Steady flow and stability analyses of cavitation in finite blade count impeller

The seady flow and stability analyses of cavitation in flat plate cascades corresponding to 2, 3, 4 and 5 bladed impeller were carried out to find out all of the steady cavity patterns and destabilizing modes. For this purpose each blade is treated independently. In steady flow analysis the alternate blade cavitation was found only for impellers with even number of blades. It was shown that the alternate blade cavitation occurs since the local flow near the cavity closure reduces the angle of attack to the opposing blade when the cavity closure point approaches the leading edge of the opposing blade. For 2 or 4 bladed impeller, it was confirmed that there exists no additional destabilizing mode to those found in an analysis assuming inter-blade phase difference. It was shown that the modes with total cavity volume fluctuation depend on the inlet duct length while the modes without total cavity volume fluctuation are independent on the system.