Spatio-temporal stress evolution during high-speed elliptical droplet impact on rigid walls

High-speed liquid droplet impingement erosion is governed by transient impact pressures and wall shear stresses that are nearly impossible to measure experimentally. Computational models are therefore essential for understanding the underlying mechanisms. This study employs a compressible Volume-of-Fluid (VoF) solver to predict the wall stress and force evolution during high-speed impact of liquid droplets on rigid surfaces. The model is validated against experimental force–time profiles at low velocities for spherical droplets and subsequently extended to higher speeds and elliptical shapes relevant to impact-induced erosion. Compressibility effects within the impacting droplet drive the early-stage stress localisation observed in high-speed impacts. The evolution of compression and expansion waves within the droplet are compared against theoretical models for model verification. We establish resolution thresholds required by this VoF-based framework to avoid unphysical results and solver divergence through a systematic grid and time-step refinement study. Parametric studies with varying impact velocity and droplet size are conducted, and their influence on impact stress predictions are presented. We show that deviation from a perfect spherical shape leads to significant shifts in stress localisation behaviour that are not captured by classical analytical models. A database of transient normal and tangential wall stresses across a range of impact velocities and droplet sizes is also provided to support future erosion modelling, fluid–structure interaction studies, and the benchmarking of multiphase solvers operating in the high-inertia regime.