Basic methods and applications of a multiphase-flow solver in fluid-body interaction problems

This paper introduces MultiPHydro, an in-house computational solver developed for simulating hydrodynamic and multiphase fluid—body interaction problems, with a specialized focus on multiphase flow dynamics. The solver employs the boundary data immersion method (BDIM) as its core numerical framework for handling fluid—solid interfaces. We briefly outline the governing equations and physical models integrated within MultiPHydro, including weakly-compressible flows, cavitation modeling, and the volume of fluid (VOF) method with piecewise-linear interface reconstruction. The solver’s accuracy and versatility are demonstrated through several numerical benchmarks: single-phase flow past a cylinder shows less than 10% error in vortex shedding frequency and under 4% error in hydrodynamic resistance; cavitating flows around a hydrofoil yield errors below 7% in maximum cavity length; water-entry cases exhibit under 5% error in displacement and velocity; and water-exit simulations predict cavity length within 7.2% deviation. These results confirm the solver’s capability to reliably model complex fluid-body interactions across various regimes. Future developments will focus on refining mathematical models, improving the modeling of phase-interaction mechanisms, and implementing GPU-accelerated parallel algorithms to enhance compatibility with domestically-developed operating systems and deep computing units (DCUs).