Study on Scale Effects of Hydrodynamics around Prismatic Planing Surface by using CFD

Abstract

The purposes of this study are to propose a procedure for accurate calculation of the flow field around a prismatic planing surface by using an existing commercial CFD cord (Star-CCM+), and investigate the scale effects of its hydrodynamic phenomena. First, according to ITTC Recommended Procedure 3)4) , the hydrodynamic forces acting on a prismatic planing surface are calculated and compared with the measured results. As a result, it is found that the calculation accuracy of the frictional force is poor by appearance of numerical ventilation. In order to obtain highly accurate calculation, the resolution of the partial mesh around stagnation line are made higher and the surface tension model is included, moreover, un-steady calculation is applied. The above-mentioned mesh generation procedure is applied for the 10 times large prismatic planing surface and the scale effects of hydrodynamic phenomena are investigated, and it is shown that the pressure coefficients acting on the wetted surface area are same regardless of model size and the frictional resistance coefficients acting on the wetted surface and spray area are near the turbulent frictional coefficient line of the equivalent flat plate. On the other hand, the pressure coefficients acting on the spray area has the scale effects if model size is too small because of the surface tension effects.