Research on the Collapse Characteristics of Cavitation Bubbles near a Semi-Cylindrical Groove

Cavitation research is critical for anti-cavitation design of fluid machinery flow components, but the collapse dynamics of cavitation bubbles near common wall types, such as semi-cylindrical grooves, remain unrevealed. In this paper, the morphological evolution, vortex ring evolution, and bubble migration characteristics of the cavitation bubble near a semi-cylindrical groove were investigated by means of dual-view high-speed photography. The results show that (1) when the bubble is located at the symmetric position of the semi-cylindrical groove, four typical vortex ring phenomena appear during its collapse: longitudinal elliptical vortex ring, double-layer elliptical vortex ring, circular vortex ring, and transverse elliptical vortex ring. (2) Longitudinal elliptical vortex rings, the most frequently observed type, are concentrated in regions with small to moderate dimensionless distances. Double-layer elliptical vortex rings and circular vortex rings correspond to moderate and large dimensionless distance intervals, respectively. Transverse elliptical vortex rings tend to form when the bubble has a small dimensionless radius and is located near the groove center, a phenomenon strongly associated with the initial bubble position. (3) When the bubble is located at an asymmetric position, three cases are found, namely, the bubble migrates from the groove to the flat wall, the bubble impacts the flat wall vertically downward, and the bubble migrates from the flat wall to the groove.