Experimental investigation of the influence of micro vortex generator on the bubble cavitation around a hydrofoil

The objective of the present paper is to investigate the effect of micro vortex generator (mVG) on the travelling bubble cavitation. The mVG are mounted at two different locations on the leading edge of the NACA 66 hydrofoil. The structural parameters of mVG-1 are the same as those of mVG-2, but it is closer to the leading edge of hydrofoil. A high-speed camera is employed to capture the transient evolution characteristics of the cavitation flow field. Then, the modal structure of the field is further analyzed using the Proper Orthogonal Decomposition and Dynamic Mode Decomposition methods. The results show that for mVG hydrofoil, mVG-induced “fingerlike” vortex cavitation replaces travelling bubbles, thus leading to cavity shedding dominated by the re-entrant flow and shockwave coupling mechanisms. Vortex cavitation cannot be completely cut off by the re-entrant flow, and the shockwave on the mVG-2 hydrofoil are unable to fully trigger the collapse of the vortex cavitation. Interestingly, the initial position of the vortex cavitation is relatively fixed, originating in the tail of the mVG, while the bubbles are random. The dominant mode of the baseline hydrofoil occurs in the bubble collapse region, while the mVG hydrofoil occurs in the “fingerlike” vortex cavitation and its merging attachment cavities.