应用μ-ω方法进行气动弹性稳定性分析的数值研究

结合最近提出的一种频域颤振预测μ-ω方法,将其推广应用到静气动弹性发散分析中,进行了复杂气动弹性系统的稳定性分析数值研究。首先采用该方法进行了某大展弦比后掠机翼模型的颤振分析,与p-k法得到的颤振速度相对误差为0.83％,颤振频率相对误差仅为0.39％。然后计算了某三角翼模型的静发散速度,与p-k法求得的发散速度相对误差为2.02％。结果表明μ-ω方法具有良好的求解精度,适用于复杂气动弹性系统的稳定性分析。     

用解耦挂架抑制机翼/外挂颤振的低速风洞试验研究

进行了用解耦挂架抑制机翼/外挂颤振的低速风洞试验研究。试验分别在二元机翼及大展弦比机翼颤振模型上进行。试验结果表明:机翼/固接外挂颤振速度低于单独机翼颤振速度;而当外挂俯仰频率落入柔性区范围时,机翼/铰接外挂颤振速度高于单独机翼颤振速度,且其颤振速度对外挂惯性特性的变化比较不敏感。试验结果还表明:阻尼对用解耦挂架抑制机翼/外挂颤振的效果有重要影响。阻尼过小时,可能发生以外挂模态为主的颤振,使颤振速度降低。文中还讨论了外挂铰点弦向、展向位置的影响。同时进行了相应的理论计算,计算结果与试验结果基本相符。     

Structural optimization of an aeroelastically tailored composite flat plate made of woven fiberglass/epoxy

Summary Effects of aspect ratio, sweep angle, and stacking sequence of laminated composites were studied to find the optimized configuration of an aeroelastically tailored composite wing idealized as a flat plate in terms of flutter speed. The aeroelastic analysis has been carried out in the frequency domain. The modal approach in conjunction with doublet-lattice method (DLM) has been chosen for structural and unsteady aerodynamic analysis, respectively. The interpolation between aerodynamic boxes and structural nodes has been done using surface splines. To study the effect of stacking sequence the classical lamination theory (CLT) has been chosen. The parametric studies showed the effective ply orientation angle to be somewhere between 15 and 30 degrees, while the plates with lower aspect ratio seem to have higher flutter speeds. Forward-swept configurations show higher flutter speed, yet imposed by divergence constraints.     

气动扰流对飞机T型尾翼跨音速颤振影响的试验研究

跨音速颤振试验通常在稳定的理想流场中进行,不考虑实际非稳定流场的气动扰流对颤振特性的影响。在飞机T型尾翼跨音速颤振试验中,通过设置一种气动扰流装置对风洞流场实施干扰以研究气动扰流对飞机T型尾翼跨音速颤振特性的影响。试验结果表明,气动扰流可以将飞机T型尾翼的颤振耦合模态从平尾弯扭耦合型改变为垂尾弯扭耦合型;可显著降低飞机T型尾翼的颤振动压,翼面外气动扰流较翼面内气动扰流对飞机T尾颤振特性的影响作用大。其原因在于施加的气动扰流所诱导产生的跨音速激波作用在垂尾翼面上改变了垂尾的非定常气动力,引起气动刚度和气动阻尼发生改变,由于平尾的气动阻尼相对较大,可以预计,一旦气动扰流引起垂尾的气动阻尼迅速减小到其临界颤振阻尼,则会引起垂尾弯扭耦合颤振型先于平尾弯扭耦合颤振型发生,从而表现出T尾颤振动压的降低。在颤振模型风洞试验中,当风洞试验结果与期望不一致时,需要研究气动扰流的影响。     

机翼跨音速风洞颤振试验模型的计算分析

以某民机机翼跨音速颤振模型为研究对象,采用N-S方程求解固定边界流场的气动力,简化的跨音速小扰动方程求解运动边界流场的气动力,结合结构动力学的模态分析结果进行颤振特性分析。模型风洞试验前完成所有计算工作,试验后通过比较表明,计算结果与试验结果吻合:(1)颤振频率一致;(2)颤振速度随马赫数的变化趋势一致;(3)跨音速凹坑的底部位置一致;(4)颤振速度的偏差最大不超过10%,且在马赫数0.60和0.70处,偏差1%。由此可见该计算方法的计算精度高,可用于风洞试验结果的预判,提升风洞试验结果的可信度和风洞试验的效率,也可作为民机适航符合性验证的一种手段。     

超临界机翼跨音速颤振风洞试验研究

某先进民用支线飞机采用超临界机翼设计,跨音速颤振特性是超临界机翼的重要关键技术之一。颤振模型风洞试验是民机研制阶段最有效的跨音速颤振特性适航验证试验。本文设计了某民机超临界机翼跨音速风洞颤振试验模型并进行了颤振风洞试验,根据试验结果并结合亚音速颤振分析和压缩性数值分析,得到了超临界机翼的跨音速颤振压缩性修正曲线。研究表明,超临界机翼跨音速颤振速度最大压缩性修正系数较小,风洞试验结果与理论分析吻合较好,试验结果可以用于飞机的适航取证。     

复合材料前掠机翼的气弹剪裁

近年来随着复合材料结构在高速飞行器上的广泛应用,前掠机翼布局型式越来越引起重视。本文将对国外在前掠复合材料机翼的气动弹性方面研究工作,作一简要介绍。主要以气弹剪裁概念,研究根梢比、压心位置、重心位置、展弦比等变化的影响。并对前掠、后掠作以比较。      

基于多项式修正片条气动力的跨音速颤振分析方法及其试验验证

提出一种基于多项式修正片条气动力的跨音速颤振分析方法,以片条内升力和力矩随攻角变化斜率为修正目标,采用多项式方程模拟片条力矩分布,使整个翼面的气动力大小和分布都与目标相符,进而使用修正后的气动力进行跨音速区的颤振分析.计算结果经跨音速颤振风洞试验验证,该方法对翼吊发动机构型的机翼颤振型、带操纵面的尾翼颤振型都有较高的计...     

带有调整系统的远铰解耦挂架风洞试验研究

进行了带有调整系统的远铰解耦挂架抑制机翼/外挂颤振的低速风洞试验研究.试验是在大展弦比机翼颤振模型上进行的.试验结果表明:当外挂俯仰频率落在柔性区范围时,机翼/远铰解耦挂架/外挂的颤振速度比机翼/常规挂架/外挂的颤振速度有显著提高;且其颤振速度对外挂惯性特性的变化不敏感.试验结果还表明;调整系统可将外挂与机翼的相对静偏移修正到很小的设计角度内.文中还进行了单铰和远铰两种解耦挂架方案颤振抑制效果的比较,试验结果表明:远铰方案中外挂俯仰振动加速度响应比单铰时明显减小;且调整电机启动频率也比单铰时为低.文中还讨论了远铰挂架四连杆机构参数对外挂俯仰频率的影响.     

飞机T型尾翼跨音速颤振特性研究

由于飞机T型尾翼的结构与气动布局特点,T型尾翼颤振计算不能套用常规尾翼的分析方法,而需要考虑平尾面内运动以及静升力等因素的影响。而跨音速空气压缩性效应和非定常气动力计算的不准确性,使得T型尾翼跨音速颤振计算更加困难,准确性较低。因此,需要采用试验为主计算为辅的方法来研究飞机T型尾翼跨音速颤振特性。针对某T型尾翼结构,用ZAERO软件等价片条势流跨音速颤振(ZTAIC)方法计算T型尾翼跨音速颤振特性,研究了马赫数、风洞气流密度和平尾迎角对T型尾翼颤振特性的影响。通过升力系数斜率空气压缩性修正计算方法和跨音速颤振模型风洞试验方法得到了飞机T型尾翼的跨音速颤振的凹坑曲线和空气压缩性特性,两种方法得到结果一致。     

跨音速流中壁板流固耦合效应的形态演化分析

高速飞行器部件多采用轻质薄壁加筋结构,当飞行器长时间跨音速或低超音速飞行时,这种薄壁结构在非定常气动载荷的作用下会表现出强非线性的流固耦合特征,其中激波运动、边界层效应、流动分离等流场非线性与几何大变形等结构非线性相互耦合作用会使壁板产生失稳行为,引起结构疲劳或损毁。该文基于CFD/CSD耦合数值模拟技术,预测和判别壁板在跨音速气流中随马赫数变化过程中响应形态,发现在跨音速区内会出现明显的单模态颤振形式。随马赫数的增大,其形态演化次序为稳态收敛、第一模态极限环振荡、屈曲、稳态收敛、跨音速颤振、非共振型极限环振荡、共振型极限环振荡、高频周期振荡、高频非周期振荡、第一模态极限环振荡到稳态收敛的过程。当壁板厚度增加、来流密度减小,演化形态会发生变化。同时,当考虑非定常加速效应和粘性效应后,会出现一定的延迟和阻尼效应,对高频非周期振荡起到抑制作用,这对于降低结构的疲劳损伤有积极效果。     

What makes the difference between shock boundary-layer interaction on an airfoil and on a swept wing?

Summary Swept wing flows are characterized by the curvature of the streamlines in the projection to the wing plan and by the skewing of the velocity profile in the boundary layer. The aerodynamic performance of supercritical wings at transonic speeds is trongly influenced by the interaction between a weak shock front and a turbulent boundary layer. The characteristic elements of this interaction are the precompression, the post-shock expansion, and the shock diffusion. The differences between the interactive flow over an airfoil and over a swept wing are elaborated by the comparison between the two-dimensional case and the flow with superposed tangential velocity.     

Two‐dimensional transonic aeroservoelastic computations in the time domain

A computational method to perform transonic aeroelastic and aeroservoelastic calculations in the time domain is presented, and used to predict stability (flutter) boundaries of 2‐D wing sections. The aerodynamic model is a cell‐centred finite‐volume unsteady Euler solver, which uses an efficient implicit time‐stepping scheme and structured moving grids. The aerodynamic equations are coupled with the structural equations of motion, which are derived from a typical wing section model. A control law is implemented within the aeroelastic solver to investigate active means of flutter suppression via control surface motion. Comparisons of open‐ and closed‐loop calculations show that the control law can successfully suppress the flutter and results in an increase of up to 19 per cent in the allowable speed index. The effect of structural non‐linearity, in the form of hinge axis backlash is also investigated. The effect is found to be strongly destabilizing, but the control law is shown to still alleviate the destabilizing effect. Copyright © 2001 John Wiley & Sons, Ltd.     

考虑发动机推力影响的机翼颤振分析

发动机安装在机翼上时,其推力具有典型的随动特征,并对机翼颤振产生重要影响.基于有限元分析软件MSC/Nastran的DMAP开发,提出了一种考虑发动机推力和几何非线性影响的机翼颤振分析方法.作为验证,分析了推力对某高空长航时飞行器机翼颤振速度的影响,与已有结果吻合良好.对一带有两个发动机的复杂机翼结构进行了结构建模和颤振分析,重点分析了推力大小及作用位置对颤振速度的影响.结果表明,发动机的推力效应在颤振分析中是不应忽略的.     

Computation of three-dimensional transonic viscous flow using the JUMB03D code

Summary A vertex based finite volume method for the solution of the three dimensional Reynolds averaged Navier-Stokes equations has been developed. The computations can be carried out blockwise after dividing the computational domain into smaller blocks to reduce the memory requirement for a single processor computer and also to facilitate parallel computing. A five stage Runge-Kutta scheme has been used to advance the solution in time. Enthalpy damping, implicit residual smoothing, local time stepping, and grid sequencing are used for convergence acceleration. In order to get smooth convergence for transonic, viscous flows, the artificial dissipation has been modified by using the time step for advective and diffusive equations. An algebraic turbulence model has been used to determine the turbulent eddy viscosity. The method has been used to compute transonic flow over a cropped delta wing and the ONERA M-6 wing, and subsonic flow over a launch vehicle configuration. The results obtained show good agreement with available experimental data.     

采用等效刚度有限元模型的复合材料机翼颤振分析

采用等效刚度方法,研究了一种适用于机翼初步设计阶段的动力学和颤振分析的结构有限元模型。该方法首先计算不同布局形式的加筋壁板的刚度矩阵,然后将其赋予与加筋壁板平面形状相同的光板（等效板）上,使加筋壁板和等效板具相同的力学性能。该方法的优点是避免了加强筋的有限元建模,从而使有限元模型的复杂程度大大降低,但同时等效刚度结构有限元模型仍能反映机翼加筋壁板的结构特性。以某客机概念方案的机翼为例,建立了反映实际结构详细有限元及其等效刚度有限元模型。计算结果和对比分析表明,两种模型的固有频率、振动模态和颤振分析结果吻合得很好,从而验证了等效刚度方法在机翼结构动力学和颤振分析方面的准确性。由于该方法具有简单快速和准确的优点,可用于机翼初步设计阶段对颤振特性的评估。     

Computation of transonic potential flow past wing-body configurations

Summary A simple approach has been developed to use the two dimensional grid generation method by solving elliptic partial differential equations to generate the three dimensional grid for wingfuselage configurations. This simple method can be applied to generate grids for arbitrary fuselage fitted with any swept wing with dihedral. Three dimensional transonic analysis code TWING, with approximate factorization (AF2) scheme has been suitably used as a flow solver. As an example, RAE-WING-A with body-B2 configuration has been considered. The results obtained have been compared with available numerical and experimental results. It has been observed in the present computations that AF2 scheme is not sensitive to grid stretching.     

Effect of one-sided periodic pulsed energy supply on aerodynamic characteristics of wing profiles

The possibility of controlling the aerodynamic characteristics of wing profiles by means of local periodic pulsed energy supply in transonic flight regimes has been studied. A change in the flow structure near a symmetric wing profile was determined, depending on the amount of energy supplied from the lower side of the wing profile, using a numerical solution of two-dimensional nonstationary equations of gasdynamics. The results are compared to the data obtained from calculations of a transonic flow past the same profile at various incidence angles without energy supply.     

大展弦比夹芯翼大攻角颤振分析

首先导出大展弦比复合材料梁弯扭耦合模态的半解析解，对具有NACA0012翼型的大展弦比的夹芯翼，在模态空间内建立了运动方程。然后采用半经验的ONERA非线性气动力模型描述空气动力，形成了对大展弦比夹芯翼大攻角气动弹性问题的描述。通过结构求解器和空气动力求解器联合求解来完成非线性颧振边界的计算。为了验证非线性颤振边界的求解方法，还利用ONERA气动力模型中的线性部分建立了夹芯翼的线性颤振方程。结果表明：零翼根攻角时，线性颤振速度与用非线性颧振边界求解方法得到的颧振速度完全一致；颤振速度随翼根攻角的增加而迅速减小；复合层铺设方式对颤振速度有较大影响。     

Divergence and flutter of shear deformable aircraft swept wings subjected to roll angular velocity

The aeroelastic modeling and instability of shear deformable swept wings under roll angular velocity is investigated. The structural wing model was originally developed by Librescu and consists of non-classical effects such as warping inhibition and transverse shear flexibility. This model is used to study divergence and flutter instabilities when the aircraft wing is subjected to a roll moment created during a maneuver. The aeroelastic governing equations and boundary conditions are determined via Hamilton’s variational principle. The resulting partial differential equations are transformed into a set of eigenvalue/boundary value equations through the Extended Galerkin approach and solved by numerical integration. The effects of roll angular velocity, sweep angle, and wing aspect ratio on divergence and flutter speed are presented for classic and shear deformable wings. Validations of selected results against the previous publications are also supplied. Results indicate that roll angular velocities have a significant influence on the static and dynamic aeroelastic instability region.