Non-linear dynamic analysis of the response of moored floating structures

Abstract

© 2016 Elsevier Ltd. The complexity of the dynamic response of offshore marine structures requires advanced simulations tools for the accurate assessment of the seakeeping behaviour of these devices. The aim of this work is to present a new time-domain model for solving the dynamics of moored floating marine devices, specifically offshore wind turbines, subjected to non-linear environmental loads. The paper first introduces the formulation of the second-order wave radiation-diffraction solver, designed for calculating the wave-floater interaction. Then, the solver of the mooring dynamics, based on a non-linear Finite Element Method (FEM) approach, is presented. Next, the procedure developed for coupling the floater dynamics model with the mooring model is described. Some validation examples of the developed models, and comparisons among different mooring approaches, are presented. Finally, a study of the OC3 floating wind turbine concept is performed to analyze the influence of the mooring model in the dynamics of the platform and the tension in the mooring lines. The work comes to the conclusion that the coupling of a dynamic mooring model along with a second-order wave radiation-diffraction solver can offer realistic predictions of the floating wind turbine performance.Postprint (published version

A time-domain second-order FEM model for the wave diffraction-radiation problem. Validation with a semisubmersible platform

“…In the following sections, a brief description of the mathematical model is given. Details on 18 the numerical implementation of the mooring solver, the body dynamics solver, and their coupling can be 19 found in [17,18,19,20]. 20…”

“…The dynamic equations for a mooring cable with length L with negligible bending and torsional 11 stiffness can be formulated as [18]: 12…”

“…Details about the 5 mathematical and numerical dynamic model are provided in Gutierrez-Romero et al [18]. solution for the fix hemisphere was obtained by Fernandes and Levy [22], and for the freely floating 13…”

Acquisition of offshore engineering design skills on naval architecture master courses through potential flow CFD tools

“…The study of marine cables structures has reached great interest due to wide range of application in deep‐ocean engineering. These applications include mooring line for marine structures, flexible risers, umbilical catenaries, towing hawser, subsea installations, or fishing cages composed of suspended cables subjected to marine currents . Mooring structures are composed of a set of cables, chains, or wire ropes, which are attached to floating structures at different points with lower ends of these cables anchored at the seabed.…”

“…It is well known that the visualization and understanding of the flow pattern are critical objectives, which can be achieved using numerical simulation techniques [3,4]. In fact, CFD techniques are employed in topics concerning with shape hull optimization for reducing resistance and powering in Marine Engineering [5,6], with the offshore industry applications , or for instance, with the response analysis of moored floating structures using tools such as the Potential Flow Solver (PFS) and the non‐linear Finite Element Method (FEM) approach .…”