Theoretical analysis of transitional and partial cavity instabilities

This paper describes a new time marching calculation of blade cavitation using a linearized free streamline theory with a singularity method. In this calculation, closed cavity models for partial and super-cavitation are combined to simulate the transitional cavity oscillation between partial and super-cavitation. The results for partial cavitation instabilites on a single blade 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 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.