Abstract:In order to quickly find the flutter boundary of a nonlinear aeroelstic system based on CFD/CSD. This paper use Lyapunov stability theory to analyses the stability of nonlinear fluid-structure coupling system. Firstly, through a small perturbation theory, a linearized state space model is obtained based on nonlinear fluid-structure coupling system; then a reduced order model is got by reduce the high dimensional linearized model through a POD (proper orthogonal decomposition) method. According to all the eigenvalues of the ROM system, the stability of the original nonlinear system can be determined. Lyapunov stability theory is mainly aimed at the nonlinear system, and the POD method is adopted to realize the process. Different from other stability methods, the mathematical theory is reflect the stability of the original nonlinear fluid-structure coupling system. As the POD/ROM used in this paper is based on the CFD fluid field, so it can better reflect the internal characteristics of the original nonlinear coupling system. Numerical cases including two dimensional aerofoil and three dimensional wing’s models are tested to validate the accuracy of the stability method. The results show that in subsonic domain, the stability is determined by structural model; But in transonic and supersonic domain, the aeroelastic stability is mainly effected by fluid characteristic.
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