蝙蝠翼主动和被动变形的流动物理研究

The flow physics of the active and passive morphing wing in bat flight will be investigated in this project. The active morphing wing is decomposed into four elementary models: twisting, cambering, bending in spanwise direction and the area-changing. To study the aerodynamic performance of these models and the composed morphing models is the first step to reveal the mechanisms of the high lift and thrust generation. Also, the moment-equilibrium mechanisms of the integrated “wing-body”, and the additional lift and thrust mechanisms in the maneuvering flight are another two research targets in the present project. Furthermore, the passive deformation of the flapping bat wing and related aerodynamic performance will be studied by two approaches: the computational method of fluid-structure interaction and the model experiment. Now, the experimental observation of bat flight has been improved with the high speed photography and the particle image velocimetry technologies, and the detailed experimental data has been published, but the mechanisms of the high aerodynamic forces is not clear. Therefore, it is necessary to investigate the aerodynamics and mechanisms of bat flight with numerical methods and model experiments. To discover the aerodynamics and the mechanisms of active and passive morphing wing will not only provide the mechanical evidence to understand the physiology, morphology and evolution of a bat, but also help the bionic design for morphing micro air vehicles.

本项目旨在探索蝙蝠翼挥拍过程中主动大变形和被动变形的气动响应，并分析其间蕴含的流动物理。通过分析各种周期性的基元变形(扭转、弓形变形、展向弯曲和面积变化)及其它们的不同组合对气动性能的影响，揭示蝙蝠翼大变形产生高升力和高推力的机制，以及“翼身一体化”的力矩平衡控制机理，并根据所得结果进一步探讨机动飞行中增升或增推的变形优化途径。进一步地，通过流固耦合的计算方法探索蝙蝠翼膜结构的被动变形特征及其气动响应，并辅以“模型实验”验证。当前国际上对蝙蝠飞行的实验观测研究已经获得了长足的进展，已有详细的运动学和变形测量数据发表，但对高气动力成因的认识并不一致。因此，有必要开展数值计算和“模型实验”研究，深入分析蝙蝠飞行中的空气动力学原理，这不仅有助于增加对蝙蝠生理结构、形态适应及进化的认识，还有助于仿生新概念可变性飞行器的设计。

本项目完成了四个内容：1)蝙蝠形态学、运动学数据采集和建模,开展了几何、翼膜和手指骨骼的材料属性测量、棕果蝠和小黄蝠的飞行运动学测量，发现翼膜具有各项异性的弹性模量，蝙蝠翼具有扭转、弦向和展向弯曲、面积连续变化几大特征；2)蝙蝠变形模式的气动力影响，发现流场的旋涡控制是主要因素，扭转变形大大提高推力，弓形弯曲提高升力，翼身一体化能提高20%的升力系数，且升力主要由翼前缘提供，推力主要由翼尖提供；3)蝙蝠飞行中可能的力矩控制表明，后肢-尾翼纵向移动和翼面前掠对俯仰力矩调控有效，弓形变形和翼面伸缩对滚转力矩调控有效；4)模型蝙蝠翼挥拍的被动变形进行了测量和气动力/力矩分析，结果表明翼面的被动变形可以较好地模拟蝙蝠翼的扭转和弓形变形，对提高推力和升力有效。本项目资助下完成了图像数据提取程序开发和薄翼动态大变形的面元法程序开发，为后续工作提供了基础。对蝙蝠本体的飞行测量是计划外的工作，填补了国内无飞行数据的空白。