Experimental study on hydrodynamic characteristics of cavitating flows around hydrofoil under different water temperatures

In order to study the influence of the thermal effect on hydrodynamic characteristics of cavitating flows, the unsteady cavitating flows around a Clark-y hydrofoil under 279 K, 298 K and 318 K conditions are respectively investigated experimentally. Experiments are carried out in a rectangular test section of a cavitation tunnel. A high-speed video camera is used to visualize the unsteady cavitating flow patterns, and the lift and drag coefficients are measured by dynamics force measurement system. The spectral analysis of the measured data is conducted and the spectrum characteristic of the lift force around the hydrofoil is obtained. The results show that when the water temperature is increased, the average values of lift and drag coefficients decrease as well as the lift fluctuation tends to be mild by keeping the caviation number consistent. The influence on the lift and drag coefficients by temperatures becomes weaken with increases of the cavitation number. The fluctuating scale of the lift coefficient is correlated to the unsteady cavity closely. The temperature has little effect on the frequency of lift when it is cavitation inception or sheet. But when cloud cavity appears, the temperature greatly affects on the frequency based on lift. To interpret the conclusions above, it is inferred that when cavitation number is constant, the cavitation region decreases with the increasing of temperature. Moreover, the influence of the temperature is more distinct when the cavitation region is larger.