Consistent Boundary Conditions for Multicomponent Real Gas Mixtures Based on Characteristic Waves

Previously developed characteristic-wave-based boundary conditions for multicomponent perfect gas mixtures are here extended to real gas mixtures. The characteristic boundary conditions are derived from the one-dimensional wave decomposition of the Euler equations, and the wave amplitude variations are determined from the prescribed boundary conditions on the flow variables. The viscous conditions are applied separately. For multidimensional simulations, the boundary conditions for each coordinate direction are applied additively. These boundary conditions are tested on a representative two-dimensional problem—the propagation of an incompressible vortex by a supersonic flow with outflow conditions specified as nonreflecting—solved using a high-order finite-difference scheme. Simulations conducted for a heptane–nitrogen mixture flow with strong real gas effects display excellent, nonreflective wave behavior as the vortex leaves the computational domain, verifying the suitability of this method for the multidimensional multicomponent real gas flows computed.