Supercavitating Flat-Plate with an Oscillating Flap at Zero Cavitation Number

The results of experimental and theoretical investigations on a supercavitating flat-plate with an oscillating flap at zero cavitation number are presented. The experiment was carried out in a vertical free-jet water tunnel using 3 in. chord and 2 in. chord flat-plate hydrofoils, both having flap-chord ratios of 0.29. Various relative locations of the free surfaces were used and the reduced frequency range of zero to four was covered. Amplitude and phase angle of lift, drag, and moment as well as the surface wave speed were measured. The problem was also solved, analytically by means of a first order perturbation theory using complex acceleration potential. Numerical values were obtained for the cases of infinite fluid, symmetrical jet, and zero spray thickness using three flap-chord ratios (0.25, 0.30, 0.40). Fairly good agreement between the experimental data and the analytical results was obtained.