研究生: |
張庭瑋 Ting-wei Chang |
---|---|
論文名稱: |
平板受小圓柱尾流衝擊時之流場特徵與氣動力性能 Effect of a Small-diameter Circular Cylinder wake on Flow Characteristics and Aerodynamic Performance |
指導教授: |
黃榮芳
Rong-Fung Huang |
口試委員: |
林怡均
Yi-Jiun Lin 許清閔 Ching-Min Hsu |
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: | 2018 |
畢業學年度: | 106 |
語文別: | 中文 |
論文頁數: | 383 |
中文關鍵詞: | 小圓柱 、尾流 、氣動力性能 、平板 |
相關次數: | 點閱:332 下載:2 |
分享至: |
查詢本校圖書館目錄 查詢臺灣博碩士論文知識加值系統 勘誤回報 |
本研究藉由實驗方法,探討小圓柱尾流衝擊平板時所生成之流場特徵與氣動力性能。藉由雷射光頁輔助煙霧可視化技術,觀察小直徑圓柱尾流之流場特徵以及衝擊平板時之流場特徵。使用熱線風速儀量測小直徑圓柱下游區的速度分佈、紊流強度以及平板上游表面的速度分佈。以質點影像速度儀(PIV)量測受小直徑圓柱尾流衝擊時的平板上游流場結構,並與流場可視化之特徵比對。使用壓力掃描器量測平板上、下游的表面壓力,探討小直徑圓柱尾流衝擊平板時,對平板上、下游表面壓力的影響,並分析壓力係數以及阻力係數。改變雷諾數、小直徑圓柱直徑以及平板寬度,流場可視化、熱線風速儀量測、迎風面壓力量測及速度場的實驗結果顯示:當平板寬度固定時,在雷諾數與小圓柱直徑的場域內,流場特徵模態可分為穩態域(stable regime)與非穩態域(unstable regime)兩種,大約在雷諾數大於6000以及小圓柱直徑與平板寬度比值大於9/1000時,流場為非穩態;大約在雷諾數小於6000以及小圓柱直徑與平板寬度比值小於9/1000時,流場為穩態。穩態域中的流場特徵,為小圓柱尾流在接近平板表面的上游區引致流場特徵結構,可分成三個子模態:在低雷諾數區形成兩個轉向相反且近似對稱的迴流;在中雷諾數區形成一蕈狀渦漩結構;在高雷諾數區,蕈狀渦漩結構上游呈現一至三個小渦漩結構。在非穩態域中的流場特徵,平板表面的蕈狀渦漩結構不會穩定存在於平板上方,而是呈現不規則的逸放行為。在穩態域中,由於平板表面上游區的蕈狀渦漩結構的生成,因此避免橫風直接衝擊平板表面,使得平板上游表面壓力係數降低,阻力係數也隨之下降,且當平板上游表面出現多個蕈狀渦漩結構時,平板的阻力係數下降最明顯。
The effect of small-diameter circular cylinder wake impinging a flat plate on the flow characteristics and aerodynamic performance were experimentally studied in a wind tunnel. The aims were focused on improving the flow behavior and aerodynamic performance of the flat plate. The effects of varying the small-diameter circular cylinder diameter on the flow characteristics upstream the flat plate were observed by laser-assisted smoke flow visualization technique. The instantaneous velocities and turbulent intensities in the wake of the small-diameter circular cylinder were detected by a one-component hot-wire anemometer. By installing a few pressure taps on the front and rear surface of the flate plate, the pressure distributions on the pressure surfaces were measured by a home-made pressure scanner. The pressure coefficients were calculated by dividing the measured surface pressure by the dynamic pressure of freestream. The drag coefficients were subsequently obtained by integrating the pressure coefficients over the surface area of the flat plate. The particle image velocitry (PIV) was employed to measure the velocity field. The streamline patterns and turbulence properties were derived from the measured velocity data. Two characteristic flow regimes (stable and unstable) were identified in the domain of small circular cylinder diameter and the flat plate width by flow visualization. Three characteristic flow modes were found in the stable regime: two reverse flows appeared at low Reynolds numbers; mushroom type vortices appeared at mediate Reynolds numbers; one, two, or three small vortices appeared upstream the mushroom type vortices at large Reynolds numbers. The surface pressure coefficients on the upstream surface and drag coefficients of the flat plate were reduced. The drag coefficients of the flat plate decreased the most significantly when a mushroom type multi-vortex appeared near the upstream surface of the flat plate.
[1] Nakayama, Y. and Boucher, R. F., Introduction to Fluid Mechanics, Arnold, Great Britain, 1999.
[2] Prandtl, L., “Über Flüssigkeitsbewegung bei sehr kleiner Reibung,” Proc. Third Int. Math. Congr., Heidelberg, Germany, 1904, pp. 484-491.
[3] In, K. M., Choi, D. H., and Kim, M. U., “Two-dimensional viscous flow past a flat plate,” Fluid Dynamics Research, Vol. 15, No. 1, 1995, pp. 13-24.
[4] Dennis, S. C. R., Qiang, W., Coutanceau, M., and Launay, J. L., “Viscous flow normal to a flat plate at moderate Reynolds numbers,” Journal of Fluid Mechanics, Vol. 248, Mar. 1993, pp. 605-635.
[5] Nakamura, Y., “Vortex shedding from bluff bodies and a universal strouhal number,” Journal of Fluids and Structures, Vol. 10, No. 2, 1996, pp. 159-171.
[6] Schewe, G., “Reynolds-number effects in flow around more-or-less bluff bodies,” Journal of Wind Engineering and Industrial Aerodynamics, Vol. 89, No. 14-15, 2001, pp. 1267-1289.
[7] Bearman, P. W. and Harvey, J. K., “Control of circular cylinder flow by the use of dimples,” AIAA Journal, Vol. 31, No. 10,1993, pp.1753-1756.
[8] Fiedler, H. E., “Control of free turbulent shear flows,” Flow Control-Fundamentals and Practices, edited by M. Gad-el-Hak, A. Pollard, and J. P. Bonnet, Springer-Verlag, Berlin, 1998, p.335-429.
[9] Gad-el-Hak, M., Flow Control-Passive, Active, and Reactive Flow Management, Cambridge University Press, New York, 2000.
[10] Ghee, T. A. and Leishman, J. G., “Unsteady circulation control aerodynamics of a circular cylinder with periodic jet blowing,” AIAA Journal, Vol. 30, No. 2, 1992, pp. 289-299.
[11] Strykowski, P. J. and Sreenivasan, K. R., “On the formation and suppression of vortex shedding at low Reynolds numbers,” Journal of Fluid Mechanics, Vol. 218, Sep. 1990, pp. 71-107.
[12] Wang, A. -B. and Chang, Y. -C., “Experimental investigation of suppression of vortex shedding from a circular cylinder,” Transactions of the Aeronautical and Astronautical Society of the Republic of China, Vol. 28, 1996, pp. 249-254.
[13] Sakamoto, H., Tan, K., and Haniu, H., “An optimum suppression of fluid forces by controlling a shear layer separated from a square Prism,” Journal of Fluids Engineering, Vol. 113, No. 2, 1991, pp. 183-189.
[14] Sakamoto, H. and Haniu, H., “Optimum suppression of fluid forces acting on a circular cylinder,” Journal of Fluids Engineering, Vol. 116, No. 2, 1994, pp. 221-227.
[15] Prasad, A. and Williamson, C. H. K., “A method for the reduction of bluff body drag,” Journal of Wind Engineering and Industrial Aerodynamics, Vol. 69-71, Jul-Oct 1997, pp. 155-167.
[16] Tsutsui, T. and Igarashi, T., “Drag reduction of a circular cylinder in an air-stream,” Journal of Wind Engineering and Industrial Aerodynamics, Vol. 90, No. 4-5, 2002, pp. 527-541.
[17] Bouak, F. and Lemay, J., “Passive control of the aerodynamic forces acting on a circular cylinder,” Experimental Thermal and Fluid Science, Vol. 16, No. 1-2, 1998, pp. 112-121.
[18] Lienhard, J. H., Synopsis of lift, drag and vortex frequency data for rigid circular cylinders, Research Division Bulletion 300, Washington State University, 1966.
[19] Huang, R. F., Chen, J. M., and Hsu C. M., “Modulation of surface flow and vortex shedding of a circular cylinder in the subcritical regime by self-excited vibration rod,” Journal of Fluid Mechanics, Vol. 555, May 2006, pp. 321-352.
[20] Zdravkovich, M. M., “Different modes of vortex shedding: an overview,” Journal of Fluids and Structures, Vol. 10, No. 5, 1996, pp. 427-437.
[21] Roshko, A, “On the wake and drag of bluff bodies,” Journal of Aeronautical Sciences, Vol. 22, No. 2, 1955, pp. 124-132.
[22] Tritton, D. J., “Experiments on the flow past a circular cylinder at low reynolds numbers,” Journal of Fluid Mechanics, Vol. 6, No. 4, 1959, pp. 547-567.
[23] Etkin, B., Kovbaoher, G. K., and Keefe, R. T., “Acoustic radiation froma stationary cylinder in fluid stream (aeolian tones),” The Journal of the Acoustical Society of America, Vol. 29, No. 1, 1957, pp. 30-36.
[24] Weaver, W., “Wind-induced vibrations in antenna members,” Journal of the Engineering Mechanics Division, ASCE, Vol. 87, No. 1, 1961, pp. 141-165.
[25] Gerrard, J. H., “An experimental investigation of the oscillating lift and drag of a circular cylinder shedding turbulent vortices,” Journal of Fluid Mechanics, Vol. 11, No. 2, 1961, pp. 244-256.
[26] Roshko, A., On the Development of Turbulent Wakes from Vortex Streets, NACA TN 2913, 1954.
[27] In, K. M., Choi, D. H., and Kim, M. U., “Two-dimensional viscous flow past a flat plate,” Fluid Dynamics Research, Vol. 15, No. 1, 1995, pp. 13-24.
[28] Dennis, S. C. R., Qiang, W., Coutanceau, M., and Launay, J. L., “Viscous flow normal to a flat plate at moderate reynolds numbers,” Journal of Fluid Mechaics, Vol. 248, Mar 1993, pp. 605-635.
[29] Nakamura, Y., “Vortex shedding from bluff bodies and a universal strouhal number,” Journal of Fluids and Structures, Vol. 10, No. 2,1996, pp. 159-171.
[30] Igarashi, T., Nobuaki, T., “Drag reduction of flat plate normal to airstream by flow control using a rod,” Journal of Wind Engineering and Industrial Aerodynamics, Vol. 90, No. 4-5, 2002, pp. 359-376.
[31] Sichlichting, H. Boundary layer theory, 7th ed, Mcgraw-Hill, New York, 1993, p. 699.
[32] Flagan, R. C. and Seinfeld J. H., Fundamentals of air pollution engineering, Prentice Hall, Englewood Cliffs, New Jersey, 1988, p.295-307.
[33] 張冠翔, 小圓柱尾流衝擊平板時的流場特徵與氣動力性能, 國立台灣科技大學機械工程研究所碩士論文, 2017.