Leading edge interfacial phenomena of sheet and cloud cavitation

The formation and dynamics of cavity leading edge cell-like structures on a NACA 16-029 section hydrofoil has been investigated for a range of Reynolds numbers for stable (supercavitation) and shedding cavities (cloud cavitation). Optical measurements of the cavitating structures are made to quantify geometric properties including the size range and shape of the socalled cells, as well as the dynamic behaviour involving growth, division, decline and elimination. Leading edge cell structure was found to be in a state of dynamic equilibrium for the supercavitating case with cell mean cell size a function of the overlying boundary layer thickness. For shedding cavities, the leading edge evolved cyclically from surface related nuclei into streaks, merging to form a contiguous, shedding modulated, cellular structure. In both cases cells grow and with the onset of destabilization division occurs, indicative of the Saffman-Talyor instability.