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14
A Class of Approximate Riemann Solvers and Their Relation to Relaxation Schemes
 J. Comput. Phys
, 2001
"... We show that a simple relaxation scheme of the type proposed by Jin and Xin [Comm. Pure Appl. Math. 48(1995) pp. 235276] can be reinterpreted as defining a particular approximate Riemann solver for the original system of m conservation laws. Based on this observation, a more general class of appro ..."
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Cited by 23 (5 self)
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We show that a simple relaxation scheme of the type proposed by Jin and Xin [Comm. Pure Appl. Math. 48(1995) pp. 235276] can be reinterpreted as defining a particular approximate Riemann solver for the original system of m conservation laws. Based on this observation, a more general class of approximate Riemann solvers is proposed which allows as many as 2m waves in the resulting solution. These solvers are related to more general relaxation systems and connections with several other standard solvers are explored. The added flexibility of 2m waves may be advantageous in deriving new methods. Some potential applications are explored for problems with discontinuous flux functions or source terms.
Explicit Diffusive Kinetic Schemes For Nonlinear Degenerate Parabolic Systems
 Parabolic Systems, Math. Comp
, 2000
"... We design numerical schemes for nonlinear degenerate parabolic systems with possibly dominant convection. These schemes are based on discrete BGK models where both characteristic velocities and the sourceterm depend singularly on the relaxation parameter. General stability conditions are derived, a ..."
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Cited by 13 (2 self)
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We design numerical schemes for nonlinear degenerate parabolic systems with possibly dominant convection. These schemes are based on discrete BGK models where both characteristic velocities and the sourceterm depend singularly on the relaxation parameter. General stability conditions are derived, and convergence is proved to the entropy solutions for scalar equations.
Entropy stability theory for difference approximations of nonlinear conservation laws and related timedependent problems
 ACTA NUMERICA
, 2003
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A MULTIWAVE APPROXIMATE RIEMANN SOLVER FOR IDEAL MHD BASED ON RELAXATION II NUMERICAL IMPLEMENTATION WITH 3 AND 5 WAVES
"... Abstract. In the first part of this work ([5]), we introduced an approximate Riemann solver for onedimensional ideal MHD derived from a relaxation system. We gave sufficient conditions for the solver to satisfy discrete entropy inequalities, and to preserve positivity of density and internal energy ..."
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Cited by 8 (4 self)
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Abstract. In the first part of this work ([5]), we introduced an approximate Riemann solver for onedimensional ideal MHD derived from a relaxation system. We gave sufficient conditions for the solver to satisfy discrete entropy inequalities, and to preserve positivity of density and internal energy. In this paper we consider the practical implementation, and derive explicit wave speed estimates satisfying the stability conditions of [5]. We present a 3wave solver that well resolves fast waves and material contacts, and a 5wave solver that accurately resolves the cases when two eigenvalues coincide. A full 7wave solver, which is highly accurate on all types of waves, will be described in a followup paper. We test the solvers on onedimensional shock tube data and smooth shear waves. (1.1) (1.2)
A Reduced Stability Condition for Nonlinear Relaxation to Conservation Laws
 J. Hyperbolic Differ. Equ
, 2003
"... We consider multidimensional hyperbolic systems of conservation laws with relaxation, together with their associated limit systems. A strong stability condition for such asymptotics has been introduced by Chen, Levermore, Liu in Comm. Pure Appl. Math. 47, 787830, namely the existence of an entr ..."
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Cited by 7 (0 self)
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We consider multidimensional hyperbolic systems of conservation laws with relaxation, together with their associated limit systems. A strong stability condition for such asymptotics has been introduced by Chen, Levermore, Liu in Comm. Pure Appl. Math. 47, 787830, namely the existence of an entropy extension. We propose here a new stability condition, the reduced stability condition, which is weaker than the previous one, but still has the property to imply the subcharacteristic or interlacing conditions, and the dissipativity of the leading term in the ChapmanEnskog expansion. This reduced stability condition has the advantage to involve only the submanifold of equilibria, or maxwellians, so that it is much easier to check than the entropy extension condition.
Numerical approximations of the 10moment Gaussian closure
, 2004
"... Abstract. We propose a numerical scheme to approximate the weak solutions of the 10moment Gaussian closure. The moment Gaussian closure for gas dynamics is governed by a conservative hyperbolic system supplemented by entropy inequalities whose solutions satisfy positiveness of density and tensorial ..."
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Cited by 6 (1 self)
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Abstract. We propose a numerical scheme to approximate the weak solutions of the 10moment Gaussian closure. The moment Gaussian closure for gas dynamics is governed by a conservative hyperbolic system supplemented by entropy inequalities whose solutions satisfy positiveness of density and tensorial pressure. We consider a Suliciutype relaxation numerical scheme to approximate the solutions. These methods are proved to satisfy all the expected positiveness properties and all the discrete entropy inequalities. The scheme is illustrated by several numerical experiments. 1.
Entropysatisfying relaxation method with large timesteps for Euler IBVPs
, 2007
"... This paper could have been given the title: “How to positively and implicitly solve Euler equations using only linear scalar advections. ” The new relaxation method we propose is able to solve Eulerlike systems —as well as initial and boundary value problems — with real state laws at very low cost, ..."
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Cited by 4 (3 self)
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This paper could have been given the title: “How to positively and implicitly solve Euler equations using only linear scalar advections. ” The new relaxation method we propose is able to solve Eulerlike systems —as well as initial and boundary value problems — with real state laws at very low cost, using a hybrid explicitimplicit time integration associated with the Arbitrary LagrangianEulerian formalism. Furthermore, it enjoys many desirable properties, such as: (i) the preservation of positivity for densities; (ii) the guarantee of minmax principle for mass fractions; (iii) the satisfaction of entropy inequality, under an expressible bound on the CFL ratio. The design of this optimal timestep, which takes into account data not only from the inner domain but also from the boundary conditions, is the main novel feature we emphasize on.
NUMERICAL COMPARISON OF RIEMANN SOLVERS FOR ASTROPHYSICAL HYDRODYNAMICS
"... Abstract. The idea of this work is to compare a new positive and entropy stable approximate Riemann solver by Francois Bouchut with stateof theart algorithms for astrophysical fluid dynamics. We implemented the new Riemann solver into an astrophysical PPMcode, the Prometheus code, and also made a ..."
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Cited by 1 (1 self)
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Abstract. The idea of this work is to compare a new positive and entropy stable approximate Riemann solver by Francois Bouchut with stateof theart algorithms for astrophysical fluid dynamics. We implemented the new Riemann solver into an astrophysical PPMcode, the Prometheus code, and also made a version with a different, more theoretically grounded higher order algorithm than PPM. We present shock tube tests, twodimensional instability tests and forced turbulence simulations in three dimensions. We find subtle differences between the codes in the shock tube tests, and in the statistics of the turbulence simulations. The new Riemann solver increases the computational speed without significant loss of accuracy. 1.
Boltzmann and FokkerPlanck Equations Modelling Opinion Formation in the Presence of Strong Leaders
"... ISBN 9783902627025 c ○ Alle Rechte vorbehalten. Nachdruck nur mit Genehmigung des Autors. ASC TU WIENThe BGK model with external confining potential: Existence, longtime behaviour and timeperiodic Maxwellian equilibria ..."
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ISBN 9783902627025 c ○ Alle Rechte vorbehalten. Nachdruck nur mit Genehmigung des Autors. ASC TU WIENThe BGK model with external confining potential: Existence, longtime behaviour and timeperiodic Maxwellian equilibria