Second-Order Wave Forces on Vertical CyLinder

Second-order diffraction effects are included in evaluating the maximum horizontal forces on a vertical cylinder under a second-order deep water progressive wave. For large cylinders, the values of the maximum horizontal force are significantly higher than are predicted by linear theory due to second-order terms. Current engineering practice for slender cylinders is to compute the maximum horizontal force using fifth-order Stokes theory with a mass coefficient taken from linear theory. It is shown that this gives an adequate approximation to second-order diffraction effects in the maximum horizontal force, to within 5% for the steepest wave. Further examination of these results is encouraged.