本文藉著風洞實驗來探討均勻紊流場流經 二維矩形斷面柱體後之分離剪力層發展情形。 實驗之控制參數為:一、逼進流場紊流強度;二 、紊流長度尺度;三、模型側風面高度與迎風 面寬度之比值。 實驗以裂膜探針對模型之分離剪力層進行 速度量測,同時以壓力計由模型側面之壓力孔 來量測風壓。以求得之速度剖面和壓力場之分 布,來說明前述控制參數對分離剪力層的影響 。 研究結果顯示矩形模型之分離剪力層隨紊 流強度增加而變厚,如有再接觸現象的發生,則 會縮短分離氣泡的長度,亦即紊流強度會增加 剪力層之曲率。另外結果也顯示,模型側面壓 力場之分布,再接觸前受逼進流場所影響,再接 觸後則受下游渦漩區所主控。模型平均壓力和 擾動壓力皆隨高寬比之增加而減少。至於紊流 長度所造成之影響則並不明顯。 An experimental investigation was carried out to study the characteristics of the separated shear layer of rectangular cylinders in two dimensional homogeneous turbulent flows. The data were collected due to the variations of (1) turbulence intensity (2) turbulence length scale (3) depth-to-height ratio. Simultaneously measurements of the surface pressure on the lateral side and the shear layer velocity were performed using pressure taps and split-hot-film respectively. The results were utilized to characterize the effects of the above variations on the development of the separated shear layer. The result shows that turbulence intensity increases the thickness of the separated shear layer and decrease the length of separation bubble when reattachment occurs. In other words turbulence intensity will increase the curvature of the shear layer. The pressure distribution on the lateral side before reattachment zone is influenced by the approach flow. However, after the reattachment zone the mean pressure coefficient and rms. pressure coefficient decrease when the depth-to-height ratio increases. The effects of turbulence length scale are not significant.
關聯:
中華民國力學學會第十七屆全國力學會議論文集(上)=Proceedings of the 17th National Conference on Theoretical and Applied Mechanics(I)，頁431-439
