Comparison of subcritical interface approximations at high temperature and pressure conditions

摘要

In this paper two interface approximation methods are compared that are suitable approximations for the resolution of compressible subsonic flows at high temperatures and pressures. The focus of the paper is on the modeling of the subsonic phase interface in case phase transition effects are present. In this case a mixed hyperbolic-elliptic problem has to be solved due to the influence of the subsonic phase interface. The first approach is a sharp interface method based on the Ghost-Fluid approach. The macroscopic scales are resolved by a discontinuous Galerkin (DG) solver and the necessary interface jump conditions are provided by an interface Riemann solver applied at the interface position. The interface solver handles all interface physics and provides consistent numerical states for the flux calculation at the interface. The second approach is a diffuse interface approach, the dense gas approximation. Within the flow field we assume thermodynamic equilibrium implying that the thermodynamic time scales are faster than the resolved numerical ones. The phase interface is smeared over a few grid cells and the interface physics, like phase transfer effects, are described by a consistent mixing of the fluid within the coexistance lines. The underlying equation of state is modified in the multi-phase region to ensure a purely hyperbolic problem.