Influences of Surface Characteristics of Underwater Vehicle on Its Hydrodynamic Properties

To optimize the headform design of an underwater vehicle, water tunnel experiment was conducted to analyze the influences of different surface characteristics of the headform on hydrodynamic properties of the vehicle. The headform includes grooved surface, concave surface and smooth surface. The natural cavity shape, the periodical fluctuation of the cavity and the drag coefficient for different head surface were obtained. The results show that: 1) for same cavitation number, the vehicle with smooth head surface has higher cavitation resistance, but the grooved and concave head surfaces are easier to generate cavitation with complete and transparent partial cavities; 2) the smooth head surface produces unsteady and non-observable cavities, while the grooved and concave head surfaces produce steady cavities with periodic fluctuation; and 3) in a certain speed range, the unsmooth head surfaces (i.e. grooved head surface and concave head surface) can gain better drag reduction property compared with the smooth head surface, and at a speed of 12.8 m/s they can obtain the best drag reduction amount of 5% and 8%, respectively.