Fine structures of wing scales in Sasakia charonda butterflies as photonic crystals

We investigate the microstructure of scales in the wings of male Sasakia charonda charonda butterflies by scanning electron microscopy with the aid of optical microscopy. Six types of scales are identified: B1, W1 and R1 in brown background yellow spots and red spots, respectively; B2 in iridescent purple-blue and W2 in white pearl, both of which characterize the male and B3 in the wing edges. The B1, W1 and R1 scales are almost the same in structure and the B2 and W2 scales are almost the same. The difference among the B, W and R scales is in species and content of pigment. The B1, W1 and R1 scales have only two layers of cuticle lapped on the ridges. In contrast with them, the B2 and W2 scales have seven multilayers of cuticle piled on the ridge. The multiple interference of light that occurs among these cuticle layers, spaced with air layers, generates the significant iridescence of the B2 and W2 scales. Thus, the characteristic purple-blue of the male wings is ascribed to the combination of the structural and chemical colouration in the B2 scales with melanin. The photonic crystals of these scales may be applicable to fine light manipulators such as reflection elements in laser diodes. B3 has many holes between the ridges and no multilayers of cuticle on the ridges. These structures may play any role in aerodynamically easy flight and/or in drainage of wet wings.     

Microstructure and material properties of hind wings of a bamboo weevil Cyrtotrachelus buqueti (Coleoptera: Curculionidae)

Wings of flying insects, as representative biomaterials, are composed of a flexible membrane and a stiff vein structure that are prone to bending and deformation under aerodynamic forces. Therefore, we must investigate the application value of insect wings in the field of engineering design from the perspective of bionics, which is a new challenge. In this study, we measured the mechanical properties of the hind wings of Cyrtotrachelus buqueti including “dried” and “fresh” samples. The wing membrane samples were prepared by carefully cutting the hind wings into 2.0 mm by 8.0 mm rectangular segments using a gauge. As the major wing veins are the main loading units under aerodynamic forces, we also separated them from the wings as a kind of investigative specimen. The wing membranes were adhered to a specially designed paper fixture and the mechanical properties of the wing veins and membranes were evaluated using a tensile testing machine. We observed the microstructure of the samples using a scanning electron microscope and accurately measured the thicknesses of desired the wing membranes and veins. The results show that there is a difference in the mechanical properties of the two samples. The elastic modulus and Poisson's ratios vary over the region in hind wing, so we can conclude that the wing membrane is an anisotropic and non‐uniform material.     

Micro- and nanostructures of iridescent wing scales in purple emperor butterflies (Lepidoptera: Apatura ilia and A. iris)

Apatura ilia (Denis and Schiffermüller, 1775) and A. iris (Linnaeus, 1758) are fascinating butterflies found in the Palaearctic ecozone (excepting the north of Africa). The wings of these insects are covered with a great number of two types of scales positioned like roof tiles. Type I scales are on the surface, while type II scales are situated below them. The structural color of the type I scales is recognized only on the dorsal side of both the fore and hind wings of the males of the aforementioned species. Both types of scales are responsible for pigment color of the wings, but iridescence is observed only in the type I scales. The brilliant structural color is due to a multilayer structure. The features of the scales, their dimensions and fine structure were obtained using scanning electron microscopy. Cross sections of the scales were then analyzed by transmission electron microscopy. The scales of the "normal" and clytie forms of A. ilia have a different nanostructure, but are of the same type. A similar type of structure, but with a different morphology, was also noticed in A. iris. The scales of the analyzed species resemble the scales of tropical Morpho butterflies.     

Investigations on color variations of Morpho rhetenor butterfly wing scales

Experiments and simulations are carried out to investigate the optical properties of Morpho rhetenor butterfly wing scales. The upper surface of a male Morpho rhetenor butterfly wing presents a single-layer of scales, the microstructures of which are responsible for the brilliant blue color. The color varies from cyan blue to yellow green and soon afterwards returns back to cyan blue when some ethanol is dropped on the upper surface. At the start of the ethanol volatilization process, the reflection spectrum remains stable. As the ethanol further volatilizes, the peak reflectance decreases slightly, then increases dramatically. Meanwhile, the peak wavelength keeps approximately constant, then decreases, and keeps almost stable at the end of the process. Therefore, the optical properties depend strongly on the varying ambient conditions, including the refractive index and the thickness of the packing medium. Moreover, the possible causes for the scales in dark green region after several dropping ethanol experiments are clarified. This research benefits our understanding of the color variation mechanisms of the wing scales, and provides inspiration for further studies and applications.     

Numerical analysis of ship’s propulsion mechanism of two-stage Weis-Fogh type by discrete vortex method

Flow patterns and dynamic properties of two-stage Weis-Fogh type ship propulsion mechanism are studied by a discrete vortex method. To study mutual interference between two wings, two cases are considered — wing motions with the same and reverse phases. The predicted flow patterns correspond to the available flow visualization results. Time histories of thrust and drag coefficients are also calculated, and the interference between the two wings are numerically clarified.     

Computational investigation of variation in wing aerodynamic load under effect of aeroelastic deformations

The evaluation of the variation in aerodynamic load on a wing under the effect of elastic deformations requires solving the problem of wing deformation when wings are subjected to distributed aerodynamic load. This paper presents the calculation of coupling the aeroelastic system for 3D wings. The aerodynamic problem was solved by the doublet–source method for 3D wings, with wing thickness considered. The problem of elastic deformation was solved by the finite element method for hollow 3D wings, with beams arranged inside. Results concerning aerodynamic load on the wing were considered input parameters for the calculation concerning the problem of wing deformation, and those about the deformed wing geometry were deemed input parameters for the calculation regarding the problem of wing aerodynamics for the second calculation. The calculations concerning these problems were repeated until the wing twist angle converged. Analyses and comparisons were performed on the distributions of aerodynamic loads on the rigid and deformed wings to examine the change of the aerodynamic load depending on the structure (aerodynamic loads being functions of the external geometry of the wing, the incidence angle, and the velocity at infinity are solutions of the pure aerodynamic problem). Results regarding wing twists and stress distributions for hollow wings with and without beams inside were presented to assess the cause of changes in aerodynamic load and wing static durability. Aeroelastic calculations were formulated with different velocities at infinity to indicate the need for a suitable structural solution when the aerodynamic load is expected to reach a high value.     

Antifatigue properties of dragonfly Pantala flavescens wings

The wing of a dragonfly is thin and light, but can bear high frequent alternating stress and present excellent antifatigue properties. The surface morphology and microstructure of the wings of dragonfly Pantala flavescens were observed using SEM in this study. Based on the biological analysis method, the configuration, morphology, and structure of the vein were studied, and the antifatigue properties of the wings were investigated. The analytical results indicated that the longitudinal veins, cross veins, and membrane of dragonfly wing form a optimized network morphology and spacially truss‐like structure which can restrain the formation and propagation of the fatigue cracks. The veins with multilayer structure present high strength, flexibility, and toughness, which are beneficial to bear alternating load during the flight of dragonfly. Through tensile‐tensile fatigue failure tests, the results were verified and indicate that the wings of dragonfly P. flavescens have excellent antifatigue properties which are the results of the biological coupling and synergistic effect of morphological and structural factors. Microsc. Res. Tech. 77:356–362, 2014. © 2014 Wiley Periodicals, Inc.     

基于昆虫翅膀运动机理的仿昆拍式翅研究

仿昆拍式翅是以昆虫翅膀运动机理为基础的仿生设计。对仿昆拍式翅翅膀进行了研究，提出几种控制翅膀空气流动的方法以及升力估算方法，并对翅膀的设计和制造等问题进行详细探讨。简要分析了仿昆拍式翅的运动机构和驱动系统，设计出了一种新颖的小型仿昆拍式翅。     

半转翼的Weis-Fogh效应及推力的仿真研究

针对仿生飞行研究中具有重要应用前景的新型动力翼—半转翼的推力计算问题,提出了一种半转翼模型,导出了该模型参数的计算方法;基于XFLOW建立了两个半转翼CFD模型,即无固壁和有固壁半转翼模型,通过选择合理的流场计算区域和边界条件,采用湍流计算模型和刚性翼运动模型,结合半转翼实验模型参数和运动参数对半转翼流场速度、压力分布及推力进行了数值计算,获得了Weis-Fogh效应对半转翼运动流场特性和半转翼推力的影响规律,并与一个运动周期的实验推力进行了分析比较。研究结果表明:有固壁的半转翼流场中速度分布始终受到"急张"和"相拍"的影响,可大大提高半转翼的推力;由半转翼-固壁模型获得的推力计算曲线能真实反映半转翼推力的变化规律,这对计算不同参数的半转翼-固壁模型的推力具有参考价值。     

一种柔性微型扑翼设计及其气动力特性的试验研究

微型扑翼机以其优良的机动性、低噪音、低成本、执行任务的多功能性以及在现代高科技局部战争中的潜在应用价值而得到各科技先进国家的重视,投入了大量精力开展研究工作。在我国也已经初步开展对微型扑翼机研究。但由于与微型扑翼飞行相关的低雷诺数空气动力学研究还处于萌芽阶段,对微型扑翼的设计研究工作尚无可供指导的成熟理论和借鉴的经验,目前微型扑翼的设计研究基本上是以试验为主。本文参照动物的扑翼飞行实例和固定翼飞行器机翼设计的经验,在对扑翼飞行基本原理分析研究的基础上,设计制作了一种微型扑翼及扑翼的驱动机构,采用直流电动机作为动力,通过调节驱动电压来控制扑动的频率。并对该微型扑翼进行了空气动力特性试验,得到了微型扑翼的空气动力特性,并从中得出了影响扑动升力的一些因素。实验结果表明,具有柔性翼面的扑翼,其产生的升力和推力较高而且比较稳定。     

Functional morphology and structural characteristics of wings of the ladybird beetle,Coccinella septempunctata (L.)

In recent years, the surface morphology and microstructure of ladybird (Coccinella septempunctata) wings have been used to help design the flapping‐wing micro air vehicle (FWMAV). In this study, scanning electron microscopy (SEM) was used to verify the functional roles of the ladybird forewing and hindwing. Surface morphology and the cross‐sectional microstructure of the wings are presented. Detailed morphology of ladybird forewings was observed using atomic force microscopy (AFM) and the composition of the wings was characterized using Fourier transformed infrared spectroscopy (FTIR). The ladybird forewing may possess different performance characteristics than the beetle, Allomyrina dichotoma. Additionally, the circular holes in the forewing might be important for decreasing the weight of the forewing and to satisfy requirements of mechanical behavior. Microsc. Res. Tech. 79:550–556, 2016. © 2016 Wiley Periodicals, Inc.     

仿生扑翼飞行器翅翼驱动方式的研究现状及展望

随着仿生扑翼飞行器的微型化，当扑翼飞行器达到昆虫置级的时候，任何复杂的运动系统都将面临难以实现的问题，翅翼的驱动方式也将面临新的挑战。本文从仿生飞行的历史与现状出发，论述了国内、外各类仿生扑翼飞行器翅翼驱动方式的研究状况。基于将昆翅视为柔性翅的观点，提出了仿生扑翼飞行器未来的研究前景翅翼在自适应变形状态下施以简单的节律运动将是仿生扑翼飞行器翅翼驱动方式的发展趋势之一。     

内置涡核破碎翼参数对旋风分离器性能影响的仿真研究

内置涡核破碎翼旋风分离器具有保持较高效率同时降低压降的特点。研究涡核破碎翼参数对分离器性能的影响有重要的意义。本文利用计算流体动力学方法(CFD),采用雷诺应力模型(RSM)和离散化模型(DPM),模拟涡核破碎翼参数对分离器性能的影响。结果发现:随着相邻涡核破碎翼间距增大,分离器收集效率及压降均呈现缓慢增长趋势,而随着每组涡核破碎翼个数增加,分离器收集效率及压降均呈缓慢下降趋势。     

Dynamic and motion consistency analysis for a planar parallel mechanism with revolute dry clearance joints

The aim of the research was to introduce a methodology for dynamic response and motion consistency research on multibody system with multiple revolute clearance joints. An improved impact force model and a modified friction force model were introduced to evaluate the effects of impact and friction in clearance joints. A planar parallel mechanism which has two clearance joints in the left wing and the right wing was also used as an example. From the results based on different conditions, clearance has slight influence on the angular displacement and angular velocity, but obvious effect on angular acceleration. And with same clearance values of left wing and right wing, the motion consistency of the parallel mechanism is very good, which means the dynamic response of two wings is almost symmetrical. When the two clearance joints have different clearance values, the motion consistency and relative error between two wings are much obvious, especially the angular acceleration.     

拍翅式微型飞行器运动学的研究

对于拍翅式微型飞行器,设计了一种能产生大升力的翅拍动形式,分析计算了翅拍动所产生的气动力和气动力矩,导出了拍翅式微型飞行器机体的运动微分方程。利用该运动微分方程,可以对拍翅式微型飞行器的位置和姿态进行控制。     

仿生微扑翼飞行器的翅翼设计与优化

提出了微扑翼机构翅翼的共振激励放大驱动机理及其对翅翼的振动模态要求,并依据该机理用有限元方法研究了微扑翼飞行器的仿生翼设计和优化问题。通过对3种仿昆虫翅翼的模态分析,总结出能够满足共振激励要求的翅翼外型和翅脉布局,建立了参数化的自定义仿生翼模型。在此基础上,以翅翼的展弦比和翅脉关键点的坐标为主要参数,使用有限元优化方法,对仿生翅翼的模态优化进行了初步探讨。文中的建模、分析方法和结论对微扑翼飞行器的分析、设计和应用提供了一定的理论依据。     

Investigation of wind tunnel wall effect and wing-fuselage interference regarding the prediction of wing aerodynamics and its influence on the horizontal tail

The calculation of aerodynamic characteristics of a wing is the basic problem for aerodynamic design of aircraft. Wing aerodynamics can be determined experimentally and numerically. The method of fixing the wing in the test chamber of wind tunnel is related to disturbance of flow through the wing. When the wing is entirely fixed in the test chamber, the disturbance is usually caused by the sting connecting the wing to the test chamber. The experiments in this paper fixed the wing by clamping to the wind tunnel wall at the wing symmetry surface (root section). With this wing fixation, it was possible to take advantage of the wingspan twice, but to obtain the 3D wing experiment results, it was necessary to evaluate the impact of the wind tunnel wall effect. As for aircrafts, the aerodynamic force of the aircraft’s wing will have certain difference than that of the wing alone. The intersection region between the wind tunnel wall and wing root (for the experiment), as well as between the fuselage and wing root have complex interactions of boundary layers, in particular separation phenomena in the boundary layers. By solving the differential equation for viscous flows, it was possible to visualize the picture of streamlines and flow separations in this interference region and the aerodynamic characteristics of the wing. The singularity method was also used to compare results within its application range. The aerodynamic coefficients in the two cases with and without interference were analyzed. Complex interactions in the interference region could alter the predicted aerodynamic force calculated for the wing alone, which should be estimated. Very strong separations in the wing-fuselage interference region at large angles of attack turned into vortices at the rear impacting on the horizontal tail aerodynamics that is related to the balance problem of the aircraft.

     

相似分析在结构仿生设计中的应用研究

指出了仿生相似分析内容和步骤,并对生物骨架与小型梁肋机翼结构进行了模糊相似评价,表明叶脉承力性能与小型梁肌机翼具有高的相似度;针对机翼结构设计要求,借鉴叶脉结构特征,设计了仿生型机翼结构.有限元分析表明,仿生型机翼具有更高的结构效能.     

Bioinspiration of the vein structure of dragonfly wings on its flight characteristics

Dragonflies have excellent flight characteristics, which are inextricably related to the characteristics of their wings. Their wings not only support a variety of loads during flight but also maintain high-efficiency flight characteristics. In this study, the forewing of a dragonfly (Pantala flavescens (Fabricius)) was used as a research object to explore the microstructure of the surface, cross section, and the vein distribution. Three-dimensional models of three different structures of the forewing vein, including an oval-shaped hollow tube, a circular hollow tube, and a circular solid tube, were established. Fluid dynamics analysis of these three forewing models under different angles of attack during gliding was carried out by FLUENT software, and subsequently, the influence of the dragonfly forewing vein structure on its flight characteristics was analyzed. The numerical simulation results indicated that the vein structure has a considerable influence on the lift, drag, and lift–drag ratio of the P. flavescens forewing. It was indicated that among the tested models, the forewing model with oval-shaped hollow tubular veins has better flight efficiency and aerodynamic characteristics. The results of this study may provide the basis for a novel bionic concept of flapping wing microaircraft design.     

考虑铰间隙的折叠翼展开机构展开过程碰撞动力学仿真分析

基于“二状态模型”的非线性等效弹簧阻尼模型,建立折叠翼展开机构的铰间隙碰撞模型,利用ADAMS软件对折叠翼展开机构的展开过程动力学进行仿真分析．包括间隙大小和间隙摩擦在折叠翼展开机构展开过程中引起的碰撞力变化规律。结果表明,在折叠翼展开机构整个展开过程中,由于间隙的影响,产生随机持续的碰撞力;随着间隙增大,碰撞次数减少,碰撞力幅值有增大的趋势;摩擦加快系统能量的损耗,一定程度上抑制了间隙碰撞次数和展开机构动力学扰动效应。