A parameter map of cavitation from impacts between solids immersed in water

Abstract

Cavitation when two solids immersed in water collide has been studied theoretically and experimentally. A dimensionless parameter map showing a threshold line that delimits with good agreement the cavitation and non-cavitation zones was constructed. The threshold line was set by a cavitation number established with a lubrication model. Experiments were conducted using a device with a solid steel sphere colliding with a solid aluminum plane for different impact velocities and water column heights. When the impact forces are in the order of 100 to 1000 N, only cavitation generated by the rapid separation of solids in the liquid (CSSL) is observed; however, this type of cavitation along with cavitation due to tensile waves (TWC) are perceived for collision forces greater than 1000 N. In some events in which both types of cavitation (TWC-CSSL regime) appear, light emission also takes place. The kinematic coefficient of restitution and impact speed can be used to determine the cavitation onset, the transition from CSSL to TWC-CSSL regimes and the collision events in which photon production occurs. The obtained map will provide key information to develop potential applications as cavitation machining and surface treatment.