Numerical and Experimental Study of Ventilation Effects on Ventilated Cavitating Flow

One of the least cost methods to reduce drag on under-water projectiles is to create ventilated cavitation. So, many of researchers have focused on this subject during recent decade. In this research, ventilated cavitating flow around 30o cavitator is studied numerically and experimentally. The main objective of this research is studying the effects of some important parameters such as the air ventilation rate and flow velocity on the drag coefficient and the dimensions of cavities developed around the body. The experiments were done in a semi open-loop water tunnel. The fluid flow velocity in the test section was between 14 to 22 m/s. Also the 3D multiphase fluid flow over the cavitators within the test section are modeled and analyzed numerically by solving the corresponding governing equations using finite element method and mixture model and is coupled with the Rayleigh-Plesset equation to capture the cavity development. A comparison between numerical results and experiments shows that the numerical method using CFX accurately simulates the physics of ventilated cavitation phenomena such as the cavity length, cavity diameter and cavity shape. In final, after comparison result, effect of gas ventilation on drag coefficient and shape of cavity is presented. The results show that increasing air ventilated rate causes the amount of drag force and drag coefficient to be reduced to 36%. Also at constant air ventilated rate, with reducing cavitation number, length and diameter of the cavity are increased to 77 percent and 20 percent respectively.