Control of leading-edge separation on bioinspired airfoil with fluttering coverts
Control of leading-edge separation on bioinspired airfoil with fluttering coverts
复制标题
带有扑翼隐蔽物的仿生翼型的前缘分离控制
DOI：
10.1103/physreve.105.025107
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发表时间：
2022
影响因子：
2.4
通讯作者：
Nan Jiang
中科院分区：
文献类型：
--
作者：
Xingyu Ma;Xuan Gong;Zhanqi Tang;Nan Jiang
本文在风洞中对人工隐羽(隐羽)在翼型上的气动作用进行了实验研究，以考察流动控制对前缘分离的影响。我们在大迎角翼型上应用了灵活的羽状装置。我们使用热线风速仪测量了下游尾流的速度分布和湍流脉动。以NACA 0018翼型模型为基线，在弦向雷诺数为1.0×105的情况下，将其迎角设置为15°，产生了较强的前缘和后缘剪切层以及高达0.35弦长的低速尾流区。当展开在机翼上表面时，柔性盖在局部非定常气流的影响下自适应颤振。热线测量结果表明，前缘盖板有效地抑制了流动分离，减小了尾迹流区尺寸。功率谱密度的变化表明，由于剪切层的非定常运动的抑制，作为基频和谐频的主要峰值都被衰减了。另一方面，尾缘的颤振通过将湍动能重新分配到高频分量来修正尾缘剪切层。通过双点同时测量，我们发现前缘和后缘剪切层相互拉近，并且两个剪切层在相干谱上表现出一个增大的峰值。进一步的多尺度小波分析表明，60%弦长的扰动增加了小尺度湍流的大尺度调幅，从而使前缘和后缘剪切层变得稳定。同时，尾迹流区外的流动间歇性也得到了减弱。本文的有效流动控制效果与前人对鸟类飞行的直接观测结果吻合较好。文献表明，在大迎角飞行中，机翼上表面的隐蔽物在流动分离控制中起着重要作用。这些发现促进了对鸟翼上盖子的气动贡献的理解，并揭示了生物启发的盖子在飞机和无人飞行器的流动分离控制中的工程潜力。
In this work, the aerodynamic role of the artificial covert feathers (i.e., coverts) on an airfoil is experimentally studied in a wind tunnel to investigate the flow control effect on the leading-edge separation. We apply flexible featherlike devices on a high-angle-of-attack airfoil. We use a hot-wire anemometer to measure the velocity pro-files and turbulent fluctuations in the downstream wake flow. As a baseline of flow separation, a two-dimensional NACA 0018 airfoil model is set at the angle of attack of 15 ° at the chord-based Reynolds number of 1.0 × 105,causing strong leading-edge and trailing-edge shear layers and a low-speed wake flow area in between as large as 0.35 chord length. When deployed on the upper wing surface, the flexible coverts adaptively flutter under the influence of the local unsteady airflow. Hot-wire measurement results show that the leading-edge coverts effectively suppress the flow separation and reduce the size of the wake flow area. The change of power spectral density shows that the predominant peaks as the fundamental and harmonic frequencies are both attenuated due to the suppression of unsteady motions of the shear layers. On the other hand, the fluttering coverts at the trailing edge modify the trailing-edge shear layer by redistributing the turbulent kinetic energy to the high-frequency components. By simultaneous double-point measurement, we find that the leading-edge and trailing-edge shear layers are drawn closer to each other, and the two shear layers show an increased peak in the coherence spectrum..Further multiscale wavelet analysis shows that the perturbations at the 60% chord length increase the large-scale amplitude modulation of small-scale turbulence and therefore they stabilize the leading-edge and trailing-edge shear layers. Meanwhile, the flow intermittency outside of the wake flow area is attenuated as well. The effective flow control effects in the present work are in good agreement with the previous direct observations of bird flight.in literature that the coverts on the upper wing surface play an important role in flow separation control during high-angle-of-attack flight. These findings advance the understanding of aerodynamic contribution of the covers on bird wings and reveal the engineering potential of bioinspired coverts for flow separation control of aircrafts and unmanned air vehicles.