Robust implementation of the four equation model for compressible two-phase flows using ENO-type schemes and application to simulation of "cold" combustors

ENO-type schemes provide a general approach to capturing flow discontinuities without adding substantial numerical dissipation. While these schemes have "essentially" non-oscillatory solutions, for high-Mach flows even small oscillations in flow variables can lead to simulation failure. In particular, the high-density ratios common in two-phase flows demand stricter robustness criteria than single-phase compressible flow. Obtaining robust solutions for high-Mach two-phase flow requires enforcing positivity of pressure, mass, the squared speed-of-sound, and boundedness of phase volume fraction. In this work, a positivity-preserving framework was constructed for the four-equation two-phase model and implemented into the highly-parallel Hypersonic Task based Research (HTR) Solver. The positivity-preserving scheme is conservative and applied locally for minimum degradation of the base-line ENO-type scheme. The positivity-preserving framework was applied to multiple high-Mach two-phase flows including the simulation of a multiphase "cold" combustor on curvilinear grids.