Cavitation structures in a venturi flow with various backward facing steps

Cavitation inception and development caused by a backward facing step in a Venturi-type test section were studied experimentally for different step heights (0.8-4 mm). High-speed cinematography and particle image velocimetry images were used to demonstrate the cloud shedding process and cavitation development stages. It was found that for small step height (0.8 mm, h/delta(0)=1.7) cavitation started in the reattachment region in the form of a reentrant jet, and caused cloud shedding in its developed stage. For high step height (4 mm, h/delta(0)=8.5) cavitation started midway downstream of the shear layer and resembled the spanwise vortices in the separated shear layer. This study contributes experimental results for better understanding of cavitation inception and development in the separated shear layer.