Effect of geometric scale and blockage on the partial cavity shedding dynamics on NACA0015 hydrofoils

Partial cavitation and the transition to shedding cavities is a significant source of noise and performance deterioration. Cavity shedding dynamics and mechanisms (namely bubbly shock propagation) observed in water tunnels vary significantly with geometric scale and blockage ratio. Understanding these variations is critical for revealing underlying flow physics at a range of scales. In this study, partial cavitation occurring on a NACA0015 hydrofoil is compared between two different geometric scales and blockage ratios. Corrections for the effects of blockage and geometric scale on the observed features of the cavitating flow are discussed. It is shown that the blockage correction accounts for variation in the mean cavity length. However, it does not sufficiently account for changes in bubbly shock properties such as shock speeds and pressure rises. An explanation for the observed differences is suggested based on the cavity pressure and desinence cavitation number of the two models.