带外挂后掠机翼极限环颤振的分析与实验研究

从理论及实验两方面，研究了带外挂后掠机翼的极限环颤振分叉现象，得到了稳定、半稳定及不稳定极限环。理论分析采用谐波平衡法，并通过在时域拟合非定常空气动力后，用数值积分法对所得结果进行了比较。风洞实验结果验证了理论分析结果的正确性。     

Genetic Algorithm Optimisation of Mathematical Models Using Distributed Computing

In this paper, a process by which experimental, or historical, data are used to create physically meaningful mathematical models is demonstrated. The procedure involves optimising the correlation between this real world data and the mathematical models using a genetic algorithm which is constrained to operate within the physics of the system. This concept is demonstrated here by creating a structural dynamic finite element model for a complete F/A-18 aircraft based on experimental data collected by shaking the aircraft when it is on the ground. The processes used for this problem are easily broken up and solved on a large number of PCs. A technique is described here by which such distributed computing can be carried out using desktop PCs within the secure computing environment of the Defence Science & Technology Organisation without compromising the PC or network security.     

面向飞机颤振模型设计的结构拓扑优化研究

飞机颤振模型的结构设计是一个以固有频率为目标、兼具结构相似要求的反求问题。针对拓扑优化方法只能得到不规则孔洞而无法满足模型相似要求的难题,提出了一种含规则几何约束的结构拓扑优化方法,并将基于单元材料特性更改的方法与双向渐进结构法相结合,利用敏度再分配方法,实现了以频率为目标、具有规则孔洞的结构拓扑优化,且有效抑制了优化中的棋盘格式和局部模态现象。某飞机机身壁板的优化算例证明,该方法能设计出具有给定固有频率的结构,并使之与原机身具有一定的结构相似性。     

Flutter of delaminated three-phase nano-composite beam-plates

ABSTRACT

In this article the supersonic flutter instability of delaminated carbon nanotube reinforced three-phase composite plate is investigated. The classical laminate plate theory and piston aerodynamic theory are developed to construct the governing equation of delaminated three-phase nano-composite plates. The effective material properties are obtained using Halpin-Tsai relation and rule of mixture. The effects of different parameters including carbon nanotubes (CNTs) weight percentage, fiber volume fraction, CNTs aspect ratio and different fiber orientation on flutter pressure of delaminated reinforced composite plates are considered. According to the results, appending small amount of CNTs (4% wt) into the matrix epoxy can improve the flutter critical pressure by 33% in comparison to the neat matrix epoxy.     

暂冲式高速风洞连续变速压颤振试验流场控制系统研究

相对于阶梯变速压颤振试验,连续变速压颤振试验具备更高的可靠性和效率,可以为先进飞行器的颤振边界预测及颤振特性分析提供更为安全可靠的技术支撑。为实现定马赫数连续变速压颤振试验技术,设计了连续变速压流场控制系统,通过引入解耦控制与专家PID控制优化了控制效果。风洞验证试验结果表明,该系统具有良好的控制效果,可满足定马赫数连续变速压流颤振试验对风洞流场控制指标的要求。     

体自由度颤振飞行试验的边界预测方法研究EI北大核心CSCD

体自由度颤振频率低,参与颤振的模态频率在亚临界状态往往已经极为接近,加之基于大气紊流激励的颤振飞行试验数据信噪比通常较低,增加了体自由度颤振飞行试验模态辨识以及颤振预测的难度。对此提出了一种基于Matrix Pencil模态辨识方法的体自由度颤振预测方法。通过随机减量技术对输出响应信号进行系集平均,得到随机衰减标记;运用Matrix Pencil方法拟合随机衰减标记获取模态参数,并通过频率和阻尼稳定判据筛选真实模态,再通过阻尼比与颤振稳定性判据变量外插获取颤振点。通过对仿真数据与试验数据的应用,可得到以下结论:Matrix Pencil模态辨识方法能有效辨识密集的颤振模态,并获得清晰的模态辨识稳态图。基于阻尼比及稳定性判据变量外插获得的颤振预测结果较为合理,其中DTFM(Discrete-Time Flutter Margin)判据变量的下降趋势更明显,外插结果与试验值更接近。该方法适用于体自由度颤振飞行试验的亚临界预测。     

Observer‐based synthesis of linear parameter‐varying mixed sensitivity controllers

This article presents a computationally efficient way of synthesizing linear parameter‐varying (LPV) controllers. It reviews the possibility of a separate observer and state feedback synthesis with guaranteed performance and shows that a standard mixed sensitivity problem can be solved in this way. The resultant output feedback controller consists of an LPV observer, augmented with dynamic filters to incorporate integral control and roll‐off properties, and an LPV state feedback gain. It is thus highly structured, which is beneficial for implementation. Moreover, it does not depend on scheduling parameter rates regardless of whether parameter‐dependent Lyapunov matrices are used during synthesis. A representative control design for active flutter suppression on an aeroelastic unmanned aircraft demonstrates the benefits of the proposed method in comparison with state‐of‐the‐art LPV output feedback synthesis.     

基础激励作用下悬臂输流管的振动实验研究

通过实验的方法对基础激励作用下悬臂输流管的动力学行为进行振动测试分析.设计并搭建了悬臂输流管振动测试的实验平台,深入研究了悬臂输流管在不同流速及不同参数情况下的振动行为,分析了在基础激励作用下,悬臂输流管振幅的变化规律.结果表明,悬臂输流管的物理参数对悬臂输流管发生颤振失稳的临界流速有着极其显著的影响,在基础激励作用下,悬臂输流管的振幅明显增大,并且当激振力频率接近悬臂输流管的固有频率时,输流管的振幅达到最大.     

考虑航天器舱体—附件耦合效应的热颤振准则

考虑具有端部附加质量的柔性附件及其和舱体的耦合效应,本文系统地推导出了一个带柔性附件的航天器热颤振准则,并用有限元程序进行了模拟校验.该准则揭示了柔性附件和舱体的质量特性和系统热诱发振动稳定性之间的关系.当舱体的质量特性远大于柔性附件的质量特性时,该准则就退化为悬臂柔性附件的热颤振准则.     

基于定常吸气方式的大跨桥梁风致颤振抑制方法

以改善桥梁断面空气动力特性,提高大跨桥梁风致颤振稳定性为目的,提出了基于绕流控制原理的定常吸气方法。以我国虎门大桥为研究对象,采用基于计算流体动力学的数值方法模拟来流风与桥梁断面定常吸气共同作用下的桥梁断面绕流风场。采用Scanlan颤振分析方法分析了该桥梁在定常吸气作用下的颤振稳定性。计算结果表明,吸气作用使主流更加贴近壁面,降低了模型扭转运动下的气动扭矩,定常吸气提高了大跨桥梁的风致颤振稳定性。