A nonlinear calculation of rotating cavitation in inducers

In the previous linear analysis (Tsujimoto et al., 1993) it was found that there can be a backward rotating cavitation as well as a forward mode which rotates faster than impeller. Although some shaft vibration has been observed, which might be caused by the backward mode, experimental evidence has been obtained only for the forward mode. The purpose of the present study is to find out the factors which determine the amplitude of each mode of rotating cavitation by taking into account several nonlinearities. A time marching nonlinear 2-D flow analysis was carried out for this purpose. It was found that the increase of cavitation compliance at lower inlet pressure can be a factor which limits the amplitude. The mode selectivity is mainly dependent on the stability limit obtained by a linear analysis for which the phase delay of cavity has a most important effect.