Performance of Supercavitating Hydrofoils with Flaps, with Special Reference to Leakage and Optimization of Flap Design

A modified linearized theory was developed for supercavitating, flapped foils of arbitrary form in which effects of fluid leakage through the flap hinge were considered. It was found that the performance at conditions other than design conditions was improved with the use of trailing edge flaps. The drag-lift ratio may be reduced by a factor of 1/2 to 1/3. The foil performance is dependent on the flap-chord ratio, e, and the flap deflection, performance increasing with small e. Effects produced by leakage through the flap hinge were significant in their influence on velocity distribution and flap effectiveness (increment in lift coefficient per unit change in flap angle). The effect of hinge leakage on the overall performance, i. e., lift, drag, and moment, was small and may be neglected in most cases.