Many natural flyers and swimmers routinely flex their lifting or propulsive surfaces to control the leading-edge vortex (LEV) that forms on the suction side during maneuvering at a high angle of attack. In this paper, we studied the effect of a similar bending on the vortex dynamics of a flat-plate airfoil of aspect ratio 3 (chord $5\text{cm}$) and held at an angle of attack of ${30}^{\circ }$. This flat plate is accelerated from rest to a Reynolds number of 2400, while being dynamically bent along the span in a controlled manner with a bending ratio of 0.65 and a maximum bending angle of ${30}^{\circ }$. We investigated the effect of such spanwise bending on the resultant vorticity transfer via both experiments and numerical simulation. It shows that a dynamic spanwise bending induces a change in the effective shear layer velocity along the span's bent part and creates spanwise vorticity convection. As a result, the growth of circulation in the LEV gets delayed along the bent part, and the final circulation is smaller than the no-bending case.

中文翻译：

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由于受控的展向弯曲而导致的前涡旋中的涡度传递

许多天生的飞行者和游泳者通常会弯曲自己的提升或推进表面，以控制在大迎角操纵过程中在吸力侧形成的前缘涡流（LEV）。在本文中，我们研究了类似弯曲对长宽比为3（弦）的平板翼型的涡流动力学的影响。$5\text{厘米}$）并以 ${30}^{\circ }$。该平板从静止加速到雷诺数2400，同时以受控的方式沿跨距动态弯曲，弯曲比为0.65，最大弯曲角度为${30}^{\circ }$。我们通过实验和数值模拟研究了这种翼展方向弯曲对最终涡旋传递的影响。它显示了动态的展向弯曲会引起有效剪切层速度沿展跨弯曲部分的变化，并产生展向涡旋对流。结果，LEV中的循环的增长沿弯曲部分被延迟，并且最终的循环小于无弯曲情况。