Dual leading-edge vortices on flapping wings
Dual leading-edge vortices on flapping wings
复制标题
扑翼上的双前缘涡
DOI：
10.1242/jeb.02614
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发表时间：
2006-12-15
影响因子：
2.8
通讯作者：
Lai, Guo Jun
中科院分区：
文献类型：
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作者：
Lu, Yuan;Shen, Gong Xin;Lai, Guo Jun
本文的实验研究有两个目的：（1）阐明扑翼双前缘涡（即背风翼面上方靠近前缘的两个具有相同旋转方向的涡）的存在;（2）系统地研究运动学和几何参数对这种涡结构的影响。基于一个放大的水槽内拍动机电模型，采用染料流动显示技术对前缘涡核进行了可视化，并采用高空间分辨率的数字粒子图像测速技术（DPIV）对前缘涡的亚结构进行了显示。对五种机翼展弦比（AR）（1.3、3.5、5.8、7.5和10）、八种中冲程迎角（αm）（10-80°）和六种雷诺数（Re）（160-3200）进行了试验。此外，还重新审查了研究充分的果蝇案例。结果首次证实了双LEV扑翼的存在。截面流动结构类似于在非细长三角翼上观察到的双涡。对AR不敏感，当αm和Re达到一定的高水平时，可以产生这样的双LEV系统。主涡附着在机翼上，而在外翼处，次涡脱落，在后面产生一个同向涡。
SUMMARY An experimental investigation was performed with two aims: (1) to clarify the existence of the dual leading-edge vortices (i.e. two vortices with the same sense of rotation located close to the leading edge above the leeward wing surface) observed on flapping wings in previous studies; (2) to study systematically the influences of kinematic and geometric parameters on such a vortical structure. Based on a scaled-up electromechanical model flapping in a water tank, the leading-edge vortex (LEV) cores were visualized via dye flow visualization, and the detailed sub-structures of LEV were revealed through digital particle image velocimetry (DPIV) with high spatial resolution. Five wing aspect ratios (AR) (1.3, 3.5, 5.8, 7.5 and 10), eight mid-stroke angles of attack (αm) (10-80°), and six Reynolds numbers (Re) (160-3200) were examined. In addition, the well-studied case of the fruit fly Drosophila was re-examined. The results confirm for the first time the existence of dual LEVs on flapping wings. The sectional flow structure resembles the dual-vortex observed on non-slender delta wings. Insensitive to AR, a dual LEV system such as this could be created when αm and Re reached certain high levels. The primary vortex was attached to the wing, while at the outer wing the minor vortex shed, generating a same-sense vortex behind.