Incipient Cavitation Studied Under Strong Thermodynamic Effect
Incipient cavitation was studied under simulated cryogenic conditions on a NACA0015 hydrofoil in a tunnel filled with the perfluorinated ketone 2-trifluoromethyl-1, 1, 1, 2, 4, 4, 5, 5, 5-nonafluoro-3-pentanone. Through pressure measurements on the hydrofoil, laser-illuminated high-speed photography, and flash-illuminated photography, the extent of cavitation and the characteristic frequencies of its oscillation were studied under varying speeds in the range of 1.7-6.7 m/s and several angles of attack. The results presented in this paper are limited to a 5.1-degree angle of attack. It was found that the vapor formation was much stronger in fluoroketone than in cold-water tests at similar cavitation numbers. The formed bubbles were significantly smaller and there existed an extended speed range over which fluctuation amplitudes grew with no well-defined frequency peaks, as was observed in water.