The effects of inlet casing geometries on unsteady cavitation were investigated with a 3-bladed inducer. Through the experiments with various types of casings, the unsteady cavitation occurrence range in cavitation number was examined for various flow rates. It was found that the onset point of rotating cavitation moves to lower cavitation number when the tip clearance was increased. The size and location of casing enlargement affected the occurrence of cavitation instabilities significantly. Backflow at inducer inlet and tip cavity were also investigated to obtain the information to understand the mechanism of suppression of unsteady cavitation by changing the geometry of the casing.
