Under certain environmental conditions, the nonlinear wave effects on offshore structures are important. In particular, the second-order diffraction effects on both fixed and floating structures may produce large forces and motions that are worth considering in the design of such structures. One such structure that has received considerable attention in the past few years is a vertical cylinder fixed on the ocean floor extending above the free surface. An approximate solution for forces on a vertical cylinder using Stokes' fifth order wave and diffraction theory was derived by the author in which the nonlinear free surface boundary condition was disregarded. Since then many investigators have attempted to obtain a complete and consistent second-order solution for the forces on a vertical cylinder. Unfortunately, they all disagree in the numerical results. This paper reviews these solutions and discusses the deficiency of some of these solutions. The basic nonlinear theory is outlined and a consistent second-order solution satisfying all boundary conditions is obtained. The contribution from various terms in the second-order solutions are shown separately and they are derived in closed form. Numerical results from these expressions are presented in nondimensional quantities so that they may be used in design. These curves also allow the comparison of these various terms regarding their relative importance.
Non-linear wave effects on large offshore structures
Nichtlineare Welleneffekte auf grosse Offshore-Strukturen
1983
31 Seiten, 13 Bilder, 27 Quellen
Conference paper
English
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