Numerical simulations with a finite-difference method have revealed that a Lamb dipole when placed in a viscous fluid moves along a straight line with decreasing velocity and increasing radius. The relationship betwee...
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Numerical simulations with a finite-difference method have revealed that a Lamb dipole when placed in a viscous fluid moves along a straight line with decreasing velocity and increasing radius. The relationship between vorticity and streamfunction, which initially is linear, becomes more and more sinh-like as the dipole decays. Some other initial dipolar vorticity distributions (like two oppositely signed monopolar vortices) were found to evolve to a dipolar structure with Lamb-like characteristics. (C) 1998 The Japan Society of fluid Mechanics Incorporated and Elsevier Science B.V. All rights reserved.
A new class of lattice BGK models is proposed which is based on a nonperturbative discrete Maxwellian ansatz for the local equilibria. This new class extends the range of stability of previous models.
A new class of lattice BGK models is proposed which is based on a nonperturbative discrete Maxwellian ansatz for the local equilibria. This new class extends the range of stability of previous models.
Solid particles (such as snow or sand) can get eroded and transported by the wind, and little understanding has been achieved in this domain. We propose a description of the phenomenon in terms of a cellular automata ...
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Solid particles (such as snow or sand) can get eroded and transported by the wind, and little understanding has been achieved in this domain. We propose a description of the phenomenon in terms of a cellular automata and lattice Boltzmann model. Numerical simulations show that plausible mechanisms are sufficient to explain a wide range of deposition patterns occurring at different space scales. In particular, we reproduce the so-called ripples, that is oscillations of the deposition surface for which no formation mechanism is clearly established.
The lattice Boltzmann equation can be viewed as a discretization of the continuous Boltzmann equation. Because of this connection it has long been speculated that lattice Boltzmann algorithms might obey an H-theorem. ...
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The lattice Boltzmann equation can be viewed as a discretization of the continuous Boltzmann equation. Because of this connection it has long been speculated that lattice Boltzmann algorithms might obey an H-theorem. In this letter we prove that usual nine-velocity models do not obey an H-theorem but models that do obey an H-theorem can be constructed. We consider the general conditions a lattice Boltzmann scheme must satisfy in order to obey an H-theorem and show why on a lattice, unlike the continuous case, dynamics that decrease an H-functional do not necessarily lead to a unique ground state.
A model for the flow of fluids with particles in them is introduced. It relies on the coupling of discretely represented particles and a fluid pressure field that is given by a continuum description - a local Darcy la...
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A model for the flow of fluids with particles in them is introduced. It relies on the coupling of discretely represented particles and a fluid pressure field that is given by a continuum description - a local Darcy law. In order to validate the qualitative behavior of the model, it is applied to simulate two different sedimentation processes. These processes include an initially homogeneous sedimenting bed of particles and a fluid bubble rising through a sedimenting field of particles. Agreement with experiments is observed on the qualitative level.
The algorithm for Dissipative Particle dynamics (DPD), as modified by Espanol and Warren, is used as a starting point for proving an H-theorem for the free energy and deriving hydrodynamic equations. Equilibrium and t...
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The algorithm for Dissipative Particle dynamics (DPD), as modified by Espanol and Warren, is used as a starting point for proving an H-theorem for the free energy and deriving hydrodynamic equations. Equilibrium and transport properties of the DPD fluid are explicitly calculated in terms of the system parameters for the continuous time version of the model.
We present a generalization of dissipative particle dynamics that includes shear forces between particles. The new algorithm has the same structure as the (isothermal) smoothed particle dynamics algorithm, except that...
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We present a generalization of dissipative particle dynamics that includes shear forces between particles. The new algorithm has the same structure as the (isothermal) smoothed particle dynamics algorithm, except that it conserves angular momentum and includes thermal fluctuations consistently with the principles of equilibrium statistical mechanics. This clarifies the connection of dissipative particle dynamics with numerical resolution algorithms of the macroscopic Navier-Stokes equations.
Dissipative particle dynamics (DPD) does not conserve energy and this precludes its use in the study of thermal processes in complex fluids. We present here a generalization of DPD that incorporates an internal energy...
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Dissipative particle dynamics (DPD) does not conserve energy and this precludes its use in the study of thermal processes in complex fluids. We present here a generalization of DPD that incorporates an internal energy and a temperature variable for each particle. The dissipation induced by the dissipative forces between particles is invested in raising the internal energy of the particles. Thermal conduction occurs by means of (inverse) temperature differences. The model can be viewed as a simplified solver of the fluctuating hydrodynamic equations and opens up the possibility of studying thermal processes in complex fluids with a mesoscopic simulation technique.
The stochastic differential equations for a model of dissipative particle dynamics with both total energy and total momentum conservation in the particle-particle interactions are presented. The corresponding Fokker-P...
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The stochastic differential equations for a model of dissipative particle dynamics with both total energy and total momentum conservation in the particle-particle interactions are presented. The corresponding Fokker-Planck equation for the evolution of the probability distribution for the system is deduced together with the corresponding fluctuation-dissipation theorems ensuring that the ab initio chosen equilibrium probability distribution for the relevant variables is a stationary solution. When energy conservation is included, the system can sustain temperature gradients and heat flow can be modeled.
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