Please use this identifier to cite or link to this item: `http://hdl.handle.net/11455/1742`
 標題: 渦流與矩柱交互作用之實驗研究Experimental Investigation of Vortex and Rectangular Cylinder Interaction 作者: 闕河誠Chueh, Ho-Cheng 關鍵字: Side Ratio;弦長厚度比;Reynolds Number;Second Vortex;Jitter;Circulation;雷諾數;二次渦流;流場敏感性現象;環流量 出版社: 機械工程學系 摘要: 本文主要是以實驗方法探討渦流與矩柱交互作用時之流 場。實驗利用可視化觀察，並配合表面壓力與頻率的量測，來探討不同弦 長厚度比之矩柱，在不同流場條件下，所產生的流場型態及其氣動力特性 。實驗在開放式的風洞中進行，測試模型之三種不同弦長厚度比分別為 3、6與10，其基於矩柱厚度之雷諾數為1600。 在卡門渦流與矩柱交互 作用的實驗中顯示，矩柱前緣低主頻的產生是由矩柱前端中分離泡再黏附 到矩柱表面所產生的不穩定拍擊運動所致。這種伴隨著二次渦流出現及成 長的混合渦流結構中流場敏感性現象，會重組且強化流場的結構。 此 外，實驗亦利用渦流產生器以非正弦波振動方式，產生逆時針渦流與下游 矩柱進行交互作用。結果顯示，矩柱受逆時針渦流之影響，產生順時針之 環流量。當渦流位於矩柱前端上游時，會產生上洗氣流，使升力漸增。當 渦流通過矩柱後，矩柱升力下降。渦流的垂直位移與矩柱之升力係數差值 有密切關係。當渦流愈靠近矩柱時，矩柱之升力係數變化愈劇烈。而渦流 從矩柱下方通過時的DCL值比從上方通過時的DCL值還大，這是由於逆時針 渦流有向上飄移的現象所導致。This study investigates the interaction of an incident vortex withrectangular cylinders of different side (chord-to-thickness) ratios by theuse of flow visualization and surface pressure measurements. Theexperiment was carried out in an open-type wind tunnel. The side ratiosof the rectangular cylinders are 3,6 and 10. During the Karman vortexstreet and rectangular cylinder interaction, it is observed that thegeneration of the low frequency is accompanied by enlargement andshrinkage of the bubble and also by a flapping motion of the shear layernear the separation line. Associated with the secondary vortexgeneration and growth of the flow is a "jitter", or irregularity, in thegrowth and amalgamation of the vortical structures. The experimental study also looks at the interaction between a freevortex and the cylinder. A two-dimensional counter-clockwise rotatingvortex was formed by employed a vortex generator that pitched in atailored nonsinusiodal schedule. The experimental results show that asthe vortex approaching the leading edge of the rectangular cylinder thelift of the cylinder increases due to an upwash effect. The lift decreasesas the vortex passes over the rectangular cylinder due to a downwasheffect. The amplitude of the transient lift was found to be dependent onthe transverse offset of the vortex generator with respect to therectangular cylinder. Because the counter-clockwise rotating vortexconveys slightly upward, the lift amplitude induced by the vortex thatpasses below the cylinder appears to have a large value than that for thevortex passing above the cylinder. URI: http://hdl.handle.net/11455/1742 Appears in Collections: 機械工程學系所