Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/16120
標題: 應用小波轉換法探討圓柱近平板間隙流不穩定搖擺之特性
Study on the Intermittent Switching Characteristics of Gap Flow behind a Circular Cylinder Placed near a Plane Boundary
作者: 蔡明邑
Tsai, Ming-I
關鍵字: wavelet transform
小波轉換
switching
frequency of vortex shedding
間隙流不穩定搖擺
渦流脫離頻率
出版社: 土木工程學系所
引用: 參考文獻 1. Alam, M. M., Moriya, M., and Sakamoto, H. (2003). “Aerodynamic characteristics of two side-by side circular cylinder and application of wavelet analysis on the switching phenomenon.” J. Fluids and Struct., 18(3-4), 325-346. 2. Angrilli, F., Bergamaschi, S. and Cossalter V. (1982)︰Investigation of Wall Induced Modifications to Vortex Shedding From a Circular Cylinder, Transcations of the ASME, Vol. 104, pp.518-522. 3. Bearman, P. W., and Zdravkovich, M. M. (1978). “Flow around a circular cylinder near a plane boundary.” J. Fluid Mech., 89, 33-47. 4. Blevins, R. D. (1977). Flow-induced vibration. Van Nostrand Reinhold, New York 5. Buresti, G., and Lanciotti, A. (1992). “Mean and fluctuating forces on a circular cylinder in cross-flow near a plane surface.” J. Wind. Eng. Ind. Aerodyn., 41(1-3), 639-650. 6. Grass, A. J., Raven, P. W. J., Stuart, R. J., and Bray, J. A. (1984). “The influence of boundary layer velocity gradients and bed proximity on vortex shedding from free spanning pipelines.” J. Energy Resour. Tech., 106(1), 70-78. 7. Lei, C., Cheng, L., and Kavanagh, K. (1999). “Re-examination of the effect of a plane boundary on force and vortex shedding of a circular cylinder.” J. Wind. Eng. Ind. Aerodyn., 80(3), 163-286. 8. Lin, W. J., Lin, C., Hsieh, S. C., and Dey, S.(2009). “Flow Characteristics around a Circular Cylinder Placed Horizontally above a Plane Boundary.”J. Eng. Mech.,135(7), 697-716 9. Price, S. J., Sumner, D., Smith, J. G., Leong, K., and Paidoussis, M. P. (2002). “Flow visualization around a circular cylinder near to a plane wall.” J. Fluids and Struct., 16(2), 175-191. 10. Taniguchi, S., and Miyakoshi, K. (1990). “Fluctuating fluid forces acting on a circular cylinder and interference with a plane wall.” Exp. Fluids, 9(4), 197-204. 11. Torrence, C., and Compo, G. P., (1998) “A Practical Guide to Wavelet Analysis.” Bull. Amer. Metor. Soc., 79(1), 61-78. 12. Wang, X. K., and Tan, S. K. (2008). “Near-wake flow characteristics of a circular cylinder close to a wall.” J. Fluids and Struct., 24(5), 605-627. 13. 林 呈、顏光輝、郭正雄 (1995) :「臨界淨間距比條件下並列雙圓柱尾流場特性之實驗研究─雷諾數效應之影響」,中國土木水利工程學刊,第七卷第四期,第487-500頁。 14. 林 呈、顏光輝 (1996) :「應用流場可視化法探討並列雙圓柱尾流場之特性研究」,中國土木水利工程學刊,第八卷第二期,第151-160頁。 15. 林蔚榮 (2000) :「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」,國立中興大學土木工程研究所碩士學位論文。 16. 白佳燕 (2003) :「應用FLDV與PIV探討並列鈍形體尾流場之特性」,國立中興大學土木工程研究所碩士學位論文。 17. 楊婷勻 (2004) :「應用小波轉換法探討並列鈍形體間隙流不穩定搖擺之特性」,國立中興大學土木工程研究所碩士學位論文。 18. 謝世圳 (2008) :「建置具高時間解析之PIV系統並應用於圓柱近域尾流特性之探討」,國立中興大學土木工程研究所博士學位論文。 19. 何宗浚 (2009) :「孤立波通過不同長高比之潛沒構造物時周邊渦流流場特性探討」,國立中興大學土木工程研究所博士學位論文。
摘要: 本研究運用流場可視化法及改良式PIV系統,針對圓柱近平板之尾流流場,於雷諾數(Re) = 1600 ~ 4000、無因次邊界層厚度(δ/D) = 0.50 ~ 1.00、淨間距比(G/D) = 0.10 ~ 4.00條件下,進行定性觀察及定量量測,並輔以快速傅立葉轉換方法,對間隙流型態加以分類,且使用小波轉換法,對間隙流不穩定搖擺與剪力層渦流脫離頻率之關係進行分析、探討。 於Re = 1600、δ/D = 0.50條件下,改變間隙比至有明顯間隙流不穩定搖擺現象時(G/D = 0.15 ~ 0.20),間隙流往上游擺動所對應之瞬時渦流脫離頻率增加;反之,間隙流往下游移動時,相對應之瞬時頻率遞減。此外,於G/D = 0.20實驗條件下,間隙流與剪力層流交會處之小波轉換分析結果顯示:間隙流於相同位置時,相異時間下瞬時渦流脫離頻率相近。 本研究於Re = 1600、G/D = 0.20改變δ/D介於0.50 ~ 1.00進行探討,發現δ/D = 0.50 ~ 0.75間之間隙流擺動方向與瞬時渦流脫離主頻之趨勢,將與上述之G/D = 0.20所分析之趨勢一致。δ/D = 0.75 ~ 1.00間之間隙流擺動方向與瞬時主頻並無明顯趨勢。且於δ/D = 0.50 ~ 1.00隨著邊界層厚度增加,頻率有遞減情形。 當G/D = 0.20、δ/D = 0.50改變Re = 2100 ~ 4000,發現在Re = 4000時,流場中之渦流脫離頻率不受間隙流影響。於Re = 2100時,間隙流往上游擺動,則瞬時主頻增加;反之,則減少。此趨勢與Re = 1600、δ/D = 0.50、G/D = 0.15 ~ 0.20條件下之結果一致。
Flow characteristics around a circular cylinder positioned near a plane boundary were investigated for Reynolds numbers (Re) ranging from 1600 to 4000, ratios of boundary layer thickness to circular cylinder diameter (δ/D) varying from 0.50 to 1.00 and gap ratios (G/D) changing from 0.10 to 4.00, using qualitative flow visualization technique and quantitative PIV measurement system. The classification of gap flow was made by applying spectra analysis of vortex shedding frequency and flow visualization. In addition, the gap flow switching was further studied using wavelet transforms. It was found that the gap flow switching would influence the frequency of vortex shedding. The vortex shedding frequency increases as the deflected gap flow switching to the upstream of the upper shear layer and then decreases as the deflected gap flow switching to the downstream of the upper shear layer at Re = 1600, δ/D = 0.50. Furthermore, the results showed that the values of vortex shedding frequency would be very close when the gap flow impinges upon to the same position at different times during the switching process for G/D = 0.20. Systematic measurements were also carried out for δ/D varying from 0.50 to 1.00 at Re = 1600 and G/D = 0.20. For δ/D = 0.50 ― 0.75, the vortex shedding frequency would be influenced by the gap flow switching. However, for δ/D = 0.50 ― 0.75, there is no clear evidence to show that the gap flow switching would influence the vortex shedding frequency. For Re = 4000, G/D = 0.20 and δ/D = 0.50, the vortex shedding frequency seems almost to be independent of the gap flow switching. However, as the Re decreasing from 4000 to 2100, the gap flow switching do influence the vortex shedding frequency. For Re = 2100, the vortex shedding frequency would show the same changing tendency when the gap flow switches to different positions of the upper shear layer like aforementioned flow condition at Re = 1600 and δ/D = 0.50.
URI: http://hdl.handle.net/11455/16120
其他識別: U0005-2808200913115400
文章連結: http://www.airitilibrary.com/Publication/alDetailedMesh1?DocID=U0005-2808200913115400
Appears in Collections:土木工程學系所

文件中的檔案:

取得全文請前往華藝線上圖書館



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