Second-order diffraction by a bottom-seated compound cylinder

The second-order diffraction potential around a bottom-seated compound cylinder is considered. The solution method is based on a semi-analytical formulation for the double-frequency diffraction potentials, which are properly decomposed into a rational number of components in order to satisfy all boundary conditions involved in the problem. The solution process results in two different Sturm–Liouville problems which are treated separately in the ring-shaped fluid regions defined by the geometry of the structure. The matching of the potentials on the boundaries of adjacent fluid regions is established using the ‘free’ wave components of the potentials. Different Green's functions are constructed for each of the fluid regions surrounding the body. The calculation of integrals of the pressure distribution on the free surface is carried out using an appropriate Gauss–Legendre numerical technique. The efficiency of the method described in the present work is validated through comparative calculations. Finally, extensive numerical predictions are presented concerning the complete second-order excitation and the nonlinear wave elevation for various configurations of vertical axisymmetric bodies.