Studies of weak and strong nonlinear sea loads on floating marine structures

摘要

This thesis consists of four selected papers of my work for the paste few years, which considers some problems of weak and strong nonlinear sea loads on floating marine structures. The weak nonlinear problem that we study here, is hydrodynamic loads on marine structures due to wave-current-body interaction. The strong nonlinear problem that we consider, is slamming loads on conventional and high-speed vessels. The first two papers deal with the wave-current-body interaction problem. A theoretical and numerical method to analyse wave-current interaction effects on large-volume structure is developed. The theory is based on matching a local solution to a far-field solution. In the far-field the waves ''ride'' on the undisturbed current velocity, while in the near-field the waves ''ride'' on the local steady flow. A boundary element method based on Green's second identity has been applied to solve the problem. The far-field solution is represented by a sum of multipoles with singularities inside the body. The multipoles satisfy the radiation condition and the far-field free-surface condition. The problem has been solved to first-order in incident wave amplitude and current velocity. In the free-surface conditions and body boundary conditions the local steady flow has been taken care of. The last two papers consider the slamming loads on marine structures. A numerical method for studying water entry of a two-dimensional body of arbitrary rigid cross-section is presented. A boundary element method has been used to solve the problem with nonlinear free-surface and body boundary conditions. Important features are how the jet flows occurring at the intersections between the free-surface and the body are handled, and how conservation of fluid mass is satisfied in areas of high curvature of the free-surface. The numerical results have been checked by satisfying conservation of mass, momentum and energy. 103 refs., 45 figs., 5 tabs.