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 non-linear theory of Wu and Wang for two-dimensional foils at non-zero 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, νc/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 quasi-steady assumptions were valid only at low reduced frequencies.
Cavity wash-off was found to occur due to wave-induced changes in the angle of attack. The angle at which wash-off occurred was related to the wave characteristics for low aspect ratio foils. For a foil with an aspect ratio of 4, cavity wash-off generally occurred at the same angle of attack as that
required to maintain a cavity in smooth water.
Prepared for Office of Naval Research, Department of the Navy under Contract Nonr 710(47), Task NR 062-286
Foerster, K. E..
Force Characteristics of Restrained, Naturally Ventilated Hydrofoils in Regular Waves.
St. Anthony Falls Hydraulic Laboratory.
Retrieved from the University of Minnesota Digital Conservancy,
Content distributed via the University of Minnesota's Digital Conservancy may be subject to additional license and use restrictions applied by the depositor.