Design principles of ghost fluid method

By analyzing ghost fluid method for compressible multi-medium flows, fundamentals for defining ghost fluid state with a general equation of state are described. All possible definitions of ghost fluid states are derived according to wave patterns and free variables in ghost fluid region. Following these treatments, it reveals that solution of multi-medium Riemann problem can be obtained exactly in theory. Several simple but effective definitions independent with wave patterns in ghost fluid region, are further summarized. One of these ways is similar to reflective boundary condition. An essential prerequisite is that interfacial velocity must be predicted exactly. Numerical results show that this methodology indeed works reasonably for multi-medium flows.