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標題: NACA機翼系列作簡諧擺盪時渦漩結構特性之探討
The Investigations of Vortical Structure for NACA Series Airfoil by the Effect of S.H.M.
作者: 潘建良
Liang, Pan Jiann
關鍵字: Vortical structure
dimensionless pitching frequency
dynamic stall
pitching S.H.M.
出版社: 機械工程學系
摘要: 本研究是以實驗方法探討NACA系列機翼作大振幅週期性俯仰運動時,針對不同翼形與攻角下之近翼面、翼面上方其流場結構特性之渦漩潰散位置與發展模式作一探討分析。本實驗於開放式風洞中進行,模型為NACA0012、NACA0015、NACA0018等機翼,以機翼1/4弦長為中心作5度,10度及15度振幅的俯仰運動。實驗自由流速為2m/sec,對應雷諾數為1.5×104。機翼俯仰頻率為0.5 Hz。 本實驗研究因不同翼形所造成之流場結構變化,藉由煙線法觀察機翼前緣生成之動態失速渦流的出現、成長、移動與脫落的發展,進而能了解其渦流強度之發展與演化行為。本文由實驗的結果得知,翼形的改變及俯仰角度是影響流場的重要參數之一。當翼形改變流場結構也跟著變化。隨著CR的增加其渦漩產生的時間及位置都跟著改變。經由大振幅之簡諧擺盪時,可使邊界層內外流體產生強烈地交互作用,有效地將已分離之流體,由剪力層之外緣捲入機翼表面內,增加機翼表面流體之動量,使已產生分離之流體重新附著於機翼上表面,以致延遲流體分離之位置。
In this study, an experimental method was used to visualize the flow structure and vortex breakdown at the upper of NACA series airfoils for the different model type and angle of attack with large amplitude pitching motion. This experiment was proceeded by the open-type wind tunnel, the model type were NACA0012, NACA0015, NACA0018 airfoil, the pitching motion center was at 1/4 chord length and pitching amplitude were 50, 100, and 150. The free stream velocity is 2 m/sec, Reynolds number is 1.5104, and the frequency of pitching is 0.5Hz. In this study, we investigate the flow phenomenon at different NACA series airfoils model by flow visualization and observe appearing, growth, movement, and breakdown of the dynamic stall vortex from the leading edge. The results of this experiment shows that the flow vortex structure were change with different airfoil models and different pitching amplitude. The time and position of appearing vortex were change when the CR was increased. The effects of S.H.M. on NACA airfoils will make the boundary layers strongly reciprocation, the separated flow reattach to the surface of airfoil again, increasing the momentum of the flow upper of the airfoil. Therefore, the location of separation flow will delay when the S.H.M. of large magnitude is proceeded.
Appears in Collections:機械工程學系所



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