應用PIV於對稱突張流場之探討

Study of the flow field characteristics in symmetric sudden expansion by using PIV method

黃立文(Li-Wen Huang)

指導教授 ： 蔡國隆

國立臺北科技大學/機電學院/車輛工程系所/碩士(2008年)

https://doi.org/10.6841/NTUT.2008.00592

摘要

本文以實驗的方式探討紊流流經突張比R = D/d = 1.8與寬高比A = W/H = 4的對稱突張室之流場，藉由不同的噴嘴收縮比C = 1、C = 1/2與C = 1/9於雷諾數Re = 5,358、Re = 8,546與Re = 11,853時，觀測其對流場的影響。利用PIV所得到的速度場，從平均軸向速度場U、平均橫向速度場V、軸向紊流強度u'、橫向紊流強度v'、雷諾應力u'v'，以及渦流強度分別討論之。實驗結果發現，於剪流層中有最大軸向紊流強度u'、橫向紊流強度v'與雷諾應力u'v'分佈，且於分離點產生的小渦漩會影響剪流層的偏折與擺盪。另外，噴嘴收縮比減小，有助於低雷諾數時的流場對稱性，且隨著雷諾數愈高，流場不對稱性愈強。但噴嘴收縮比由C = 1縮小至C = 1/2時，對流場的影響幅度會大於噴嘴收縮比由C = 1/2縮小至C = 1/9時的影響。

關鍵字

PIV ； 對稱突張室 ； 雷諾數 ； 噴嘴收縮比

並列摘要

This study devoted to an experimental investigation of turbulent flow through a plane sudden expansion which is of expansion ratio R = D/d = 1.8 and aspect ratio A = W/H = 4. The downstream of a sudden expansion is installed with a nozzle which the contract ratios are C = 1, C = 1/2 and C = 1/9. The Reynolds numbers used in this work are 5358, 8546 and 11853. A particle image velocimetry ( PIV ) was used in this study and the main discussion focus on the distributions of the mean axial velocity U, the transverse velocity V, the axial turbulence u', the transverse turbulence v', the Reynolds shear stress u'v', and the vorticity. The results show that the maximum axial turbulence u', transverse turbulence v' and the Reynolds stress u'v' are located in the shear layer. The vortices arise from the separating point own the influence on the slant and the fluctuation of the shear layer. The pattern of the flow field is more symmetric with decreasing the contract ratio of a nozzle at low Reynolds number. While the flow field turns to be asymmetric as the Reynolds number increases. The influence of the contract ratio of a nozzle from C = 1 to C = 1/2 is more substantial than that of the contract ratio of a nozzle from C = 1/2 to C = 1/9.

並列關鍵字

PIV ； symmetric sudden expansion ； Reynolds number ； the contract ratio of a nozzle

參考文獻

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