Effect of water injection on tip leakage vortex cavitation for a NACA0009 hydrofoil with medium clearance

Tip leakage vortex cavitation (TLVc) often causes flow blockage, performance loss, noise, and operational instability. In this paper, an active control method of water injection is specially designed for disrupting the structure of TLV in NACA0009 hydrofoil and suppress its cavitation. Using an adaptive mesh technique, the TLV cavitating flow at medium tip clearance (tau = 1.0) is analyzed via the LES method. The cavitation morphology, resolved with the Schnerr-Sauer cavitation model, shows good agreement with existing experimental results. Results indicate that the water injection substantially eliminates TLVc, reducing the average vapor volume by 97.31% compared with control group. It is worth noting that the water injection altered the evolution of vapor phase, shifting from the original TLVc development, collapse, and rebound to that of tip separation vortex cavitation (TSVc). The water injection reduces the drag coefficient by 3.5%. Moreover, water injection hinders the fusion of the TLV and TSV, significantly increasing the TLV radius, as indicated by a 15.40% reduction in maximum circumferential velocity and a 16.11% decrease in vortex circulation. Finally, evidence shows that an increase in the proportion of vortex stretching term explains the mechanism by which water injection mitigates TLVc.