An analytical approximation for the horizontal drift force acting on a deep draught spar in regular waves

An analytical solution is presented for the horizontal drift force acting on a uniform circular cylinder that is undergoing surge and pitch motion in regular waves. The solution is exact to second order, for a perturbation expansion in terms of wave steepness, but is limited in a strict sense to the hypothetical case when the draught is equal to the water depth. The formulation is used to provide an analytical approximation for investigating the influence of key parameters on the horizontal drift force acting on a deep draught spar.