Pulsating bubbles dynamics near a concave surface

Bubble dynamics near different boundaries have always been a hot topic in ocean engineering and many other fields. In the present study, we investigate the dynamics of high-pressure pulsating bubbles near a concave surface via experimental and numerical methods. Pulsating cavitation bubbles are generated by the electric discharge technique, and the violent expansion, contraction, and jet formation are observed through high-speed photography. Additionally, a multi-vortex ring model implemented in the boundary integral method is established to simulate the bubble motion near a curved surface. The precise non-spherical bubble shapes during bubble pulsation and detailed information on the jet velocity and wall pressure are obtained. The numerical results are found to be in good agreement with the experimental results, indicating the validity of the numerical model. Finally, a quantitative study is provided on the influence of two parameters: the distance parameter γ=L/Rm (L is the distance between the initial bubble center and the lowest point of the concave surface and Rm is the maximum bubble radius) and the concave curvature ξ=Rm/Rs (Rs is the radius of concave boundary).