Experimental and numerical investigation of high-speed particle collisions on wet surfaces

This study investigates the influence of liquid films on high-speed particle–wall collisions. The relationship between the behavior of liquid film and the Coefficient Of Restitution (COR) is experimentally and numerically examined. Experiments are conducted for normal impacts on both dry and wet surfaces with varying the impact speed, the liquid temperature and the film thickness. Observations show that increasing the impact speed induces a morphological transition of the liquid film from a bridge to a dome. The transition is accompanied by an increase in the COR ratio (defined as the ratio of wet-to-dry COR), implying that the extra dissipation in the presence of the liquid film is attenuated. Numerical simulations are performed using a coupled model incorporating the Volume Of Fluid (VOF) method and the Hirt (1990) cavitation model. Validated through qualitative and quantitative comparisons with the experiments, the numerical method is confirmed to well capture the change in the COR ratio in connection with the morphological transition. The simulated results reveal that the increase in the COR ratio is attributed to the cavitation-induced disappearance of liquid in the particle–wall gap owing to the pressure drop therein immediately after the rebound. Our findings would provide valuable insights into the multiphase flow dynamics of interaction between high-speed particles and wet walls, thereby enhancing the prediction accuracy of practical numerical simulations such as CFD–DEM.