考虑柔性气动力的机翼结构优化方法研究

分析研究了大展弦比弹性机翼结构静弹性变形对气动载荷的影响，在传统结构优化方法基础上进行了弹性机翼的结构优化设计方法研究。实现了在真实飞行条件下考虑静气动弹性变形影响的大展弦比弹性机翼的结构优化设计。结构优化设计算例验证了方法的可行性，优化结果表明结构重量收益明显。     

一种三维弹性机翼气动优化新方法

基于控制理论方法和有限元分析软件,通过将网格生成、流场计算、有限元分析、粘性伴随方程数值求解、梯度求解和拟牛顿优化算法等几方面的有效结合,研究与发展了计及静气动弹性影响的三维机翼气动优化设计方法,其中,雷诺平均Navier-Stokes方程为主控方程,气动载荷和结构静弹性变形量由气动/结构方程的耦合迭代求解得到,目标函数梯度信息由共轭方程数值求解得到。典型大展弦比机翼气动减阻设计结果表明：研究及发展的计及静气动弹性影响的三维机翼气动优化设计方法是有效的,能够有效考虑静气动弹性的影响。     

大展弦比机翼型架外形优化方法探究

大展弦比飞机一般针对巡航外形设计,以巡航性能作为设计点,而飞机在实际飞行过程中,其气动特性会由于机翼产生弹性变形而变化。文中通过开展大展弦比飞机CFD/CSD耦合方法,对巡航外形进行多次静气动弹性分析,进行位移比对,进而获得满足要求的型架外形,从而初步得到机翼型架外形优化设计方法,为之后的大展弦比飞机气动结构设计一体化打下基础。     

考虑气动弹性变形影响的跨声速机翼设计方法研究

根据气动－结构一体化的设计思想,发展了一种考虑气动弹性变形影响的跨声速机翼ＣＦＤ设计方法。设计实践表明,采用适当的结构弹性模型,方法可以在计算机机翼静弹性变形影响的情况下设计出压力分布收敛于指定目标的新机翼,因此在跨声速机翼型架外形的设计和史 起初外形设计中具有良好的实用价值。     

基于伴随方程和自由变形技术的跨声速机翼气动设计方法研究

将连续伴随方程法与自由变形技术(Free Form Deform-FFD)相结合开展了跨声速机翼气动外形优化设计方法研究。采用Bernstein基函数建立了空间FFD参数化方法,并应用基于控制理论的连续伴随方程方法建立了目标函数对于待优化几何外形的梯度求解模式,将几何外形参数化方法、连续伴随方法以及CFD数值模拟技术相结合,研究、构建了适合跨声速机翼的气动外形优化设计系统。利用该系统对ONERA M6机翼及某型民用客机机翼进行了气动减阻设计,算例验证表明该方法应用于跨声速机翼气动减阻设计效果明显,并且能较好的保持几何表面连续性和光滑性。     

跨声速运输机机翼气动/结构优化平台AeroStruct的发展及应用

跨声速运输类飞机由于机翼展弦比大,使得气动加载下机翼变形量大,气动/结构耦合效应明显,因而开展耦合优化设计对提升飞机综合性能具有重要意义.本文研发了一种对该类机翼进行变可信度气动/结构耦合优化设计的自主软件平台(AeroStruct),气动数值模拟可选用N-S/Euler/全速势方程,结构数值模拟集成了结构有限元分析平...     

跨声速飞机高可信度多设计点多约束气动优化设计技术研究

本文目的是研究和开发工程实用的高可信度数值优化设计技术,并应用于先进跨声速飞机机翼的三维气动外形优化设计。本文综合应用了自由几何变形(FFD)几何外形参数化方法、弹簧比拟非结构网格变形方法、基于RANS方程的高可信度计算流体力学(CFD)分析方法、径向基函数(RBF)代理模型方法、粒子群寻优(PSO)方法等技术,分别对NASA CRM模型、航空工业设计的W2机翼模型展开了单设计点和多设计点的三维气动外形优化设计。通过对单设计点优化设计后的CRM翼身组合体、双设计点优化设计后的W2机翼模型气动外形进行详细的气动分析,发现优化后的CRM翼身组合体、W2机翼模型相对初始外形气动性能得到显著改进,证实了数值优化设计技术应用于先进跨声速飞机机翼三维气动外形设计的有效性。同时证实了开发的数值优化设计技术和工具的正确性和实用性。     

基于CFD／CSD的大展弦比机翼气动弹性分析

大展弦比飞机在飞行过程中受气动载荷影响,其大展弦比机翼产生弯曲和扭转变形,这种弹性变形严重影响飞机的飞行性能和飞行安全,不能将此种飞机机翼当作传统的刚性机翼进行气动分析。针对一大展弦比机翼,采用气动／结构耦合分析方法,利用计算流体动力学（CFD）软件CFX和计算结构动力学（CSD）软件ANSYS联合求解,研究了在不同载荷情况下大展弦比机翼静气动弹性变形对机翼气动特性的影响。结果表明,大展弦比无人机机翼受载变形后升阻比降低,升力下降明显,阻力略有上升,机翼翼尖容易失速。     

机翼静气动弹性数值模拟研究

通过求解基于三维非结构网格的欧拉方程计算机翼气动特性,采用结构柔度影响系数方法进行机翼静弹性变形的计算,利用三维非结构弹性网格技术进行几何外形变形下的网格修正,将以上三部分进行耦合迭代.实现了机翼的静弹性特性的数值模拟.采用开发的数值分析程序,进行了某支线飞机机翼静弹性特性的计算分析,计算结果合理,表明所发展的数值模拟方法可用于机翼静弹性气动特性的分析研究.     

考虑气动弹性影响的机翼气动外形设计研究

采用三维Euler方程为控制方程,耦合静气动弹性平衡方程,进行机翼静气动弹性数值模拟;在机翼静气动弹性分析的基础上,结合Takanashi余量修正方法对三维大展弦比机翼进行气动外形反设计,以确定机翼的型架外形.以某型支线飞机的大展弦比机翼为算例,进行了静气动弹性数值模拟和机翼型架外形设计研究,设计结果表明发展的机翼静气动弹性数值模拟和型架外形设计方法是合理可行的.     

Optimal thickness distributions of aeroelastic flapping shells

The severe weight limitations of flapping wing micro air vehicles necessitates the use of thin flexible wings, which in turn requires an aeroelastic modeling tool for proper numerical characterization. Furthermore, due to the unconventional nature of these vehicles, wing design guidelines for thrust and/or power considerations are not generally available; numerical design optimization then becomes a valuable tool. This work couples a nonlinear shell model to an unsteady vortex lattice solver, and then computes analytical design gradients: the derivative of aerodynamic force/power quantities with respect to a large vector of thickness variables. Gradient-based optimization is then used to locate the wing structure that maximizes the thrust, or minimizes the power under a thrust constraint, for a variety of shell boundary conditions. Changes in the topological features of the optimal wing thicknesses highlight important aeroelastic interactions that can be exploited for efficient flapping wings.     

基于CFD/CSD的非线性气动弹性分析方法

提出了一种基于计算流体力学/计算结构动力学(CFD/CSD)的非线性气动弹性分析方法,并应用于切尖三角翼的非线性颤振和极限环振荡(LCO)研究。该方法将非线性有限元(FEM)和CFD计算相结合,并辅以高精度的界面插值,能够分析结构和气动非线性共存的气动弹性问题。结构部分以四边形平板壳元为基础,采用更新的拉格朗日(UL)方法分析结构大变形引起的几何非线性问题。气动部分以Navier-Stokes(N-S)方程作为控制方程,采用CFD方法计算跨声速气动力。机翼的非线性颤振计算表明了方法的有效性。最后应用该方法研究了切尖三角翼的LCO现象,其计算精度明显优于已有结果。     

An efficient aerodynamic boundary element method for aeroelastic simulations and its experimental validation

An unstructured aerodynamic boundary element method employing panel clustering and iterative solution techniques for efficiency has been implemented. The solver is used in unsteady coupled simulations including applications in subsonic aeroelasticity. In comparison to existing linear methods, it allows more consistent modeling of complex three-dimensional geometries without requiring excessive mesh generation and computational effort. Due to a time-domain approach, simulations involving nonlinear structures or flight dynamics can be performed. A dynamic aeroelastic validation experiment is presented which shows that the solver predicts highly transient, damped aeroelastic motion with good accuracy.     

压气机转子叶片的气动弹性数值模拟

采用了交替迭代算法,对某压气机转子叶片进行了气动弹性数值模拟.自行开发了基于有限元的结构求解器用于结构动力学求解,引用他人开发的非定常流体求解器用于气动力的求解.结构求解器提供叶片的表面位移给流体求解器以改变流场,流体求解器提供气动载荷给结构求解器来计算叶片的变形,界面处理系统在这两个求解器之间进行信息传递.算例表明,这种交替迭代算法在气动弹性数值模拟中是可行的,可以得到叶片的瞬态响应,从而判断叶片是否发生颤振.      

压气机叶片流固耦合数值计算

采用流固耦合方法对压气机单排跨声叶片进行气动弹性数值模拟.首先对压气机流场进行三维定常求解,并与试验结果进行比对.在定常流场分析的基础上,进行流固耦合计算,采用非定常方法分别求解流体域Navier-Stokes(N-S)方程和固体域结构动力学方程.耦合过程中,流体域和固体域在物理边界上进行能量传递.计算结果表明:所采用的流固耦合数值方法用于判断叶轮机械叶片气弹稳定性是可行的,可以得到叶片的瞬态响应,从而判断叶片是否发生颤振.      

Control law design for transonic aeroservoelasticity

Existing computational transonic aeroservoelastic researches focus on directly coupling the structural dynamic equations, CFD solver and servo system in time domain, study the effect of the given feedback control laws on the responses of the aeroelastic system. These works have not involved the design of the flutter active control law. The non-linearity of transonic flow brings great difficulties to aeroservoelastic analysis and design. Recent research of the unsteady aerodynamic reduced order models (ROM) based on CFD provides a challenging approach for transonic aeroservoelastic analysis and design. Coupling the structural state equations with the aerodynamic state equations of the wing and the control surface based on the ROM, we construct a transonic aeroservoelastic model in state-space. Then the sub-optimal control method based on output feedback is used to design the flutter suppressing law. The study first demonstrates the open loop of the Benchmark Active Controls Technology (BACT) wing. The computational results of the CFD direct simulation method and the ROM analysis method are both agree well with the experimental data. Then both the closed loop time responses and the flutter results by ROM technique are compared with those of numerical aeroservoelastic simulation based on Euler codes to validate the correctness of the design method of the control law and aeroservoelastic analysis method. An increase of up to 20% of the speed index can be achieved by the control law designed by sub-optimal control method for this model.     

Aeroelastic prediction and analysis for a transonic fan rotor with the “hot” blade shape

This paper focuses on aeroelastic prediction and analysis for a transonic fan rotor with only its “hot” (running) blade shape available, which is often the case in practical engineering such as in the design stage. Based on an in-house and well-validated CFD solver and a hybrid structural finite element modeling/modal approach, three main aspects are considered with special emphasis on dealing with the “hot” blade shape. First, static aeroelastic analysis is presented for shape transformation between “cold” (manufacturing) and “hot” blades, and influence of the dynamic variation of “hot” shape on evaluated aerodynamic performance is investigated. Second, implementation of the energy method for flutter prediction is given and both a regularly used fixed “hot” shape and a variable “hot” shape are considered. Through comparison, influence of the dynamic variation of “hot” shape on evaluated aeroelastic stability is also investigated. Third, another common way to predict flutter, time-domain method, is used for the same concerned case, from which the predicted flutter characteristics are compared with those from the energy method. A well-publicized axial-flow transonic fan rotor, Rotor 67, is selected as a typical example, and the corresponding numerical results and discussions are presented in detail.     

Active aeroelastic control over a four control surface wing model

This paper describes the procedure implemented to design, develop and test an aeroelastic control system installed on a forward swept wing of the aeroelastic demonstrator X-DIA. A control method directly based on Nissim aerodynamic energy concept has been chosen. Two different modeling techniques have been adopted for the calculation of generalized aerodynamic forces, such as doublet lattice method and computational fluid dynamics and the obtained results are finally compared. The latter approach, applied to better estimate the control surfaces effectiveness, requires the capability to correctly model the control surface rotation and the grid deformation, usually addressed as non-trivial problems in CFD based aeroelastic analysis. A genetic algorithm optimization technique has been adopted to state and refine all the control gains.     

飞行器气动/结构多学科延迟耦合伴随系统数值研究

基于自主研发的大规模并行结构化网格雷诺平均Navier-Stokes（RANS）求解器PMB3D以及流固耦合代码FSC3D建立了飞行器静气动弹性数值模拟技术,进一步基于并行化伴随方程求解器PADJ3D,开展了Navier-Stokes方程与结构动力学方程耦合离散伴随的推导、构造。对各个学科伴随变量进行延迟处理,进行耦合伴随系统的解耦,学科之间的影响通过右端强迫项的形式在方程中体现,通过松耦合形式进行各个学科方程右端项数据传递,各个学科的伴随方程一定程度上能够相对独立,进一步实现了基于LDLT方法的结构伴随方程的高效求解;对典型客机柔性机翼进行梯度信息求解,并与考虑气动弹性影响的差分结果进行对比分析。数值模拟结果表明,延迟耦合伴随形式更有利于保持原有程序结构形式以及程序模块化,梯度计算精度完全满足优化设计需要,能够为柔性机翼飞行器气动/结构多学科优化设计提供研究基础与技术平台。     

Aeroelastic simulation of the first 1.5-stage aeroengine fan at rotating stall

A massive parallel aeroelastic simulation platform has been built to investigate the first 1.5-stage fan of an aeroengine at rotating stall. The Computational Fluid Dynamics (CFD) solver and Computational Structural Dynamics (CSD) solver are coupled directly by non-matching mesh interfaces. The unsteady rotor/stator interaction is solved by the Sliding Mesh Interface method. The original rotor blades are shrouded by the midspan shrouds. An unshrouded fan is also created to investigate the effects of the midspan shrouds. Both the shrouded fan and unshrouded fan have stable aeroelasticity at the designed state. At rotating stall, the stalled region rotates at 30% of the rotor speed on the absolute reference frame. The energy spectrum of the rotating stalled flow is measured quantitatively. It shows that the first two order excitations are much stronger than the higher order excitations. In the flow of rotating stall, the fifth backward travelling wave mode of shrouded fan is resonated by the fifth excitation of the rotational stalled flow because the rotational speed of the stalled region coincides with the modal rotational speed, while for the unshrouded fan, the first bending mode is resonated by the second excitation of the rotational stalled flow, forming two waves in the circumference of the annulus blades. At rotating stall, the vibration of the shrouded blades is still under control but the vibration of the unshrouded blades is diverged and out of control. A novel tool, i.e., resonance map, is proposed to predict the resonance. It provides a perspective to explain the effects of midspan shrouds at a theoretical level, and it would also be helpful in the structural design of blades.