Theoretical and Experimental Studies of an S-Catamaran

Using a nonlinear shallow-water solitary-wave theory it was demonstrated that for a ship moving at supercritical speed along the centerline of a rectangular channel, if the hull sectional-area curve is of a special form determined by the solution of an oblique double-soliton interaction and the channel width is chosen to ensure complete wave cancelation through sidewall reflection, the ship waves can be made to form a purely localized pattern around the ship so that its wave resistance, which results only from far-field free waves, theoretically vanishes. To get rid of the crucial dependence on impractical sidewall reflection, this mechanism was developed further to obtain a novel catamaran comprising twin hulls with curved centerlines, yaw and skegs; it has theoretically zero wave-resistance at a chosen supercritical design speed in laterally unrestricted shallow water. Despite certain deviations from the ideal form for practical reasons, the wave-resistance of the new curved-yawed-hull catamaran with and without skeg was numerically found to be less than that of an equivalent straight-unyawed-hull catamaran by 50 and 30%, respectively. Now, the new design, albeit without skeg, has been validated by model experiment and comparison with a state-of-the-art reference catamaran of equal main dimensions that was developed and tested earlier in the VBD. Up to 28% wave-resistance reduction was achieved in the experiment, although not in the originally designed configuration but at a reduced yaw angle found by trial and error.