 230026 (China); Shu, Chi-Wang [Division of Applied Mathematics, Brown University, Providence, RI 02912 (United States); Fang, Li-Zhi [Department of Physics, University of Arizona, Tucson, AZ 85721 (United States)

2013-11-01T23:59:59.000Z

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We encourage you to perform a real-time search of NLE

to obtain the most current and comprehensive results.

441

Assessment of Combustion and Turbulence Models for the Simulation...

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

Combustion and Turbulence Models for the Simulation of Combustion Processes in a DI Diesel Engine Assessment of Combustion and Turbulence Models for the Simulation of Combustion...

442

Body Wave Tomography For Regional Scale Assessment Of Geothermal Indicators

Body Wave Tomography For Regional Scale Assessment Of Geothermal Indicators Body Wave Tomography For Regional Scale Assessment Of Geothermal Indicators In The Western Great Basin Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Conference Paper: Body Wave Tomography For Regional Scale Assessment Of Geothermal Indicators In The Western Great Basin Details Activities (8) Areas (4) Regions (0) Abstract: Body and surface wave tomography are two of the primary methods for estimation of regional scale seismic velocity variations. Seismic velocity is affected by temperature and rock composition in complex ways, but when combined with geologic and structural maps, relative temperature can in some cases be estimated. We present preliminary tomographic models for compressional and shear-wave velocity using local and regional earthquakes recorded by Earthscope Transportable Array stations, network

443

DOE Workshop - Deposition Velocity Status

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

Delivering DOE's Vision for the Delivering DOE's Vision for the East Tennessee Technology Park Mission Safely Delivering the Department of Energy's Vision for the East Tennessee Technology Park Mission DOE Workshop Deposition Velocity Status Mike Hitchler, Manager Nuclear Facility Safety June 5, 2012 Safely Delivering DOE's Vision for the East Tennessee Technology Park Mission Existing UCOR Analyses * UCOR facilities at East Tennessee Technology Park (ETTP) and Oak Ridge National Laboratory (ORNL) use various plume models depending on when they were developed and by whom. - Some use MACCS or MACCS2 for dispersion evaluation. (~5 locations) - LLLW uses ingestion modeling (multiple locations)

444

Newberry EGS Seismic Velocity Model

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

We use ambient noise correlation (ANC) to create a detailed image of the subsurface seismic velocity at the Newberry EGS site down to 5 km. We collected continuous data for the 22 stations in the Newberry network, together with 12 additional stations from the nearby CC, UO and UW networks. The data were instrument corrected, whitened and converted to single bit traces before cross correlation according to the methodology in Benson (2007). There are 231 unique paths connecting the 22 stations of the Newberry network. The additional networks extended that to 402 unique paths crossing beneath the Newberry site.

Dennise Templeton

445

Newberry EGS Seismic Velocity Model

We use ambient noise correlation (ANC) to create a detailed image of the subsurface seismic velocity at the Newberry EGS site down to 5 km. We collected continuous data for the 22 stations in the Newberry network, together with 12 additional stations from the nearby CC, UO and UW networks. The data were instrument corrected, whitened and converted to single bit traces before cross correlation according to the methodology in Benson (2007). There are 231 unique paths connecting the 22 stations of the Newberry network. The additional networks extended that to 402 unique paths crossing beneath the Newberry site.

Dennise Templeton

2013-10-01T23:59:59.000Z

446

Estimating wave energy from a wave record

Science Journals Connector (OSTI)

This note is concerned with the calculation of wave energy from a time series record of wave heights. Various methods are used to estimate the wave energy. For wave records that contain a number of different ... ...

Sasithorn Aranuvachapun; John A. Johnson

1977-01-01T23:59:59.000Z

447

Coherent structures, intermittent turbulence, and dissipation in high-temperature plasmas

An unsolved problem in plasma turbulence is how energy is dissipated at small scales. Particle collisions are too infrequent in hot plasmas to provide the necessary dissipation. Simulations either treat the fluid scales and impose an ad hoc form of dissipation (e.g., resistivity) or consider dissipation arising from resonant damping of small amplitude disturbances where damping rates are found to be comparable to that predicted from linear theory. Here, we report kinetic simulations that span the macroscopic fluid scales down to the motion of electrons. We find that turbulent cascade leads to generation of coherent structures in the form of current sheets that steepen to electron scales, triggering strong localized heating of the plasma. The dominant heating mechanism is due to parallel electric fields associated with the current sheets, leading to anisotropic electron and ion distributions which can be measured with NASA's upcoming Magnetospheric Multiscale mission. The motion of coherent structures also generates waves that are emitted into the ambient plasma in form of highly oblique compressional and shear Alfven modes. In 3D, modes propagating at other angles can also be generated. This indicates that intermittent plasma turbulence will in general consist of both coherent structures and waves. However, the current sheet heating is found to be locally several orders of magnitude more efficient than wave damping and is sufficient to explain the observed heating rates in the solar wind.

Karimabadi, H.; Roytershteyn, V. [Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093 (United States); Wan, M.; Matthaeus, W. H.; Wu, P.; Shay, M. [University of Delaware, Department of Physics and Astronomy, Newark, Delaware 19716 (United States); Daughton, W.; Nakamura, T. K. M. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Loring, B. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Borovsky, J. [Space Science Institute, Boulder, Colorado 80301 (United States); Leonardis, E.; Chapman, S. C. [Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry, CV4 7AL (United Kingdom)

2013-01-15T23:59:59.000Z

448

Kinetic cascade beyond MHD of solar wind turbulence in two-dimensional hybrid simulations

The nature of solar wind turbulence in the dissipation range at scales much smaller than the large MHD scales remains under debate. Here a two-dimensional model based on the hybrid code abbreviated as A.I.K.E.F. is presented, which treats massive ions as particles obeying the kinetic Vlasov equation and massless electrons as a neutralizing fluid. Up to a certain wavenumber in the MHD regime, the numerical system is initialized by assuming a superposition of isotropic Alfv\\'en waves with amplitudes that follow the empirically confirmed spectral law of Kolmogorov. Then turbulence develops and energy cascades into the dispersive spectral range, where also dissipative effects occur. Under typical solar wind conditions, weak turbulence develops as a superposition of normal modes in the kinetic regime. Spectral analysis in the direction parallel to the background magnetic field reveals a cascade of left-handed Alfv\\'en/ion-cyclotron waves up to wave vectors where their resonant absorption sets in, as well as a cont...

Verscharen, Daniel; Motschmann, Uwe; Müller, Joachim

2012-01-01T23:59:59.000Z

449

Differential rotation is known to suppress linear instabilities in fusion plasmas. However, even in the absence of growing eigenmodes, subcritical fluctuations that grow transiently can lead to sustained turbulence. Here transient growth of electrostatic fluctuations driven by the parallel velocity gradient (PVG) and the ion temperature gradient (ITG) in the presence of a perpendicular ExB velocity shear is considered. The maximally simplified case of zero magnetic shear is treated in the framework of a local shearing box. There are no linearly growing eigenmodes, so all excitations are transient. The maximal amplification factor of initial perturbations and the corresponding wavenumbers are calculated as functions of q/\\epsilon (=safety factor/aspect ratio), temperature gradient and velocity shear. Analytical results are corroborated and supplemented by linear gyrokinetic numerical tests. For sufficiently low values of q/\\epsilon (subcritical PVG turbulence leading to a scaling of the associated ion heat flux with q, \\epsilon, velocity shear and temperature gradient is proposed; it is argued that the transport is much less stiff than in the ITG regime.

A. A. Schekochihin; E. G. Highcock; S. C. Cowley

2011-11-21T23:59:59.000Z

450

Wind reversals in turbulent Rayleigh-Benard convection

The phenomenon of irregular cessation and subsequent reversal of the large-scale circulation in turbulent Rayleigh-B\\'enard convection is theoretically analysed. The force and thermal balance on a single plume detached from the thermal boundary layer yields a set of coupled nonlinear equations, whose dynamics is related to the Lorenz equations. For Prandtl and Rayleigh numbers in the range $10^{-2} \\leq \\Pr \\leq 10^{3}$ and $10^{7} \\leq \\Ra \\leq 10^{12}$, the model has the following features: (i) chaotic reversals may be exhibited at Ra $\\geq 10^{7}$; (ii) the Reynolds number based on the root mean square velocity scales as $\\Re_{rms} \\sim \\Ra^{[0.41 ... 0.47]}$ (depending on Pr), and as $\\Re_{rms} \\sim \\Pr^{-[0.66 ... 0.76]}$ (depending on Ra); and (iii) the mean reversal frequency follows an effective scaling law $\\omega / (\

Francisco Fontenele Araujo; S. Grossmann; D. Lohse

2005-08-29T23:59:59.000Z

451

Characterization of the magnetorotational instability from a turbulent background state

Science Journals Connector (OSTI)

Experiments in spherical Couette flow (flow between concentric rotating spheres) with an imposed magnetic field have yielded induced magnetic fields consistent with the magnetorotational instability. This might be expected due to the decreasing rotation rate profile in the base state. The observation is at odds though with existing theory in that the base state has a significant turbulent component. We characterize the observed induced magnetic fields as well as the velocity disturbance underlying the instability. The saturated state shows a variety of patterns and dynamics depending on applied magnetic field strength and rotation rate. The observed phase diagram is in qualitative agreement with linear stability theory. We also compare the observed stability diagram with that of MHD instabilities calculated by Hollerbach and Skinner.

Daniel S. Zimmerman; Santiago A. Triana; Daniel R. Sisan; W. Andrew Tillotson; William Dorland; Daniel P. Lathrop

2004-01-01T23:59:59.000Z

452

Turbulence characteristics of electron cyclotron and ohmic heated discharges

Turbulence characteristics of electron cyclotron (EC) and ohmic heated (OH) discharges has been analyzed by electrostatic gyrokinetic simulations with GYRO [J. Candy, R.E. Waltz, Journal of Computational Physics 186, 545-581 (2003)] aiming to find insights into the effect of auxiliary heating on the transport. Trapped electron modes are found to be unstable in both OH and the EC heated scenarios. In the OH case the main drive is from the density gradient and in the EC case from the electron temperature gradient. The growth rates and particle fluxes exhibit qualitatively different scaling with the electron-to-ion temperature ratios in the two cases. This is mainly due to the fact that the dominant drives and the collisionalities are different. The inward flow velocity of impurities and the impurity diffusion coefficient decreases when applying EC heating, which leads to lower impurity peaking, consistently with experimental observations.

Pusztai, Istvan; Fulop, Tunde; Timchenko, Natalia

2011-01-01T23:59:59.000Z

453

Accurate estimation of third-order moments from turbulence measurements

Politano and Pouquet's law, a generalization of Kolmogorov's four-fifths law to incompressible MHD, makes it possible to measure the energy cascade rate in incompressible MHD turbulence by means of third-order moments. In hydrodynamics, accurate measurement of third-order moments requires large amounts of data because the probability distributions of velocity-differences are nearly symmetric and the third-order moments are relatively small. Measurements of the energy cascade rate in solar wind turbulence have recently been performed for the first time, but without careful consideration of the accuracy or statistical uncertainty of the required third-order moments. This paper investigates the statistical convergence of third-order moments as a function of the sample size N. It is shown that the accuracy of the third-moment depends on the number of correlation lengths spanned by the data set and a method of estimating the statistical uncertainty of the third-moment is developed. The technique is illustrated usi...

Podesta, J J; Smith, C W; Elton, D C; Malecot, Y; Gagne, Y

2009-01-01T23:59:59.000Z

454

Science Journals Connector (OSTI)

In 1955 Wolf noticed that the mutual coherence function ? obeys two wave equations [Proc. R. Soc. London230, 246 (1955)]. The physical optics of this finding is thoroughly presented in...

Lohmann, Adolf W; Mendlovic, David; Shabtay, Gal

1999-01-01T23:59:59.000Z