Molecular dynamics investigation on the influence of surface characteristics on ultrasonic cavitation

In this work, molecular dynamics simulations were conducted to explore the effects of surface wettability and roughness on the bubble evolution characteristics during the ultrasonic cavitation process. In the calculation, the vibrating wall models with different wettabilities and varying roughness were constructed to reveal the cavitation process of water molecules under periodic ultrasonic excitation. The simulated results indicated that the hydrophobic surface facilitates the early formation of bubbles, but the hydrophilic wall contributes to the stabilization of bubble structures and their expansion into the bulk liquid. Meanwhile, the cavitation effect can be enhanced with the increasing roughness due to the generation of geometric traps. In addition, the geometric traps can promote the generation and persistence of bubbles near the boundary. Finally, the appearance, growth, and collapse of bubbles were related to the oscillation of pressure.