Numerical simulations of a ship obliquely advancing in calm water and in regular waves

Numerical simulations of the S-175 containership obliquely advancing at constant forward speed in calm water and in regular waves were conducted using a potential flow method. A double-body potential and trailing vortex sheets, which modeled the flow field around the ship obliquely advancing in calm water, yielded transverse forces and yaw moment due to the lift effect. Perturbation potentials describing the free surface flow yielded first-order wave-induced motions and second-order wave loads. Evaluating and then averaging the associated second-order wave loads obtained the steady wave drift forces and moments. Generally, numerical predictions compared favorably to experimental measurements. A systematic analysis demonstrated that, in short beam waves, the transverse wave drift force attained considerable amplitudes, and these amplitudes increased rapidly at larger drift angles. The transverse force due to wave drift effects in beam waves and due to the lift effects in calm water were nearly of equal magnitude. Therefore, when predicting wave drift loads acting on a maneuvering ship, the effect of drift angle should be accounted for.