Two-Dimensional Unsteady Planing Surface

Abstract

The two-dimensional unsteady problem of a flat planing surface is analyzed based on airfoil theory. The present analysis treats the effect of the time-varying wetted length on the added mass and damping coefficient. When the reduced frequency becomes very small, the change in wetted length approaches the displacement of the intersection of the planing surface and the undisturbed water surface. In the limiting case of zero frequency, the wetted length change reduces to zero. It is noted that the damping coefficient by the present analysis indicates the negative value in the very small reduced frequency, as Ogilvie and Bessho predicted previously in their theories derived from the different points of view.