- 期刊
懸垂纜繩與浮式結構物受波浪作用分析
Analysis of Wave Acting on Floating Structures with Catenary Moorings
摘要
本研究為探討使用懸垂式纜繩錨碇之水面浮式矩形結構物受波浪作用的問題。文中除考慮波浪與繫纜浮式結構物互制外，也同時加入繫纜所受之波力。浮式結構運動包括水平、垂直以及轉動等三個自由度。懸垂式纜繩的運動方程式為利用Hamilton 虛功原理來建立，並以有限元素法得到求解的矩陣式。作用於纜繩波力為使用Morison 公式計算，其中，拖曳力非線性項則以Lorentz’shypothesis of equivalent work 線性化表示。浮式結構運動方程式和懸垂纜繩運動方程式則藉由繫留點銜接條件合併。在問題的求解上，在靜力上為先求得問題的靜態平衡，在動力方面，為將入射波引起波浪與結構物互相作用問題，分解成散射問題與結構物三個自由度單位振幅運動的輻射問題，然後將波浪作用力代入繫纜結構物方程式求解。本研究發展繫纜浮式結構物受波浪作用之模式，計算波浪反射率與Sannasiraj et al. (1988) 的試驗以及數值結果比較，說明本文模式增加考慮作用在繫纜上的波力比較能描述試驗結果。利用本文模式對於浮式結構物繫纜鬆弛與拉緊條件下，波浪反射率以及結構物各個自由度的變化情形也同時進行探討。
並列摘要
In this paper, the problem of incident waves acting on cable moored floating structures is studied. Besides the coupled motions among incident waves and floating structures, the wave forces acting on the cables are considered. The motions of floating structure include sway, heave, and roll three degrees of freedom. The equations of motion for cables are described using the principle of virtual work, and a finite element method. The wave forces acting on mooring cables are calculated by the Morison equation, where the drag force term is linearized by using the Lorentz's equivalent work. The equations of motion of floating structure and the cables are combined by using the matching conditions at connecting points. To solve the problem, the static equilibrium position is first calculated. Secondly, for the hydrodynamic aspect, the interference wave problem is separated into the scattering and radiation problems, and then the wave forces are substituted into the structural equations to solve the problem. The model developed in this study used to calculate reflection coefficients in experimental and numerical results by Sannasiraj et al. (1998) indicates that consideration of wave forces acting on mooring cables can better describe the problem. Using the present model, effects of slack and taut mooring conditions on reflection coefficients, as well as dynamic motions of the mooring structure are also investigated.
延伸閱讀
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- 涂力夫、李兆芳（2009）。Dynamic Analysis of Mooring Cables in Nonlinear Water Waves。海洋工程學刊，9(2)，207-224。https://doi.org/10.6266/JCOE.2009.0902.05