Abstract— Tubercles on flippers of a humpback whale offer a hydrodynamic advantage. Previously, multiple attempts were made to employ them on airplane wings to get an aerodynamic advantage. The effects of the airfoil thickness, the wing planform, the Reynolds number Re, and the wavelength and amplitude are actively investigated to understand their impact on the wavy wing aerodynamic performance and the flow mechanism. However, the effect of varying wavelength along the span of the finite wing and its flow physics is yet to be explored. This research work aims at investigating the effect of varying waviness wavelength along the finite wingspan and its underlying flow mechanism in the pre-stall and post-stall regimes. The wavy wing models are designed using the NACA0021 airfoil and the simulation results are compared with the smooth leading edge (named as baseline model) at Reynolds number Re = 1.2 × 10 5 . The simulation results were validated against experimental results from the literature. Two different wavy wing models, i.e., with increasing wavelength from root to tip of the wing (λ0305h1) and decreasing wavelength from root to tip of the wing (λ0503h1) were simulated. From the aerodynamic force behavior it is estimated that in the pre-stall regime the maximum reduction in the lift-to-drag ( L / D ) ratio is 16.89% and 4.22% for λ0503h1 and λ0305h1, respectively. However, in the post-stall regime the maximum increase in the L / D ratio is estimated as 2.97% and 19.18% for λ0503h1 and λ0305h1, respectively, at 20 o angle of attack. It is observed that the λ0503h1 model has a lower L / D ratio in the post-stall regime due to the vortices produced on the wing surface. These vortices create a flow recirculation zone over the wing which causes an increase in the pressure at the upper surface of the wing. On the basis of the obtained results, it is concluded that the spanwise waviness on aircraft wing is only beneficial in the post-stall regime. It is also concluded that an increase in the waviness wavelength from the root to the tip provides higher aerodynamic advantage than for the case with decreasing waviness wavelength toward the tip.

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变展宽波长对机翼气动性能影响的研究

摘要——座头鲸鳍状肢上的结节具有流体动力学优势。以前，曾多次尝试在飞机机翼上使用它们以获得空气动力学优势。积极研究翼型厚度、机翼平面、雷诺数 Re 以及波长和振幅的影响，以了解它们对波浪机翼空气动力学性能和流动机制的影响。然而，沿有限翼展改变波长的影响及其流动物理学还有待探索。这项研究工作旨在研究沿有限翼展的不同波度波长的影响及其在失速前和失速后状态下的潜在流动机制。波浪机翼模型采用NACA0021翼型设计，仿真结果与雷诺数Re = 1.2 × 10 5 的光滑前缘（称为基线模型）进行比较。模拟结果与文献中的实验结果进行了验证。模拟了两种不同的波浪形机翼模型，即从机翼根部到尖端的波长增加（λ0305h1）和从机翼根部到尖端的波长减小（λ0503h1）。从空气动力特性估计，在预失速状态下，λ0503h1 和 λ0305h1 的升阻 (L / D) 比的最大降低分别为 16.89% 和 4.22%。然而，在失速状态下，对于 λ0503h1 和 λ0305h1，在 20 度攻角时，L/D 比的最大增加估计分别为 2.97% 和 19.18%。观察到 λ0503h1 模型由于机翼表面产生的涡流在失速状态下具有较低的 L/D 比。这些涡流在机翼上方形成一个流动再循环区，导致机翼上表面的压力增加。根据所得结果，可以得出结论，机翼展向波度仅在后失速状态下有益。还得出结论，从根部到尖端的波纹波长的增加比朝向尖端的波纹波长减小的情况提供了更高的空气动力学优势。这些涡流在机翼上方形成一个流动再循环区，导致机翼上表面的压力增加。根据所得结果，可以得出结论，机翼展向波度仅在后失速状态下有益。还得出结论，从根部到尖端的波纹波长的增加比朝向尖端的波纹波长减小的情况提供了更高的空气动力学优势。这些涡流在机翼上方形成流动再循环区，导致机翼上表面的压力增加。根据所得结果，可以得出结论，机翼展向波度仅在后失速状态下有益。还得出结论，从根部到尖端的波纹波长的增加比朝向尖端的波纹波长减小的情况提供了更高的空气动力学优势。