Numerical Analysis of Cavitation Instabilities and the Suppression in Cascade

Abstract

In this study, unsteady cavitation and cavitation instabilities are numerically analyzed around flat-plate cascade with three blades cyclic condition in water/air working fluid. The numerical method employing an original model “locally homogeneous model of compressible gas-liquid two-phase medium” is applied to numerical simulation. The method can simply treat the entire flow field inside and outside the cavity by one system equations. As a result of numerical analysis, occurrence and oscillation characteristics of three types of cavitation instabilities are reproduced, which are “cavitation surge”, “super-synchronous rotating cavitation” and “rotating-stall cavitation”. Additionally, flow fields around flat-plate cascade with slits on blades are analyzed in the conditions where the cavitation instabilities arise in the cascade without slit. Consequently, the suppression effect of the slit on the cavitation instabilities is confirmed.