仿绿头鸭扑翼飞行器的低速飞行气动特性仿真研究

Simulation Study on the Aerodynamic Characteristics of Low-speed Flight in a Mallard-inspired Flapping Wing Air Vehicle

针对仿绿头鸭扑翼飞行器,在刚性扑动基础上引入了展向弯折和弦向扭转两种运动方式,提出了4种不同扑动路径的描述方程,并对其低速飞行气动特性进行了研究。首先,根据绿头鸭翼翅外形选择NACA 6411翼型并对其弯度和长度进行修正,通过放样创建扑翼几何构型。之后,基于动网格技术构建扑翼流场网格模型,包含刚性扑动、机翼弯折和机翼扭转等3种不同扑动形态。最后,使用Fluent进行瞬态仿真,基于压力耦合求解器和k-ω湍流模型得到不同扑动形态下飞行速度为2 m/s时的气动特性。结果表明,在低速飞行时,非对称扑动效应、展向弯折效应和弦向扭转效应均可起到增加升力、降低阻力的效果。所提出的3个扑动模型相对传统的对称刚性扑动模型分别能提高3.89%、14.78%、24.44%的升力,其中弯扭组合形式的扑动提供的推力能够抵消前飞时的空气阻力。

For the mallard-inspired flapping wing air vehicle,two additional motion modes-spanwise bending and chordwise twisting are introduced based on rigid flapping.Four different equations describing these varied flapping paths were proposed,and their aerodynamic characteristics during low-speed flight were investigated.Firstly,we choose the NACA 6411 airfoil based on the shape of the mallard wing and modify its curvature and length,creating a flapping wing geometry through lofting.Afterwards,flapping wing flow field grid models are constructed using dynamic grid technology,which include three different flapping forms:rigid flapping,spanwise bending,and chordwise twisting.Finally,we use Fluent to conduct transient simulations,employing the pressure-coupled solver and the k-ωturbulence model,to obtain the aerodynamic characteristics at 2 m/s under various flapping patterns.The results demonstrate that during low-speed flight,the effects of asymmetric flapping,spanwise bending,and chordwise twisting all contribute to increased lift and reduced drag.The three flapping models proposed in this paper can increase the lift by 3.89%,14.78%,and 24.44%,respectively,compared to the traditional symmetric rigid flapping model.Among these,the combined bending and twisting flapping mode provides thrust that is sufficient to offset the aerodynamic drag during forward flight.