A moored array of circular cylinders undergoes slow oscillations in the horizontal plane,i.e.surge,sway and yaw,due to the non linear excitation of ocean waves.To evaluate wave drift damping,the slow oscillation is approximated by quasi steady motions or equivalently,a uniform flow is superposed to the wave field.In the case of yawing motion,a uniform rotation about the yawing axis is enforced to the entire fluid domain.The velocity potential is expanded into perturbation series based on two small parameters that measure wave slope and velocity of steady flow.Wave drift forces (moment) are calculated by the far field method.Experiment arrangements are also discussed.Measured data are compared to the calculated results to verify the present theory.
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