Dynamic features of a laser-induced cavitation bubble near a solid boundary

This paper deals with detailed features of bubble dynamics near a solid boundary. The cavitation bubble was created by using a Q-switched Nd: YAG laser pulse and observed using a high-speed camera (up to 100,000 frames per second). A hydrophone system was employed to monitor the acoustic signals generated by the transient pressure impulses and estimate the bubble oscillation periods. Experimental observations were carried out for bubbles with various maximum expanded radius Rmax (between 1.0 mm and 1.6 mm) and stand-off distances, ds (defined as the distance between the solid boundary and the bubble center at inception) of 0.4 ⩽ γ ⩽ 3.0, and γ = ds/Rmax. The existence of a solid boundary created asymmetry in the flow field and forced the bubble to collapse non-spherically, which finally brought forth the jet impact phenomenon. The dimensionless first and second oscillation periods were dependent on γ. A series of expansion and collapse of the bubble with cascading loss of energy were observed after the bubble had been generated. This study revealed that most bubbles lost about two-thirds of the total energy from the first maximum expansion to the second maximum expansion.

► A set of experiments were taken to investigate the laser-induced cavitation bubble dynamics near a solid boundary. ► Images of the bubble evolution were captured using a high-speed camera (up to100,000 frames per second). ► Indirect monitoring of the bubble oscillation periods was performed using a hydrophone system. ► A useful method of estimating the volume of non-spherical bubble using AutoCAD software tools was proposed. ► Detailed analyses on the pertinent global features of the evolution of the bubbles are made.