NUMERICAL INVESTIGATION OF 3-D WING MOVING OVER FREE SURFACE IN WATER OF FINITE DEPTH.

Three-dimensional (3-D) wing moving steadily over free water surface with the effects of finite depth has been investigated numerically using an iterative boundary element method (IBEM), which was developed for cavitating 3-D hydrofoils advancing under a free surface. The IBEM has been modified and extended for this purpose. The water is incompressible, inviscid and the flow is irrotational. All variables and equations are made dimensionless. In this way the convergence of the numerical scheme is achieved very quickly and consistently. The IBEM is based on Green's theorem. The wing part of problem (including its wake), the free surface problem and the bottom surface problem are solved separately with the effects on each other. The 3-D wing surface, the bottom surface and free surface are modeled with constant strength source and doublet panels. The kinematic boundary condition is applied both on the wing surface and on the bottom surface. On the other hand, the linearized kinematic and dynamic combined condition is applied on the free water surface. The method is first applied to a rectangular wing with a high aspect ratio to compare the pressure distribution on mid-section strip with that of two-dimensional method. Later, the IBEM is applied to a tapered swept-back wing and the effects of finite depth on wing performance have been examined. It is noted that the reduced water depth causes an increase in Kelvin wedge angle, wave height and wave length compared to the infinite depth case. It is also found that a decrease in the depth of bottom surface causes an increase in the loading on the wing. [ABSTRACT FROM AUTHOR]