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研究生:李權庭
研究生(外文):Chiuan-Ting Lee
論文名稱:平板混合紊流結構之實驗分析
論文名稱(外文):Experimental research of turbulent structure in planar mixing layer
指導教授:張克勤張克勤引用關係王覺寬
指導教授(外文):Keh-Chin ChangMuh-Rong Wang
學位類別:碩士
校院名稱:國立成功大學
系所名稱:航空太空工程學系碩博士班
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:2004
畢業學年度:92
語文別:中文
論文頁數:90
中文關鍵詞:循環參數無因次速度比雷諾數自相關性自我保持動量厚度
外文關鍵詞:autocorrelationReynolds numbermomentum thicknessloop parameterself-preservingdimensionless velocity ratio
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摘 要

  本文探討平板混合紊流場的控制參數(r,Reθ)對流場平均及擾動特性的影響,藉由調整兩側高低速度差可分別顯現出各參數的效應。於低速度比的上游截面中,仍存在一大尺度渦流結構流場主導之層流區域,於此區域時的流場特性與呈紊流狀態之下游截面,有截然不同的特性。亦由於此顯著的差異造成不同控制參數(r,Reθ),其側向擴散率以及往下游發展的趨勢會隨之改變。
  利用FFT(Fast Fourier Transform)與自相關性(Autocorrelation)函數的分佈趨勢來比較不同控制參數(r,Reθ)在不同截面上渦流結構所受到的影響。本文以Frenkiel 經驗式與Altinsoy et al.(2002)提出之修正式來近似自相關性函數,觀察於不同流場條件時最佳近似之循環參數m及m*值。雖然Frekiel經驗式在tau=0的位置不合乎物理現象(斜率不為零),但相較於Altinsoy et al.提出之修正式,更能代表自相關性函數的整體趨勢。對照本文與黃士軒(20 -02)使用Frenkiel經驗式整理出之自相關性函數結果,發現在剪力流區的最佳遞迴參數m值,應介於1~1.5之間。
  當流場經過一定之下游距離會發展到自我保持的狀態(self-preserving),到達此狀態時,流場特性經適當無因次化後即不會隨下游而變化,此發展完全之距離也會因為控制參數(r, Reθ)的不同而有所差異。於自我保持狀態,Townsend(1976)提出一經驗公式可近似最大雷諾應力值,由本文結果可知,經驗式中的實驗係數會隨控制參數(r,Reθ)而變。故使用此經驗式時要先找出實驗係數與控制參數間相對關係,才能得到較好的近似結果 。
Abstract

  Influences of two controlling parameters (r,Reθ) on the flow structure of a planar mixing layer are investigated. It is found that there exists a large-scale vortex structure in the very upstream regions under the conditions of low r values. Their flow characteristics in these regions are obviously different form what are observed in the downstream regions. Therefore, the lateral expansion and devel -oping tendency along the flow direction would vary significantly with adjusting the controlling parame -ters.
  Influences of the controlling parameters on the flow structure are analysed using the Fast Fourier Transform (FFT) and the auto-correlation distribution function. Two empirical functions of the autocorrelation distribution including the Frenkiel func -tion and the one currently proposed by Altinsoy et al. (2002) are used to fit the measurements.Although the Frenkiel function cannot meet the symmetric condition at tau=0, i.e. the slope at tau =0 must be equal to zero, it can represent the overall auto-correlation distribution better than what was proposed by Altinsoy et al. It is found that the loop parameter, m, used in the Frenkiel function varies between 1 and 1.5 in the shear layer, which is consistent what were observed in the previous work done by S. H. Huang (2002).
  Flow would reach its self-preserving condition after traveling a sufficiently distance. However, the distance required to reach the self-preserving condition is dependent on the parameters of r and Reθ. Townsend (1976) argued that the maximum Reynolds stress under the self-preserving condition can be well represented by an empirical formulae. However, this study found that the coefficient appeared in the empirical formulae is dependent on the parameters of r and Reθ too.
目錄……………………………………………………………i
表目錄…………………………………………………………ii
圖目錄…………………………………………………………iii
符號說明………………………………………………………iv
第一章 緒論…………………………………………………1
1.1 前言…………………………………………………1
1.2 文獻回顧……………………………………………2
1.3 實驗規劃與流程……………………………………5
1.4 研究目標……………………………………………7
第二章 自相關性模式與實驗設備…………………………8
2.1 自相關性模式………………………………………8
2.2 實驗設備……………………………………………12
第三章 結果與討論…………………………………………14
3.1 無因次速度參數-r造成之影響……………………15
3.2 Re數造成流場之影響………………………………17
3.3 FFT 分析……………………………………………19
3.4 自相關性函數之探討………………………………20
3.5 自我保持區域之平均與擾動流場特性……………23
第四章 結論與建議…………………………………………27
參考文獻………………………………………………………30
參考文獻
1. Batchelor, G. K., “Diffusion in free turbulent shear layer,” J Fluid Mech., Vol 3,pp :67-80. (1957)
2. Bradshaw, P., “The effect of initial conditions on the development of a free shear layer,” J Fluid Mech Vol 26,pp :225-236. (1966)
3. Townsend, A. A., “Structure of turbulent shear flow,” Cambridge University press (1978)
4. Pui, N. K., Gartshire I. S., “Measurement of the growth rate and structure in plane turbulence mixing layer,” J Fluid Mech., Vol 91,pp :111-130. (1979)
5. Durst, F., Milojevic, D., Schönung, B., “Eulerian and Lagrangian predictions of particulate two-phase flows: a numerical study,” Appl. Math Modeling., Vol. 8, pp :101-115. (1984)
6. Mehta, R. D., “Near-field turbulence properties of single and two stream plane mixing layer,” Exp Fluids., Vol 4 pp :257-266. (1986)
7. Mehta, R. D., “Effects of velocity ratio on plane mixing layer development: Influence of the splitter plate wake,” Exp Fluids., 10(4):194-204. (1991)
8. Abdul, Azim M., Sadrul, Islam A. K. M., “Plane mixing layers from parallel and non-parrallel merging of two streams,” Experiments in Fluids., Vol 34, pp :220-226. (2003)
9. Altinsoy, N., Tugrul, A.B., “A new proposal for Lagrangian correlation coefficient,” Heat and Fluid Flow., Vol 23, pp:766-768. (2002)
10. Manomiphiboon, K., Russell, A. G., “Evaluation of some Proposed forms of Lagrangian velocity correlation coefficient,” Heat and Fluid Flow., Vol 24, pp :709-712. (2003)
11. 劉英傑,”平面混合層流在液滴粒子負載下之過渡現象,” 國立成功大學航空太空工程研究所博士論文,1991
12. 楊進成,”兩相紊流場隨機Eulerian-Lagrangian計算法之檢視,”國立成功大學航空太空工程研究所博士論文,1999
13. 許喬筑,”兩相混合層流顆粒分散程度之預測,”國立成功大學航空太空工程研究所碩士論文,2000
14. 黃士軒,” 兩相相關性及紊流調制量之研究,” 國立成功大學航空太空工程研究所碩士論文,2001
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