聲波激擾噴流在橫風中的流場與混合特徵｜國立臺灣科技大學博碩士論文系統

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研究生：	Krisna Adi Pawitan Krisna - Adi Pawitan
論文名稱：	聲波激擾噴流在橫風中的流場與混合特徵 Flow and Mixing Characteristics of Elevated Jet in Crossflow Excited by Acoustic Waves
指導教授：	黃榮芳 Rong Fung Huang
口試委員:	許清閔 Ching-Min Hsu 陳佳堃 Jia-Kun Chen
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：	2014
畢業學年度：	102
語文別：	英文
論文頁數：	201
中文關鍵詞：	橫風噴流、聲波激擾、流體特徵、擴散
外文關鍵詞：	Jet in crossflow, Acoustic excitation, Flow characteristics, Dispersion
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本研究針對一在橫風環境中受聲波激擾之圓管噴流，以實驗方法探討在垂直及水平方向之特徵流場行為的衍化過程、噴流擴散及混合性能。使用一揚聲器作為噴流的聲波激擾裝置。藉由雷射光頁輔助之煙霧流場觀察技術搭配高速攝機擷取瞬時流場影像;利用熱線風速儀與高速資料擷取系統，針對噴流剪流層衍化生成的凝序性結構進行速度及特徵頻率診斷;透過影像邊界辨識技術取得橫風噴流的擴散高度及擴散寬度;使用追蹤氣體濃度測試法診斷噴流在橫風環境中的消散情況。藉由觀察垂直平面上的流體特徵，在噴流對應橫風之動量通量比對聲波激擾史卓數的域面，可劃分出三種流場的特徵模態，分別是「同步擺動噴流」、「過渡」與「同步剪流層渦漩」。聲波激擾頻率為共振頻率時，不同的橫風雷諾數可將同頻擺動噴流劃分為噴流氣柱振盪及泡芙狀渦漩模態。在水平面的流場觀察，泡芙狀渦漩形成兩個環狀流體結構，而噴流氣柱擺動模態僅形成一個環狀流體結構。藉由分析長時間曝光照片及追蹤氣體量測在垂直方向及水平方向的實驗結果發現，聲波激擾能夠增加橫風噴流的橫向擴散及混合。

Flow evolution processes, penetration, spread, and dispersion characteristics in both the vertical and horizontal planes of stack-issued pulsating transverse jets were experimentally studied in a wind tunnel. Jet pulsation was generated by means of acoustic excitation. Streak pictures of both instantaneous and long-exposure smoke-flow patterns, illuminated by a continuous laser-light sheet in the vertical and horizontal planes were recorded using a high-speed digital camera and digital single lens reflex camera. A hot-wire anemometer was used to digitize instantaneous velocity instabilities in the flow. Tracer-gas concentrations were measured to provide the quantitative information of the mixing quality and jet dispersions. In the vertical plane, three characteristic flow modes (synchronized flapping jet, transition, and synchronized shear-layer vortices) were identified in the domain of the jet-to-crossflow momentum flux ratio and the excitation Strouhal Number. The flow characteristics of the oscillation and puff modes have also been observed in the vertical and horizontal planes, when the flow was forced to the resonance frequency. In the horizontal plane an “outer ring” and an “inner ring” flow were observed in the puff mode, while only an “outer ring” flow was observed in the oscillation mode. The results of tracer-gas concentration measurement in the vertical and horizontal planes reveal that the lateral penetration and dispersion of the transverse jet are drastically enhanced by the acoustic excitation.

ABSTRACT…………………………………………………………………………………....i
中文摘要………………………………………………………………………………………ii
TABLE OF CONTENTS……………………………………………………………………..iii
NOMENCLATURE…………………………………………………………………………...v
TABLE CAPTION…………………………………………………………………………...vii
FIGURE CAPTION………………………………………………………………………….vii
CHAPTER 1 Introduction……………………………………………………………………..1
1	Background………………………………………………………………………..1
2	Literature survey…………………………………………………………………..2
3	Objective and scope of present work……………………………………………...4
CHAPTER 2 Experimental Methods………………………………………………………….6
1	Experimental apparatus……………………………………………………………6
1.1	Wind tunnel……………………………………………………………6
1.2	Jet flow supply system………………………………………………...7
1.3	Smoke flow generator…………………………………………………8
1.4	Acoustic excitation generator………………………………………...11
2	Experimental instruments and methods………………………………………….12
2.1	Flow visualization……………………………………………………12
2.2	Gas concentration measurement……………………………………...13
3	Uncertainty estimation…………………………………………………………...14
CHAPTER 3 Flow Visualization of an Acoustically Excited Stack-issued Transverse Jet…15
1	Jet pulsations at tube exit under zero crossflow condition……………………….15
2	Instantaneous flow patterns………………………………………………………16
2.1	Instantaneous flow patterns at jet-to-crossflow ratio 0.25…………...16
2.1.1	Flow patterns of non-excited flow……………………………...16
2.1.2	Flow patterns of excitation Strouhal number 0.1………………17
2.1.3	Flow patterns of excitation Strouhal number 0.45……………..18
2.1.4	Flow patterns of excitation Strouhal number 0.84……………..19
2.2	Instantaneous flow patterns at jet-to-crossflow ratio 1.5…………….20
2.2.1	Flow patterns of non-excited flow……………………………...20
2.2.2	Flow patterns of excitation Strouhal number 0.1………………21
2.2.3	Flow patterns of excitation Strouhal number 0.45……………..23
2.2.4	Flow patterns of excitation Strouhal number 0.84……………..24
2.3	Instantaneous flow patterns at jet-to-crossflow ratio 3.0…………….25
2.3.1	Flow patterns of non-excited flow……………………………...25
2.3.2	Flow patterns of excitation Strouhal number 0.1………………26
2.3.3	Flow patterns of excitation Strouhal number 0.45……………..27
2.3.4	Flow patterns of excitation Strouhal number 0.84……………..28
3	Long-exposure flow patterns……………………………………………………..29
3.1	Long exposure flow patterns at jet-to-crossflow ratio 0.25………….29
3.1.1	Long exposure images on vertical plane……………………….29
3.1.2	Long exposure images on horizontal plane…………………….29
3.2	Long exposure flow patterns at jet-to-crossflow ratio 1.5……………30
3.2.1	Long exposure images on vertical plane……………………….30
3.2.2	Long exposure images on horizontal plane…………………….31
3.3	Long exposure flow patterns at jet-to-crossflow ratio 3.0…………...31
3.3.1	Long exposure images on vertical plane……………………….31
3.3.2	Long exposure images on horizontal plane…………………….32
4	Frequency characteristics of flow field…………………………………………..32
CHAPTER 4 Dispersion of an Acoustically Excited Stack-issued Transverse Jet………….34
1	Vertical and horizontal dispersion at jet-to-crossflow ratio 0.25………………...34
1.1	Dispersion on vertical plane………………………………………….34
1.2	Dispersion on horizontal plane……………………………………….35
2	Vertical and horizontal dispersion at jet-to-crossflow ratio 1.5………………….36
2.1	Dispersion on vertical plane………………………………………….36
2.2	Dispersion on horizontal plane……………………………………….37
3	Vertical and horizontal dispersion at jet-to-crossflow ratio 3.0………………….39
3.1	Dispersion on vertical plane………………………………………….39
3.2	Dispersion on horizontal plane……………………………………….40
4	Correlations of jet dispersion and flow patterns at jet-to-crossflow ratios 0.25, 1.5, and 3.0……………………………………………………………………………42
CHAPTER 5 Conclusions and Recommendations…………………………………………..43
1	Conclusions………………………………………………………………………43
2	Recommendations………………………………………………………………..44
REFERENCES……………………………………………………………………………….46

                                

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