Effect of stagnation flow on high-speed droplet impact containing gaseous cavities

The critical role of high-speed water droplet impacts spans a broad range of natural and industrial applications, particularly in water droplet erosion management in steam and wind turbine blades, pipes, and aircraft wings. Understanding erosion dynamics is vital for ensuring structural integrity and operational efficiency. This paper presents a numerical investigation into high-speed droplet impacts under realistic conditions, considering factors such as air velocity and the presence of gas cavities within the droplet. The study employs a compressible volume of fluid method to accurately model droplet deformation and the resulting pressure forces. The impact modeling of compressible liquid droplets, impinged at speeds up to 150 m/s, is performed. Our simulations reveal distinct behaviors between impact with and without co-flow (stagnation flow). In co-flow conditions, additional pressure peaks emerge, reaching approximately half the magnitude of the primary peak. Furthermore, internal cavities within the droplet induce secondary pressure peaks that surpass the initial impact pressure—an effect not observed in dense droplet impacts. This newly uncovered pressure peak is expected to play a crucial role in understanding water erosion mechanisms. Additionally, the paper investigates the effects of the cavity's position, size, and number on impact pressure variations. Numerical results show that the presence of a secondary gaseous bubble increased the maximum pressure by nearly one-third under the same impingement conditions. The insight gained from this research could contribute to a deeper understanding and more effective mitigation strategies for water droplet erosion under realistic impact scenarios.