蜻蜓悬停飞行高升力产生机制的流固耦合数值模拟研究

In this study, numerical investigation on lift force generation mechanism of dragonfly hovering flight is conducted through developing a fully coupled fluid & structure interaction (FSI) model. Firstly, 3D geometrical dragonfly wing model is established according to experimental observation data. Wing mass model is conducted considering the blood in vein while visco-elasticity constitutive model is constructed considering viscousity property. By incoprating immersered membrane method, the fully coupled two-way FSI model is developed for the particular physical problem in which the wing is thin and flexible so that the model can overcome the flaws what previous 2D or 3D single FSI models have made, such as incapble of understanding the dynamic performance. The proposed FSI model is assessed and evaluaved though those cases which are well known in validation cases of rigid wing and also chordwise/spanwise flexible wings. Then, the aerodynamic properties of flexbile flapping dragon-fly wing are studied in details through a novel inversion model using the proposed FSI model. It is believed that the current study could disclose the high lift mechanism of flexible wing by considering the flexibility of whole wing and the study conclusion will be helpful for the optimised design of manmade membrane flapping-wing MAV.

蜻蜓是自然界飞行功能最强的扑翼昆虫，能够实现高超的飞行绝技。模仿蜻蜓高超飞行技能一直是仿蜻蜓类微型膜扑翼飞行器研究者的追求目标。然而，由于人们对蜻蜓飞行的高升力产生机制研究还不完善，特别是翅膀柔性对高升力产生机制的影响还没有得到公认的理论解释，导致该类扑翼飞行器飞行功能无法和蜻蜓相比，因此亟需展开研究。本项目以蜻蜓柔性翅膀为研究对象，通过双向非定常流固耦合数值模拟方法研究翅膀柔性在蜻蜓悬停飞行中对高升力产生机制的影响。在研究中根据试验与观测数据、考虑翅脉血液影响，建立三维蜻蜓翅膀的几何、物理力学模型；提出翅膀柔性运动反演模型概念，采用双向耦合数值计算模型，结合蜻蜓悬停飞行实测数据，应用翅根轨迹给定、翅面数据校核手段反演翅膀悬停飞行运动过程；考虑整翅变形影响，系统地研究翅膀柔性对蜻蜓悬停飞行高升力产生机制的影响。项目研究结论将为研发仿蜻蜓类微型膜扑翼飞行器提供更坚实的理论基础。

仿扑翼昆虫飞行是微型扑翼飞行器的灵感来源和重要理论基础。本项目以蜻蜓悬停飞行为研究对象，采用流固耦合数值模拟技术探索、揭示蜻蜓悬停飞行过程的高升力产生机制，为仿蜻蜓扑翼飞行器提供技术支持。.采用ALE流固耦合数值模拟技术，更加精确地扑捉贴近蜻蜓翅表面的涡量。归纳总结了蜻蜓翅在悬停飞行过程中产生高升力机制机理具体包括：.（1）.在蜻蜓翅刚性条件下，探究平动、转动以及平动加转动耦合对蜻蜓悬停飞行升力产生的作用。数值结果表明，平动为蜻蜓翅提供了主要升力来源，转动引起前缘涡和尾涡的生成与脱落，使得蜻蜓在悬停飞行条件下升力在拍动周期内变化更趋于稳定。.（2）.采用三种不同的变形模型分别探究对蜻蜓悬停飞行影响。三种变形模型为：全变形模型、部分变形模型和铰接变形模型。结果表明全变形模型相比于刚性模型更有利于提升升力，这是由于周期拍动过程在前缘与尾缘攻角的改变而引起的。.（3）.提出一种全新的三维蜻蜓翅扑翼拍动方式，并将其命名为部分超前模型（PAM），PAM模型平均升力提升约为16%，虽然伴随着能耗的增长，但是在不降低飞行稳定性的前提下依然能提升蜻蜓翅的平均升力。.本课题的研究成果可以对蜻蜓在悬停飞行的高升力产生提供有效的理论支持和技术指导。