Effects of wing deformation on aerodynamic forces in hovering hoverflies
Effects of wing deformation on aerodynamic forces in hovering hoverflies
复制标题
机翼变形对悬停蝇气动力的影响
DOI：
10.1242/jeb.040295
复制
发表时间：
2010-07-01
影响因子：
2.8
通讯作者：
Sun, Mao
中科院分区：
文献类型：
--
作者：
Du, Gang;Sun, Mao
本文利用最近测量的自由飞行状态下的翼面变形数据，通过求解动态变形网格上的Navier-Stokes方程，研究了翼面变形对悬停飞行状态下的翼面气动力的影响。考虑了三种食蚜蝇。通过分别提取机翼的拱度变形和展向扭转变形，并与刚性平板机翼（刚性平板机翼的迎角等于变形机翼翼面二阶矩半径处的局部迎角）的计算结果进行比较，识别出拱度变形和展向扭转的影响。主要结果如下。对于悬停的悬蝇，变形翼的升力、阻力和气动功率系数随时间的变化规律与刚性平板翼的相似，但变形翼的升力比刚性平板翼大10%左右，所需的气动功率比刚性平板翼小5%左右。升力的差异主要是由拱度变形引起的，而功率的差异主要是由展向扭转引起的。变形对气动力没有很大影响的主要原因是，在悬停过程中，机翼以很大的迎角（约50度）工作，气流分离，分离流对机翼变形不太敏感。因此，作为第一近似，悬停飞行中的可变形机翼可以用一个刚性平板机翼来模拟，其迎角等于可变形机翼翼面二阶矩半径处的局部迎角。
We studied the effects of wing deformation on the aerodynamic forces of wings of hovering hoverflies by solving the Navier-Stokes equations on a dynamically deforming grid, employing the recently measured wing deformation data of hoverflies in free-flight. Three hoverflies were considered. By taking out the camber deformation and the spanwise twist deformation one by one and by comparing the results of the deformable wing with those of the rigid flat-plate wing (the angle of attack of the rigid flat-plate wing was equal to the local angle of attack at the radius of the second moment of wing area of the deformable wing), effects of camber deformation and spanwise twist were identified. The main results are as follows. For the hovering hoverflies considered, the time courses of the lift, drag and aerodynamic power coefficients of the deformable wing are very similar to their counterparts of the rigid flat-plate wing, although lift of the deformable wing is about 10% larger, and its aerodynamic power required about 5% less than that of the rigid flat-plate wing. The difference in lift is mainly caused by the camber deformation, and the difference in power is mainly caused by the spanwise twist. The main reason that the deformation does not have a very large effect on the aerodynamic force is that, during hovering, the wing operates at a very high angle of attack (about 50deg) and the flow is separated, and separated flow is not very sensitive to wing deformation. Thus, as a first approximation, the deformable wing in hover flight could be modeled by a rigid flat-plate wing with its angle of attack being equal to the local angle of attack at the radius of second moment of wing area of the deformable wing.