Dynamique des cavités érosives : étude du collapse des vortex cavitants

Dynamics of erosive cavities: study relating to the collapse of cavitating vortexes

Institut de Machines Hydrauliques et de Mécanique des Fluides, Ecole Polytechnique Fédérale de Lausanne

Abstract

Cavitation erosion of hydraulic machines is mainly due to the collapse of transistory cavities which are formed in the wake of leading edge cavities. These cavities, known as "cavitating vortex", have the characteristics of swirling filaments which are formed according to the intense vorticity field generated in the closing zone of these pockets. With a view to analyzing the dynamics of cavitating vortex, we have used a cavitation vortex generator which allows for producing repeated and fully controlled collapses of this type of cavity. By means of a display system via a high-speed camera (1 milliom images per second) and a simultaneous follow-up of the wall pressure and vapor phase, we have established that these collapses generate waves with extremely violent impacts (10 to 20 Kbars) and which have initially provoked the damage observed.