臺灣博碩士論文加值系統

本文係應用流場可視化法與具高時間解析度之PIV量測系統針對孤立波通過位在水平底床之單一矩形潛沒構造物(長高比L/D = 0.2)周遭流場特性及渦流結構進行探討。具高時間解析度之PIV結合高速攝影機之擷取影像能力、高功率氬離子雷射切光照明及謝(2008)所提出之先進影像解析法進行量測分析，以獲得流體速度場。實驗前，先針對入射之孤立波波形、波形再現性與波速進行檢測，亦針對渦度及加速度進行敏感度測試。
本文設定不同波高水深比之孤立波條件下，單一潛沒構造物頂端渦流及後端主渦的生成因實驗參數改變而不同，並於潛沒構造物頂部前緣端、後端皆產生渦流脫離現象，其渦流尺寸隨著時間增大。潛沒構造物頂端之渦流可區分為：剪力層產生時期、渦流產生時期、渦流運動時期、渦流脫離時期以及渦流潰散時期。本文以流場加速度變化及渦流流場型態、渦流強度搭配說明，並整理出加速度的變化與渦流渦度相關性進行分析探討。
加速度與潛沒構造物頂部產生之渦流強度比對後，加速度隨著孤立波入射後開始增加，並為渦流作一能量供應來源，渦流尺寸及強度也隨著加速度的增加而增長；渦流脫離潛沒構造物頂部，潛沒構造物頂部剪力層外圍流場已開始減速，其提供之能量已不足以維持流場之穩定性，因而在潛沒構造物頂部產生亂流流場。
最後比較不同波高水深比之實驗條件下，孤立波於潛沒構造物頂部各現象發生時間，包括剪力層產生時期、渦流產生時期、渦流運動時期和渦流脫離時期，其流場之各現象發生時間隨著波高水深比增加而遞減。

This study presents an experimental investigation of the propagation of solitary waves over a rectangular submerged structure (length to height ratio L/D = 0.2) on a horizontal bottom by utilizing particle trajectory technique and high-speed particle image velocimetry (HSPIV). The velocity vector fields are obtained by HSPIV. The wave-height (H0) to water-depth (h0) ratio of the incident solitary waves are H0/ h0 = 0.10, 0.25, 0.33 and 0.50. Several preliminary tests are carried out such as the validation repeatability of the incident solitary wave free surface elevation or/and profile, testing of the spatial resolution sensitivity for vorticity calculation, and time resolution sensitivity for acceleration calculation.
The evolution of two vortices at the leading edge and the trailing edge of the top surface of the barrier are observed and the vortices grow in size respectively. The vortex developing at the trailing edge is found to get entrained into the primary vortex that generated from the leading edge and moved downstream. The evolution of the primary vortex on the top edge of the barrier can be categorized as the series of: (1) generation of the separated shear layer; (2) generation of the vortex structure; (3) movement of the vortex structure; (4) detachment of the vortex structure; and (5) breakdown of the vortex.
The relationship between the temporal variation of the flow acceleration and the vorticity of the vortex core is presented in this study. The incidence of the solitary wave supplies energy for the free stream on the top edge of the barrier and the momentum transfer to the vortex core via the separated shear layer and hence the vorticity and the vortex strength of the primary vortex increase. When the solitary wave passes over the barrier, the velocity of the free stream over the top surface of the barrier starts to decelerate and no more energy supply to the vortex core, thus leading to the dissipation of the vortex structure and the occurrence of the turbulent flow.

摘要 i
ABSTRACT iii
目錄 v
圖目錄 vii
表目錄 xiv
符號說明 xv
第一章 緒論
1-1 研究動機 1
1-2 文獻回顧 2
1-3 本文組織 5
第二章 實驗設備及研究方法
2-1 實驗配置
2-1-1實驗水槽 7
2-1-2實驗模型 8
2-2質點軌跡可視化法及HSPIV量測系統設備介紹
2-2-1雷射光源 8
2-2-2高速攝影機 10
2-2-3質點軌跡可視化法 12
2-2-4高時間解析度之PIV量測系統 13
2-2-5三維精密移動平台 16
2-2-6同步量測系統 16
2-3座標系統、拍攝區域與相關參數設定 19
2-4 實驗條件設定
2-4-1因次分析 24
2-4-2實驗條件 25
第三章 實驗檢測
3-1孤立波入射波形檢測 27
3-2孤立波入射波速檢測 29
3-3不同空間解析度下之渦度值差異比較 31
3-4不同時間解析度下加速度敏感度測試 37
第四章 實驗結果與討論
4-1潛沒構造物來流端之孤立波入射流場運動現象 42
4-2潛沒構造物來流端之加速度 57
4-3潛沒構造物頂部分離剪力層之流場特性 60
4-4潛沒構造物近岸側之渦流運動 85
4-5潛沒構造物頂部前緣端加速度與渦流強度之相關性 93
4-6不同實驗條件量測結果比較 95
第五章 結論與建議
5-1結論 98
5-2建議 99
參考文獻 100
附錄A 口試委員審查意見答覆 104
附錄B 加速度計算 106
附錄c 不同實驗條件之結果 114

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