The aerodynamics of flying snake airfoils in tandem configuration
The aerodynamics of flying snake airfoils in tandem configuration
复制标题
DOI：
10.1242/jeb.233635
复制
发表时间：
2021-07-01
影响因子：
2.8
通讯作者：
Socha, John J.
中科院分区：
文献类型：
--
作者：
Jafari, Farid;Holden, Daniel;Socha, John J.
飞蛇将身体压平，形成大致三角形的横截面形状，从而能够产生升力和水平加速。在滑翔时，它们还会呈现S形状的姿势，这可以促进船头和船尾之间的空气动力相互作用。这种相互作用已经在实验上进行了研究；然而，蛇的横截面形状使用了非常粗略的模型，并且只对下游模型测量了影响。在这项研究中，蛇的姿势产生的空气动力学相互作用是使用二维解剖精确的翼型来模拟蛇在飞行过程中的几何形状。用称重传感器测量升力和阻力，用数字粒子图像测速仪(DPIV)获得流场数据。结果表明，串列布置对气动性能有很强的依赖性，升力系数的影响一般比阻力系数大。流场数据显示，串列布置改变了分离流动和尾迹尺寸，并在尾迹涡在模型附近形成并在背部表面产生吸力的情况下增强了升力。模型在0度迎角下从腹面分离产生的下压力是另一个重要的扬程产生因素。许多显示空气动力学性能变化很大的案例包括接近空中飞蛇最可能的姿势的配置，这表明可以使用微小的姿势变化来控制滑翔轨迹。
Flying snakes flatten their body to form a roughly triangular cross-sectional shape, enabling lift production and horizontal acceleration. While gliding, they also assume an S-shaped posture, which could promote aerodynamic interactions between the fore and the aft body. Such interactions have been studied experimentally; however, very coarse models of the snake's cross-sectional shape were used, and the effects were measured only for the downstream model. In this study, the aerodynamic interactions resulting from the snake's posture were approximated using two-dimensional anatomically accurate airfoils positioned in tandem to mimic the snake's geometry during flight. Load cells were used to measure the lift and drag forces, and flow field data were obtained using digital particle image velocimetry (DPIV). The results showed a strong dependence of the aerodynamic performance on the tandem arrangement, with the lift coefficients being generally more influenced than the drag coefficients. Flow field data revealed that the tandem arrangement modified the separated flow and the wake size, and enhanced the lift in cases in which the wake vortices formed closer to the models, producing suction on the dorsal surface. The downforce created by the flow separation from the ventral surface of the models at 0 deg angle of attack was another significant factor contributing to lift production. A number of cases showing large variations of aerodynamic performance included configurations close to the most probable posture of airborne flying snakes, suggesting that small postural variations could be used to control the glide trajectory.