Nonlinear aeroelastic stability analysis based on CFD reduced order models

In order to quickly find the flutter boundary of a nonlinear aeroelstic system based on CFD/CSD, this paper used the Lyapunov stability theory to analyze the stability of a nonlinear fluid-structure coupling system. Firstly, a linearized state space model was obtained based on a nonlinear fluid-structure coupling system through the small perturbation theory; then a reduced order model was achieved by reducing the high dimensional linearized model through a POD(proper orthogonal decomposition) method. According to the eigenvalues of the ROM system, the stability of the original nonlinear system could be determined. Lyapunov stability theory was mainly aimed at the nonlinear system, and the POD method was adopted to realize the process. Different from other stability methods, the mathematical theory reflected the stability of the original nonlinear fluid-structure coupling system. As the POD/ROM used in this paper was based on the CFD fluid field, so it could better reflect the internal characteristics of the original nonlinear coupling system. Numerical cases including two-dimensional aerofoil and three-dimensional wing's models were used to validate the accuracy of the stability method. The results show that in the subsonic domain, the stability is determined by the structural model; but in transonic and supersonic domain, the aeroelastic stability is mainly affected by fluid characteristics. © 2016, Editorial Office of Journal of Vibration and Shock. All right reserved.