Three-dimensional analyses of rotating cavitation in inducers (2nd Report, Linear analysis using an annular cascade model)

In the first report, 3-D linear analysis using a finite-span cascade model was carried out, and it was shown that (1) there are not only 0th-order modes in the spanwise direction which correspond to conventional rotating cavitation previously predicted by 2-D linear analysis, but also higher order modes of rotating cavitation and (2) 0th-order modes are weakly influenced by the three-dimensionality of cavitation. The purpose of the present paper is to investigate the effects of the impeller rotation, the hub ratio, and the three-dimensionality of cavitation on rotating cavitation. Three-dimensional linear analysis using an annular cascade model is carried out based on semi-actuator disk theory. It is found that (1) there are many radial modes of rotating cavitation as previously shown using a finite-span cascade model, and that (2) a larger hub ratio has the effect of stabilizing rotating cavitation.