TIME-DOMAIN MOTION COMPUTATIONS OF TWIN- AND MONOHULL SHIPS IN HEAD SEAS

Wave exciting forces on a restrained body with steady forward speed in the time-domain were computed by the authors (1995). As one step further, radiation forces and ship motions in regular waves are computed in the present paper. With impulse response functions, the integral-differential equations of motions are solved in the time-domain. The same method is also applied to compute the radiation forces of a catamaran with forward speed. The results show that the time-domain computation for ship motions is particularly meaningful in the cases where the forward speed effect is considered. Added mass and damping coefficient of a catamaran with the Lewis-form demi-hull are computed for Froude numbers 0.15 and 0.30. Good agreements with experimental results for heave and pitch motions are obtained. A Wigley hull and a Series 60, C(B) = 0.7 hull are also adopted for the motion computation. The computed results for Froude number 0.20 are compared with experimental results.