Detailed Numerical Modeling of Chemical and Thermal Nonequilibrium in Hypersonic Flows

Abstract

The interest in hypersonic flows, which arose from the development of the European space transportation systems like HERMES, has created a large demand for physicochemical models for air flow computations around reentry bodies. It is obvious that besides the improvement of mathematical algorithms for solving the Euler or Navier-Stokes equations, detailed physicochemical models for air in chemical and thermal nonequilibrium are needed for a realistic prediction of hypersonic flowfields. In this paper we develop a model, based on elementary physicochemical processes, for a detailed description of chemical nonequilibrium together with the excitation of internal degrees of freedom. Furthermore, this model is implemented in a two dimensional Navier-Stokes code in order to show the strong influence of thermal nonequilibrium on the flowfields. The algorithm presented here is based on a fully conservative discretization of the inviscid fluxes in the conservation equations and uses the chain rule conservation law form for the viscous fluxes. The large system of ordinary differential and algebraic equations resulting from the spatial discretization is solved by a time-accurate semi-implicit extrapolation method.