1994 年 14 巻 54 号 p. 179-184
In order to clarify the mechanism of the severe erosion mainly resulted by the singular vortex cavitation, we carefully try to observe the vortex cavitation associated with the erosion around a butterfly valve by means of a high-speed video-camera, whose maximum framing rate is 40, 500 per seconds. The velocity of cavitating flow are measured with the correlation method, one of the digital-image processing-technique. It is worth noticing that the vortex cavitation develops in the boundary region between the main flow region, i. e., the orifice-jet, and the recirculating region. The cavitating vortex core consists of several tiny vortex cavitation. And the rotating velocity of the highly erosive vortex cavitation can be also detected by the technique.