基于气动力降阶模型的跨音速气动弹性稳定性分析

基于离散型输入输出差分模型,运用非定常CFD方法训练信号,然后运用最小二乘方法进行参数辨识,得到降阶的非定常气动力模型,再将该离散差分模型转换为连续时间域内的状态方程。耦合气动状态方程和结构状态方程,得到耦合系统的气动弹性状态方程。求解不同动压下状态矩阵的特征值,根据根轨迹图分析系统的稳定性特性。分析结果与直接耦合CFD/CSD方法结果相吻合,可以计算跨音速非线性气动弹性问题。其计算效率比直接耦合CFD/CSD方法提高1~2个数量级。针对Isogai wing在跨音速出现的S型颤振边界进行了较为细致的分析,阐述了该现象是由于系统诱发颤振的分支随着速度(来流动压)的提高而发生转移所导致的。

Transonic aeroelastic analysis basing on reduced order aerodynamic models

Reduced order modeling(ROM) is a conceptually novel and computationally efficient technique for unsteady aerodynamics computation.Using input-output difference model and least squares method,ROM of unsteady aerodynamic loads based on unsteady Euler codes is constructed.The input-output difference model is then turned into continuous-time model in state space.Coupled structural state equations and aerodynamic state equations,state equations of transonic aeroelastic system are constructed.By solving the eigenvalues of the state matrix at a series of dynamic pressure,the aeroelastic stability is analyzed with the roots loci map.The ROM based results agree with those by solving CFD/CSD directly coupling method.It proves that this method is available to solve the transonic aeroelasticity.An interesting S-type flutter boundary which due to the system having more than one neutral point at the transonic Mach number range is analyzed particularity.It is just because the flutter branch changes with the increasing speed(dynamic pressure).