Theoretical analysis of transitional and partial cavity instabilities

This paper describes a new time marching calculation of blade surface cavitation based on a linearized free streamline theory using a singularity method. In this calculation, closed cavity models for partial and super cavitations are combined to simulate the transitional cavity oscillation between partial and super cavitations. The results for partial cavitation instabilities on an isolated hydrofoil located in a 2-D channel are presented. Although the re-entrant jet is not taken into account, the transitional cavity oscillation with large amplitude, which is known to occur when the cavity length exceeds 75% of the chord length, was simulated fairly well. The partial cavity oscillation with relatively high frequency was also well simulated with the frequency agreeing with that of previous stability analysis and of experiments. The present calculation can be easily extended to simulate other cavity instabilities in pumps or cascades.