研究生: |
陳雅筠 YA-YUN CHEN |
---|---|
論文名稱: |
雙平面噴流之流場特徵 Flow characteristics of two parallel plane jets |
指導教授: |
黃榮芳
Rong-Fung Huang 許清閔 Ching-Min Hsu |
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: | 2019 |
畢業學年度: | 107 |
語文別: | 中文 |
論文頁數: | 156 |
中文關鍵詞: | 雙平面噴流 、槽噴流 、質點影像測速儀 |
外文關鍵詞: | Two parallel jets, Plane jet, PIV |
相關次數: | 點閱:250 下載:0 |
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研究兩道相鄰、平行且等速的二維噴流在不同間隔時的流動型態與流場特性。空氣由高壓桶供應,將空氣導入一個大體積的空腔中,經整流後從空腔頂部一片具有平行的兩道細槽之平板噴出,兩道細槽之噴流出口具有ASME low 系列噴嘴的形狀。經由置換不同的空腔頂部的平板,可以改變兩道相鄰且平行噴出之二維噴流出口之間的距離。二維噴流出口之寬度d = 4 mm,長度w = 145 mm;兩道噴流出口中心之間的距離s與噴流出口寬度d的比值為 s/d = 3, 5, 8, 10, 15。藉由電子式質量流量計量測噴流供應質量,轉化為一大氣壓標準溫度下的體積流率,除以噴流出口面積獲得噴流出口速度,再換算為噴流出口雷諾數Rej,Rej= 200 ~1600。利用雷射光頁輔助煙霧流場可視化技術搭配高速攝影機,擷取瞬時流場影像;應用高速質點影像測速儀(PIV)量測兩道相鄰二維噴流橫向速度場。觀察煙霧流場可視化之影片與照片,在噴流間隔與雷諾數變化時,可分辨出兩種流場特徵模態:(1)噴流往下游運動時互相吸引而內傾,經一段往下游距離後結合在一起,結合之後噴流因剪力效應而產生之凝聚性渦漩結構才破碎成紊流,通常發生在較小的s/d,稱為CBVB (combination before vortex breakup)、(2)噴流往下游運動,經一段往下游距離後靠攏結合在一起,結合之前噴流因剪力效應而產生之凝聚性渦漩結構已開始破碎成紊流,通常發生在較大的s/d,稱為CAVB (combination after vortex breakup)。PIV量測結果顯示,兩噴流之間靠近噴口附近會形成一個迴流區,迴流區中包含兩個轉向相反的渦流。迴流區的頂點在中心線上,稱為匯流點(merge point, MP),是個四向鞍點;在匯流點下游,兩噴流結合之後,速度在中心線變成橫向分佈最大值時的軸向位置稱為結合點(combine point, CP)。速度場的軸向與橫向分佈、CBVB與CAVB在s/d-Rej的區域分佈以及匯流點與結合點的軸向座標在本文中皆有討論。
The flow characteristics of two parallel plane jets were experimentally studied. The widths and lengths of the jet exits were 4 mm and 145 mm, respectively. The ratios of the spacing between the two neighboring jets to the width of the jet exits were 3, 5, 8, 10, and 15. According to the smoke-flow visualization results, two characteristic flow modes, combination before vortex breakup (CBVB) and combination after vortex breakup (CAVB), were identified in the domain of non-dimensional jet spacing and jet Reynolds number. Coherent structures evolved in the shear layers of the jets issued from the jet exits and expanded laterally as the jets travelled downstream. The CBVB mode appeared at small non-dimensional jet spacing. The jet columns inclined slightly toward the centerline due to the slightly low pressure existing between the neighboring jets in the near field. The shear-layer coherent structures merged together, broke up into small eddies, then combined into a single jet to evolve to downstream area. The CAVB mode appeared at large non-dimensional jet spacing. The neighboring jets combined into a single jet to evolve to downstream area first, then the shear-layer coherent structures merged together and broke up into small eddies. The PIV measured velocity fields showed a recirculation region consisted of two counter-rotating vortices existing between the jets near the jet exits. The apex of the recirculation region was a four-way saddle which was a merge point (MP) of the two parallel plane jets. Around the centerline upstream the MP, the flow velocities were reversed. Around the centerline downstream the MP the flow velocity pointed downstream. However, the lateral velocity profiles presented a deficit around the centerline. As the lateral velocity profiles evolved downstream, the velocity deficits around the centerline became smaller and smaller, and finally attained a local maximum at an axial distance downstream the MP. The location where the centerline velocity became the maximum of the lateral velocity profile was termed the combined point (CP). The velocity distribution in axial and lateral directions, characteristic flow regimes, axial lengths of the MP and CP were presented, analyzed, and discussed.
[1] Heskestad, G., “Hot-wire measurements in a plane turbulent jet,” Journal of Applied Mechanics (ASME Transaction), Vol. 32, No. 4, 1965, pp. 721-734.
[2] Van der Hegge Zijnen, B.G., “Measurements of distribution of heat and matter in a plane turbulent jet of air,” Applied Scientific Research, Sec.A, Vol. 7, No. 4, pp. 227-292.
[3] Wilson, R.A.M. and Danckwerts, P.V., “Studies in turbulent mixing-II. A hot air jet,” Chemical Engineering Science, Vol. 19, No. 11, 1964, pp. 885-895.
[4] Bradbury, L.J.S., “The structure of a self-preserving turbulent planar jet,” Journal of Fluid Mechanics, Vol. 23, 1965, pp. 31-64.
[5] Gutmark, E. and Wygnanski, I., “The planar turbulent jet,” Journal of Fluid Mechanics, Vol. 73, No. 3, 1976, pp. 465-495.
[6] Deo, R.C., Mi. J., and Nathan, G.J., “The influence of nozzle-exit geometric profile on statisticall properties of a turbulent plane jet,” Experimental Thermal and Fluid Science, Vol. 32, 2007, pp. 545-559.
[7] Hsiao, F.-B., Lim, Y.-C., Huang, J.-M., “On the near-field flow structure and mode behaviors for the right-angle and sharp-edged orifice plane jet,” Experimental Thermal and Fluid Science, Vol. 34, 2010, pp. 1282-1289.
[8] Miller, D.R., and Comings, E.W., “Forced-momentum fields in a dual-jet flow,” Journal of Fluid Mechanics, Vol. 7, No. 2, 1960, pp. 237-256.
[9] Elbanna, H., Gahin, S., and Rashed, M., “Investigation of two plane parallel jets,” AIAA Journal, Vol. 21, 1983, pp. 986-991.
[10] Lin, Y.F. and Sheu, M.J., “Investigation of two plane parallel unventilated jets,” Experiments in Fluids, Vol. 10, No. 1, 1990, pp. 17-22.
[11] Lin, Y.F. and Sheu, M.J., “Interaction of parallel turbulent plane jets,” AIAA Journal, Vol. 29, No. 9, 1991, pp. 1372–1373.
[12] Ko, N.W.M., and Lau, K.K., “Flow structures in initial region of two interacting parallel plane jets,” Experimental Thermal and Fluid Science, Vol. 2, 1989, pp. 431-449.
[13] Nasr, A. and Lai, J.C.S., “Comparison of flow characteristics in the near field of two parallel plane jets and an offset plane jet,” Physics of Fluids, Vol. 9, No. 10, 1997, pp. 2919-2931.
[14] Tanaka, E., “The interference of two-dimensional parallel jets (1st report, experiments on dual jets),” Bulletin of JSME, Vol. 13, No. 56, 1970, pp. 272-280.
[15] Tanaka, E., “The interference of two-dimensional parallel jets (2nd report, experiments on the combined flow of dual jet),” Bulletin of JSME, Vol. 17, No. 109, 1974, pp. 920-927.
[16] Nasr, A. and Lai, J.C.S., “Effects of nozzle spacing on the development of two parallel plane jets,” International Journal of Transport Phenomena, Vol. 2, 2000, pp. 2919-2931.
[17] Anderson, E.A., Snyder, D.O., and Christensen, J., “Periodic flow between low aspect ratio parallel jets,” Journal of Fluids Engineering (Transaction ASME), Vol. 125, No. 2, 2003, pp. 389-392.
[18] Fujisawa, N., Nakamura, K., and Srinivas, K., “Interaction of two parallel plane jets of different velocities,” Journal of Visualization, Vol. 7, 2004, pp. 135-142.
[19] Bunderson, N.E. and Smith, B.L., “Passive mixing control of plane parallel jets,” Experiments in Fluids, Vol. 39, No. 1, 2005, pp. 66-74.
[20] Murai, K., Taga, M., and Akagawa, K., “An experimental study on confluence of two two-dimensional jets,” Bulletin of JSME, Vol. 13, No. 56, 1970, pp. 958-964.
[21] Anderson, E.A. and Spall, R.E., “Experimental and numerical investigation of two-dimensional parallel jets,” Journal of Fluids Engineering (ASME Transaction), Vol. 123, No. 2, 2001, pp. 401-406.
[22] Spall, R.E., Anderson, E.A., and Allen, J., “Momentum flux in plane, parallel jets,” Journal of Fluids Engineering (ASME Transaction), Vol. 126, No. 4, 2004, pp. 665-670.
[23] Durve, A., Patwardhan, A.W., Banarjee, I., Padmakumar, G., and Vaidyanathan, G., “Numerical investigation of mixing in parallel jets,” Nuclear Engineering and Design, Vol. 242, 2012, pp. 78-90.
[24] Mondal, T., Das, M.K., and Guha, A., “Periodic vortex shedding phenomenon for various separation distances between two plane turbulent parallel jets,” International Journal of Heat and Mass Transfer, Vol. 99, 2016, pp. 576-588.
[25] Y.M. Shim, P.J. Richards, and R.N. Sharma, “Turbulent structures in the flow field of plane jet impinging on a circular cylinder,” Experimental Thermal and Fluid Science, Vol. 57, 2014, pp. 27-39.
[26] Amitesh Kumar, “Mean flow characteristics of a turbulent dual jet consisting of a plane wall jet and a parallel offset jet.” Computers and Fluids, Vol. 114, 2015, pp. 48-65.