Further Experiments on a Jet Flap Hydrofoil in Ventilated Flow

Experimental measurements were made of the force characteristics of a naturally ventilated hydrofoil of finite span submerged below a free surface and equipped with a jet flap. Jet momentum coefficients up to 0.35 were attained. The increment of lift associated with action of the jet flap was primarily dependent on the jet momentum coefficient and the flap angle. Measured lift increments were considerably less than those calculated by Ho from linearized theory for two-dimensional foils and zero cavitation number. Thrust recovery was dependent on the jet momentum coefficient and the flap angle, decreasing as these parameters were increased. In. all cases thrust recovery was greater than the horizontal component of the jet reaction. A brief series of tests was also conducted with a restrained, jet flap foil moving through a regular wave train. For reduced frequencies, based on the full chord, up to 0.7, the oscillatory force characteristics were essentially the same as for the foil without the jet flap for otherwise identical conditions.