Robust hyperbolic moment closures for CFD.

Moment closures offer the promise of several advantages as compared to other methods in the field of computational fluid dynamics (CFD). The extended solution vector allows for an expanded region of validity as compared to the Navier-Stokes equations. It is also expected that solutions for an approach based on partial differential equations can often be obtained more affordably than for particle-based methods. This paper details the construction of a new 14-moment closure inspired by the corresponding maximum-entropy closure. It is shown that closed-form expressions can be found for the closing fluxes that lead to equations with a hyperbolicity that is robust enough for flow situations with a high degree of nonequilibrium effects. Numerical solutions of a system with the simplified BGK collision operator are presented. These solutions are not physically accurate because of the crude treatment of the right-hand side. Nevertheless, they provide insight into the behaviour of the moment approximation of the left-hand side. It is shown that by preserving a singularity in the highest-order closing flux from the maximum-entropy closure, smooth shock profiles can be expected, even when the incoming speeds are higher than the equilibrium wavespeeds of the system. [ABSTRACT FROM AUTHOR]