An Evaluation of Roe's Scheme Generalizations for Equilibrium Real Gas Flows

The extension of Roe's approximate Riemann solver to equilibrium real gas is analyzed by means of a general formulation, allowing us to clarify the inherent nonuniqueness of the average state and the influence of the functional form of the equation of state. Several generalizations of Roe's scheme are then reviewed and their numerical performances are discussed by computing some 2D steady hypersonic flows. The flow solvers are coupled with a newly developed, efficient, and robust procedure for thermochemical air properties evaluation. All of the tested equilibrium solvers achieve very similar results. They are found of comparable numerical efficiency, the higher performances being associated with Vinokur's and Liou's solvers. It is concluded that equilibrium simulations in 2D are by no means less robust than the perfect gas ones, when coupled with the proposed procedure for properties evaluation.