Influence of Afterbody and Boundary Layer on Cavitating Flow

The characteristics of a cavitation water tunnel test setup and the experiments of cavitation around different models are given in this paper. Models of test are formed from combination of head and variable length afterbody. The experiments are performed initially with the smooth head and then with the roughened head. Cavitation initiates both in the wake and after the head. If the nose of models is roughened then cavitation initiates at the lower cavitation numbers. The cavitation inception is a function of the model geometry, nose condition and upstream flow characteristics. During the measuring process of drag force from non-cavitating flow regions to supercavitation case, only the tunnel pressure is reduced continuously. All measurements are performed at several Reynolds numbers. After cavitation inception in the wake, drag force increases continuously and fast. When cavitation initiates at the end of head, the mentioned force is maximum value and then decreases gradually. Supercavity is specified and compared with wedge case. The choking flow case is investigated around the models completely.