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Gridgen is employed for static multi-block grid generation. A rapid deforming technique is employed for dynamic grids. Flutters are numerically analyzed in the time domain with a coupled solution of unsteady Euler equations and structural equations of motion. Based on variable stiffness method of transonic flutter analysis, a time-domain method of transonic flutter analysis with multi-directional coupled vibrations is develpoed. For completeness, flutter characteristics of a wing model with winglets and an aircraft model with external stores are numerically analyzed.

The paper is concerned with a method of fast flutter boundary prediction by a reduced order modeling technique based on system identification. The method uses a full-order model to obtain ARMA training data and projects on the structural modal and the response of the modal amplitudes. These training data are used to construct a continuous time state space model of the closed-loop aeroelastic system, and the continuous state space model is used to determine the flutter boundary. The flutter boundary and flutter frequency of AGARD445.6 wing are simulated. The calculation results of the ARMA/ROM methods and full-order methods are compared with the experimental results. Applications to high aspect ratio wings are also presented. The results show that the ARMA/ROM method is efficient and accurate. This method can be used to simulate and forecast the flutter boundary of aircraft quickly.