Investigation of the Primary Mechanisms of Cavitation-Induced Damages

Erosion of solid surfaces due to cavitation has been studied for decades. However, it has been a long debate that which mechanism, namely shockwaves, microjets towards the surface, or both, during the cavitation bubble collapse is the primary factor responsible for that erosion. In this project we investigate the small-scale mechanisms of material erosion induced by the collapse of a single cavitation bubble close to a wall. More specifically, our experimental setup includes modification of the initial nucleus size, the maximum bubble radius, the stand-off distance to the wall, the material softness, and the initial flow temperature. We record the evolution of the bubble using high speed cameras as well as the local impacts on the materials. With the help of specifically designed cold-wires, we also measure the temperature in the liquid and in the bubble. Two different methods are used to generate the bubble: (i) an acoustic shockwave of variable intensity, (ii) a YAG laser, which may introduce a high temperature at the start. We also combine the two methods in which the laser initially creates a nucleus, then the shockwave triggers the expansion of the bubble. The objectives of the project are included in this paper, while some first results will be presented at the CAV2018 conference.