【作者】 崔鹏；

【导师】 韩景龙；

【作者基本信息】 南京航空航天大学 ， 固体力学， 2011， 博士

【摘要】 机翼气动弹性设计是飞行器研制和改型的关键内容。跨音速区存在颤振边界的“跨音速凹坑”，是气动弹性稳定性问题最为严重的区域。大变形改变了线性结构特性，是引起机翼极限环振荡（LCO）的重要因素。跨音速、大变形等非线性使得相应的计算分析和物理机理趋于复杂，由此展开的非线性气动弹性计算研究成为当前的理论热点和分析难点。提高跨音速气动力分析效率以满足工程设计需求，也是气动弹性领域的前沿课题。本论文紧扣上述研究进展，在高精度气动弹性计算和耦合界面插值方法、气动力降阶模型及高效颤振分析、典型机翼的气动弹性特性研究等方面开展了一些探索和应用性工作。发展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，并用于涉及大变形结构的跨音速LCO计算研究。1）建立了厚薄通用的四边形板单元和高性能的四边形膜单元，二者组合构成线性平板壳元分析；应用更新的拉格朗日（UL）格式，推导了适用于大变形、大转动、小应变的平板壳元几何非线性列式，并采用Newmark时间积分方法实现非线性动力分析。2）发展了一种新型的局部形式界面插值方法，利用薄板样条插值位移，相应函数的定义域选取局部形式。给出定义域的高效设置过程并由能量守恒原则推导出气动力的插值矩阵。3）以Euler方程作为流动控制方程，采用格心式有限体积法和双时间步长推进格式分别进行流场的空间和时间离散，且按照分区并行方式加速CFD计算。结构分析和界面插值模块以子程序形式和CFD求解器进行联接，进而形成完整的流固耦合分析能力。机翼的跨音速颤振计算表明了所建CFD/CSD方法的有效性。应用该方法研究了切尖三角翼的大幅LCO现象，其计算精度明显优于已有结果。实现了基于CFD技术的非定常气动力ARMA降阶模型（ROM），并开展跨音速颤振问题的高效计算研究。针对“3211”型多步训练输入，借鉴CFD/CSD方法完成关键的ROM训练过程。基于MATLAB系统辨识工具箱进行ARMA模型的参数估计和模型验证，并耦合结构模态叠加法构成颤振和伺服颤振分析。标准翼型和机翼的跨音速颤振计算体现了ARMA/ROM技术的精度和效率。应用该方法进行BACT二元翼段的伺服颤振分析，适当的舵面主动偏转有效提高了跨音速颤振速度。基于通用流固耦合分析程序，对新型运输机机翼和切尖三角翼模型的跨音速颤振和LCO特性进行了计算研究。运输机基本机翼的颤振结果接近于试验值，相应LCO现象是由大幅激波运动所引起的。翼梢小翼和C型翼梢对基本机翼的颤振特性产生了明显不利影响。分析中还采用虚拟质量方法分离了翼梢装置质量和气动力的作用。切尖三角翼LCO的计算和试验值吻合良好。小动压情况下，LCO主要由结构几何非线性引起；大动压情况下，LCO的产生受到结构几何及材料非线性的共同作用；源于塑性的材料非线性导致LCO幅值的急剧增大。首次发现材料非线性对气动弹性特性产生了显著影响。最后对本论文的工作进行总结，并展望了未来的研究方向。更多还原

【Abstract】 Aeroelastic design of the wings is one of the crucial contents of aircraft development and retrofit. The transonic flight region presents the most serious conditions for aeroelastic instability since the wing experiences a sharp drop of the flutter behavior (transonic dip). The large deflection normally induces obvious changes in the characteristics of original wing structure and turns into an important aspect in the occurrence of limit-cycle oscillation (LCO). Some nonlinear factors, such as transonic flow and large deflection, are usually involved in the wing aeroelasticity, and make the associated computational analyses and physical mechanism be more complicated. Therefore, numerical investigation on nonlinear aeroelasticity currently becomes the theoretic hotspot and research challenge in international community. Another leading subject in aeroelasticity, which could significantly improve the efficiency of aerodynamic analysis in the transonic region, occurs to meet the demand of engineering design. This dissertation sticks to research progresses as highlighted above and performs relevant explorations and applications that will include:high precision aeroelastic analysis and interface interpolating approaches, reduced order model for the aerodynamics and its utilization in efficient flutter prediction, and aeroelastic mechanism studies of two typical wings.A nonlinear aeroelastic analysis approach using computational fluid dynamics/computational structure dynamics (CFD/CSD) is developed and applied to the study of transonic LCO that involves large structural deflection,(ⅰ) A quadrilateral flat-shell element is established, and it consists of a plate part for thick/thin plate analysis and a membrane part with high performance. Based on updated Lagrange (UL) scheme, geometrically nonlinear formulation is derived for the modeling of the structure with large deflation, large rotation and small strain. Newmark integration method is used for the time advancing of structural dynamics.(ⅱ) A new type interface interpolating method with the character of local form is presented and applied to fluid-structure interaction (FSI) problem. Thin plate spline is selected to fitting the function for displacement interpolation, and relevant domain is set effectively in a local form. Aerodynamic interpolating matrix is derived according to the energy conservation principle.(ⅲ) The transonic flow is governed by the Euler equations. A cell-centred finite volume approximation, in conjunction with the implicit dual time-stepping scheme, is used to discretize the governing equations. Also CFD calculation is conducted by parallel computing. The modules of nonlinear structure analysis and interface interpolation present as the subroutine of CFD solver, thus producing a FSI analysis capability. The transonic flutter simulation indicates the validity of presented CFD/CSD approach. Meanwhile, large-amplitude LCO of a cropped delta wing is studied, and its analysis precision is obviously better than existing results.An ARMA-based reduce order model (ROM) of unsteady aerodynamics is developed on the basis of CFD technique and system identification theory. The aerodynamic ROM is applied to efficient numerical study on transonic flutter problem. As a key aspect of ROM, the training procedure that involves generalized "3211" type input is formally conducted by the use of CFD/CSD. Then system identification toolbox in MATLAB environment is used for the estimation of system parameters and the verification of built model. The coupling of aerodynamic ROM and structural modal superposition method constitutes the flutter and servo-flutter analysis capability. Transonic flutter simulations of NACA0012airfoil and AGARD445.6wing indicate the precision and efficiency of the proposed ARMA/ROM. Besides, servo-flutter analysis of BACT airfoil in the transonic region is conducted by the ROM method, and the results indicate that active deflection of control surface heightens the flutter speed efficiently.Numerical investigations of transonic flutter and LCO behavior of new transport-type wing and cropped delta wing models are performed based on the general purpose FSI solver. Flutter characteristics of the basic transport wing numerically approach to the existing experimental values, and relevant LCO phenomenon is caused by the large-amplitude shock-wave motion. Contrastive analyses indicate that the winglet and C-type wingtip produce remarkable adverse effects on flutter characteristics of transport wing. Also the aerodynamic and mass effects of wingtip devices are identified separately by way of setting virtual mass. The simulation of the LCO of cropped delta wing correlates well with the experimental measurement. For lower dynamic pressures, geometric nonlinearity provides the proper mechanism for the development of the LCO. For higher dynamic pressures, material nonlinearity that arises from plasticity leads to a rapid rise in the LCO amplitude. This study demonstrates that material nonlinearity could have a remarkable influence on the aeroelastic behavior in some specific situations.Finally, the accomplished work of this dissertation is summarized, and the prospect of further research is also discussed.更多还原