Abstract
Earlier measurements of steady flow force characteristics of forced ventilated hydrofoils with trailing edge flaps have been supplemented with additional measurements using naturally ventilated hydrofoils. These measurements have been compared with a few theoretical points based on the nonlinear theory of Wu and Wang for twodimensional foils at nonzero cavitation number. The theory was also modified using Cumberbatch's method to include effects of finite span. Good agreement between the theory and experimental data Was obtained. Measurements were also made of the oscillatory lift and drag forces for restrained, naturally ventilated foils of finite span moving through a regular wave train. Flat plate foils with aspect ratios of 2 and 3 were used. The experimental data for the forces agreed fairly well with calculations based on the instantaneous angle of attack and cavitation number, and the reduced force coefficients indicated little variation with reduced frequency, Î½c/V, up to about 1.1. The phase angle between the maximum lift force and the wave crest increased with increasing reduced frequency. Computations for the phase angle based on quasisteady assumptions were valid only at low reduced frequencies. Cavity washoff was found to occur due to waveinduced changes in the angle of attack. The angle at which washoff occurred was related to the wave characteristics for low aspect ratio foils. For a foil with an aspect ratio of 4, cavity washoff generally occurred at the same angle of attack as that required to maintain a cavity in smooth water.
Original language  English (US) 

State  Published  Mar 1965 
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Equipment

St. Anthony Falls Laboratory
Lian Shen (Director)
St. Anthony Falls LaboratoryEquipment/facility: Facility