Numerical Analysis of Cavitation Instabilities and the Suppression in Cascade

In this study, unsteady cavitation and cavitation instabilities are numericaly analyzed around cascades in water/air working fluid. The numerical method employing a locally homogeneous model of compressible gas-liquid two-phase medium is applied, because it permits the entire flowfield inside and outside the cavity to be simulated easily through only one system of governing equations. Three types of.cavitation instabilities, which are similar to “cavitation surge”, “forward rotating cavitation” and “rotating-stall cavitation”, are represented numerically in flat-plate cascade under three-blade cyclic condition. Additionally, flowfields around flat-plate cascade with slit on blade are analyzed in the conditions where the three types of cavitation instabilities arise in the cascade without slit. The effect of the slit on suppression of cavitation instabilities is confirmed from the present numerical results.