Numerical analysis of cavitation instabilities in inducer blade cascade

The cavitation behavior of a four-blade rocket engine turbopump inducer was simulated by the CFD code Fine/Turbo (TM). The code was modified to take into account a cavitation model based on a homogeneous approach of cavitation, coupled with a barotropic state law for the liquid/vapor mixture [1-4]. In the present study, the numerical model of unsteady cavitation was applied to a four-blade cascade drawn from the inducer geometry. Unsteady behavior of cavitation sheets attached to the inducer blade suction side depends on the flow rate and cavitation number sigma. Numerical simulations of the transient evolution of cavitation on the blade cascade were performed for nominal flow rate and different cavitation numbers, taking into account simultaneously the four blade-to-blade channels. Depending on the flow parameters, steady or unsteady behaviors spontaneously take place. In unsteady cases, sub synchronous or super synchronous regimes were observed. Some mechanisms responsible for the development of these instabilities are proposed and discussed.