A VOF-IBM Method for High-Fidelity Simulation of Fluid-Structure Interaction in Two-Phase Flows: Application to Rain Interaction With a NACA-0012 Wing

In the present study, a novel numerical method is developed to simulate fluid-structure interactions in two-phase flows, focusing on the impact of rain droplets on aircraft surfaces under wet weather conditions. The complex dynamics of raindrop deformation and breakup are captured using the Volume-of-Fluid (VOF) method, while the ghost-cell immersed boundary method (IBM) is used to resolve moving solid surfaces. The coupling between VOF and IBM is carefully handled to allow accurate prediction of drop spreading on arbitrary solid surfaces with different contact angles. The method is implemented in the open-source Basilisk solver with quadtree/octree meshes for adaptive mesh refinement (AMR). Validation tests, including Couette flows between rotating cylinders, pitching airfoils, and drop impact on a solid sphere, were performed, and the numerical results are compared against analytical solutions as well as previous experimental and simulation results. The validated method is applied to simulate a raindrop impact on a NACA-0012 wing.