Investigation on post-collapse rebound and rebound-induced pulsations of hydraulic cavitation in a Venturi

Abstract

High-frequency and high-amplitude pulsation characteristics play a significant role in the various negative effects of hydraulic cavitation, but the formation mechanism has not been explored clearly. Addressing this problem, experimental and numerical studies on internal cavitation flow, represented by Venturi cavitation, were conducted. Through high-speed photography and image processing, post-collapse rebound, a rarely reported hydraulic cavitation evolutionary link was demonstrated. Based on a self-developed simplified compressible cavitation algorithm, the evolution and formation of rebound were analyzed, and the formation mechanism of high-frequency and high-amplitude pressure pulsation was further revealed. Also, the effects of compressibility and pressure ratio were studied. The results show that reciprocating rebounds occur after the detached cavity collapses, with the rebound cavity volume successive decreasing. Rebound is the result of pressure wave propagation. The propagation of the cavity collapse-induced peak pressure tends to develop a trough pressure low to saturated vapor pressure, resulting in the post-collapse rebound. Reciprocating rebounds and collapse are key links causing strong cavitation pulsations, especially high-frequency and high-amplitude pulsations. The collapse of the detached cavity and reciprocal rebound cavities within a single evolutionary cycle induced extremely high pressure and multiple high pressures successively, forming the high-frequency and high-amplitude pressure pulsation. Besides, compressibility is the key to the numerical prediction of rebound. The number of rebounds and the volume of the rebound cavity depend on the severity of cavitation.