Tip vortex cavitation control by the micro vortex generator

The present study investigates the control effect of a vane-shaped micro vortex generator (VG) on the inception and development of tip vortex cavitation. Five different arrangements were tested by varying the position and installation angle near the tip of a NACA (National Advisory Committee for Aeronautics) 662-415 hydrofoil. The spatial and temporal evolution of the tip vortex cavity was captured using high-speed imaging. The result shows that VG can induce both streamwise vortices and bubbles that affect the cavitation inception. When the VGs are aligned parallel to the incoming flow direction, the generated bubble content is relatively small. Meanwhile, due to the interaction between the tip vortex and the streamwise vortex induced by the VG, the vortex cavity in these cases exhibits notable deformation and diameter fluctuations compared with the smooth case. As a result, the inception of cavitation is significantly delayed, resulting in a notable reduction in the sound pressure level. The optimal control is achieved when the VG is placed at the tip. Conversely, the VG mounted at a larger alignment angle generates bubbles at a high cavitation number, which causes the premature onset of vortex cavitation and results in a detrimental effect.