Scaling trends of bird's alular feathers in connection to leading-edge vortex flow over hand-wing
Scaling trends of bird's alular feathers in connection to leading-edge vortex flow over hand-wing
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DOI：
10.1038/s41598-020-63181-7
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发表时间：
2020-05-13
影响因子：
4.6
通讯作者：
Mohseni, Kamran
中科院分区：
文献类型：
--
作者：
Linehan, Thomas;Mohseni, Kamran
飞机上普遍存在的一种气动结构是伞盖；在手腕关节附近肌肉化的一小群羽毛。新的空气动力学研究表明，这种结构的主要功能是在低速飞行时，在鸟的外手翼上诱导前缘涡（LEV）流动，以提高机翼的升力。在这里，我们探讨了alula的展向位置的缩放趋势及其与该函数的联系。具体来说，我们验证了这样一个假设，即当机翼展开并在深失速飞行条件下运行时，alula与翼尖的相对距离是最大的lev升力。为了验证这一点，我们在风洞中对模型机翼进行了实验，以近似该距离，并将我们的结果与展开翼样本的alula位置测量结果进行了比较。我们发现，选择的非水禽的alula优化位置位于或接近风洞实验预测的升力最大化位置。这些发现揭示了鸟类翅膀解剖学和非传统空气动力学在塑造它的作用。
An aerodynamic structure ubiquitous in Aves is the alula; a small collection of feathers muscularized near the wrist joint. New research into the aerodynamics of this structure suggests that its primary function is to induce leading-edge vortex (LEV) flow over bird's outer hand-wing to enhance wing lift when manuevering at slow speeds. Here, we explore scaling trends of the alula's spanwise position and its connection to this function. Specifically, we test the hypothesis that the relative distance of the alula from the wing tip is that which maximizes LEV-lift when the wing is spread and operated in a deep-stall flight condition. To test this, we perform experiments on model wings in a wind tunnel to approximate this distance and compare our results to positional measurements of the alula on spread-wing specimens. We found the position of the alula on non-aquatic birds selected for alula optimization to be located at or near the lift-maximizing position predicted by wind tunnel experiments. These findings shed new light on avian wing anatomy and the role of unconventional aerodynamics in shaping it.