Direct Numerical Simulation of High-Speed Water Droplet Impact Using a Diffuse-Interface Model

High-speed water droplet impacts are critically relevant to hypersonic flight through rain, erosion of infrared sensor windows in defense systems, and the durability testing of advanced aerospace materials. Simulating high-speed droplet impacts is challenging due to the extreme flow conditions, including shocks and gigapascal pressure levels. We present direct numerical simulations of such effects using a thermodynamically consistent six-equation compressible multiphase model. Based on a diffuse-interface method with stiffened gas equations of state, this framework captures the interfacial and shock detachment dynamics of the high-speed droplet impact phenomena. A simulation of a 0.20 mm water droplet impacting a rigid wall at 500 m/s is validated against benchmark results available in the literature. The framework sets the stage for future phase change and cavitation studies during extreme impact scenarios. It is a promising numerical tool for modeling real-world aerospace propulsion and structural design applications.