Please use this identifier to cite or link to this item: `http://hdl.handle.net/11455/1981`
 標題: 尾流場波動渦漩列對機翼流場之影響分析Investigations of Wavy Vortex Array on Sinusoidally Pitching Airfoil Flow 作者: 吳嘉容Wu, Jai-Rong 關鍵字: reduced frequency;無因次俯仰頻率;separation bubble;large-scale vortex;分離泡;大尺度渦漩 出版社: 機械工程學系 摘要: 本研究主要以實驗方法探討置於平板尾流場中作俯仰運動之二維對稱型機 翼( NACA0012 ) 與尾流場渦漩列進行交互作用時機翼上方流場的特性。 實驗於封閉式循環水洞中進行，實 驗時自由流體速度為13.8cm/sec ，其 相對應的雷諾數為18400。而俯仰機翼的平均攻角為 十五度，振幅為五度 ；俯仰平板的平均攻角為零度，振幅為三度。兩者的無因次俯仰頻率 ( K )則分別為2.13、0.888。並且藉調整同一水平面上平板跟機翼之間俯仰的 相位差，以 產生不同的上游流場。首先以雷射切光做為流場可視化的方 法，藉以定性討論流場演化的 過程。另外，以雷射測速儀進行機翼速度 的量測，將所得數據藉由數值計算方法，獲得機 翼上方流場的局部環流 量及渦通量，並由渦度平衡觀念分析可視化所觀察的流場現象。由 實驗 結果得知，機翼上方由平板尾流波動渦漩列與翼前緣之分離泡所形成的大 尺度渦漩， 其形成過程及在機翼上方停留的時間對機翼昇力影響很大， 且機翼尾緣產生的渦漩其環流 量之強度亦為影響昇力重要因素。此外， 藉由局部環流量及渦通量的變化可將機翼上方流 場現象做適當的解釋。The interactions between the vortices array of the wake and over an pitching NACA0012 airfoil was experimentally investigated in a recirculation water channel. The free stream velocity is 13.8 cm/sec、Reynolds number is 18400 . The airfoil pitching motion was at a mean attack angle of 15 degree with an amplitude of 5 degree and the upstream wake flow was produced by a pitching plate with a mean attack angle of 0 degree and an amplitude of 3 degree . Their reduced frequency are 2.13 and 0.888 . By modulated the phase shift between plate and airfoil which produced the varied of upstream flow. Flow visualization was conducted by laser sheet method and observed by CCD. The velocity of airfoil is measured by LDA and the vorticity flux and local circulation of upper flow are calculated by numerical integration. The flow phenomenon of flow visualization can be understand through the concept of vorticity balance. From the experiment results, the large-scale vortex caused by wavy vortex array and separation bubble. The airfoil lift is influenced by the vortex developing and the time of vortex lasting on the upper airfoil. In addition, the strength of the circulation of the trailing-edge vortex on the airfoil lift is an important factor. The flow of airfoil can be properly interpreted by the local circulation and vorticity flux. URI: http://hdl.handle.net/11455/1981 Appears in Collections: 機械工程學系所