The combined effect of the steady potential on the unsteady motions of twin-hull ship in waves

In the present paper, the three-dimensional source distribution method including the coupled effect of the steady flow potential and unsteady potential is applied to predict the twin-hull ship motions in regular waves. The pulsating source and translating source are adopted to solve the corresponding unsteady potential and steady potential respectively. The unsteady ship motion prediction is usually made by neglecting the steady potential to solve the corresponding hydrodynamic forces under the assumptions of high frequency and low speed. However the steady potential might have significant influence on twin-hull ship motions because of the interactions between two hulls. Therefore it is included in the present calculation of the corresponding hydrodynamic pressure and forces, and the combined effects on six degrees freedom of motions are then investigated. The results calculated in the present study reveal that the combined effect on the unsteady motions due to the steady flow potential are indeed significant for some modes of motions of the twin-hull ship especially for pitch and yaw motions with high speed in long waves.