Abstract: A numerical method is presented for analyzing the nonlinear flutter characteristics of the wings with separation at high angles of attack. The nonlinear aerodynamic forces are linearized by using the describing function method. Then, the conventional v-g method can be used to solve the structural dynamic equations of the wings. To determine the ratios between the amplitudes of different modes, an iterative procedure is intro-duced.Examples of calculation show that the present numerical method behaves very good convergence characteristics. Generally, only three or four steps are needed to obtain a satisfactory results. It is found from the numerical results that the critical flutter speed of the wings decreases when the angles of attack increases, and the results are agree well with those of the Time Integration Method and experimental data. Besides, the present method takes much less computational time than the Time Integration Method, and it can be easily used for different systems with nonlinear property in practical engineering.

Key words: nonliear flutter, numerical method, separated flow, high angle of attack