A NUMERICAL MODEL FOR HYDRODYNAMICS OF PLANING SURFACES

The hydrodynamics of fast planing crafts is here numerically investigated in the framework of the potential flow approximation of an incompressible fluid. By exploiting the coordinate transformation d/dt = U d/dx, the approach is based on a 2D+t modelling of the flow that takes place in an earth fixed plane orthogonal to the hull velocity U. In the transversal plane the flow appears as the water entry of a body, shape of which changes with time. This water entry flow is described in terms of a fully nonlinear numerical approach, based on a boundary element method, which enables to evaluate the wetted area and the pressure distribution beneath the hull. Particular attention is here devoted to the description of the jet flow evolution and to the evaluation of the pressure field in the rear part of the vessel, where the fluid detaches from the solid body contour. The present model being limited to deal with bodies having the separation point clearly fixed by singularities in its shape, results are presented for prototypes of hull shapes characterised by hard chines. Comparisons with theoretical and experimental data available in literature are provided.