Experimental Study of Transition from Attached Cavitation to Nucleate Boiling on Heated NACA0015 Hydrofoil

Though wall temperature can correlate with cavitation behavior, the influence of wall temperature on cavitation have received much less attention. In this paper, we present an exploratory experimental investigation of the transition from the attached cavitation to the nucleate boiling on a heated wall. A heated NACA0015 hydrofoil was used to observe cavitation on a heated wall. At a mainstream flow velocity of 3 m/s and a temperature difference of approximately 30 K between the hydrofoil and water, a sudden transition from attached sheet cavitation to nucleate boiling was observed at cavitation number σ = 1.8. Further decreasing the cavitation number only enhanced the nucleate boiling, even though local pressure conditions allowed for fully developed cavitation. The generation of vapor bubbles were observed at the detachment of the attached cavity sheet from the wall nucleation site. After being interfered by these isolated bubbles, the cavity sheet was swept downstream by the oncoming flow. It was suggested that the vapor bubbles of nucleate boiling at the detachment of the cavity sheet could suppress the formation of attached cavitation. Owing to these observation results, we conducted an analytical examination to compare the saturation pressure condition for both the inception of the cavitation and the onset of the nucleate boiling on a heated wall. The results suggest that, based on the mainstream flow conditions, there may be a specific range of wall temperatures that allow the transition from attached cavitation to nucleate boiling.