A methodology for hybrid simulation of rarefield and continuum flow regimes

A hybrid procedure consisting of a high order continuum (HOC) model and the direct simulation Monte-Carlo (DSMC) solver is proposed in this paper, as it represents a promising approach for seamless computation of hypersonic flows in all regimes. This approach also allows the effects of thermophysics (thermal and chemical non-equilibrium) and turbulence to be included so that gas interactions can be modeled much more easily than in other approaches. Such hybrid procedures can also be developed into robust and efficient parallel computing tools for practical 3D computations. The main idea behind the proposed HOC/DSMC methodology consists of incorporating the physically realizable and computationally stable version of the Burnett equations into hypersonic codes that have the capability for calculating non-equilibrium chemistry and temperature. We explore the feasibility of simplified, yet accurate and numerically stable, versions of the Burnett equations. We discuss such a model in detail, providing an analysis of its stability and performance for Alsmeyer's shock wave problem and hypersonic flow over a sphere. We also report on the performance of the DSMC component of the proposed hybrid scheme.