FREE SURFACE EFFECT ON THE PROPULSIVE PERFORMANCE OF A SHIP (2ND REPORT)

Several experiments were carried out in the towing tank of Kyushu University in order to evaluate the effect of the free surface on hull-propeller-rudder interactions using Wigley hulls, model propellers and model rudders. An attempt was also made to elucidate the mechanism of such interactions under free surface effect using theoretical calculations involving Dawson's method, which requires double model flows around a Wigley hull and simplified propeller and rudder models. Since the singularity distributions which represent the hull, the rudder and the propeller can be obtained from the boundary conditions, forces such as hull resistance, propeller thrust and torque, and rudder drag in the self-propelled mode were calculated. Though only approximations of viscous effects are used in the calculations, it is shown that the experimental results are qualitatively explained by the numerical calculations. The effects of sinkage, mean viscous wake fractions at rudder and propeller planes and mesh divisions of the still water surface on the calculated results are dealt with in an appendix.