在壹個具有旋轉或無旋轉控制圓桿影響下圓柱周圍的流場特性討論

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研究生：	高豫立 Yu-li Kao
論文名稱：	在壹個具有旋轉或無旋轉控制圓桿影響下圓柱周圍的流場特性討論 Flow characteristics around a cylinder under the influence of another smaller cylinder with and without rotation
指導教授：	洪俊卿 Jin-Tsing Hong
口試委員:	孫珍理 Chen-li Sun 蔡尤溪 Yew Khoy Chuah
學位類別：	碩士 Master
系所名稱：	工程學院 - 機械工程系 Department of Mechanical Engineering
論文出版年：	2007
畢業學年度：	95
語文別：	中文
論文頁數：	96
中文關鍵詞：	圓柱、控制圓桿、渦旋逸放、卡門渦街、壓力梯度、分離點
外文關鍵詞：	無
相關次數：	點閱：189 下載：0
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上一筆

本研究以數值模擬的方法來探討在二維流場中，流體流經單圓柱，及流體流經在圓柱附近放置無旋轉及旋轉控制圓桿之圓柱周圍的流場特性。
當無控制圓桿的作用時，在雷諾數大於60時，圓柱周圍的流場會有因渦旋逸放形成卡門渦街(Karman vortex street)的結構，圓柱之CD、CL曲線呈週期性震盪型態。
先在圓柱附近放置無旋轉控制圓桿，則其周圍流場及對應的壓力分佈，會隨控制圓桿置放位置不同而有不同的變化，使其(St, CD, CL, θs)值都產生變化。研究發現由於控制圓桿的存在，常使圓柱表面產生兩個正向壓力梯度的區域，從而使分離點往後移至第二個正向壓力梯度範圍的地方。
本研究發現利用旋轉控制圓桿可以抑制渦旋逸放，其抑制效果，隨控制圓桿轉速增加，或流場雷諾數降低而增強。在旋轉控制圓桿作用下，圓柱CD值有可能增加，有可能減小，甚至變成負值。

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摘 要.........................................................................i
致 謝........................................................................ii
目 錄.......................................................................iii
符號索引......................................................................v
表目錄......................................................................vii
圖目錄.....................................................................viii
第一章 緒論...................................................................1
1.1 前言......................................................................1
1.2 文獻回顧..................................................................1
1.3 研究目的..................................................................4
第二章 理論分析...............................................................5
2.1 理論基礎說明..............................................................5
2.1.1 邊界層分離與渦旋的形成..................................................5
2.1.2 分離點附近流況..........................................................5
2.2 數學模式..................................................................6
2.3 流場參數定義.............................................................10
第三章 物理模型與數值方法....................................................12
3.1 計算流力軟體之介紹.......................................................12
3.2 CFD-RCTM的使用流程.......................................................13
3.3 計算網格.................................................................15
3.3.1 網格的產生方法.........................................................15
3.3.2 格點模型的建立.........................................................15
3.4 數值模擬模式與參數設定...................................................16
3.5 計算設備和時間...........................................................17
3.6 網格獨立性與數值驗證.....................................................17
第四章 單圓柱的流場特性討論..................................................19
4.1 圓柱尾流場和CD值及CL值隨時間變化曲線圖的關係.............................19
4.2 雷諾數對阻力係數及昇力係數的影響.........................................20
4.3 低雷諾數下給予圓柱擾動後流場特性討論.....................................21
第五章 無旋轉控制圓桿對圓柱流場特性的影響....................................22
5.1 雷諾數為500時的流場特性..................................................22
5.2 雷諾數為1000時的流場特性.................................................25
第六章 旋轉控制圓桿對圓柱流場特性的影響......................................28
6.1 雷諾數1000時，旋轉控制圓桿作用下(Ur = 4U)之圓柱周圍的流場特性..........28
6.2 控制圓桿旋轉速度對圓柱渦旋逸放頻率(St值)與阻力係數(CD值)的影響...........30
6.3 在旋轉控制圓桿對圓柱後方渦流有抑制效果的模型中給予流場短暫擾動對周圍流場之影響.........................................................................30
第七章 結論..................................................................32
參考文獻.....................................................................34
                                

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