基于 CFD/CSD 耦合的结构几何非线性静气动弹性数值方法研究

摘要

Flexible aircrafts tend to undergo large deformations under aerodynamic forces.As a result,structural geometric nonlinearity occurs.The linear small-deformation theory cannot provide accurate results for analyzing static aeroelasticity.Fluid structure-coupling method based on three-dimensional RANs,Navier-Stokes equations and nonlinear static equation is used for static aeroelastic analysis with structural geometric nonlinearity.The mentioned approach adopts the nonlinear incremental finite-element method to solve nonlinear static equations with assembled structure stiffness matrixes.Moreover,RBF method is used for data interpolation and mesh deformation.Based on the multi-material wing finite-element model,the numerical simulations were made to analyze the static aeroelastic behavior.Comparisons of twist angles,vertical displacements,spanwise displacements and life coefficients between linear and nonlinear structures were made.The results show that geometric nonlinearity cannot be neglected for predicting accurate static aeroelastic behavior for large,flexible airplanes.%柔性飞行器在气动力作用下会发生大变形，产生结构几何非线性，线性小变形方法难以获得准确的气动弹性分析结果。基于 RANs 的三维 N －S 流场控制方程耦合非线性结构静力学方程时域分析方法，用于考虑结构几何非线性的静气动弹性分析。该方法在结构静力学方程求解上采用非线性增量有限元方法进行迭代求解，考虑结构刚度矩阵随结构位形的变化，采用径向基函数方法实现气动／结构界面的数据交换和动网格变形。在建立某型宽体客机复材机翼三维有限元模型的基础上，对其静气动弹性进行了数值仿真，分析了线性结构和考虑结构几何非线性的结构在静气动弹性作用下翼面扭转、展向位移、垂向位移以及升力系数等物理量。算例结果表明，与线性结果相比，非线性结构由于结构几何非线性的影响，在展向和垂向变形上两者存在显著差异。为准确进行柔性结构的气动弹性分析，必须考虑结构几何非线性的影响。