Aerodynamic interaction of bristled wing pairs in fling
Aerodynamic interaction of bristled wing pairs in fling
复制标题
刚毛翼对在飞行中的空气动力相互作用
DOI：
10.1063/5.0036018
复制
发表时间：
2021-03-01
影响因子：
4.6
通讯作者：
Santhanakrishnan, Arvind
中科院分区：
文献类型：
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作者：
Kasoju, Vishwa T.;Santhanakrishnan, Arvind
体长在2毫米以下的微小飞行昆虫使用带有刚毛的翅膀的“飞行和投掷”机制，在基于弦的雷诺数（Re）为O（10）时增加升力和减少阻力。我们研究了在Re = 10时，作为初始翼间间距（δ）和旋转与线性平移之间重叠程度的函数，有刚毛的机翼在飞行中的翼-翼相互作用。使用动态缩放的机器人平台来驱动具有以下运动学（相对于竖直方向的所有角度）的刚毛翼对的物理模型：（1）围绕后缘旋转到角度θ（r），（2）以固定角度（θ（t））线性平移，以及（3）组合的旋转和线性平移。结果表明：（1）循环平均阻力系数随θ（r）和θ（t）的增大而减小;（2）由于前缘和后缘涡环量的不对称性增加，δ的减小使升力系数增大。一个新的无量纲指标，反向流动能力（RFC），被用来量化的最大可能的能力，刚毛翼泄漏的流体通过刚毛。尽管RFC较大，但对于较小的δ和θ（r），阻力系数较大，这可能是由于刷毛周围的剪切层阻塞了刷毛间流动。在旋转早期较小的三角洲导致在机翼之间形成强的正压力分布，导致阻力增加。正压力区域随着θ（r）的增加而减弱，这反过来又减小了拖曳力。以前有报道说，微小的昆虫在飞行中使用大的旋转角度，我们的研究结果表明，一个合理的原因是为了减少阻力。
Tiny flying insects of body lengths under 2mm use the "clap-and-fling" mechanism with bristled wings for lift augmentation and drag reduction at a chord-based Reynolds number (Re) onO(10 ). We examine the wing-wing interaction of bristled wings in fling at Re = 10 as a function of initial inter-wing spacing (delta) and degree of overlap between rotation and linear translation. A dynamically scaled robotic platform was used to drive physical models of bristled wing pairs with the following kinematics (all angles relative to vertical): (1) rotation about the trailing edge to angle theta (r), (2) linear translation at a fixed angle (theta (t)), and (3) combined rotation and linear translation. The results show that (1) the cycle-averaged drag coefficient decreased with increasing theta (r) and theta (t) and (2) decreasing delta increased the lift coefficient owing to increased asymmetry in the circulation of leading and trailing edge vortices. A new dimensionless index, reverse flow capacity (RFC), was used to quantify the maximum possible ability of a bristled wing to leak the fluid through the bristles. The drag coefficients were larger for smaller delta and theta (r) despite larger RFC, likely due to the blockage of inter-bristle flow by shear layers around the bristles. Smaller delta during early rotation resulted in the formation of strong positive pressure distribution between the wings, resulting in an increased drag force. The positive pressure region weakened with increasing theta (r), which in turn reduced the drag force. Tiny insects have been previously reported to use large rotational angles in fling, and our findings suggest that a plausible reason is to reduce drag forces.