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題名 | 旋轉效應對瞬間起動圓柱體尾流的渦漩結構之影響 |
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作者 | 程明忠; 朱錦洲; 廖育元; | 書刊名 | 國立臺灣大學工程學刊 |
卷期 | 63 1995.02[民84.02] |
頁次 | 頁103-115 |
分類號 | 440.137 |
關鍵詞 | 圓柱體; 旋轉; 渦漩; 環流量; 雷射激發光化學量測法; Circular cylinder; Rotation; Vortex; Circulation; LIPA; |
語文 | 中文(Chinese) |
中文摘要 | 本文係研究旋轉效應對瞬間起動圓柱體尾流區之渦漩的影響。吾人觀察 渦漩的形成及成長過程,批量測尾流中渦漩的速度場、渦度場及環流量隨時間之 變化。實驗採用雷射激發光化學量測法(LaserInducedPhotochem沁引AnemOmetw, 簡稱LIPA),該方法為一不干擾流場的量測方法,在二維非定常流中能夠量測瞬 間多點位置的速度,並可由此估算多點位置的渦度,此外UPA方可作為流場顯像 的工具。本實驗量測雷諾數(Re=UD/v)1000及3000,轉速比(α=ΩD/2U)為0.2至1.5 的流場。以固定於圓柱體,但不隨其轉動的拉氏坐標(Lagrangian coordinates)為觀 點,從事圓柱體由靜止起動且轉動所生成的流場於初期發展階段之定性觀察與定 量分析。實驗結果顯示旋轉效應改變圓柱表面邊界層的性質,以致於影響渦漩的 發展及渦漩的流散。同時旋轉效應降低渦漩流散時的飽和環流量值;轉速比α值 對該飽和值的大小無明顯的影響,但α愈大使得渦漩較快達到飽和環流量。 |
英文摘要 | The flow structure in the near wake of an impulsively started rotating cylinder has beenstudied experimentally. The emphasis is on the formation and growth of the vortices in thenear wake region. Detailed measurements were made using Laser Induced photochemicalAnemometry (LIPA), a nonintiusive visualization technique which enables multipoint simultaneous measurement of the unsteady velocity field: thus, the vorticity distribution and thecirculation can be calculated. LIPA technique was also used for flow visualization. In thepresent study, the Reynolds numbers based on the steady state velocity of the cylinder, U,and the diameter of the cylinder, D. were 1000 and 3000 with the angular-to-translationalspeed ratio, α, varied from 0.2 to 1.5. Observalions on the early stage of flow developmentwere made based on the Lagrangian coordinates translating but not rotating with the cylinder.Results show that the effect of cylinder rotation changes the characteristic of the boundarylayer on the cylinder surface; thus, the growth of vortices and the saturated circulation ofthe primary vortex upon vortex shedding are affected thereafter. In addition, the saturatedcirculation is observed to be independent of α in the range of study. |
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