Simulation of vapor bubble collapsing near or on wall in stationary water or high speed water

Collapse processes of a vapor bubble which was near or on the wall under the condition in stationary water or high speed water were simulated by numerical calculation. The results show that the stability of a bubble was influenced by the distance between the bubble and the wall as well as the flow velocity. The collapse time of the bubble on the wall was shortest in the high speed water and longest in the stationary water. The instability of the bubble was increased when it was apart from the wall. When a bubble collapsed at a certain distance to the wall, the jet could not impact the wall directly so the wall suffered only from the shock wave. Moreover, the pressure to the wall was less than the maximum pressure generated in the time of the bubble collapsed completely due to the rapid attenuation of the shock wave. When the collapse center was just on the wall, the micro pit damage was produced by jets impacting the wall directly and the ring damage was formed due to the alternate stress generated by the shock waves. The bevel jet was generated contrary to the flow direction when the bubble collapsed in the high speed water, which may cause the ripple and fish-scale pit damage on the transition parts of many hydraulic systems.