蜻蜓扑翼飞行多体动力学仿生计算理论

A dragonfly's flight structures are very delicate, they can generate self-adaptive deformation according to varied surrounding actions. Thus, a dragonfly at free flight is able to fulfill various flight modes by flapping wings, such as hovering, forward and inverted flights, sideways flight, quick turning and sharp rising flight, and backward landing, with high agility. This project aims to explore the mechanisms of a dragonfly's active flights by adopting multi-body dynamics and bionics. The multi-body dynamics model of a dragonfly at free flight will be developed using advanced co-rotational beam and shell elements in modeling of its two pairs of flexible wings and body, and proper models of the joints and the interaction between wings and body will be employed, a numerically stable time-history algorithm with high computational accuracy and efficiency, and satisfying approximately energy and momentum preservation will be proposed. Computational programs based on above theories and solution procedure will be developed, and employed in bionic modeling of the whole flapping flight process of a dragonfly, and the superior dynamic performance of the venation pattern of wings will be explored, and the special roles of pterostigma and nodus in active flight will be disclosed. The fluid-structure interaction between dragonfly wings and surrounding air-flow will be studied after we complete the research work of the present project. The fruits can provide support theory for bionic design of intelligent flapping-flight aircraft.

蜻蜓的飞行结构十分精妙，它们可根据外界条件的改变产生自适应变形。自由飞行的蜻蜓能够通过拍动翅膀实现悬停、前飞、倒飞、侧飞、急转、急升及倒着降落等各种高难度、高机动性的特技飞行动作。本课题拟对机动飞行的蜻蜓开展多体动力学仿生研究.利用申请人已研制的新型协同转动梁元和曲壳单元，将自由飞行的蜻蜓模拟成由两对拍动的柔性翅膀结构和躯干组成的多体动力学计算模型，合理解决其翅膀结构与躯干间的连接约束和相互作用问题，提出计算精度高、数值求解稳定、能近似满足能量守恒和动量守恒的多体动力学时程分析算法；再基于以上多体动力学计算新理论和求解方法，研制数值仿真软件；对蜻蜓机动飞行时拍动翅膀的过程进行数值模拟，分析其网状翅脉结构动力性能的优越性，及翅痣和关节在飞行过程中发挥的独特作用。考虑到问题的复杂性，翅膀结构与其周围空气流场间的流固耦合作用留到下一阶段进行研究。课题研究成果可为智能飞行器的仿生设计提供理论依据。

自由飞行的蜻蜓能够实现悬停、前飞、倒飞、侧飞、急转、急升及倒着降落等各种高难度、高机动性的特技飞行动作。蜻蜓卓越的飞行能力非常值得人类去研究和借鉴。如果能研制出像蜻蜓一样具有高机动性飞行能力的智能飞行器，它必将在民用和国防等领域有广阔的应用前景。本课题对机动飞行的蜻蜓开展多体动力学仿生研究，将自由飞行的蜻蜓模拟成由两对拍动的柔性翅膀结构和弹性躯干组成的多体动力学计算模型，采用转动弹簧单元，解决了翅膀结构与躯干间的连接约束和相互作用问题；基于申请人已建立的采用矢量型转动变量的新型协同转动有限单元法，发展了一套多体动力学计算新理论和求解方法，并研制了数值仿真计算程序。在新发展的用于模拟蜻蜓翅膀网状翅脉结构中翅膜的9节点四边形和6节点三边形协同转动光滑/非光滑曲壳单元中，采用了新型矢量型转动变量，求解结构非线性问题的增量求解过程中，这些变量可采用简单的加法进行增量更新，且在计算局部坐标系下的单元切线刚度矩阵（通过计算单元应变能对局部节点变量的二阶偏微分得到）和局部坐标系与整体坐标系间的转换矩阵（通过计算局部坐标系下的节点变量对整体坐标系下的节点变量的二阶偏微分得到）时，微分变量的先后次序是可以互换的，因此得到了对称的单元切线刚度矩阵，提高了数值仿真程序的计算效率。利用探针轮廓仪，对蜻蜓翅膀结构的三维坐标进行了精确测量，为建立较精确的蜻蜓扑翼飞行多体动力学模型提供了保障。2篇论文成果分别发表在权威国际期刊International Journal for Numerical Methods in Engineering和Acta Mechanica上， 1篇论文发表在中文期刊工程力学上。基于课题研究内容，培养了4位硕士研究生；指导了6组共18名本科生开展科研训练计划项目研究。课题研究成果可为智能飞行器的仿生设计提供理论依据和数值仿真软件。