Numerical study of wave loads on a submerged cylinder at low KC numbers

The study of wave-induced forces on circular cylinders is traditionally one of the fundamental topics related to the design of more complex marine and offshore structures. For this reason, a relevant amount of research has been developed, particularly in the case of vertical cylinders, with the goal to contribute to the understanding of the problem of wave and current loads. In this work the case of a submerged horizontal circular cylinder in regular wavy flow with incoming wave crests parallel to the cylinder axis is analyzed by means of numerical simulations and experimental data. In particular, when the Keulegan Carpenter number is low enough and the diffraction parameter is well above the standard diffraction threshold, then the wave-body interactions leads to higher order loads that make the standard value of the inertia coefficient of Morison equation fail completely. The results of the computations are systematically compared with those from the experimental data obtained by one of the authors. The entire set of numerical experiments are conducted at Keulegan-Carpenter number regime up to KC = 2 and varying the depth of submergence of the cylinders to highlight the influence of the free surface. The spectral analysis evidences the effects of the submergence of the cylinder axis on the surface elevation and on the higher frequency components of the pressure at the cylinder surface.