Experiments on unsteady cavitation

 The unsteady behaviour of cloud cavitation is obviously influenced by its internal flow pattern. The main purpose of this work is to investigate such a two phase flow during a cavitation cycle. The tests are carried out with a convergent divergent nozzle. Observations are made by using a classical video set in combination with a stroboscopic light sheet. The use of a double optical probe enables void fraction and velocity to be measured inside the two phase flow structure. Data acquisition is governed by a pressure signal measured near the cavity closures to follow their evolution during the shedding process. Special care has been taken in validating the experimental techniques because they have not been used in such flows. The measurements show an extended reversed flow occurring along the solid surface. It plays a significant function in the vapour cloud shedding process. Received: 11 September 1995 / Accepted: 28 June 1996