Boundary Element Simulation of Wave Interaction with Underwater Floating Structures

水下浮式結構物與波浪交互作用問題的邊界元素模擬

陳誠宗(Cheng-Tsung Chen) ； 李兆芳(Jaw-Fang Lee) ； 羅鈞瀚(Chun-Han Lo)

《海洋工程學刊》 18卷1期 (2018/05) Pp. 23-38

摘要

The problem of underwater floating structures subjected to water waves is considered in this study. The two-dimensional problem is considered, and the spring moored structure can have heave, sway, and roll motions. The linear potential wave theory is applied to describe the wave problem, and a boundary element method is used to solve the problem. The unknown wave potentials are expressed in terms of scattered and radiated waves, which are solved using the boundary element method, separately. The wave potentials are then substituted into the equations of motions of the floating structure, and the amplitudes of the structural motions are solved. Accuracy of the present numerical model is first examined. The principle of energy conservation is used to evaluate correctness of the problem, as energy dissipation is not included in the analysis. Using the present numerical model effects of structural width, height and underwater submergence on wave reflection and transmission, as well as characteristics of structural motions are investigated. The present study indicates that the underwater floating structures can have better wave resistance at deep water than shallow water. However, resonance can occur as far as effects of structural width and height are concerned.

關鍵字

Boundary element ； water waves ； underwater floating structure

並列摘要

本文探討水中浮式結構物受波浪作用的問題。波浪場的描述使用二維線性勢函數波浪理論。由彈簧繫住的結構物可以有橫移（sway）起伏（heave）以及轉動（roll）三個自由度。在問題的求解上，波浪勢函數表示為散射波和輻射波合成，而利用邊界元素法分別求解。結構物運動則使用運動方程式，而其中的波力則代入波浪表示式，然後求解。本研究所發展的數值模式先以能量守恆原理確認正確性。本文接著探討結構物寬度、高度、和沒水深度對於波浪反射率和透過率的影響。結果顯示結構物越寬、結構物越高都提供更好的抵擋波浪能力，而寬度增加的效果較好。結構物沉沒深度方面，較淺的沒水深度防坡能力較好。結構物運動方面，結構物水下位置的改對於變橫移和轉動較無影響，而結構物自然頻率會影響起伏運動。

並列關鍵字

邊界元素法 ； 線性波理論 ； 水中浮式結構物