Effects of oscillating curved wall on behavior of a collapsing cavitation bubble

The behaviors of a collapsing cavitation bubble were investigated using numerical simulations, focusing on the effects of a controlled oscillating wall with a spherically curved geometry. Different wall-controlled oscillation conditions were modeled. The collapse of the laser-induced cavitation bubble near the curved wall was observed experimentally to validate the numerical model at the same fixed standoff condition S = 1.2. A good agreement was observed between experimental and numerical results. A compressible model for the two-phase flow, based on a geometric volume of the fluid technique, was employed for numerical simulation. High-speed camera experiments captured the behaviors of the laser-induced cavitation bubbles. Both in-phase and out-of-phase oscillating motion of a rigid with spherical surface was modeled by using a sinusoidal function within a curvilinear moving grid framework. The study explored the effects of oscillating walls through numerical comparisons between the fixed and oscillating conditions, considering different initial phase conditions as φ0=−90°, 0°, φ0=+90°, and +180°. The upward jet flow forms at φ0=−90°, 0°, and +90°, while the downward jet flow forms at φ0=+180°. Numerical analyses reveal significant effects of motion conditions at in-phase (φ0=−90°, 0°) and out-of-phase (φ0=+90°, +180°) conditions, which vary with the scaled amplitude parameter, As=A/R0, defined by the ratio of the oscillating amplitude, A, and the maximum bubble radius, R0. Various features were analyzed, including oscillation and deformation of bubble shape, the formation of jet flow, and pressure peaks on the wall. Critical values of As = 0.1, 0.2, and 0.3 were identified, influencing bubble collapse time, jet flow speed, and peaks of pressure under both in-phase and out-oscillation motion.