臺灣博碩士論文加值系統

本研究以複合邊界元素法(Composite Boundary Element Method，CBEM)為數值計算方法，來探討當結構物位於等水深下，規則波浪通過六根透水垂直同心雙圓柱群之水動力特性，以及在港池前放置五根相連之透水圓形離岸堤時，不同放置距離對港內之影響。
本文中所討論離岸結構配置為六根透水雙圓柱，用以模擬碼頭或風力發電機組之樁基，在外海直線排列，以不同角度的波浪入射，在固定外圓柱的半徑，改變內圓柱半徑下，所產生的繞射情形，以平面及立體之Kd值分佈情形討論其波浪特性。當內圓半徑增加，成為不透水圓柱後，附近水域的Kd值振幅提高，繞射作用變得明顯，且在圓柱迎浪面形成很大的溯上值，但遮蔽效果最好；而減少內圓柱半徑至零，形成一完全透水之圓柱，雖說迎浪面的溯上減少了，可是對於後方水域的保護作用也降低。在圓形離岸堤部分，波浪正向入射下(β=90度)，當離岸堤與港池之間的距離為0.75倍波長，港內波浪振幅下降，水面變化較為平穩；波浪改為斜向入射(β=45度)，離岸堤距港池越遠，波浪易進入港內且在港壁夾角處堆積；而波浪側面入射(β=0度)，離岸提越接近港池時，在波浪入射方向之港外壁上形成越大之溯上，而港內則越為穩定。

In this study, we used Composite Boundary Element Method (CBEM) to calculate the hydrodynamic characteristics of water waves passing through the concentric porous cylinders on a horizontal sea bottom of depth h. We determined the effects of a proposed breakwater, comprising five porous cylinders arranged in straight lines at various distances from the front of the harbor.
We arranged six concentric porous cylinders in straight lines. We discussed the diffraction for several angles of incident wave by two-dimensional and three-dimensional Kd distributions. As the radius of the inner cylinder was increased, thereby increasing the amplitude of Kd vibration, with an obvious effect on diffraction. Where the face of the wave had a large run-up, the shelter effect was the optimal, however reducing the radius of the inner cylinder had the opposite effect.
When wave incidence on the front of the cylinder breakwater was (β=90), and the distance between the breakwater and harbor was 0.75 of a multiple of wavelength, water tranquility in the harbor was excellent. When wave incidence was oblique (β=45), and the distance between the breakwater and harbor was increased, water tranquility in the harbor deteriorated. When wave incidence was from the side (β=0), and the distance between the breakwater and the harbor was reduced, wave run-up increased at the outer wall of the harbor in the direction of the incidence of the wave, and water tranquility in the harbor improved.
Keywords: porous, concentric cylinders, run-up, cylinder breakwater.

摘要 I
Abstract II
目錄 III
圖目錄 IV
照片目錄 VII
第一章　緒論 1
1-1　前言 1
1-2　研究目的及方法 7
1-3　前人研究 8
第二章　理論解析 13
2-1　基本假設與速度勢之表示 13
2-2　邊界條件 15
2-3　數值方法 17
2-4　繞射係數(K_d)之求解 19
第三章　數值計算步驟與模式驗證 20
3-1　數值計算步驟 20
3-2　模式驗證 21
第四章　數值計算結果與討論 30
4-1　六根透水雙圓柱群 30
4-2　六根不透水圓柱群 33
4-3　六根全透水圓柱群 36
4-4　透水圓形離岸堤 66
第五章　結論 81
參考文獻 83
謝誌 85

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