大展弦比复合材料机翼非线性气动弹性特征与颤振研究

For a wide-bodied airplane, its high-aspect ratio wing is a light-weight flexible structure that undergoes large deflection and torsion under aerodynamic force, and the deflection and torsion of the wing presents nonlinear characteristic obviously. This project is focused on the investigation of nonlinear aero-elastic property and flutter of the high-aspect ratio composite wing. Integrated into account the geometrical nonlinearity of the structure, the aerodynamic nonlinearity and the material anisotropy, the nonlinear dynamical model for coupling vibrations of a torsional and flexible beam is established for the high-aspect composite wing which is considered to be a slender cantilever beam with variable cross-sections. The aerodynamic force is formulated by the ONERA-Edlin model, the linear part of which can be approximated as the model from Theodorsen unsteady aerodynamic theory. According to the static equations of the high-aspect ratio wing, a simple and effective approach is developed to solve the static equilibrium position of the wing, and the corresponding experiments will be conducted. The perturbation method is adopted to set the vibration equations of the wing nearby the equilibrium position, and the natural vibration property is investigated and its relevant modal experiment is conducted accordingly. Based on the natural property analysis, the modern nonlinear dynamic theory is employed to predict the flutter speed of instability and the nonlinear flutter boundaries of instability, and to study the limit cycle vibration after the flutter instability and its bifurcation problem. The achievements acquired here may provide basis for the design of structure and aerodynamic configuration of the high-aspect ratio wing for the large wide-bodied airplane.

针对大飞机大展弦比机翼结构重量轻、柔性大，在气动载荷作用下会产生显著的弯曲和扭转变形，并呈现出明显的几何非线性特征的问题，开展大展弦比复合材料机翼非线性气动弹性特征与颤振研究。综合考虑结构几何非线性、气动非线性和材料各向异性对机翼运动状态的影响，将复合材料机翼考虑成变截面细长梁，建立其弯扭耦合振动的非线性动力学模型；气动力则采用ONERA-Edlin模型，其线性部分可以近似成非定常的Theodorsen模型。在此基础上，寻求简捷有效的方法以求解机翼的静平衡位置，并进行实验验证；采用小扰动分析的方法得到机翼在平衡位置附近的振动方程，研究其固有振动特性，并进行相关的模态试验；在固有特性分析的基础上，预测机翼的颤振失稳速度和非线性颤振失稳边界，研究颤振失稳后的极限环振动及其分岔等问题为大。取得的成果将为大飞机的结构与气动设计提供技术支持。

大展弦比机翼由于可以降低诱导阻力，广泛地应用在飞机设计中。由于其细长的几何特征，在计算机翼的变形时需要考虑机翼的几何非线性。本项目针对大展弦比复合材料机翼，研究了其非线性气动弹性特性，并讨论了其非线性颤振特征。利用能量等效方法，将复合材料细长机翼抽象为梁模型。基于机翼的梁模型，根据机翼在变形时大转动小应变的特征，建立了机翼的非线性动力学方程。对于作用于机翼上的气动力，采用非线性非定常的ONERA气动力模型进行求解，并利用Duhamel积分法在对ONERA模型的求解方式进行了优化。结合机翼的非线性动力学方程与ONERA模型，建立了机翼的气动弹性方程。利用所建立机翼气动弹性方程，探索了机翼的静平衡位置求解方法，对机翼在静平衡位置附近的动力学特性进行了探讨。通过数值仿真，得到了机翼的非线性颤振临界速度与颤振后响应特征。此外，考虑到实际应用中的机翼常常带有外挂装置，将分析方法拓展应用于带外挂细长机翼的非线性气动弹性性质研究。探讨了外挂的位置、连接的刚度以及连接处的间隙特征对机翼外挂系统的气动弹性特征的影响，发现外挂与机翼的间隙连接特征将会诱发机翼外挂系统发生亚临界Hopf分叉。本项目的相关结果有望用于大展弦比机翼以及带外挂细长机翼的设计。