Experimental Study of the Effects of a Gap Clearance on the Performance of a Fully Cavitating Flat Plate with and without a Flap

Abstract

Experimental results are presented for the effect of a hinge gap on the fully cavitating performance of a flat plate hydrofoil without and with a flap. From the results of the tests it is concluded that for the zero flap deflection, no significant effects of the gap are apparent for the range of the parameters investigated. However, for a 20% flap-to-chord ratio and a 20° flap deflection a significant drop occurs in the lift and moment coefficients for a given gap ratio. This effect increases with increase in gap width. The drag on the other hand is unaffected for the range of values tested. Certain qualitative effects of the jet, arising from the gap, on the cavity appearance are discussed. Comparison of the experimental results for zero gap, with established non-linear theories, show very good agreement.