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系統識別號 U0026-2703202000010500
論文名稱(中文) 高寬比對有限高圓柱流場於臨界區特性之影響
論文名稱(英文) Effect of aspect ratio on the flow around finite circular cylinder in the critical regime
校院名稱 成功大學
系所名稱(中) 航空太空工程學系
系所名稱(英) Department of Aeronautics & Astronautics
學年度 108
學期 2
出版年 109
研究生(中文) 吳霽麒
研究生(英文) Ji-Ci Wu
學號 P46064346
學位類別 碩士
語文別 中文
論文頁數 169頁
口試委員 指導教授-苗君易
口試委員-周榮華
口試委員-呂宗行
口試委員-葉思沂
中文關鍵字 有限高圓柱  高寬比  臨界雷諾數  風洞試驗  流場可視化 
英文關鍵字 Finite cylinder  Critical Reynolds number  Drag crisis  Wind tunnel Experiment  Flow visualization 
學科別分類
中文摘要 本研究探討有限高圓柱表面流場於臨界區之空氣動力特性,並探討不同高寬比(Aspect ratio)圓柱模型之差異,使用的圓柱模型高寬比分別為4、3、2、1,並依據流場特性,將臨界區分為次臨界轉單分離泡區、單分離泡區、單分離泡轉雙分離泡區、雙分離泡區作討論。
在壓力的量測上,每種高寬比之圓柱模型皆分三個高層:接近自由端之上層、中間層以及接近基部之下層,並探討每個高層±90^°與180^°的壓力訊號,以判定各高寬比圓柱流場隸屬之區域分界,並以瞬時壓力訊號以及C_(〖P±90〗^° )差值與C_pb之變化相態圖,探討各高層之壓力訊號於臨界雷諾數各區域特性以及過渡區之間歇性現象。另外,也以高寬比4、1之圓柱模型進行油膜視流實驗,探討在臨界雷諾數下,自由端流場、基部流場以及分離泡交互影響下之表面流場特性,並與量測之壓力結果作比較討論。
同時,透過二維力平衡儀,量測各高寬比圓柱模型於臨界雷諾數之阻力係數和升力係數,探討Drag crisis現象,並以瞬時升力、阻力訊號和升力與阻力之變化相態圖,探討升力、阻力在臨界雷諾數各區域之變化及特性以及過渡區之間歇性現象。並利用快速傅立葉轉換及加總經驗模態分析法對阻力係數和升力係數進行時頻分析,探討無因次化升、阻力頻率,探討渦流溢放之變化。
英文摘要 This study aims on the aerodynamic characteristics of flow around finite circular cylinder at critical Reynolds number. Four different cylinder models are tested in the low speed wind tunnel. Their aspect ratios are 1, 2, 3 and 4. Concerned with the effects due to the configuration of the finite circular cylinder, the flow phenomenon observed could be categorized into three regions, namely, the free end at the upper level of the model, the middle level where the flow can be regarded as passing over an uniform circular cylinder, and the lower level where the flow is constricted by the junction of the cylinder model and the ground floor. At each level, the pressure signals of ±90^° and 180^° on the surface of models are measured. The instantaneous flow characteristics in the critical transition range can be discussed with the real-time C_(〖P±90〗^° ) and C_pb data.
Also, the drag coefficient and the lift coefficient at critical Reynolds number of each finite cylinder are measured by a two-dimensional force balance. From the experimental result, drag crisis phenomenon can be observed when the aspect ratio of the model is from 2 to 4. When the model’s aspect ratio comes to 1, the drag crisis phenomenon doesn’t occur. The instantaneous flow characteristics in the critical transition range can be discussed with the real-time C_L and C_D data.
Furthermore, oil-film visualization method is applied. The oil film is prepared with the mixture of paraffin oil and TiO2 powder, and is applied on the model surface. The aspect ratio of the model in this test is 4 and 1. Discussion on the flow visualization results are focus on the effect due to the configuration of the finite circular cylinder and the unsteadiness of laminar separation bubble(s) to the aerodynamic flow around the finite circular cylinder model.
論文目次 摘要 I
Abstract III
誌謝 XIII
目錄 XIV
表目錄 XVIII
圖目錄 XIX
符號索引 XXIX
第一章 緒論 1
1.1 研究動機與目的 1
1.2 文獻回顧 2
1.2.1 臨界雷諾數特性 2
1.2.2 有限高圓柱流場 6
第二章 實驗設備與模型 11
2.1 風洞設備 11
2.2 三維移動機構 12
2.3 熱線式風速計 12
2.4 實驗用模型 13
2.4.1 有限高圓柱模型介紹 13
2.4.2 實驗座標定義與實驗模型角度劃分 15
2.4.3 壓力孔設置 16
2.5 皮托管 17
2.6 壓力轉換器 17
2.7 二維力平衡儀與放大器 18
2.8 資料擷取系統 20
2.9 手提式壓力校正器 21
2.10 油膜視流工具 22
第三章 實驗步驟與訊號分析 23
3.1 風洞實驗步驟 23
3.1.1 空流場量測 23
3.1.2 表面壓力與受力量側 24
3.2 油膜視流實驗 24
3.3 實驗參數分析 25
3.3.1 雷諾數 25
3.3.2 壓力係數 25
3.3.3 阻力係數與升力係數 27
3.3.4 無因次化頻率 29
3.4 訊號分析 29
3.4.1 統計性訊號分析 29
3.4.2 快速傅立葉轉換 30
3.4.3 經驗模態分析法與加總經驗模態分解法 31
3.4.4 相關性分析 32
第四章 結果與討論 34
4.1 空流場量測 34
4.1.1 流場不均勻度 34
4.1.2 邊界層厚度 36
4.2 AR=4~1有限高圓柱之臨界雷諾數的劃分 38
4.2.1 AR = 4有限高圓柱 40
4.2.2 AR = 3有限高圓柱 47
4.2.3 AR = 2有限高圓柱 54
4.2.4 AR = 1有限高圓柱 60
4.2.5 AR=1~4有限高圓柱與二維圓柱CD、|CL |比較 64
4.3 油膜視流實驗 67
4.3.1 AR=4有限高圓柱 67
4.3.2 AR=1有限高圓柱 71
4.4 AR=4、3、2、1有限高圓柱之瞬時訊號分析 74
4.4.1 AR =4有限高圓柱 74
4.4.2 AR = 3有限高圓柱 98
4.4.3 AR = 2有限高圓柱 122
4.4.4 AR = 1有限高圓柱 148
4.4.5 相關性分析 152
4.4.6 綜合討論 159
第五章 結論與未來建議 163
5.1 結論 163
5.2 未來建議 165
參考文獻 166
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