摘 要

本研究探討，張力纜繩固定於等水深的底床上的透水式浮堤，在波流場的交互作用。在研究內容方面可分為：（1）浮堤中的多孔介質流場，以“孔流運動方程式“做為控制方程式。（2）浮堤受力分析使用（Control volume system）的理論，將纜繩張力、浮堤運動與流場的關係作結合。（3)流場中因均勻流與波浪的方向不一致，造成波流同向與波流反向，使用自行發展的分散關係式。（4）流場假設在微小振幅波的線性理論下，以邊界元素法的數值解解析流場狀況。
本文目的分為兩部份：（1）在不具均勻流得狀況下，所求得的數值解與前人解析解結果作比較，以證實邊界元素法計算的正確性。（2）比較透水浮堤在純波浪場與波流共存場的消波狀況。研究結果大致可以分為：（1）邊界元素法所得到的結果與解析解比較大致吻合，其顯示自行發展的理論與數值方法有其正確性。（2）在波流共存場中波浪的能量不易消減，但是此種現象在全反射發生時卻相反。(3)當浮堤浸水深增加，消減能量較大；堤寬增長，消減能量大；但在兩權比較下，增加堤寬的效用較為顯著。所以設計浮堤時，建議仍以增加浮堤寬重於增加浸水深為設計原則。

Abstract

This study investigates the waves and current field interaction with a perforated floating breakwater which is fastened by tension lags. As the predecessor done, the porous media governing equation is adopted inside the perforated floating breakwater, but a control volume concept has been applied in the breakwater in order to find the external forces on the system. A new dispersion equation has been introduced with the fact of the uniform current influence on the reflection waves (moving upstream direction) and the transmission waves (moving downstream direction). Since the whole system belongs to a domain problem and also assumes it can be linearlized, a boundary element method (BEM) is developed to solved the problem.

To confirm this new BEM is correct and accuracy, a zero current has been set and compared its results with analytical solutions that was published by the predecessor. The comparison between the new BEM and analytical solutions has good agreements. It means the BEM developed by this paper has its own accuracy. Based on the same numerical model, a floating breakwater and waves/current interaction problems are investigated. The results have shown that the uniform current will degrade the reflection coefficients but increase the transmission coefficients. In general, the perforated floating breakwater, which is deeper under the water and longer in width, has smaller transmission coefficients. But practically when designing a perforated floating breakwater, we still suggest to increase the width rather than to deepen the depth. It is because the effects of dissipating wave energy are more obvious when increasing the width.

中文摘要…………………………………………………….Ⅰ
英文摘要……………………………………………………Ⅱ
目錄………………………………………………………Ⅲ
表目錄………………………………………………….…Ⅴ
圖目錄…………………………………………………….. Ⅴ

第一章 序論…….…………………………………………… 1
1.1前言………….….…………………………………..1
1.2文獻回顧…………..…………………………………2
1.3研究目的……………..……………………………..3

第二章 基本理論…………………………………………….4
2.1導論與狀況述………………………………………..4
2.2控制方程式………….…….…………………………4
2.3流場的邊界條件…………………….…….…………5
2.3.1純流體區的邊界………………………………6
2.3.2孔隙結構物區的自由表面邊界條……………9
2.3.3孔隙結構物區與純流體區交界邊…….…..10
2.3.4張力纜繩與流場的關係式…………….…..12

第三章 邊界元素法數值模式 …………………………….21
3.1邊界元素法基本原理………………..……………21
3.1.1控制方程式與各邊界條件……….……...21
3.2張力纜繩方程式…………..………..……………27
3.3數學模式聯立解之建立…………………………..27

第四章 數值分析結果與討論………………………………31
4.1 邊界元素法數值解的驗證…….………………….31
4.2 流場中各參數的決定………….……………………32
4.3 具有均勻流的數值解討論……….…………………33

第五章 建議與結論…………………………………………47

參考文獻……………………………………………………53

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