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題名 | Vortex Shedding from Fixed and Oscillating Rectangular Prisms in Shear Flows=剪力流中矩柱之渦散現象研究 |
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作者 | 盧博堅; 鄭啟明; 梁弘昇; | 書刊名 | 中國工程學刊 |
卷期 | 20:5 1997.09[民86.09] |
頁次 | 頁501-509 |
分類號 | 440.137 |
關鍵詞 | 渦散; 剪力流; 格元分界; Vortex shedding; Shear flow; Wake cell boundary; |
語文 | 英文(English) |
中文摘要 | 本文主要以風洞實驗探討不同高寬比(H/D)之矩柱,在靜止及振動下分別受兩種剪 力參數β=0.024及β=0.032(β=dU/dyxD/Uc)之剪力流場作用下,矩柱後方所產生的渦散現 象,並與在均勻流場中之渦散現象作比較。 結果顯示,剪力流場的速度梯度剖面產生縱向渦漩,破壞了渦散現象的二維性,進而在 軸向上的渦散頻率呈現階梯狀的格元(cell)現象隨著矩柱高寬比的增加,格元分界(cell boundary)往高速端移動,在同一模型中隨著剪力參數增大,格元分界愈往低速端移動。由於 剪力流速度梯度所造成的相位變化,在剪力參數增大時相位差拉大且高速端格元長度變長。 於柱體振動時,在各流場中則明顯提升其相關性及格元內渦漩的一致性。 |
英文摘要 | The main focus of this paper is to study the results of experiments on six different rectangular prisms with varied side ratios, with and without forced oscillation, displaced in two shear free streams and one uniform flow. The setting of free stream shear parameters β=dU/dyxD/Uc are 0.024 and 0.032. With respect to vortex shedding phenomena. a comparison between shear flows and uniform flows is also part of the focus. Experimental results indicate that disturbance on the two-dimensional vortex shedding of the uniform flow is caused by the longitudinal vortex of the shear flow gradient. As a result, a spanwise distribution of cells among the vortex shedding frequencies is created. Increases in the side ratios of the rectangular prisms can cause a shifting of cell boundaries toward the high-speed end. As shear parameters for the same prism increase, the cell boundaries move toward the low-speed end. During oscillation, differences arise between the vorticity structures of cells, and the vortices of each cell are more unified, with improvements in correlation. |
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