Results 1  10
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15
Turbulent Wind Fields for Gaseous Phenomena
, 1993
"... The realistic depiction of smoke, steam, mist and water reacting to a turbulent field such as wind is an attractive and challenging problem. Its solution requires interlocking models for turbulent fields, gaseous flow, and realistic illumination. We present a model for turbulent wind flow having a d ..."
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Cited by 127 (10 self)
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The realistic depiction of smoke, steam, mist and water reacting to a turbulent field such as wind is an attractive and challenging problem. Its solution requires interlocking models for turbulent fields, gaseous flow, and realistic illumination. We present a model for turbulent wind flow having a deterministic component to specify largescale behaviour, and a stochastic component to model turbulent smallscale behaviour. The smallscale component is generated using spacetime Fourier synthesis. Turbulent wind fields can be superposed interactively to create subtle behaviour. An advectiondiffusion model is used to animate particlebased gaseous phenomena embedded in a wind field, and we derive an efficient physicallybased illumination model for rendering the system. Because the number of particles can be quite large, we present a clustering algorithm for efficient animation and rendering. CR Categories and Subject Descriptors: I.3.7 [Com puter Graphics]: ThreeDimensional Graphics...
On the Viscosity and Thermal Conduction of Fluids With Multivalued Internal Energy
"... This work is concerned with an extension of the classical compressible Euler model of fluid dynamics in which the fluid internal energy is a measurevalued quantity. This model can be derived from the hydrodynamic limit of a kinetic model involving a specific class of collision operators. In the pre ..."
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Cited by 7 (3 self)
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This work is concerned with an extension of the classical compressible Euler model of fluid dynamics in which the fluid internal energy is a measurevalued quantity. This model can be derived from the hydrodynamic limit of a kinetic model involving a specific class of collision operators. In the present paper, we investigate diffusive corrections of this fluid dynamical model derived from a ChapmanEnskog expansion of the kinetic model, in the case where the collision time depends on the particle energy in the fluid frame. We show that the closure relations for the stress tensor and heat flux vector differ from their expression in the usual NavierStokes model. We argue why such a feature could be used as a tool towards an understanding of fluid turbulence from kinetic theory. Key words: Boltzmann equation, Euler equation, NavierStokes equation, viscosity, heat conduction, ChapmanEnskog expansion, Turbulence. AMS Subject classification: 41A60, 35Q20, 76P05, 35C20, 35L65, 76F99, 76N9...
INSTABILITY OF THE IONOSPHERIC PLASMA: MODELING AND ANALYSIS ∗
"... Abstract. This paper is concerned with the theory and modeling of plasma instabilities in the ionosphere. We first consider the socalled ’striation model ’ which consists of balance equations for the density and momenta of the plasma species, coupled with an elliptic equation for the potential. The ..."
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Cited by 5 (3 self)
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Abstract. This paper is concerned with the theory and modeling of plasma instabilities in the ionosphere. We first consider the socalled ’striation model ’ which consists of balance equations for the density and momenta of the plasma species, coupled with an elliptic equation for the potential. The linearized instability of this model is analyzed in the framework of Fourier theory, both for smooth and discontinuous steadystates. Then, we show that the dissipation mechanisms at work in the more refined ’dynamo model ’ allow to stabilize high wavenumber perturbations. We also analyze turbulence as a possible source of additional dissipation (in a similar way as in fluid mechanics). To this aim, we use the statistical approach to turbulence and derive a socalled ’turbulent striation model’, of which we analyze the stability properties. Numerical experiments are used to support our investigations. Key words. EulerMaxwell system, dynamo model, striation model, ionospheric plasma, striations, turbulence, statistical approach, linearized stability analysis AMS subject classifications. 82D10, 76N99, 76X05, 76W06, 78M35
unknown title
, 2008
"... Energy transfer in twodimensional magnetohydrodynamic turbulence ..."
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Abstract Magnetohydrodynamics With the Eddy Damped QuasiNormal Markovian Closure
, 2003
"... When a ferromagnet is heated, it loses its magnetism. Stars and planets have magnetic elds, as does the Earth. But it is known that the center of the Earth is very hot. Therefore, to sustain the large magnetic eld of a planet, we cannot look to simple ferromagnetism like that of a bar magnet, but w ..."
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When a ferromagnet is heated, it loses its magnetism. Stars and planets have magnetic elds, as does the Earth. But it is known that the center of the Earth is very hot. Therefore, to sustain the large magnetic eld of a planet, we cannot look to simple ferromagnetism like that of a bar magnet, but we have to look at the movement of electric charges within the Earth's molten core to generate magnetic eld. This magnetic eld sustainment against ohmic dissipation by turbulent ow is referred to as the turbulent dynamo effect. Theoretical research into the mechanisms that create the dynamo has been actively pursued for several decades, culminating recently in massive computer simulations of the Earth's core. Most of these studies have employed the equations of magnetohydrodynamics (MHD), a nonlinear theory of electrically conducting uids. The EDQNM (EddyDamped QuasiNormal Markovian) closure is a statistical model designed so that the turbulence equations derived from NavierStokes dynamics can be closed and satisfy the realizability condition of positivity of the kinetic energy spectrum. In case of MHD turbulence, realizability requires more
Diffusion Processes in Turbulent Magnetic Fields
, 707
"... Abstract. We study of the effect of turbulence on diffusion processes within magnetized medium. While we exemplify our treatment with heat transfer processes, our results are quite general and are applicable to different processes, e.g. diffusion of heavy elements. Our treatment is also applicable t ..."
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Abstract. We study of the effect of turbulence on diffusion processes within magnetized medium. While we exemplify our treatment with heat transfer processes, our results are quite general and are applicable to different processes, e.g. diffusion of heavy elements. Our treatment is also applicable to describing the diffusion of cosmic rays arising from magnetic field wandering. In particular, we find that when the energy injection velocity is smaller than the Alfven speed the heat transfer is partially suppressed, while in the opposite regime the effects of turbulence depend on the intensity of driving. In fact, the scale lA at which the turbulent velocity is equal the Alfven velocity is a new important parameter. When the electron mean free path λ is larger than lA, the stronger the the turbulence, the lower thermal conductivity by electrons is. The turbulent motions, however, induces their own advective transport, that can provide effective diffusivity. For clusters of galaxies, we find that the turbulence is the most important agent for heat transfer. We also show that the domain of applicability of the subdiffusion concept is rather limited.
unknown title
, 2001
"... Alongslope current generation by obliquely incident internal waves ..."
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unknown title
, 2006
"... physics pp. 1129–1140 Modetomode energy transfers in convective patterns ..."
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physics pp. 1129–1140 Modetomode energy transfers in convective patterns
physics pp. 447–453 Fieldtheoretic calculation of kinetic helicity flux
, 2005
"... Abstract. In this paper we apply perturbative fieldtheoretic technique to helical turbulence. In the inertial range the kinetic helicity flux is found to be constant and forward. The universal constant KH appearing in the spectrum of kinetic helicity was found to be ..."
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Abstract. In this paper we apply perturbative fieldtheoretic technique to helical turbulence. In the inertial range the kinetic helicity flux is found to be constant and forward. The universal constant KH appearing in the spectrum of kinetic helicity was found to be