抄録
We performed experiments to clarify mechanism of cavitation erosion at the exit of a long orifice. In order to find this mechanism, we used a high speed video camera. As the result, we observed bubble collapses near the exit of the orifice when flow condition was oscillating. So bubble collapses due to the oscillation might cause the first stage erosion at the exit of the orifice. Using the orifice which had the tapered exit, we observed that bubble collapsed near the exit and after that bubble collapsed at the upstream of the taper like a chain reaction. The propagation speed of the bubble collapses agreed well with sonic velocity in two phase flow. So this bubble collapse mechanism could be concluded as follows : shock wave was generated by bubble collapse near the exit, then it propagate upwards, cosequently it caused bubble collapse at the upstream.
