Attached cavitation in a laminar separation bubble

The present study aims at studying the inception, the growth and the potential unsteady dynamics of attached vapour cavities in large laminar separation bubbles. A viscous silicon oil has been used in a venturi geometry in order to explore the flow for Reynolds numbers ranging from Re = 800 to Re = 2000. The results show that at low Reynolds number the attached sheets that are attributed to cavitation do not have any obvious dynamics and abruptly transit to supercavitation when lowering the cavitation number. For Re 1200, cavitating vortices are intermittently observed in the wake of the attached cavity with no clear period. Finally, a periodic shedding/shrinking of the main cavity is first observed for Re 1400, in a narrow range of cavitation numbers, together with a slower growth of the cavities when lowering the cavitation number. This regime is then present at higher Reynolds numbers, in a wider range of cavitation numbers.