結合實驗與數值方法研析波浪型前緣葉片應用於俯仰葉片與單葉片垂直風力機之空氣動力特性

座頭鯨有極佳的追捕獵物能力，這可歸功於其具有突起狀前緣之鰭狀肢(flipper)，觀察發現其鰭狀肢突起狀前緣(tubercle leading-edge)能發揮類似被動式流場控制的功能，透過流體通過非平滑翼前緣產生渦旋，有延遲氣流分離、增加失速攻角的效用。本文採用Ansys fluent，並使用具SST K-ω紊流模組進行數值模擬，探討改變在不同波浪型前緣葉片之波高、波長、厚度及展弦比之靜態氣動力特性，以及在俯仰運動狀態下不同葉片厚度、俯仰速度、最大俯仰角之具波浪型前緣葉片，同時探討該型機翼安裝在單葉片垂直風力機在不同葉片厚度及尖速比(TSR)之性能。　　分析葉片穩定狀態在自由流風速12m/s，發現當空氣經過波浪型葉片時，波峰區會產生渦流並向後延伸，在波谷處產生的流體分離現象較平滑形葉片明顯，但在波峰處流體分離的現象較不明顯。探討波浪型葉片的影響發現，在低攻角時，升力係數較平滑型葉片低，在高攻角時，有較佳之升力係數，當波高越大，其影響效果越明顯，當波長越大，低攻角時，較無明顯差異，高攻角時，其升力係數有所增加，但波長＞0.4c時，升力有下降的趨勢。當葉片厚度越薄時，波浪型葉片在高攻角時能有較高的升力係數，相較於平滑機翼呈現更佳之氣動力性能，在展弦比的效應方面，展弦比越高有越好的氣動力性能。　　在俯仰機翼之動態氣動力特性探討中，隨著機翼厚度減少，失速角提前發生，波浪型前緣機翼改善升力的效果越好。在低俯仰角速度時，波浪型前緣機翼其改善效果越明顯。當αm= 20°時，在高攻角時，波浪型前緣機翼有較好的改善效果區域出現。在三維單葉片風力機，翼型厚度越小的波浪型前緣機翼，其改善效果越好，其中NACA0008，其整體效果優於平滑型前緣機翼，在尖速比的探討中，其增益值在TSR=0.5、1.5、2時，分別為38.5%、894.5%、345.1%。

關鍵字

波浪型；流場控制；突起狀前緣；空氣動力

並列摘要

Humpback whales utilize extremely mobile, wing-like flipper for banking and turning. The tubercles on the leading edge act as passive-flow control devices that improve performance and maneuverability of flipper.The 3-D numerical simulation is performed in this study to thoroughly investigate the flow structure and aerodynamic characteristics of the designed wavy wing with different amplitude, wave length, thickness and aspect ratio, which is simulated from the tubercles flipper on humpback whales. This study integrated the SST k-ω turbulence module into the computational fluid finite volume method to explore the variation of the flow fields and aerodynamic performance of a pitching wing as well as VAWT. 　　The flow separation is more serious at the wave trough than at the wave crest due to the counter rotate vortex induced by the flow pass through the wavy leading edge. Comparing with the smooth leading edge, the lift coefficient of wavy wing is lower in low angle of attack, but is better at higher angle of attack. The lift increases as the amplitude of wavy leading edge is increase. The lift coefficient is firstly raised as wave length is increased in higher angle of attack region, but is decreased as wave length greater than 0.4c. The thinner of the thickness as well as the larger of aspect ratio of the wavy wing will enhance the aerodynamic performance more clearly. 　　For the pitching wing cases, the aerodynamic performance enhancement of wavy wing is obvious in the lower pitching rotating speed and αm= 20° at high angle of attack region. For the single blade VAWT, the thinner of the thickness of the wavy wing will enhance the aerodynamic performance more clearly. Comparing with the smooth leading edge, the average torque coefficient CQ enhancement of wavy wing are 38.5%、894.5%、345.1% as TSR=0.5、1.5、2 respectively.

並列關鍵字

Wavy ； Flow control ； Tubercle leading edge ； Aerodynamic

參考文獻

[2] F. E. Fish, P. W. Weber, M. M. Murray and L. E. Howle, "The tubercles on Humpback Whales’ Flippers: Application of Bio-Inspired Technology", Integrative and Comparative Biology, Vol. 51, No.1 pp.203-213, 2011

[3] F. E. Fish and J. M. Battle. "Hydrodynamic Design of Humpback Whales",Journal of Morphology, Vol.51,pp.51-60,1995

[5] D. S. Miklosovic, M. M. Murray, L. E. Howle, and F. E. Fish, "Leading-Edge Tubercles Delay Stall on Humpback Whale (Megaptera novaeangliae) Flipper", Physics of Fluids, Vol. 16, No.5, pp.39-42, 2004

[6] B. stein and M. M. Murray,"Stall Mechanism Analysis of Humpback Whale Flipper Model", Proceeding of Unmanned Untethered Submersible Technology (UUST), UUST05, Durham, New Hampshire, August, 2005.

[7] M. M. Murray, D. S. Miklosovic, F. E. Fish, L. Howle, "Effects of Leading-edge Tubercles on a Representive Whale Flipper Model at Vary Sweep Angles", Proceeding of Unmanned Untethered Submersible Technology (UUST), UUST05, Durham, New Hampshire, August, 2005.

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結合實驗與數值方法研析波浪型前緣葉片應用於俯仰葉片與單葉片垂直風力機之空氣動力特性

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