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研究生:謝仁泓
研究生(外文):Ren-Hong Hsieh
論文名稱:圓噴流受側風衝擊時的斷面流場結構
論文名稱(外文):Tomographic Flow Structures of a Round Jet in a Crossflow
指導教授:黃榮芳黃榮芳引用關係
指導教授(外文):R. F. Huang
學位類別:博士
校院名稱:國立臺灣科技大學
系所名稱:機械工程系
學門:工程學門
學類:機械工程學類
論文種類:學術論文
論文出版年:2002
畢業學年度:90
語文別:中文
論文頁數:161
中文關鍵詞:橫風噴流側風噴流尾流尾流管後尾流
外文關鍵詞:crossflowjet waketube wakewakejet
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本文探討一個由凸出於壁面某一高度的圓管射出之高速噴流受到橫風衝擊時近尾流區流場的結構。橫風由一個開迴路風洞提供,噴流則由高壓空氣經由整流裝置與一凸出於風洞測試段底面18cm的不鏽鋼管垂直射入橫風中。使用雷射光頁煙霧流場可視化技術獲得定性的流場形態;應用雷射都卜勒測速儀量測垂直縱剖面以及水平橫切面的速度場,從而得到流線和渦度的定量特性。這些結果經由簡單的拓樸特性考量,提供了流場結構清晰的模型。在噴流對側風的通量動量比為0.9以下時,由於噴流動量太小,近尾流區的流場主要特徵為側風經過噴流管出口所引發的下洗效應所形成的下洗迴流泡。此時管後方會形成一條分歧線,此分歧線的出發點可溯至管出口處。當動量比在0.9至1.9之間時,下洗效應受噴流增加的作用,沒有那麼明顯,但側風仍舊主導流場,噴流後方維持一個迴流泡,而管後方的分歧線則從噴流後方迴流泡衍生出來。當動量比在1.9至5.9之間時,可以觀察到複雜的過渡流場,包括噴流後迴流泡、管後迴流泡、源點、鞍點等等現象。在動量比超過5.9之後,近尾流區的流場受到強大噴流的主導,往上方的衝擊與剪切蓋過橫向流的下洗作用,使得對稱縱剖面的流動特徵顯示出在噴流尾流及管後尾流各有一條分歧線,這兩游分歧線由同一個源點衍生出來。在分歧線上游屬於逆流區,而分歧線下游的流體則往下游逸去。噴流尾流,噴流出口及管後尾流的垂直與水平切面的流線和渦度顯示出不同特徵的拓樸結構的非封閉式漩渦層,同時,本文亦詳述並討論噴流尾流及管後尾流在各個特性區段的速度分佈與紊流特徵。
Flow structures in the near wake of an elevated jet in a crossflow at various jet-to-crossflow momentum flux ratios are experimentally studied in a wind tunnel. A laser-light sheet is employed to illuminate fine smoke tracers for flow visualization. A laser Doppler velocimeter is used to measure the velocity field. Flows on the vertical symmetry plane and three horizontal planes across the jet-wake, jet-exit, and tube-wake regions are investigated. Tomographic smoke patterns show qualitatively apparent differences in different regions of the flow field. The measured velocity fields in the symmetry and several horizontal planes present tremendous variations in different characteristic regimes of jet-to-crossflow momentum flux ratios. They are typically termed down-wash, crossflow-dominated, transitional, and jet-dominated regimes. Quantitative characteristics of the streamlines, vorticities, and topological features of the flow structures display significant differences among different flow regimes. The complex flow behaviors are the results of the interactions among the downwash effect which is induced by the crossflow passing over the tube-tip, the up-shear effect induced by the issuing jet, and the wakes behind the jet and the tube. Sketches of the topological flow patterns are proposed to delineate the measured flow structures. Impact effects of the crossflow on the jet are discussed in two aspects, i.e., the geometry and the turbulence properties of the central streamline. The geometric characteristics of the deflected jet in different flow regimes are presented and compared with previous results. The velocity components and turbulence properties along the central streamlines of different flow patterns show that the premier turbulence generation which is observed in this flow arrangement occurs in the impingement and jet bend-over regions. Details of the flow structures and differences in the jet and tube wakes are presented and discussed.
中文摘要………………………………………………….…………… i
英文摘要………………………………………………….…………… ii
致謝……………………………………………………………………. iii
目錄…………………………………………….……………………… iv
符號表…………………………………………………………………. vii
表圖索引………………………………………………………………. viii
第一章 緒論…………………………………………………………. 1
1.1 研究動機………………………………………………….. 1
1.2 文獻回顧………………………………………………..... 2
1.3 本文目的………………………………………………….. 4
第二章 實驗設備、儀器及方法……………………………………. 6
2.1 實驗設備………..………………………………………… 6
2.2 實驗儀器及方法….………………………………………. 7
2.2.1 皮托管與壓力轉換器..………………………………. 7
2.2.2 流量量測—浮子式流量……………….…………….. 8
2.2.3 流場可視化—雷射光頁煙霧流場觀察法.…………. 8
2.2.4 速度場量測—雷射都普勒測速儀………………..… 11
2.2.5 移動機構…………………………………………….. 13
2.2.6 重要參數…………………………………………….. 13
第三章 流場觀察與特性……………………………………………. 15
3.1 下洗模態………………………………………………….. 15
3.2 橫流支配模態………………………….……..………….. 17
3.3 過渡模態…………………………………………………. 19
3.4 噴流支配模態………………………….…………………. 20
第四章 速度場分析與探討…...…….…………………………….… 23
4.1 下洗模態………………………………………………….. 23
4.1.1 軸對稱垂直縱剖面的速度場……………………….. 23
4.1.2 水平橫切面的速度場…………….……..…………… 24
4.2 橫流支配模態………………………….……..………….. 25
4.2.1 軸對稱垂直縱剖面的速度場……………………….. 25
4.2.2 水平橫切面的速度場…………….……..…………… 26
4.3 過渡模態………………………………………………….. 27
4.3.1 軸對稱垂直縱剖面的速度場………………………... 27
4.3.2 水平橫切面的速度場…………….……..…………… 30
4.4 噴流支配模態………………………….…………………. 34
4.4.1 軸對稱垂直縱剖面的速度場……………………….. 34
4.4.2 水平橫切面的速度場…………….……..…………… 35
4.5 特徵流線與結構…………………………………………. 36
4.6 迴流泡的幾何特徵徵……….……..….………………….. 39
4.7 應用實例………………………………………………….. 40 
第五章 拓樸分析…………….……..…………….…………………. 42
5.1 垂直縱剖面的拓樸分析…………….……...…………….. 43
5.2 水平橫切面的拓樸分析……….……..….……………….. 46
第六章 渦度場分析…………….……..………….…………………. 50
6.1 下洗模態…………….……..………………….………….. 50
6.2 橫流支配模態…………….……...……………………….. 51
6.3 過渡模態……….……….……..………………………….. 52
6.4 噴流支配模態…………….……..……………..…………. 54
第七章 速度分佈與紊流性質…….………………………………… 56
7.1 噴流出口的速度分佈…………………………………….. 56
7.2 軸對稱垂直縱剖面的速度分佈………………………….. 57
7.3 水平橫切面的速度分佈………………………………….. 59
7.4 紊流特性………………………………………………….. 62
7.4.1 噴流的幾何特徵…..………….…..….………………. 62
7.4.2 迴流泡的幾何特徵……...…………………………… 65
7.4.3 水平橫切面中心軸線之紊流特性…………..………. 66
第八章 結論與建議………………...…………………..…………… 68
6.1 結論…………………………………………..…………… 68
6.2 建議………………………………….…………………… 67
參考文獻……………………………………………………..……….. 71
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