Kolomenskiy Dmitry, Maeda Masateru, Engels Thomas, Liu Hao, Schneider Kai, Nave Jean-Christophe
Graduate School of Engineering, Chiba University, Chiba, Japan.
Department of Mathematics and Statistics, McGill University, Montreal, QC, Canada.
PLoS One. 2016 Mar 28;11(3):e0152072. doi: 10.1371/journal.pone.0152072. eCollection 2016.
Aerodynamic ground effect in flapping-wing insect flight is of importance to comparative morphologies and of interest to the micro-air-vehicle (MAV) community. Recent studies, however, show apparently contradictory results of either some significant extra lift or power savings, or zero ground effect. Here we present a numerical study of fruitfly sized insect takeoff with a specific focus on the significance of leg thrust and wing kinematics. Flapping-wing takeoff is studied using numerical modelling and high performance computing. The aerodynamic forces are calculated using a three-dimensional Navier-Stokes solver based on a pseudo-spectral method with volume penalization. It is coupled with a flight dynamics solver that accounts for the body weight, inertia and the leg thrust, while only having two degrees of freedom: the vertical and the longitudinal horizontal displacement. The natural voluntary takeoff of a fruitfly is considered as reference. The parameters of the model are then varied to explore possible effects of interaction between the flapping-wing model and the ground plane. These modified takeoffs include cases with decreased leg thrust parameter, and/or with periodic wing kinematics, constant body pitch angle. The results show that the ground effect during natural voluntary takeoff is negligible. In the modified takeoffs, when the rate of climb is slow, the difference in the aerodynamic forces due to the interaction with the ground is up to 6%. Surprisingly, depending on the kinematics, the difference is either positive or negative, in contrast to the intuition based on the helicopter theory, which suggests positive excess lift. This effect is attributed to unsteady wing-wake interactions. A similar effect is found during hovering.
扑翼昆虫飞行中的气动地面效应对于比较形态学很重要，并且受到微型飞行器（MAV）领域的关注。然而，最近的研究显示出明显相互矛盾的结果，有的表明存在显著的额外升力或功率节省，有的则显示零地面效应。在此，我们进行了一项关于果蝇大小昆虫起飞的数值研究，特别关注腿部推力和翅膀运动学的重要性。使用数值建模和高性能计算来研究扑翼起飞。基于具有体积惩罚的伪谱方法，使用三维纳维 - 斯托克斯求解器计算气动力。它与一个飞行动力学求解器耦合，该求解器考虑了体重、惯性和腿部推力，同时仅具有两个自由度：垂直和纵向水平位移。将果蝇的自然自主起飞作为参考。然后改变模型参数，以探索扑翼模型与地面之间相互作用的可能影响。这些修改后的起飞情况包括腿部推力参数减小和/或具有周期性翅膀运动学、恒定机身俯仰角的情况。结果表明，自然自主起飞期间的地面效应可忽略不计。在修改后的起飞情况中，当爬升率较慢时，与地面相互作用导致的气动力差异高达6%。令人惊讶的是，根据运动学的不同，这种差异可能是正的也可能是负的，这与基于直升机理论的直觉相反，直升机理论认为会有正的额外升力。这种效应归因于不稳定的翼 - 尾流相互作用。在悬停期间也发现了类似的效应。
