臺灣博碩士論文加值系統

摘 要

本研究於直立式水洞中進行單一無窮長方柱模擬二維效應，在不同雷諾數及攻角下之流場結構、尾流特性、和阻力係數的實驗研究。實驗將以質點軌跡流場可視化法( particle tracking flow visualization , PTFV )來確認方柱側表面以及尾流的流場模態；而流場結構、紊流性質、和阻力將以質點影像速度量測儀( particle image velocimetry , PIV )進行量測。研究將對質點軌跡呈現的流場模態、速度向量、流線、渦度場、紊流動能、速度分佈、紊流性質、阻力、以及渦漩逸放頻率等方向進行探討，而拓樸學技術也將被運用來分析解釋流場的模態。依據不同的雷諾數及攻角下得到的實驗結果，我們可將方柱側表面的特徵模態分成三類：邊界層分離模態、具有分離泡的流場模態、以及黏附流場模態。研究中發現方柱尾流渦漩的逸放頻率史卓赫數將會趨近0.13，並且尾流渦漩的縱橫比b/a = 2 Std與圓柱流場相同。

Abstract

Flow field structures, wake flow characteristics, and drag coefficients of an infinite square cylinder at various Reynolds numbers and angles of attack were experimentally studied in a straight water tunnel. Flow patterns on the edge of this cylinder and in the wake were identified by using the particle tracking flow visualization method (PTFV). The flow structures, turbulent properties and drags were measured by an particle image velocimetry system (PIV). The particle tracking flow patterns, velocity vectors, streamlines, vorticity contours, turbulent kinetic energy contours, velocity distributions, turbulence properties, drags and the vortex shedding frequency are presented and discussed. Topological techniques were applied to analyze and interpret the flow patterns. With the variation of the Reynolds number and angles of attack, the results revealed the characteristics on the cylinder edge (Side A) of flow fields can be classified into three regimes : boundary layer separation, separation bubble, and attached flow. It was found in this study that the Strouhal number saturates and approaches to the value 0.13. Also, the longitudinal / lateral spacing ratio of vortices b/a = 2 Std was found to agree with the result for circular cylinder.

目 錄
頁次
致謝……………………………………………………………… i

摘要……………………………………………………………… ii

Abstract………………………………………………………… iii

目錄……………………………………………………………… iv

符號索引………………………………………………………… vi

圖表索引………………………………………………………… viii

第一章 緒論……………………………………………………… 1
1-1 研究動機………………………………………………… 1
1-2 文獻回顧………………………………………………… 1
1-3 研究目的………………………………………………… 5
第二章 實驗設備、儀器與方法………………………………… 7
2-1 實驗設備………………………………………………… 7
2-2 實驗儀器及方法………………………………………… 8
2-2.1 流量量測………………………………………… 8
2-2.2 流場可視化……………………………………… 8
2-2.3 速度場量測……………………………………… 9
2-2.4 雷射光頁………………………………………… 15
第三章 單一方柱的流場特徵…………………………………… 16
3-1 流場的特徵模態………………………………………… 16
3-2 流場特徵模態之PIV分析……………………………… 18
3-2.1 速度向量場、流線、渦度及紊流動能………… 20
3-2.2 特徵模態的拓樸分析…………………………… 22
第四章 方柱尾流場的速度及渦漩逸放特性…………………… 26
4-1 速度特性………………………………………………… 26
4-2 阻力係數………………………………………………… 27
4-3 渦漩逸放特性…………………………………………… 28
4-3.1 流場的衍化過程………………………………… 29
4-3.2 尾流紊流特性的統計分析……………………… 30
4-3.3 特徵長度尺度…………………………………… 31
4-3.4 渦漩逸放頻率…………………………………… 32
4-3.5 渦漩之相關位置………………………………… 34
第五章 結論與建議……………………………………………… 36
5-1 結論……………………………………………………… 36
5-2 建議……………………………………………………… 37
參考文獻………………………………………………………… 38
作者簡介………………………………………………………… 73

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