Force Characteristics of Flapped, Ventilated Hydrofoils in Smooth and Rough Water

Abstract

Experimental measurements were made of the lift and drag forces on superventilated hydrofoils of finite span submerged below a free surface. The foils were equipped with fixed trailing edge flaps of various angles of deflection. Experimental lift data taken with the foil in smooth water and extrapolated to zero cavitation number agreed well with two-dimensional theory modified to include effects of finite span and submergence. Measurements of the oscillatory forces for an artificially ventilated foil moving through a regular progressive wave train agreed well with quasi-steady calculations for near zero σ. At the higher σ, the calculated values were greater than the measured, primarily through deficiencies in the prediction of the oscillatory cavity pressure.