Effect of micro vortex generators on cavitation collapse and pressure pulsation: An experimental investigation

The cloud cavitation phenomenon has destructive effects on high-speed hydraulic machinery. It is vital to develop effective methods to control cloud cavitation. In this study, the dynamics of cavitation on the NACA0015 hydrofoils with and without the micro vortex generators (micro-VGs) were investigated experimentally. The current work focuses on the effect of micro-VGs on cavitation collapse and pressure pulsation. The results show that the cavitation collapse on the smooth hydrofoil involves two stages: the local cavity collapse caused by the first re-entrant jet as well as the shedding and collapse of cloud cavitation caused by the second re-entrant jet, which are related to the two peaks of pressure obtained by the sensors at 60% of chord length on the smooth hydrofoil. These characteristics have also been well identified by the proper orthogonal decomposition method because there are significant burrs in low-order modes and numerous short-time pulse signals in the corresponding time fluctuation terms. Micro-VGs induced the micro vortex flows and caused the vortex cavitation, improving the cavity stability in the midstream of the foil. Thus, there is no local cavitation collapse during the growth of the attached cavity and only one peak of pressure exists in a cavitation cycle.