Improved computational models for temperature depression of developed cavitation on hydrofoils

Temperature depression in the cavitation zone is necessary for the thermodynamic effect of developed cavitation of a liquid flowing in a device. Proper estimation of temperature depression is useful for determining the required net positive suction head of a rotodynamic pump operating under cavitating flow conditions, where the thermodynamic effect is dominant. In this paper, following a brief review of computational models for temperature depression in the literature, a novel model is identified for temperature depression of cavitating water flowing over hydrofoils. However, this model fails to take account of important variables such as the vapor volume flow rate coefficient and cavity area coefficient and the cavitation number. To remedy this deficiency, two improved computational models are developed by introducing the vapor volume flow rate coefficient and cavity area coefficient and the cavitation number, respectively. The two models are validated by employing experimental data on developed cavitation of water flowing around NACA 0015 hydrofoils at 12° angle of attack. They are best-fitted to experimental curves of temperature depression vs temperature and temperature depression vs cavitation number, respectively, with respective errors of 4.87%–10.91% and 5.11%–8.30%. The determined constants in the improved models are appropriate for prediction of temperature depression–temperature curves. The incorporation of Reynolds number and Mach number slightly reduces the error of temperature depression–temperature curve fitting at both low far-field temperature and large cavitation number.