Abstract The vortex-induced motion (VIM) of semi-submersible is gaining increasing attention from both industry and academia with the recent development of deep draft semi-submersible platforms. Field measurements of semi-submersibles reveal that the VIM responses are typically found to be smaller than those observed in model tests. The possible factors causing the VIM response reduction in the field measurements include Reynolds number, wave effects, mass ratios, and external damping from mooring lines. The objective of this study is to investigate the mooring-induced damping effects on VIM. The Finite Analytic Navier-Stokes (FANS) code is integrated with an in-house six degree-of-freedom (DoF) motion solver and an in-house nonlinear finite element (FEM) code MOORING3D, for the coupled CFD-FEM analysis of the VIM of a moored semi-submersible. The large eddy simulation (LES) turbulence model is used to provide accurate estimation of hydrodynamic loading. Simulations are performed for the 1:70 model of the platform under varying reduced velocities. Full-scale mooring systems with different water depths and mooring line numbers are designed to represent different levels of mooring damping effects. The simulated VIM response is compared with the experiments. The study reveals that mooring-induced damping is a critical factor contributing to the VIM response reduction in the field.

中文翻译：

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通过耦合 CFD-FEM 分析研究系泊阻尼对深吃水半潜器涡激运动的影响

摘要 随着近来深吃水半潜平台的发展，半潜平台的涡激运动（VIM）越来越受到工业界和学术界的关注。半潜器的现场测量表明，通常发现 VIM 响应比模型测试中观察到的要小。导致现场测量中 VIM 响应降低的可能因素包括雷诺数、波浪效应、质量比和系泊绳的外部阻尼。本研究的目的是研究系泊引起的阻尼对 VIM 的影响。有限分析纳维-斯托克斯 (FANS) 代码与内部六自由度 (DoF) 运动求解器和内部非线性有限元 (FEM) 代码 MOORING3D 集成，用于耦合 CFD-FEM 分析系泊半潜器的 VIM。大涡模拟 (LES) 湍流模型用于提供流体动力载荷的准确估计。在不同的降低速度下对平台的 1:70 模型进行了模拟。具有不同水深和系泊线编号的全尺寸系泊系统旨在代表不同级别的系泊阻尼效果。将模拟的 VIM 响应与实验进行比较。研究表明，系泊引起的阻尼是导致现场 VIM 响应降低的关键因素。具有不同水深和系泊线编号的全尺寸系泊系统旨在代表不同级别的系泊阻尼效果。将模拟的 VIM 响应与实验进行比较。研究表明，系泊引起的阻尼是导致现场 VIM 响应降低的关键因素。具有不同水深和系泊线编号的全尺寸系泊系统旨在代表不同级别的系泊阻尼效果。将模拟的 VIM 响应与实验进行比较。研究表明，系泊引起的阻尼是导致现场 VIM 响应降低的关键因素。