An improved particle method for simulating three-dimensional fluid-complex-structure interaction with moving polygon wall boundary and hybrid turbulence models

Conventional mesh-based computational fluid dynamics methods face challenges in accurately capturing fluid motion within complex moving geometries due to their inherent limitations, such as cumbersome geometric modeling, high computational costs, and difficulties in resolving phase interfaces. To address these issues, this study improves the moving particle semi-implicit method by incorporating a polygonal wall boundary condition to simplify the modeling of intricate geometries. Furthermore, a hybrid turbulence model is developed for simulating turbulent flows, combining large eddy simulation with a zero-equation Reynolds-averaged Navier-Stokes approach. Additionally, a novel boundary force integration model is introduced to compute the hydrodynamic forces and torque acting on moving solid structures based on wet-area integration. The proposed method is validated through three benchmark cases: turbulent channel flow, a water entry experiment, and an oil churning experiment. The numerical results demonstrate good agreement with reference data, successfully capturing key flow features such as surface oil films, coated oil layers, and reverse hill oil domains in disk churning simulations. In a complex gearbox application, the predicted torque values fall within the experimental error range. Moreover, the study systematically investigates the influence of fluid viscosity, fluid level, and rotational speed of complex geometries on the resulting hydrodynamic torque. The developed methodology offers an accurate and computationally efficient framework for analyzing complex fluid-structure interaction problems.