中文摘要
地面效應對有限長機翼尾流發展之實驗研究
研究生:李姿葳
指導教授:蕭飛賓
本研究欲探討當有限長機翼接近地面時，尾流的特性以及發展情形。實驗是以NACA0012翼型的有限長矩形翼作為量測模型，藉由改變模型於風洞中與洞壁底部的高度，來模擬飛機近地時的情形。實驗過程中風洞的風速維持在20m/s，也就是雷諾數為Re=8.9×104，模型攻角為12度。流場資料由X型熱線測速儀得到流線方向及側向的瞬時速度，經由資料分析後，可以看到尾流沿著下游下降的情形。在本研究中，將尾流下降(wake descending)的發展區分成兩區域討論: 在第一區域中，尾流的下降是由於下洗效應(downwash)造成的；然而在第二個區域中，尾流的下降率明顯減緩，是由於地面效應造成的影響。在研究中，同樣地觀察到二次渦流(secondary vortex)會影響翼尖渦流的運動模式，二次渦流最後會跟尾流融合在一起，使得尾流區域明顯擴大。藉由流場等高線分佈圖可以明顯看出流場的發展情形。
此外，本研究附加了一個流場控制的實驗，在機翼模型的翼後緣加裝可以自由擺動的振動片(free-flap)做激擾，實驗所得到的結果發現，翼後緣的自由擺動振動片的確可以有效地潰散尾流結構。

ABSTRACT
Experimental Study of Ground Effect on Finite-Wing Wake Flow Development
Student: Miss Tzu-Wei Lee
Advisor: Prof. Fei-Bin Hsiao
This thesis studies the flowfield characteristics in finite wing wake flow under the ground effect. The wing mode having the NACA0012 airfoil section of AR=6 is used to investigate the ground effect by changing the height between the wing surface to the wind tunnel wall. The freestream velocity is operated at 20m/s with the corresponding Reynolds number of 8.9×104 based on the wing chord. The wing mode is maintained at AoA=12°throughout the experiments. The finite-wing wake development under the ground effect is obtained by streamwise and transverse information, which was measured by a cross-type hot wire anemometer. Experimental results indicate that flow development with the ground effect can be divided into two ranges. In the first range, the wake is descending with downstream which was caused due to the downwash effect from the wing model; while in the second range, the wake is strongly affected by the existence of the wall and the descending rate gets slower than that in the first range.
It is observed as well that the secondary vortex in the wake will interact with the tip-vortex and both will merge with each other into the wake region eventually. However, the wake development motion can be cleanly seen by means of the mean velocity contour with the downstream.
Moreover, an additional experiment of flow control was presented in this study. It was conducted by the original model with an attachment of trailing-edge free flap. The results of this experiment show that the free flap excitation at trailing edge can effectively destroy the wake structures and no clear shedding vortices were seen in the downstream of the wake flow.

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