下反前掠地效翼三维数值模拟

为研究下反前掠地效翼的气动性能,利用FLUENT求解定常不可压N-S方程和可实现的k-ε湍流模型,建立在地面效应下地效翼流场的三维数值模型,对不同下反角和前掠角的地效翼进行数值模拟.计算结果揭示出下反角和前掠角对地效翼空气动力特性、流场特性和纵向稳定性的影响规律.对下反前掠地效翼的三维数值模拟可以为地效飞行器的设计和优化提供参考.     

翼稍装置对翼尖涡耗散的影响研究

针对不同安装角的情况下翼梢小翼对翼尖涡耗散问题,利用thin-cut技术生成六组非结构网格,采用SST k-omega湍流模型与三维雷诺平均N-S方程对不同安装角度的翼梢小翼与未安装翼梢小翼的机翼进行模拟仿真与数值计算,得到了距离机翼不同距离区域翼尖涡的涡量分布云图.研究表明,翼梢小翼通过生成正向涡旋与翼尖涡相互作用降低翼尖涡的涡旋强度,合适的翼梢小翼安装角度能大幅度提高翼尖涡耗散效率,减小翼尖涡的危害,提升民航运行效率.     

Z型折叠机翼的非线性动力学与模态分析研究

针对Z型折叠机翼这种复杂多体结构,运用多种不同的方法得到了结构的前4阶振动模态.将Z型折叠机翼假设为由三块碳纤维复合材料板组成,两板之间均以刚性铰链相连接.其中内翼左侧是固定端,并与机身相连接;中间翼以对边简支形式连接在内外翼之间;外翼的外端是自由端.在第一个铰链上施加驱动力矩M1为机翼提供折叠角速度,使中间翼进行转动;同时施加力矩M2于第二个铰链处,使外翼与内翼始终保持平行.本文首先利用Hamilton原理与von Karman大变形理论建立Z型折叠机翼的动力学模型,然后通过ANSYS软件设置合理的边界条件进行模态分析与谐响应分析,其次根据ANSYS模拟的Z型折叠机翼的振动形式,假设合适的模态函数,通过结构边界条件和系统动力学方程求出来的边界条件,求出三个板的横向振动模态函数,最后通过Maple验证得出的模态函数与ANSYS模拟的振动形式相符合.该研究不仅是Z型机翼的受迫振动响应分析的前提,而且对于Z型机翼的设计与实验也具有参考价值.     

带升力风扇飞机的短距起飞建模和仿真研究

着重研究带升力风扇飞机在考虑地效时的短距起飞性能.结合地面效应在飞机起飞时的影响,气动舵面和推力矢量融合控制技术的飞机运动状态,建立了考虑地效的飞机纵向动力学数学模型.最后以某ASTOVL验证机为背景机,借助Matlab7.1/Simulink环境,对三种不同动力方案飞机的起飞过程进行仿真计算,并与飞行试验结果相比较,结果表明考虑地效时建立的数学模型具有更好的可信度;同时可以看出采取不同推力矢量动力方案对飞机起飞性能的改善有很大的差异,尤其是带升力风扇的推力矢量飞机在短距起飞性能上可以获得明显的收益.     

一种基于智能材料的可收放变后掠翼飞行器设计

本文通过对高超声速客机和变体飞行器的研究,设计了一种采用智能材料驱动的可收放机翼的超声速飞行器。该设计主要针对机翼构型,采用展向可调的智能材料驱动机翼翼梁沿展向伸缩,并结合机翼柔性蒙皮材料进行调节。本论文对该新型超音速客机平台的总体设计参数进行了估算,分析了包括飞机外形、机翼设计、变体飞行器技术等关键技术设计方案,并对该飞行平台的一般任务过程进行了描述。通过研究我们认为,该机翼构型在概念上具有创新,通过展向可调机构来改变机翼后掠角,解决了低速起降和超音速巡航这一设计矛盾,为下一代超音速飞行器发展提供一个有参考价值的思路。     

变截面Z型折叠机翼振动特性的有限元与实验分析

Z型变截面折叠机翼作为一种可变体机翼结构,不同的折叠角对机翼稳定性有着重要的影响,因此研究不同折叠角度下的特性参数对机翼动态稳定性有着重要的意义.本文首先设计加工了Z型变截面可折叠机翼结构的实验模型,通过建立与实验模型相匹配的有限元模型,仿真得到不同折叠角度下机翼的前5阶固有频率和振型,针对不同折叠角度下机翼的固有特性,通过扫频实验得到机翼前5阶固有频率和模态振型,以及横向外激励作用下三段翼的频响曲线,对比分析有限元仿真与实验结果,验证结果的可靠性,这将对机翼结构设计以及特性参数的选取提供参考依据.     

变截面Z型折叠机翼振动特性的有限元与实验分析

Z型变截面折叠机翼作为一种可变体机翼结构,不同的折叠角对机翼稳定性有着重要的影响,因此研究不同折叠角度下的特性参数对机翼动态稳定性有着重要的意义.本文首先设计加工了Z型变截面可折叠机翼结构的实验模型,通过建立与实验模型相匹配的有限元模型,仿真得到不同折叠角度下机翼的前5阶固有频率和振型,针对不同折叠角度下机翼的固有特性,通过扫频实验得到机翼前5阶固有频率和模态振型,以及横向外激励作用下三段翼的频响曲线,对比分析有限元仿真与实验结果,验证结果的可靠性,这将对机翼结构设计以及特性参数的选取提供参考依据.     

仿生机翼流场的数值模拟

利用有限体积法对标准NACA63-210机翼进行了三维数值模拟计算,利用相同的模拟方法、网格结构和边界条件对仿生NACA63-210机翼进行数值模拟。分析了两种机翼表面的流场特性,并从压差阻力和摩擦阻力两个方面讨论了仿生翼气动特性提高的特性。     

基于形状上下文与粒子滤波的机翼跟踪

针对飞机地面牵引移动过程中存在的潜在危险,研究了一种基于视频的翼尖跟踪方法。针对机场光照、背景变化等复杂外界情况,为克服常规图像目标跟踪方法的不足,通过简化和改进形状上下文描述翼尖轮廓特征,以粒子滤波为基本框架实现翼尖跟踪,并根据机翼的不同运动速度自适应调节状态转移方程参数,增加有效粒子个数,避免粒子衰竭。实验结果表明,该方法能够有效跟踪翼尖,具有较好的跟踪效果和鲁棒性。     

仿生扑翼“0”形轨迹机构的设计及气动力特性

针对仿生扑翼飞行器的驱动结构进行设计,提出了一种空间摇杆式的驱动机构与机翼扭转机构,实现机翼扑动过程中的"0"形空间运动轨迹.针对机翼的空间"0"字形运动,建立仿生飞行器气动分析模型,采用动网格与非定常数值计算方法,对机翼拍动过程中不同相位下的升阻特性进行分析,并通过空气动力效率与流场对比分析,得到不同参数条件下的气动效率,为仿生扑翼飞行器的设计及扑动模式的选择提供参考.通过气动力测量实验、台架姿态标定和外场飞行测试,验证了结构设计的合理性.     

Nonlinear prediction of subsonic aerodynamic loads on wings and bodies at high angles of attack

This paper predicts numerically the nonlinear aerodynamic loads on wings and bodies at high angles of attack in subsonic flow separating along certain known lines. It is assumed that the separation vortices are symmetric and unbursting. The wing mean surfaces and body surfaces are simulated by bound vortex lattices, and the separation vortex surfaces by free vortex lines. The vortex system satisfies boundary conditions on wing and body surfaces, separation conditions, and the condition that free vortex lines are tangent to local velocity. The velocity induced by a vortex is computed by the Biot-Savart law with Göthert transformation for subsonic small perturbation flows. The vortex strengths and the free vortex locations are solved by relaxation method. Then the aerodynamic loads on wings and bodies are computed. They agree well with experimental tests.     

Hybrid numerical technique for evaluating wing aerodynamic loading with propeller interference

A computational investigation of the interference between wings having different aspect ratios and a tractor propeller has been carried out to accurately determine the time-averaged aerodynamic characteristics of the aircraft in terms of the modified wing loads. At first, the aerodynamic interaction has been studied by modeling the wakes both of propeller and wing, in isolated and coupled configurations. The model is based on a hybrid numerical technique, the free wake analysis (FWA) and boundary element method (BEM), applied to the wakes of a propeller and a wing, respectively. The output data has been compared with those available from the experimental procedures. Subsequently, to describe the effects of the two interacting wakes, a three-dimensional BEM approach for an untapered wingspan was applied to evaluate the wing quasisteady loads. The research focused on the wing pressure coefficient distribution related to the altered upstream conditions of the coupled propeller, hence the wing loads and the pitching moment are computed. The results confirm the advantages of the present approach using the FWA and BEM to identify the aerodynamic features of the mutual interference of a wing and a propeller at angle of attack and at a fixed propeller operating condition. Applications of this numerical hybrid scheme to an isolated wing and propeller, in quasisteady flow conditions, as well as to coupled configurations, are shown in the present paper. They demonstrate that accurate results can be obtained with very low computational effort.     

Computation of supersonic inviscid flow around wings with a detached shock wave

The numerical method for computing inviscid supersonic flow around the front part of the arbitrary planform wings was presented in [1,2]. The aim of this paper, which is the extension of the previous ones, is to present a numerical method for computing the flow field above the remaining parts of the wing—the wingtip section and the central section of the wing. Here the problems are formulated for a three-dimensional steady gas-dynamic system of equations written in special curvilinear coordinates. Complicated physical domains of the solution are mapped on simple computational domains. For approximation of the differential equations the finite-difference second-order implicit schemes are used. The approximation of the wing surfaces is made with the help of the local cubic splines. According to the obtained algorithms calculations were made for the wing with elliptical planform and thick airfoil at M_∞ = 2 and M_∞ = 3.5 with the angle of attack α = 5°.     

Aeroelastic topology optimization of membrane structures for micro air vehicles

This work considers the aeroelastic optimization of a membrane micro air vehicle wing through topology optimization. The low aspect ratio wing is discretized into panels: a two material formulation on the wetted surface is used, where each panel can be membrane (wing skin) or carbon fiber (laminate reinforcement). An analytical sensitivity analysis of the aeroelastic system is used for the gradient-based optimization of aerodynamic objective functions. An explicit penalty is added, as needed, to force the structure to a 0–1 distribution. The dependence of the solution upon initial design, angle of attack, mesh density, and objective function are presented. Deformation and pressure distributions along the wing are studied for various load-augmenting and load-alleviating designs (both baseline and optimized), in order to establish a link between stiffness distribution and aerodynamic performance of membrane micro air vehicle wings. The work concludes with an experimental validation of the superiority of select optimal designs.     

Finite element flutter analysis of composite skew panels

A finite element method is used to study the dynamic instability of laminated composite skew panels subjected to supersonic flow. The FEM employs eight-noded isoparametric elements which take into account transverse shear deformation. The linearized Piston theory is applied to assess the aerodynamic loads. The effects of skew angle on critical aerodynamic parameters are investigated for different aspect ratios, boundary constraints, fibre orientations and lamination schemes. It is observed that the skew angle has a stabililzing effect on the flutter boundary, whereas couplings have a destabilizing effect. The higher aspect ratio is also found to exhibit a stabilizing effect on the flutter boundary.     

基于FLUENT的机翼损伤小型无人机气动分析

研究小型无人机机翼不同程度受损条件下无人机气动特性,仿真无人机损伤多少比例机翼时可保持飞行。设计一个无人机模型,研究基于有限元分析的机翼损伤下的气动分析。在CATIA三维软件中对无人机建模,在ANSYS ICEM中进行模型曲面划分与流场网格划分,ANSYS FLUENT中进行气动分析。先分析完整机翼的无人机模型,再逐步切除一定比例的机翼,对比分析机翼损伤前后的气动特性,得出切除多少比例面积的翼面时无人机模型仍可保持飞行,为将来实际无人机设计和风洞试验提供依据。     

迷你翼梢小翼增升减阻效应

选取某窄体客机的翼梢小翼为研究对象,采用Spalart Allmaras模型对无翼梢小翼、全尺寸翼梢小翼和迷你翼梢小翼3种机翼构型进行数值模拟,通过流场分析和速度分解等手段,研究翼梢小翼的增升减阻机理。结果表明：迷你翼梢小翼有恢复涡核流速、减弱涡流掺混程度和梳理翼梢气流的作用;增升减阻的关键在于迷你翼梢小翼对气流方向的修正;翼梢小翼的局部流动差异会对整体机翼近场造成影响。由于尺寸较小,迷你翼梢小翼能在较大攻角范围内改善传统翼梢小翼的性能,具有一定的实践意义。     

Modeling a supersonic flowfield in the core of the wingtip vortex at Mach 6

In this paper numerical calculations of a wingtip vortex for various wing angles of attack are presented, and the resulting flow modes are compared with each other and with the experimental data. Numerical computations were performed at the Keldysh Institute of Applied Mathematics, making use of the Spalart-Allmaras turbulence model. Experiments were carried out at the Institute of Theoretical and Applied Mechanics, Siberian Branch (SB), Russian Academy of Sciences (RAS), Khristianovich, Russia.