Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/13017
標題: 應用PIV與FLDV於低雷諾數下鈍形體來流端穩態馬蹄型渦流特性之探討
Study on the Characteristics of Steady Horseshoe Vortex near the Juncture of the bluff obstacles at low Reynolds number
作者: 何宗浚
Tsung-Chun, Ho
關鍵字: Horseshoe vortex;馬蹄型渦流;laminar boundary layer;bluff obstacles;necklace vortex;PIV;層流邊界層;鈍形體;鍊狀渦流;質點影像測速儀
出版社: 土木工程學系
摘要: 
本研究以先進之質點影像測速儀(PIV)與雷射光纖杜普勒測速儀(FLDV),配合定水頭染液注入以及懸浮微粒追蹤可視化法,以層流邊界層為來流條件,對於低雷諾數(Re = 200 ~ 1200),且邊界層高度較大的情形下(H/δ< 2),各類鈍形體來流端之穩態馬蹄型渦流流場加以分析研究,並分析各項參數(雷諾數Re、未擾動邊界層δ、模型高寬比H/W)對於渦流流場的影響。歸納分析後,發現雷諾數對於渦流結構與能量有著較其他參數強的影響力;而未擾動邊界層之變動則影響了停滯點與主渦渦心高度變化,且當未擾動邊界層高度超過模型時,其變化趨勢則不相同。另外對於低雷諾數下展弦比與邊界層厚度之相互影響關係加以定性研究。
在渦流結構與強度變化的定量研究方面,發現不論主渦渦心位置、模型上停滯點高度、模型前端下降流、及主渦環流量強度等渦流特性皆可在考慮展弦比效應並以邊界層參數為無因次尺度的情形下,與H/δ呈現線性或對數變化的關係。並且進一步對於定量分析的結果加以歸納探討。

When a laminar boundary layer encounters a bluff obstacle extending from a horizontal bottom, a three-dimensional flow field, so-called laminar horseshoe vortex formed in the junction region. These types of flow fields develop in many real systems, and they have significant consequences. The characteristics of horseshoe vortex system in the junction region of three bluff bodies with different shapes (vertical plate, circular cylinder and rectangular pillar) were studied experimentally. The present study concentrates on steady behavior of horseshoe vortex at low Reynolds number and relatively large boundary layer thickness using particle image velocimetry (PIV), fiber laser Doppler velocimeter (FLDV), and two flow visualization techniques. The range of the Reynolds number Re, based upon the free stream velocity (U0 ) and the width of vertical plate (W), is from 200 to 1200. The purpose of the present study is to provide the qualitative and quantitative properties of the steady state of horseshoe vortex system. The structure of horseshoe vortex was observed at low Reynolds number when flow parameters changed. Detail characteristics of the steady horseshoe vortex behavior including the position of primary vortex core, the position of stagnation point on the model, down-flow velocity profile, and the circulation of primary vortex are quantified and discussed in detail in the present study.
URI: http://hdl.handle.net/11455/13017
Appears in Collections:土木工程學系所

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