扑翼飞行器气动力测量技术研究进展与展望

扑翼飞行器是一种仿照鸟类飞行的新概念小型无人飞行器,区别于传统固定翼和旋翼飞行器,它主要通过机翼扑动与空气相互作用来提供飞行动力,从而实现飞行器的姿态变动。扑翼飞行器气动特性测试的实质是揭示在非定常流场环境下,扑翼飞行器气动力的产生机制,以及相关扑翼飞行器设计参数对气动特性的影响。通过气动试验方法为扑翼飞行器飞行控制和结构优化等研制工作提供数据支持,将对新型扑翼飞行器理论研究以及飞控品质的提升起到巨大的推动作用。     

扑动轨迹对扑翼气动特性影响的数值研究

国内外对扑翼飞行的气动性能进行了大量研究,这些研究大多针对特定运动轨迹下的扑翼,然而大量观察发现,昆虫在飞行时其翅膀会出现各种不同的运动形式,这些不同的翅膀运动方式必定对其气动性能产生重要影响。该文基于对昆虫的实验和数值模拟中常用的几种扑动轨迹模型分析,建立了三种具有相同准稳态气动力的扑翼扑动轨迹,并采用数值求解N-S 方程的方法,研究了前飞状态下不同扑动轨迹对扑翼气动特性产生的影响。结果显示扑动和转动均为简谐函数轨迹形式的扑翼具有较高的升举效率和推进效率。进一步通过对不同扑动轨迹扑翼流场分析得出,扑动轨迹不能改变扑翼产生的尾流性质,但可以影响涡的强度,从而使扑翼产生不同的气动性能。     

扑翼飞行器测力平台设计与振动特性仿真分析

扑翼飞行器是基于鸟类仿生学理论衍生出的新型无人飞行器,主要通过机翼周期性上下扑动来提供飞行器所需的升力和推力,在军用和民用飞行器领域均有广阔的应用前景。扑翼飞行器气动力测量作为样机气动性测试的重要手段,多维气动力的准确测量可为新型扑翼飞行器设计优化和飞控品质的提高提供试验数据支持。本文介绍了一种新型组合式多维小量程测力平台,可实现扑翼飞行器六维气动力和气动力矩的测量。考虑到扑翼飞行器机翼上下扑动过程动态测力需求,应用Ansys Workbench有限元分析软件对测力平台进行了模态分析和频响分析,获得在工作频率下的频率响应,仿真结果表明测力平台的振动特性满足设计要求。     

柔性扑翼气动性能的数值研究

国内外对扑翼飞行的气动特性进行了大量研究,这些研究大多基于简谐扑动的刚性翼,然而大量观察发现鸟或昆虫飞行时,翅膀存在明显的柔性变形,这种变形对其气动性能具有显著的影响。该文针对一简化的二维柔性扑翼模型,采用数值求解N-S方程并耦合扑翼柔性变形方程的计算方法,研究了扑翼柔性变形对其气动性能的影响。结果显示扑翼的柔性变形改变了扑翼周围的涡结构,从而影响扑翼的气动性能;适当的柔性变形能延迟前缘涡的脱落,从而有效地改善扑翼的推进效率,但同时减弱了扑翼在低雷诺数环境中产生高升力的尾迹捕捉机制。     

扑翼式飞行器的发展与展望

本文简要介绍了扑翼式飞行器的国内外发展史,以及扑翼式飞行器相比于其他飞行器的优势,概述了当前扑翼式飞行器在国内外研究现状。以此为基础,讨论了现阶段扑翼式飞行器研究的关键技术,并对我国未来扑翼式飞行器的发展方向进行了展望。     

一种超低空飞行的仿生扑翼飞行器的设计及分析

为研制既具备一定的负载能力,又具有高隐蔽性的飞行器,依据鸟类的飞行方式,设计了一种可以超低空飞行的仿生扑翼飞行器.首先,计算了扑翼飞行器传动机构的自由度,从原理上确定了设计方案的可行性,并确定了飞行器各个构件的尺寸;其次,利用设计软件Creo绘制飞行器三维模型,通过运动仿真得出飞行器的扑动符合设计要求;然后,利用ADA...     

仿生扑翼模态分析研究与优化设计

微型扑翼飞行器是微型飞行器和扑翼飞行器的结合,是飞行器设计领域的研究热点,但在低雷诺数下存在升力不足的现象。已有研究表明,扑翼的弯扭耦合对于提高升力有效,弯扭耦合可通过共振激励放大驱动机理来实现,但该机理对扑翼的模态提出要求。本文首先建立仿生扑翼有限元模型,对其进行模态分析,并提出1种适用于扑翼的模态种类判别方法。为满足模态要求,提出了2种改进方案,并进行了有限元仿真验证。结合两种改进方案,提出双斜梁-主梁变截面扑翼模型。基于PCL语言对该模型进行参数化建模,采用遗传算法对其进行尺寸优化,得到满足模态要求的相对理想的仿生扑翼,为仿生扑翼的设计和优化提供重要的科学依据和工程应用价值。     

仿生扑翼飞行器的气动效率研究

该文主要采用BLU-SGS混合动态网格隐式算法进行时间推进,空间离散采用二阶迎风格式的有限体积法。求解非定常Navier-Stokes方程,完成了二维不可压缩流场的数值模拟。在该基础上,通过积分计算的形式得到整个机翼平面的气动力,研究揭示了不同扑动频率、风速参数、减缩频率、雷诺数与飞行气动效率的关系,表明参数的合理调试对仿生扑翼飞行器的有效飞行起到重要影响。针对不同参数条件,研究分析了气动力以及气动效率结果,为后续气动特性问题的研究提供参考。     

飞行器翼肋零件橡皮囊成形研究与模具设计

飞行器的翼肋就像鸟类翅膀的骨骼,飞行器缺少它不能实现在天空飞行。随着科学技术不断地发展,翼肋零件成形技术也在不断的提高和改进,本文研究的翼肋零件的橡皮囊成形、翼肋零件成形模具型面设计、成形模具设计,从零件的结构、材质以及成形方面分析,进一步提高这类零件的质量和精度。     

基于Unity3D的扑翼飞行器自主寻路的设计与实现

随着虚拟现实的飞速发展,Unity3D引擎成为此项技术的主要平台,相较传统仿真软件,存在高可视化的优势,其在工业仿真领域的应用逐步深入.基于U nity3D引擎对扑翼飞行器的自主寻路进行仿真设计,在U nity3D中导入扑翼飞行器,然后设计搭建寻路场景,通过NavM esh系统的应用和编写的脚本,实现扑翼飞行器的自主寻路.     

A quantitative comparison of bird and bat wakes

Qualitative comparison of bird and bat wakes has demonstrated significant differences in the structure of the far wake. Birds have been found to have a unified vortex wake of the two wings, while bats have a more complex wake with gradients in the circulation along the wingspan, and with each wing generating its own vortex structure. Here, we compare quantitative measures of the circulation in the far wake of three bird and one bat species. We find that bats have a significantly stronger normalized circulation of the start vortex than birds. We also find differences in how the circulation develops during the wingbeat as demonstrated by the ratio of the circulation of the dominant start vortex and the total circulation of the same sense. Birds show a more prominent change with changing flight speed and a relatively weaker start vortex at minimum power speed than bats. We also find that bats have a higher normalized wake loading based on the start vortex, indicating higher relative induced drag and therefore less efficient lift generation than birds. Our results thus indicate fundamental differences in the aerodynamics of bird and bat flight that will further our understanding of the evolution of vertebrate flight.     

Sequentially-coupled space–time FSI analysis of bio-inspired flapping-wing aerodynamics of an MAV

We present a sequentially-coupled space–time (ST) computational fluid–structure interaction (FSI) analysis of flapping-wing aerodynamics of a micro aerial vehicle (MAV). The wing motion and deformation data, whether prescribed fully or partially, is from an actual locust, extracted from high-speed, multi-camera video recordings of the locust in a wind tunnel. The core computational FSI technology is based on the Deforming-Spatial-Domain/Stabilized ST (DSD/SST) formulation. This is supplemented with using NURBS basis functions in temporal representation of the wing and mesh motion, and in remeshing. Here we use the version of the DSD/SST formulation derived in conjunction with the variational multiscale (VMS) method, and this version is called “DSD/SST-VMST.” The structural mechanics computations are based on the Kirchhoff–Love shell model. The sequential-coupling technique is applicable to some classes of FSI problems, especially those with temporally-periodic behavior. We show that it performs well in FSI computations of the flapping-wing aerodynamics we consider here. In addition to the straight-flight case, we analyze cases where the MAV body has rolling, pitching, or rolling and pitching motion. We study how all these influence the lift and thrust.     

State-space aerodynamic model reveals high force control authority and predictability in flapping flight

Flying animals resort to fast, large-degree-of-freedom motion of flapping wings, a key feature that distinguishes them from rotary or fixed-winged robotic fliers with limited motion of aerodynamic surfaces. However, flapping-wing aerodynamics are characterized by highly unsteady and three-dimensional flows difficult to model or control, and accurate aerodynamic force predictions often rely on expensive computational or experimental methods. Here, we developed a computationally efficient and data-driven state-space model to dynamically map wing kinematics to aerodynamic forces/moments. This model was trained and tested with a total of 548 different flapping-wing motions and surpassed the accuracy and generality of the existing quasi-steady models. This model used 12 states to capture the unsteady and nonlinear fluid effects pertinent to force generation without explicit information of fluid flows. We also provided a comprehensive assessment of the control authority of key wing kinematic variables and found that instantaneous aerodynamic forces/moments were largely predictable by the wing motion history within a half-stroke cycle. Furthermore, the angle of attack, normal acceleration and pitching motion had the strongest effects on the aerodynamic force/moment generation. Our results show that flapping flight inherently offers high force control authority and predictability, which can be key to developing agile and stable aerial fliers.     

Dimensional analysis of spring-wing systems reveals performance metrics for resonant flapping-wing flight

Flapping-wing insects, birds and robots are thought to offset the high power cost of oscillatory wing motion by using elastic elements for energy storage and return. Insects possess highly resilient elastic regions in their flight anatomy that may enable high dynamic efficiency. However, recent experiments highlight losses due to damping in the insect thorax that could reduce the benefit of those elastic elements. We performed experiments on, and simulations of, a dynamically scaled robophysical flapping model with an elastic element and biologically relevant structural damping to elucidate the roles of body mechanics, aerodynamics and actuation in spring-wing energetics. We measured oscillatory flapping-wing dynamics and energetics subject to a range of actuation parameters, system inertia and spring elasticity. To generalize these results, we derive the non-dimensional spring-wing equation of motion and present variables that describe the resonance properties of flapping systems: N, a measure of the relative influence of inertia and aerodynamics, and K^, the reduced stiffness. We show that internal damping scales with N, revealing that dynamic efficiency monotonically decreases with increasing N. Based on these results, we introduce a general framework for understanding the roles of internal damping, aerodynamic and inertial forces, and elastic structures within all spring-wing systems.     

Beyond robins: aerodynamic analyses of animal flight

Recent progress in studies of animal flight mechanics is reviewed. A range of birds, and now bats, has been studied in wind tunnel facilities, revealing an array of wake patterns caused by the beating wings and also by the drag on the body. Nevertheless, the quantitative analysis of these complex wake structures shows a degree of similarity among all the different wake patterns and a close agreement with standard quasi-steady aerodynamic models and predictions. At the same time, new data on the flow over a bat wing in mid-downstroke show that, at least in this case, such simplifications cannot be useful in describing in detail either the wing properties or control prospects. The reasons for these apparently divergent results are discussed and prospects for future advances are considered.     

Stable hovering of a jellyfish-like flying machine

Ornithopters, or flapping-wing aircraft, offer an alternative to helicopters in achieving manoeuvrability at small scales, although stabilizing such aerial vehicles remains a key challenge. Here, we present a hovering machine that achieves self-righting flight using flapping wings alone, without relying on additional aerodynamic surfaces and without feedback control. We design, construct and test-fly a prototype that opens and closes four wings, resembling the motions of swimming jellyfish more so than any insect or bird. Measurements of lift show the benefits of wing flexing and the importance of selecting a wing size appropriate to the motor. Furthermore, we use high-speed video and motion tracking to show that the body orientation is stable during ascending, forward and hovering flight modes. Our experimental measurements are used to inform an aerodynamic model of stability that reveals the importance of centre-of-mass location and the coupling of body translation and rotation. These results show the promise of flapping-flight strategies beyond those that directly mimic the wing motions of flying animals.     

介质阻挡面放电等离子体流动控制研究进展

介质阻挡面放电（Surface Dielectric Barrier Discharge,SDBD）等离子体主动流动控制技术可以显著改善飞行器的气动性能,已经成为国内外研究的热点问题。通过介绍国外针对SDBD特性、流动控制机理、气动激励数学模型、流动控制影响因素等的研究现状,总结了国内在SDBD等离子体流动控制实验、数值模拟和机理研究方面的进展,归纳出现阶段研究中面临的问题及未来需要解决的问题,并指出提高抑制流动分离能力的等离子体冲击流动控制方式是一种重要研究方向。     

Modelling of Bird Strike on an Aircraft Wing Leading Edge Made from Fibre Metal Laminates – Part 1: Material Modelling

Fibre Metal Laminates with layers of aluminium alloy and high strength glass fibre composite have been reported to possess excellent impact properties and be suitable for aircraft parts likely to be subjected to impacts from objects such as runway debris or birds. In a collaborative research project, aircraft wing leading edge structures with a glass-based FML skin have been designed, built, and subjected to bird strike tests that have been modelled with finite element analysis. In this first part of a two-part paper, a material model developed for FML suitable for use in impact modelling with explicit finite element analysis is presented. The material model is based on a recent implementation in the commercial finite element code PAM-CRASH/SHOCK of a Continuum Damage Mechanics (CDM) model for composites, incorporating anisotropic strain rate effects. Results from the model are compared with experimental results on FML at variable strain rates and the model is shown to be capable of capturing most of the complex strain rate dependent behaviour exhibited by these materials.