Suppression of Cavitation Instabilities in an Inducer by J Groove

The suppression of cavitation instabilities was attempted through the control of tip leakage vortex cavitation. The control was made by using shallow grooves, called J groove, on the casing wall. With J grooves, the onset regions of the rotating cavitation and the asymmetric cavitation could be diminished. However, a cavitation surge appeared at higher cavitation numbers. From the observation of cavitation, it was found that the cavitation surge occurred when the tip leakage vortex cavitation started to interact with the leading edge of the next blade. This type of cavitation surge could be avoided by extending the leading edge of the J groove upstream. However, in this case, another type of cavitation surge occurred at much lower cavitation numbers, which was caused by the cavitation between the blade surface and the tip leakage vortex cavitation. These results highlight the importance of the tip leakage vortex cavitation for cavitation instabilities.