Numerical Study on the Characteristics of Natural Supercavitation by Planar Symmetric Cavitators With Streamlined Headforms

A novel supercavitation-based device named Rotational Supercavitating Evaporator (RSCE) was recently designed for desalination. In order to improve the blade shape of rotational cavitator in RSCE for performance optimization and then design three-dimensional blades, two-dimensional numerical simulations are conducted on the supercavitating flows (with cavitation number ranging from 0.055 to 0.315) around six planar symmetric cavitators with different streamlined headforms utilizing k – ε – v′² – f turbulence model and Schnerr-Sauer cavitation model. We obtain the characteristics of natural supercavitation for each cavitator, including the shape and resistance characteristics and the mass transfer rate from liquid phase to vapor phase. The effects of the shape of the headform on these characteristics are analyzed. The results show that the supercavity sizes for most cavitators with streamlined headforms are smaller than that for wedge-shaped cavitator, except for the one with the profile of the forebody concaving to the inside of the cavitator. Cavitation initially occurs on the surface of the forebody for the cavitators with small curvature of the front end. Even though the pressure drag of the cavitator with streamlined headform is dramatically reduced compared with that of wedge-shaped cavitator, the pressure drag still accounts for most of the total drag. Both the drag and the mass transfer rate from liquid phase to vapor phase are in positive correlation with the supercavity size, indicating that the cavitators with the elliptic and hyperbolic cosine-type forebodies could be utilized for the optimal design of three-dimensional blade shape of RSCE.