Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/15901
標題: 建置具高時間解析度之PIV系統並應用於圓柱近域尾流特性之探討
Establishment of High Time-Resolved PIV System and Application on the Characteristics of Near-Wake Flow behind a Circular Cylinder
作者: 謝世圳
Hsieh, Shih-Chun
關鍵字: PIV;質點影像測速儀;wake;shear layer flow;wavelet transfrom;尾流;剪力層流;小波轉換法
出版社: 土木工程學系所
引用: 1. Antonia, R. A., L. W. B. Browne, and D. K. Bisset, “A description of the organized motion in the turbulent far wake of a cylinder at low Reynolds number,” Journal of Fluid Mechanics, Vol. 184, pp. 423 - 444 (1987). 2. Antonia, R. A., T. Zhou, and G. P. Romano, “Small-scale turbulence characteristics of two-dimensional bluff body wakes,” Journal of Fluid Mechanics, Vol. 459, pp. 67 - 92 (2002). 3. Blevins, R. D., “Flow-induced vibration,” Van Nostrand Reinhold, New York, N.Y. 4. Bloor, M. S., “The transition to turbulence in the wake of a circular cylinder,” Journal of Fluid Mechanics, Vol. 19, pp. 290-304 (1964). 5. Braza, M., R. Perrin, and Y. Hoarau, “Turbulence properties in the cylinder wake at high Reynolds numbers,” Journal of Fluids and Structures, Vol. 22, pp. 757-771 (2006). 6. Cantwell, B. and D. Coles, “An experimental study of entrainment and transport in the turbulent near wake of a circular cylinder,” Journal of Fluid Mechanics, Vol. 136, pp. 321 - 374 (1983). 7. Cowen, E. A. and S. G. Monismith, “A hybrid digital particle tracking velocimetry technique,” Experiments in Fluids, Vol. 22, pp. 199-211 (1997). 8. Dong, S., G. E. Karniadakis, A. Ekmekci, and D. Rockwell, “A combined direct numerical simulation-particle image velocimetry study of the turbulent near wake,” Journal of Fluid Mechanics, Vol. 569, pp. 185 - 207 (2006). 9. Gonzalez, R. C. and R. E. Woods, “Digital image processing,” 2nd edition, Prentice Hall (2002). 10. Görtler, H., “Berechnung von aufgaben der freien turbulenz auf grund eines neuen näherungsansatzes,” ZAMM, Vol. 22, pp. 244-254 (1942). 11. Hussain, A. K. M. F. and W. C. Reynolds, “The mechanics of an organized wave in turbulent shear flow,” Journal of Fluid Mechanics, Vol. 41, Part 2, pp. 241 - 285 (1970). 12. Hussian, A. K. M. F. and M. Hayakawa, “Eduction of large-scale organized structures in a turbulent plane wake,” Journal of Fluid Mechanics, Vol. 180, pp. 193 - 229 (1987) . 13. Kiya, M. and M. Matsunura, “Incoherent turbulence structure in the near wake of a normal plate,” Journal of Fluid Mechanics, Vol. 190, pp. 343 - 356 (1988). 14. Kiyani, G. A., and N. Rajaratnam, “Discussion: Experimental study on mean velocity characteristics of flow over vertical drop.” Journal of Hydraulic Research, IAHR, Vol. 46, No. 3, pp. 424 - 425(2008). 15. Labbé, D. F. L. and P. A. Wilson, “A numerical investigation of the effects of the spanwise length on the 3-D wake of a circular cylinder,” Journal of Fluids and Structures, Vol. 23, pp. 1168 - 1188 (2007). 16. Liepmann, H. W. and J. Laufer, “Investigation of free turbulent mixing,” N.A.C.A., Tech. Note, pp. 1257 (1947). 17. Lin, C., S. C. Hsieh, and K. T. Chang, “The formation length and convection velocity of vortex structures in the near wake of a circular cylinder,” Proceedings of the Fifth International Conference on Hydrodynamics, pp. 245 - 249 (2002). 18. Lin, C. and S. C. Hsieh, “Convection velocity of vortex structures in the near wake of a circular cylinder,” Journal of Engineering Mechanics, ASCE (2003) Vol. 129, No. 10, pp. 1108 ~ 1118.(2003) 19. Lin, C., W. Y. Huang, S. C. Hsieh, and K. A. Chang, “Experimental study on mean velocity characteristics of flow over vertical drop,” Journal of Hydraulic Research, IAHR, Vol. 45, No. 1, pp. 33 - 42 (2007). 20. Lin, C., W. Y. Huang, S. C. Hsieh, and K. A. Chang, “Reply to the Discussion: Experimental study on mean velocity characteristics of flow over vertical drop.” Journal of Hydraulic Research, IAHR, Vol. 46, No. 3, pp. 425-428 (2008). 21. Lourenco, L. M. and C. Shih, “Characteristics of the plane turbulent near wake of a circular cylinder, a particle image velocimetry study,” Published in Beaudan and Moin (1994), data taken from Kravchenko and Moin (2000). 22. Mori, N. and K. A. Chang, “Introduction to MPIV,” PIV toolbox in MATLAB, version 0.95, pp. 1-13 (2003). 23. Perry, A.E., M. S. Chong, and T. T. Lim, “The vortex-shedding process behind two-dimensional bluff bodies,” Journal of Fluid Mechanics, Vol. 116, pp. 70 - 90 (1982). 24. Pfeil, H. and J. Eifler, “Measurements in turbulent wakes of cylinders,” Forschung in Ingenieurwesen, Vol. 41, pp. 137 - 145 (1975). 25. Reichardt, H., “Gesetzmässigkeiten der freien turbulenz,” VDI- Forschungsheft (1942). 26. Roshko, A., “On the development of turbulent wakes from vortex streets,” NACA Report 1191 (1954). 27. Schlichting, H., “On the plane wake problem,” Ingenieur Archiv, vol. 1, pp. 533 - 571 (1930). 28. Schlichting, H., “Boundary-layer theory,” McGraw-Hill (1979). 29. Steiner, T. R. and A. E. Perry, “Large-scale vortex structures in turbulent wakes behind bluff bodies, Part 2. Far wake structure in the near wake of a normal plate,” Journal of Fluid Mechanics, Vol. 190, pp. 343 - 356(1987). 30. Tennekes, H. and J. L. Lumley, “A first course in turbulence,” Journal of Massachusetts Institute of Technology, pp. 104 - 145 (1972). 31. Unal, M. F. and D. Rockwell, “On vortex formation from a cylinder,” Journal of Fluid Mechanics, Vol. 190, pp. 491 - 512 (1988). 32. Wissink, J. G. and W. Rodi, “Numerical study of the near wake of a circular cylinder,” International Journal of Heat and Fluid Flow, Vol. 29, pp. 1060 - 1070 (2008). 33. Wu, S. J., J. J. Miau, C. C. Hu and J. H. Chou, “On low-frequency modulations and thtee-dimensionality in vortex shedding behind a normal plate,” Journal of Fluid Mechanics, Vol. 526, pp. 117 - 146 (2005). 34. Zdravkovich, M. M., “Flow around circular cylinders,” Oxford University Press Inc., New York (1997). 35. 田中周治、村田暹,「計算機援用可視化法による圓柱の後流構造の研究(第1報うず度の生成と減衰)」,日本機械學會論文集(B編),第51卷,第469號,第2838 - 2854頁(1985)。 36. 林 呈、顏光輝、郭正雄,「矩形柱體尾流場組織結構之實驗研究」,中國土木水利工程學刊,第7卷,第2號,第199 - 213頁(1995)。 37. 林 呈、顏光輝、孫洪福、邱鵬豪,「應用質點影像測速儀於圓柱近域尾流場之研究」,第二十屆海洋工程研討會論文集,第297 - 304頁(1998)。 38. 林 呈、林蔚榮、張國棟、白佳燕、翁健銘,「應用PIV與流場可視化技術於近一平板之圓柱近域尾流流場特性探討」,第二十二屆海洋工程研討會論文集,第154 - 161頁(2000)。 39. 林 呈、謝世圳、高明哲、徐華勇,「應用PIV及FLDV同步量測技術於圓柱近域尾流平均速度場特性之探討」,中國土木水利工程學刊,第16卷,第1號,第80 - 98頁(2004)。 40. 陳矛章,「黏性流體動力學基礎」,高等教育出版社,pp. 477 - 486 (1993)。 41. 黃煌煇,「平面紊亂射流與微小振幅波作用後速度與溫度分佈之研究」,博士論文,國立成功大學土木工程研究所,台南(1981)。 42. 黃煌煇、林 呈,「應用流場可視化法及LDV探討斜坡上波動內部流場及底部邊界層之特性」,國立成功大學台南水工試驗所研究論文,第十六號(1989)。
摘要: 
本研究首先利用高速攝影機及高功率氬離子雷射光源,分別替代傳統質點影像測速儀(簡稱PIV)量測系統之CCD電子耦合攝影機及脈衝式雷射光源,配合高通影像濾波等數位影像處理技術,據以建置具備高時間解析度之PIV速度量測系統,大幅提升PIV之量測速度。另利用高速攝影機之連續影像擷取特性,提出多時間間距之速度計算方法,改善傳統PIV僅能以單一時間間距進行速度計算之缺點,即分別以短時間間距計算流場中之高速區域,而以長時間間距計算低速區域,根據實際測試結果,多時間間距計算法確實能有效解析速度場中高速與低速間之變化,有助於變化複雜之流場速度量測。
其次,本文利用所建置之高時間解析PIV系統,並搭配流場可視化技術,針對圓柱近域尾流流場之範圍(x/d < 12.0,d為圓柱直徑),雷諾數( , 為流體密度, 為來流速度, 為動力黏滯度) Re = 600 ~ 10000來流條件下之流場特性進行量測與分析,另外,應用小波轉換法對尾流流場週期性變化過程進行瞬時頻譜與瞬時相位分析,以分別探討流場中平均與週期性變化過程中之速度場及紊流特性。
綜觀過去文獻或專書中有關流場相似性問題之探討,一般認為只有在完全發展流況中,流場之相似性才存在,對於流場發展過程中受局部特性影響之範圍,則無法對其相似性特性加以探討。對於圓柱尾流場之相似性研究,均僅探討遠域尾流場(x/d > 50.0)中之結果,對於近域尾流場之相似性分析則無進一步的討論。因此,本文首先提出沿流向分段進行之概念,即根據近域尾流場之特性對流場進行分段,再探求各區段內之流場相似性特性。經研究結果顯示,以中心軸水平平均速度對順流方向座標x的一次及二次偏微分特性,可將圓柱近域尾流場區分為S1、S2、W1、W2及W3等5個區段(如本文中圖6-1-1所示),並利用各區段範圍之長度作為特徵長度尺度,獲得近域尾流場中心軸水平平均速度分佈的相似性結果。
對於S1及S2區內垂直水流方向之水平速度剖面相似性分析,本文提出以剪力層本身之觀點為主進行分析,即平移觀察座標至剪力層中心,並利用剪力層水平平均速度剖面之一次及二次偏微分特性,決定剪力層中心(ysc)、剪力層特徵厚度(bs)及特徵厚度上下層速度(us1、us2)等特徵值,以無因次特徵參數 及 分別求得S1及S2區之相似曲線。W1 ~ W3內之相似性分析則利用傳統之半寬度b作為特徵長度尺度,欠損速度( 或 )為特徵速度尺度,分別獲得各區之相似性結果
對於圓柱近域尾流主渦脫離及傳輸等具週期性變化之流場特性,本文則提出以小波轉換法所推求之瞬時相位進行全域流場的相位平均分析,以剖析渦流傳輸過程之相關特性。此外,利用本文所建置之具備高時間解析特性的PIV系統,對圓柱近域尾流流場中之紊流特性分佈情形,分別以穩態及週期性流場之觀點進行探討,並利用流場相位平均後之結果分離主渦之波動成分與紊流擾動量之特性,發現紊流擾動量之分佈於時間上並非隨機發生,而是與該瞬間之渦流流場特性有關。

The purpose of this study is to establish high time-resolved PIV system and to apply this system to the study on characteristics of near-wake flow behind a circular cylinder. For the high time-resolved PIV system, high speed camera and high power argon-ion laser were employed instead of CCD camera and pulse laser, which are frequently used in traditional PIV system. Combining the high speed camera and the argon-ion laser, the repetition rate for measuring instantaneous velocity fields can be highly increased up to 1,000 frames per second. Therefore, both the mean velocity and the turbulence characteristics in the flow field could be obtained due to high spatial and high temporal resolutions used this system. Digital image high-pass filter technique is also used to enhance the signal of each particle in the image captured by the camera. Moreover, multi-time interval method is used for the high time-resolved PIV technique to modify the velocity field especially in the measuring area with both high-speed flow and low-speed flow characteristics.
The characteristics of velocity field in the near-wake (x/d < 12.0) of a circular cylinder were investigated experimentally for Reynolds number Re ( ) ranging from 600 ~ 10,000. Based upon the data obtained by high time-resolved PIV and flow visualization technique, the flow in the near wake could be classified into five regions as S1, S2, W1, W2 and W3. These five regions can be separated and defined clearly by the variation of the first and second derivative of the streamwise mean velocity along the center line.
In the S1 and S2 regions, the characteristics of streamwise mean velocity profiles can be described by the center point of shear layer, ysc, the specific width, bs, and the velocities of the upper and lower boundary of the specific width, us1 and us2,. The similarity of the velocity profiles in S1 and S2 regions can be established by plotting of versus . As regards the W1, W2, and W3 regions, using the traditional half-velocity-defect width b as a length scale, similarity profile of the relationship between the non-dimensional velocity [ or ] and longitudinal coordinate ( ) can be obtained. The similarity of the non-dimensional Reynolds stress distributions in W2 regions is also proposed.
Furthermore, this study also focuses on phase analysis of velocity field in the near wake of a circular cylinder. Wavelet transform is used for identifying the phase, then the phase-averaged velocity fields can be obtained. The time-varying velocity signal can be decomposed into a global mean component, a periodic mean component and a residual random component. The present study also demonstrates the variations of the vorticity, the circulation, and convection velocity of primary vortex during shedding process.
URI: http://hdl.handle.net/11455/15901
其他識別: U0005-2908200817013600
Appears in Collections:土木工程學系所

Show full item record
 

Google ScholarTM

Check


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.