Song Jialei, Luo Haoxiang, Hedrick Tyson L
Department of Mechanical Engineering, Vanderbilt University Nashville, TN 37235, USA.
Bioinspir Biomim. 2015 Jan 19;10(1):016007. doi: 10.1088/1748-3190/10/1/016007.
In hovering flight, hummingbirds reverse the angle of attack of their wings through pitch reversal in order to generate aerodynamic lift during both downstroke and upstroke. In addition, the wings may pitch during translation to further enhance lift production. It is not yet clear whether these pitching motions are caused by the wing inertia or actuated through the musculoskeletal system. Here we perform a computational analysis of the pitching dynamics by incorporating the realistic wing kinematics to determine the inertial effects. The aerodynamic effect is also included using the pressure data from a previous three-dimensional computational fluid dynamics simulation of a hovering hummingbird. The results show that like many insects, pitch reversal of the hummingbird is, to a large degree, caused by the wing inertia. However, actuation power input at the root is needed in the beginning of pronation to initiate a fast pitch reversal and also in mid-downstroke to enable a nose-up pitching motion for lift enhancement. The muscles on the wing may not necessarily be activated for pitching of the distal section. Finally, power analysis of the flapping motion shows that there is no requirement for substantial elastic energy storage or energy absorption at the shoulder joint.
在悬停飞行中，蜂鸟通过俯仰反转来改变翅膀的攻角，以便在向下和向上挥动翅膀时都能产生气动力升力。此外，翅膀在平移过程中可能会俯仰，以进一步增强升力的产生。目前尚不清楚这些俯仰运动是由翅膀的惯性引起的，还是通过肌肉骨骼系统驱动的。在这里，我们通过纳入实际的翅膀运动学来进行俯仰动力学的计算分析，以确定惯性效应。还利用先前对悬停蜂鸟进行的三维计算流体动力学模拟得到的压力数据纳入了空气动力学效应。结果表明，与许多昆虫一样，蜂鸟的俯仰反转在很大程度上是由翅膀的惯性引起的。然而，在旋前开始时需要在根部输入驱动功率来启动快速俯仰反转，并且在向下挥动翅膀的中间阶段也需要输入驱动功率，以使翅膀向上俯仰运动以增强升力。翅膀远端的俯仰不一定需要激活翅膀上的肌肉。最后，对扑翼运动的功率分析表明，肩关节处不需要大量的弹性能量储存或能量吸收。
