Characteristics of High-Speed Propeller's Foils in the Pseudo-Supercavitating Region 891781

There have been not many fundamental researches reported on practical supercavitating foils until now. Therefore, we have investigated the lift and drag performances of three types of supercavitating foil, which have been successfully applied to several high-speed boat propellers. The test was conducted in the closed type cavitation tunnel with two-dimensional foils of those blades. As a result, those foils show fairly large values of the lift coefficient C_L compared to the existing foils. In addition, it proves that there is a linear relationship between the cavitation numbers σ and C_L in the supercavitating region. Conversely, the values of the drag coefficient C_D are rather higher than those of the existing foils, so that there is much room for further drag reduction. Besides, the moment photographs of the cavitation aspects show the fact that the cavity is filled with a bubble cloud even in the supercavitating region, what is called, “pseudo-supercavitation”.