A.Yu. Kravtsova, K.S. Pervunin, M.V. Timoshevskiy
Institute of Thermophysics, SB RAS,
Novosibirsk State University

High-speed imaging and velocity field measurement about cavitating plate with rounded nose and NACA0015 hydrofoil

The paper reports on high-speed imaging and PIV study of cavitating flows around a flat plate with semi-circular leading edge and sharp-cut end, and a NACA0015 hydrofoil. Both test foils were investigated at a series of attack angles ranging from 0 to 9 degrees with varying cavitation number. Several known types of cavitation common to both foils, but also some different patterns, were registered. At small angles of incidence (less than 3°), cavitation on the plate was found to begin in form of a streak array (bubble-band) whereas the one on the hydrofoil in the form of travelling bubbles. For the regimes with developed cavitation on the NACA0015 hydrofoil, the scattered and discontinuous bubble streaks grow but subsequently merge into larger bubble clouds forming a remarkably regular lattice pattern. However, once the incidence angle increased to 9°, the cavitation pattern on the hydrofoil changed to a streaky pattern like that for the plate at small attack angles, whereas the regime on the plate showed no significant changes. The time-averaged velocity and turbulent characteristics distributions show that the incipience of cavitation is governed by the development of the carrier-fluid flow around the foil leading edges, but the subsequent flow pattern depends strongly on the cavitation regime and showed markedly different distributions compared to the noncavitating regime.
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