Diffraction of second-order Stokes waves by three-dimensional floating ocean structures: A time-domain approach

The research presented herein is a contribution to the understanding of the nonlinear interaction between second-order Stokes waves and offshore structures in bichromatic waves by a time-domain approach. The first part of the work involves a study of the generation and propagation of second-order Stokes waves in two-dimensional flume by a generic planar wavemaker undergoing both monochromatic and bichromatic motions. Particular attention is focused on the radiation boundary condition at second-order. A novel second-order radiation boundary is applied at the far-field computational boundary and its efficiency tested for a variety of wavemaker and tank configurations.; The second portion of the work is an investigation of the interaction of second-order Stokes waves with a vertical bottom-mounted surface-piercing, circular cylinder. The boundary-value problems for the first- and second-order potentials are solved at each instant of time using a three-dimensional boundary integral method with higher order isoparametric elements. A robust numerical technique is presented to treat the second-order free-surface boundary condition and radiation boundary condition at this order. Particular attention is focused on numerical accuracy and on the stability of the numerical approach. The form of the second-order radiation condition used above is modified for this three-dimensional problem and its efficiency is evaluated.; The third part of the work involves an investigation of the hydrodynamic interactions between an array of cylinders in Stokes waves, both bottom-mounted and truncated four cylinders in bichromatic are considered. Particular attention is focused on the effect of cylinder spacing and cylinder draft and the incident wavelengths on the hydrodynamic loads to second order.; The fourth part of the work consists of a study of the dynamic response of a moored floating truncated cylinder in bichromatic waves. In this case, special numerical techniques are developed to deal with the structure motion and the coupling between the hydrodynamic loads and structural response are investigated. Numerical results are presented for a range of wave and structural parameters which illustrate the influence of these quantities on the structural response.