Dynamics of the supercavitating hydrofoil with cavitator in steady flow field

Abstract

Maintaining stability remains a crucial issue for the safety of underwater vehicles, especially during high-speed navigation where flow cavitation may occur. Cavitators are small protrusions on the hydrofoil surface, which can be used to control the patterns of flow cavitation. In this study, we investigate the effect of cavitators on supercavitating flow and hydrodynamic forces for high-speed hydrofoil. The volume of fluid method and the large eddy simulation turbulence model with the Kunz cavitation model are used in the simulations in order to accurately capture the interface between two phases (water and vapor) and the region of flow supercavitation. To validate the numerical method, the time-averaged simulated results of the supercavitating flow over a wedge-shaped hydrofoil are compared and validated against the experimental data by Kermeen (“Experimental investigations of three-dimensional effects on cavitating hydrofoils,” Technical Report No. 47-14, Engineering Division of the California Institute of Technology, Pasadena, CA, 1960). Then, the numerical method is used to simulate the supercavitating flow of two-dimensional and three-dimensional cases with and without the cavitator placed on the lower side of the hydrofoil. The simulations were conducted for the cavitator located at the 1/32, 1/16, 1/8, and 1/4 chord of the hydrofoil at various angles of attack 1°–12° and cavitation numbers at 0.1, 0.2, and 0.4. A detailed analysis is made to examine the relations between cavitation pattern, hydrodynamic forces, and cavitator placement location. Compared to the cases without the cavitator, the supercavitating flow over the hydrofoils controlled by the cavitator demonstrates a significant difference in lift, whereas the drag does not change much. The changes in lift are closely related to the cavitator location. These findings can serve as a good guidance on how to improve the hydrodynamic performance and stability condition of a high-speed hydrofoil/wing using the cavitator.