High-speed photography and particle image velocimetry of cavitation in a Venturi tube

This article details the construction of an experimental visualization platform for observing cavitation. The platform uses high-speed photography and particle image velocimetry (PIV) techniques to conduct experimental research into the flow pattern and vortex field of cavitation in Venturi tubes. Dynamic mode decomposition is employed to extract the energy distribution characteristics of the cavitation flow field. Cavitation occurs at an exit-to-inlet pressure ratio of 0.595, and the length of the cavitation zone increases as this ratio decreases. When the pressure ratio reaches 0.280, the flow rate remains almost constant and the flow becomes chocked. The cavitation shape evolves periodically in the chocking flow, and the cavitation zone can be divided into three parts: an initiation and development area, a fusion area, and a collapse area. The fusion area exhibits periodic changes in the form of contraction, expansion, and re-contraction. Near the wall, the collapse area exhibits complex boundary conditions, with re-entrant jet causing bubble aggregation, rolling, and shedding. PIV and energy extraction reveal that vortices primarily appear near the wall, where they undergo a periodic process of fragmentation and fusion. The strength of the vortices exhibits a small–large–small pattern that is related to the cloud aggregation, rolling, and shedding caused by the re-entrant jet.