Enhanced Diffuse Interface Method for Multiphase Flow Simulations Across All Mach Numbers

This paper enhances the Diffuse Interface Method (DIM) for simulating compressible multiphase flows across all Mach numbers by addressing the accuracy challenges posed at low Mach regimes. A correction to the Riemann solver is introduced, designed to mitigate excessive numerical diffusion while maintaining simplicity and efficiency. The validity of this correction is established through rigorous asymptotic analysis of the governing equations and their discrete counterparts. The proposed correction is implemented within a six-equation model framework with instantaneous relaxation using an HLLC-type solver. Numerical test cases demonstrate significant improvements in accuracy, confirming the effectiveness of the approach in capturing multiphase flow dynamics across a wide range of Mach numbers.