可变形翼帮助鸟类自由滑翔

通过肌肉控制骨骼的活动关节,鸟类可以不断变换羽毛的交叠状态,从而改变翅膀的形状和大小,不必拍打翅膀就能在空中轻松滑翔。为了深入了解其中的机理,荷兰研究者研究了风洞中的普通雨燕。具有高超滑翔本领的雨燕,大部分时间都处在空中(甚至不用拍打翅膀)。他们发现雨燕翅膀在充分向外展开时最适于缓慢滑翔,此时需要的新陈代谢最少。当雨燕翅膀向外伸展并以每秒8~10米的稳定速度滑翔时,实际上是在休息。而翅膀朝尾部后掠收回(见图)不仅能高速滑翔,而且动作更加轻盈。特别是翅义常行.8.膀后掠可以负担更多载荷,在每秒30米高速转弯时承受住不断…     

基于雨燕翅膀的仿生三角翼气动特性计算研究

针对低雷诺数微型飞行器的气动布局, 设计出类似雨燕翅膀的一组具有不同前缘钝度的中等后掠($\varLambda =50^{\circ}$)仿生三角翼. 为了定量对比研究三角翼后缘收缩产生的气动效应, 设计了一组具有同等后掠的普通三角翼. 为了深入研究仿生三角翼布局的前缘涡演化特性以及总体气动特性, 采用数值模拟方法详细地探索了低雷诺数($Re=1.58\times 10^{4})$流动条件下前缘涡涡流结构和气动力随迎角的变化规律. 分析结果表明, 前缘钝度和后缘收缩对仿生三角翼前缘涡的涡流强度和涡破裂位置有显著影响. 相对于钝前缘来说, 尖前缘使仿生三角翼上下表面的压力差增大, 涡流强度也更大, 增升作用也更显著. 相对于普通三角翼构型, 仿生三角翼的前缘斜切使其阻力更大, 但后缘的收缩使涡破裂位置固定在此位置, 因此整个上翼面保持低压, 总的升力更大. 由于小迎角时升力增大更明显, 因此仿生三角翼的气动效率在小迎角时明显大于普通三角翼. 这些结论对于揭示鸟类的飞行机理以及未来微型仿生飞行器的气动布局设计具有重要的研究价值.      

拓扑优化与仿生设计在空间太阳能电站热设计中的应用

高效热设计与热控制是高功率连续微波无线传能与空间太阳电站(SSPS)领域的研究热点之一,引起了国内外同行专家的高度关注与浓厚兴趣.本文针对欧米伽空间太阳能电站(SSPS-OM EGA)的结构特点及其对热设计与热控提出的巨大挑战,基于拓扑优化与仿生的思想,提出了一种新的热设计策略与方法.首先,联合流体出口边界与流道构型,建立最小化表面平均温度和流道压力损失的优化模型,得到陀螺馈源光伏阵上背板流道最优的出口位置与最佳拓扑构型,使馈源中的热量导出效率明显提高.其次,建立了仿蝴蝶翅膀形状与结构的对自由空间辐射散热的布局与拓扑优化模型,在满足性态前提下显著提升辐射效率.再者,分析推导了非线性目标和约束函数关于设计变量的灵敏度计算公式与迭代格式.最后,将本文模型与方法应用于欧米伽空间太阳能电站热设计,得到了满意的结果.     

带翅膀降落伞

《简式防务周刊》杂志日前报道称，科学家们研制出了一种新型的降落伞系统，这种降落伞可在空降人员的背上插上“双翼”，使他们在跃入空中后可以飞翔200千米（合124英里）．     

Experimental investigations of the functional morphology of dragonfly wings

Nowadays, the importance of identifying the flight mechanisms of the dragonfly, as an inspiration for designing flapping wing vehicles, is well known. An experimental approach to understanding the complexities of insect wings as organs of flight could provide significant outcomes for design purposes. In this paper, a comprehensive investigation is carried out on the morphological and microstructural features of dragonfly wings. Scanning electron microscopy （SEM） and tensile testing are used to experimentally verify the functional roles of different parts of the wings. A number of SEM images of the elements of the wings, such as the nodus, leading edge, trailing edge, and vein sections, which play dominant roles in strengthening the whole structure, are presented. The results from the tensile tests indicate that the nodus might be the critical region of the wing that is subjected to high tensile stresses. Considering the patterns of the longitudinal corrugations of the wings obtained in this paper, it can be supposed that they increase the load-bearing capacity, giving the wings an ability to tolerate dynamic loading conditions. In addition, it is suggested that the longitudinal veins, along with the leading and trailing edges, are structural mechanisms that further improve fatigue resistance by providing higher fracture toughness, preventing crack propagation, and allowing the wings to sustain a significant amount of damage without loss of strength.     

Surface integral analogy approaches for predicting noise from 3D high-lift low-noise wings

Three surface integral approaches of the acoustic analogies are studied to predict the noise from three concep- tual configurations of three-dimensional high-lift low-noise wings. The approaches refer to the Kirchhoff method, the Ffowcs Williams and Hawkings （FW-H） method of the permeable integral surface and the Curle method that is known as a special case of the FW-H method. The first two approaches are used to compute the noise generated by the core flow region where the energetic structures exist. The last approach is adopted to predict the noise specially from the pressure perturbation on the wall. A new way to con- struct the integral surface that encloses the core region is proposed for the first two methods. Considering the local properties of the flow around the complex object-the actual wing with high-lift devices-the integral surface based on the vorticity is constructed to follow the flow structures. The surface location is discussed for the Kirchhoff method and the FW-H method because a common surface is used for them. The noise from the core flow region is studied on the basis of the dependent integral quantities, which are indicated by the Kirchhoff formulation and by the FW-H formulation. The role of each wall component on noise contribution is analyzed using the Curle formulation. Effects of the volume integral terms of Lighthill＇s stress tensors on the noise pre-diction are then evaluated by comparing the results of the Curle method with the other two methods.     

蝴蝶翅膀表面水滴各向异性黏附性质

采用扫描电子显微镜(SEM)观察了双带闪蝶(Morpho Achilles)翅膀表面的微观形貌, 通过样品的表观接触角表征了其浸润性, 采用高敏感性微电力学天平比较了水滴在蝴蝶翅膀表面不同方向运动时受到的黏附力. 实验结果表明, 水滴沿着干燥的蝴蝶翅膀鳞片堆叠方向运动时受到的黏附力要明显小于其它方向运动时受到的力, 且受力较稳定; 当蝴蝶翅膀被水滴浸润后, 水滴沿着湿润的蝴蝶翅膀鳞片堆叠方向运动时受到的黏附力接近甚至大于逆着鳞片堆叠方向运动时受到的力.     

一个新的网格多翅膀混沌系统及其电路实现

提出了一个新的三维二次自治混沌系统,与大多数广义Lorenz系统一样,该系统只能产生双翅膀吸引子.依据该双翅膀混沌系统平衡点和吸引子的拓扑结构,设计合适的非线性函数可以将其改进为一个产生网格多翅膀吸引子的混沌系统.对该网格多翅膀混沌系统的基本动力学特性进行了分析,证实了多翅膀吸引子的混沌特性.最后设计了混沌电路,给出了多翅膀混沌吸引子的电路仿真结果,证实了理论设计与电路实现的一致性.     

蜻蜓翅膀的力学研究进展

本文对蜻蜓翅膀的力学问题研究进展进行了综述.蜻蜓之所以成为自然界最优秀的飞行者之一,是因为其翅膀的特殊结构.翅结和翅痣的作用,是在飞行中平衡翅膀前后两部分和消除翅膀振颤.常用的翅膀模型有四种:概念模型、物理模型、简单分析模型和数值分析模型.其中前三种模型过于简化,数值模型虽然可以进行三维数值模拟,但是忽略了翅膀的材料组成.本文还分析了蜻蜓翅膀的飞行机制和力学特点,认为蜻蜓的飞行力学分析必须考虑非定常流的影响;介绍了翅膀的弹性模量、硬度和抗弯刚度的测量方法,指出翼展方向的抗弯刚度(EI)与翼展长度的三次方(L3)成正比,翼弦方向的抗弯刚度(EI)与翼弦长度的平方(D2)成正比;最后提出了对蜻蜓翅膀力学的研究展望和有待于进一步解决的问题.     

纳米量级的伽伐尼实验

伽伐尼实验是18世纪意大利物理学家利用带电的解剖刀使青蛙肌肉发生收缩的实验。最近在美国波士顿召开的美国真空协会的科学与技术会议上，橡树岭国家实验室的S．Kalinin博士与他的同事们演示了一项新的、纳米量级的伽伐尼实验。他们的实验对各种不同的生物组织，例如软骨、牙齿以及蝴蝶翅膀等，都显示出了许多新的、未知的电机械信息。