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This article aims at giving a simplified presentation of a new adaptive semi-Lagrangian scheme for solving the (1+1)-dimensional Vlasov-Poisson system, which was developed in 2005 with Michel Mehrenberger and first described in (Campos Pinto and Mehrenberger, 2007). The main steps of the analysis are also given, which yield the first error estimate for an adaptive scheme in the context of the Vlasov equation. This article focuses on a key feature of our method, which is a new algorithm to transport...
We present a domain decomposition theory on an interface problem for the linear transport equation between a diffusive and a non-diffusive region. To leading order, i.e. up to an error of the order of the mean free path in the diffusive region, the solution in the non-diffusive region is independent of the density in the diffusive region. However, the diffusive and the non-diffusive regions are coupled at the interface at the next order of approximation. In particular, our algorithm avoids iterating...
We present a domain decomposition theory on an interface problem
for the linear transport equation between a diffusive and a non-diffusive region.
To leading order, i.e. up to an error of the order of the mean free path in the
diffusive region, the solution in the non-diffusive region is independent of the
density in the diffusive region. However, the diffusive and the non-diffusive regions
are coupled at the interface at the next order of approximation. In particular, our
algorithm avoids iterating...
In this article the linear Boltzmann equation is derived for a particle interacting with a Gaussian random field, in the weak coupling limit, with renewal in time of the random field. The initial data can be chosen arbitrarily. The proof is geometric and involves coherent states and semi-classical calculus.
We study a new Hermite-type interpolating operator arising in a semi-Lagrangian scheme for solving the Vlasov equation in the D phase space. Numerical results on uniform and adaptive grids are shown and compared with the biquadratic Lagrange interpolation introduced in (Campos Pinto and Mehrenberger, 2004) in the case of a rotating Gaussian.
In this short note we correct a conceptual error in the
heuristic derivation of a kinetic equation used for the
description of a one-dimensional granular medium in the so
called quasi-elastic limit, presented by the same authors in
reference[1]. The equation we derived is however correct so that,
the rigorous analysis on this equation, which constituted the
main purpose of that paper, remains unchanged.
The study of the fluctuations in the steady state of a heated granular system is
reviewed. A Boltzmann-Langevin description can be built requiring consistency with the
equations for the one- and two-particle correlation functions. From the Boltzmann-Langevin
equation, Langevin equations for the total energy and the transverse velocity field are
derived. The existence of a fluctuation-dissipation relation for the transverse velocity
field is also...
We recover the Navier–Stokes equation as the incompressible limit of a stochastic lattice gas in which particles are allowed to jump over a mesoscopic scale. The result holds in any dimension assuming the existence of a smooth solution of the Navier–Stokes equation in a fixed time interval. The proof does not use nongradient methods or the multi-scale analysis due to the long range jumps.
Numerically solving the Boltzmann kinetic equations with the small Knudsen number is challenging due to the stiff nonlinear collision terms. A class of asymptotic-preserving schemes was introduced in [F. Filbet and S. Jin,J. Comput. Phys. 229 (2010) 7625–7648] to handle this kind of problems. The idea is to penalize the stiff collision term by a BGK type operator. This method, however, encounters its own difficulty when applied to the quantum Boltzmann equation. To define the quantum Maxwellian...
Numerically solving the Boltzmann kinetic equations with the small Knudsen number is
challenging due to the stiff nonlinear collision terms. A class of asymptotic-preserving
schemes was introduced in [F. Filbet and S. Jin,J. Comput. Phys. 229 (2010)
7625–7648] to handle this kind of problems. The idea is to penalize the stiff collision
term by a BGK type operator. This method, however, encounters its own difficulty when
applied to the quantum Boltzmann...
We give two direct proofs of Sobolev estimates for the positive part of Boltzmann's kernel. The first deals with a cross section with separated variables; no derivative is needed in this case. The second is concerned with a general cross section having one derivative in the angular variable.
We propose and study semidiscrete and fully discrete finite element schemes based on appropriate relaxation models for systems of Hyperbolic Conservation Laws. These schemes are using piecewise polynomials of arbitrary degree and their consistency error is of high order. The methods are combined with an adaptive strategy that yields fine mesh in shock regions and coarser mesh in the smooth parts of the solution. The computational performance of these methods is demonstrated by considering scalar...
We propose and study semidiscrete and fully discrete
finite element schemes based on appropriate relaxation models for
systems of Hyperbolic Conservation Laws.
These schemes are using piecewise polynomials of arbitrary degree and
their consistency error is of high order.
The methods are combined with an adaptive strategy that yields
fine mesh in shock regions and coarser mesh in the smooth parts of the
solution.
The computational performance of these methods is demonstrated by considering
scalar...
A computer aided method using symbolic computations that enables the calculation of the
source terms (Boltzmann) in Grad’s method of moments is presented. The method is extremely
powerful, easy to program and allows the derivation of balance equations to very high
moments (limited only by computer resources). For sake of demonstration the method is
applied to a simple case: the one-dimensional stationary granular gas under gravity. The
method should...
Continuum mechanics (e.g., hydrodynamics, elasticity theory) is based on the assumption
that a small set of fields provides a closed description on large space and time scales.
Conditions governing the choice for these fields are discussed in the context of granular
fluids and multi-component fluids. In the first case, the relevance of temperature or
energy as a hydrodynamic field is justified. For mixtures, the use of a total temperature
and single...
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