摘要:

After pointing out that the usual thermodynamics relations are contradictory when applied to a discrete velocity gas, it is shown that the usual relation between the entropy rate and the heat supplied to a gas is not valid and must be replaced by another one that eliminates all the paradoxical aspects of the matter.

ISSN:0041-1450    

DOI:10.1080/00411459408203851

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Extended kinetic equations, taking into account removal and generation interactions, and presence of a background medium, are considered in the discrete velocity formalism, and applied for studying the problem of a gas in a uniform host medium according to a planar 8-velocity model. After deriving the relevant governing equations, equilibria are investigated in detail for varying absorption, generation and scattering properties of the fixed, but in general not isotropic, background. Some stability properties and preliminary results about shock wave structure are also discussed.

ISSN:0041-1450    

DOI:10.1080/00411459408203852

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The class of random discrete velocity models is extended. An approximation procedure for sequences of random measures is studied such that momentum and energy are preserved. The theorem concerning convergence to an approximate Boltzmann equation is generalized to the extended class of models.

ISSN:0041-1450    

DOI:10.1080/00411459408203853

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In order to have, a kinetic equation suited to liquid dynamics and phase transitions, the intermolecular potential is split into a repulsive hard-core and an attractive tail. The hard-core is treated as in the revised Enskog equation, whereas the tail enters the equation only linearly, in a mean-field term. Such an equation is called the Enskog-Vlasov equation.

ISSN:0041-1450    

DOI:10.1080/00411459408203854

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In the kinetic theory of the discrete Boltzmann models (DBMs) the standard similarity shock waves solutions are, like the Broadwell shock waves, solutions of scalar Riccati equations. The corresponding microscopic densities, as well as the macroscopic conservative quantities: mass, momentum and energy, are monotonic. In thefirst part of the paper we construct new exact similarity shockwavessolutions of systems of coupled Riccati equations, which arise for the DBMs with n conservation laws andn+kindependent densities (here withn= 3,k= 2). The former standard shock waves are rational functions of two linear polynomials with an exponential variable while for the new waves the polynomials are quadratic and consequently nonmonotonic behaviours are possible. We stress that from the mathematical point of view we enter into a new domain of exact self-similar solutions associated to the systems of coupled Riccati equations. Due to the fact that, for the considered models, there exists a linear differential relation between two microscopic densities we obtain two different classes of solutions. For one class these two densities are necessarily of the former standard type while for the other all densities are of the new type of self-similar solutions. Furthermore we prove an important result: Let us consider microscopic densities associated to opposite velocities along the shock-axis. To any solution, there exists another one, called partner solution, such that those densities are exchanged with opposite similarity variable. This means that from any solution with mass, energy and pressure given, there exists a partner solution where these macroscopic quantities have opposite similarity variable.

ISSN:0041-1450    

DOI:10.1080/00411459408203855

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

An interaction has been added to the classical lattice gas model that exchanges momentum between sites. The hydrodynamic limit of the model can be obtained from a Chapman-Enskog expansion and all the coefficients can be expressed explicitly. The interaction contributions to viscous terms are independent of the initial interaction-free model and grow like r2. When the interaction range r is large enough, the pressure acquires a negative slope for certain densities. The model then has a phase transition, observed in simulations. Some examples of a three-dimensional phase separation are shown. Whatever the dimension of space, the model can be represented by a cellular automaton with only nearest neighbor communications, using messenger particles or photons. In 2 dimensions of space, this allows fitting the model into a 16 bit table adequate for a special purpose cellular automaton machine like the RAP1.

ISSN:0041-1450    

DOI:10.1080/00411459408203856

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The stochastic lattice gas introduced in [1] was shown to simulate the one-dimensional Burgers' equation and the phenomena it embodies: travelling shocks and rarefaction waves. However, shock widening not characteristic of the actual solution is intrinsic to the model. In the present contribution, we consider a variant of this lattice model in which shock widening is inhibited. In addition, in [1] we supposed decorrelated occupation probabilities in the lattice system in order to derive the approximate master equation, a finite difference version of Burgers equation. Here we reconsider the master equation, incorporating the effect of the correlation into the derivation. We see that the master equation is in fact a finite difference discretization of the one-dimensional Navier-Stokes equation for incompressible parallel flow. 11.5

ISSN:0041-1450    

DOI:10.1080/00411459408203857

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We study the velocity field in a two-dimensional hexagonal lattice gas for flow around a cylinder at Reynolds numbers of 100 and 185. We discuss drag, lift and Strouhal number. Agreement with data is at best semi-quantitative.

ISSN:0041-1450    

DOI:10.1080/00411459408203858

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Lattice gas models violating detailed balance may be unstable against long wavelength sound excitations, as is demonstrated by a study of the eigenvalue spectrum of the hydrodynamic modes of the lattice Boltzmann equation, and confirmed by computer simulations of the structure function.

ISSN:0041-1450    

DOI:10.1080/00411459408203859

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Numerical simulations of two-dimensional flows past a thin plate are presented using a finite-volume formulation of the Lattice Boltzmann equation.

ISSN:0041-1450    

DOI:10.1080/00411459408203860

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor