Experimental and numerical studies on the partial cavitation in a Venturi

Abstract

Abstract To effectively control the adverse effects of cavitation, it is crucial to understand the mechanism behind the formation of cloud cavitation. The transition from sheet to cloud cavitation, or cavitation shedding, can be caused by two mechanisms: re-entrant jet and condensation shock. This study investigated the shedding mechanism of partial cavitation in a Venturi using high-speed photography and Large-Eddy Simulation. The Rankine-Hugoniot equation was used to verify that the cavitation shedding mechanism: the condensation shock at σ = 0.37 and the re-entrant jet mechanism at σ = 0.98. Both operating conditions exhibit backflow, which can cause variations in image grayscale values. The relation between backflowing velocity and grayscale variation was identified in different shedding mechanisms. When the adverse pressure gradient is constant, the shock velocity is inversely proportional to the image grayscale variation, while the re-entrant jet velocity is proportional to it. These findings may contribute to a better understanding of cavitation shedding mechanism.