Wave forces on a large horizontal cylinder near a plane boundary

Abstract

The present paper describes the formulation of the boundary value problem for a large horizontal cylinder fixed parallel to the crests of the oncoming regular waves in a finite water depth using the Green's second identity and linearized potential flow theory. The resulting integral equation is numerically solved for the potential functions in the flow field which encompasses the cylinder. In-line and transverse forces on a horizontal circular cylinder are computed using the evaluated potential functions on the cylinder, and the corresponding maximum force coefficients are correlated with the scattering parameter or dimensionless wave number, gap ratio of the cylinder from the plane boundary and depth parameter. Experiments are also carried out on a large diameter fully submerged horizontal cylinder held fixed at various gaps from a plane boundary, and parallel to the crests of the waves under regular wave conditions. Numerical results are first compared with other existing solutions to validate the present formulation and numerical evaluations, and further supported by the present experimental investigation. Effects of water depth and gap between the cylinder and bottom boundary on the maximum force coefficients are also illustrated. Both the maximum force coefficients for a fully submerged circular cylinder in a finite water depth increase with the increase in scattering parameter, reach their maxima and then decrease gradually with a further increase in the scattering parameter. © 1992.