Low-Diffusion Flux-Splitting Methods for Real Fluid Flows with Phase Transitions

Abstract

Methods for extending the AUSM+ low-diffusion flux-splitting scheme toward the calculation of real fluid flows at all speeds are presented. The single-phase behavior of the fluid is defined by the Sanchez-Lacombe equation of state, a lattice-fluid description. Liquid-vapor phase transitions are modeled through a homogeneous equilibrium approach. Time-derivative preconditioning is utilized to allow effective integration of the equation system at all flow speeds and all states of compressibility. Modifications to the preconditioned variant of AUSM+ necessary to preserve solution accuracy under such conditions are presented in detail. One-dimensional results are presented for the faucet problem, a classic test case for multifluid algorithms, as well as for liquid octane flow through a converging-diverging nozzle. Two-dimensional calculations are presented for water flow over a hemisphere/cylinder geometry and liquid carbon dioxide flow through a capillary nozzle