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Gu Y.,Northwestern Polytechnical University | Gu Y.,Institute of Structural Dynamics and Control | Yang Z.,Northwestern Polytechnical University | Yang Z.,Institute of Structural Dynamics and Control
AIAA Journal | Year: 2012

The g method equation is reformulated and solved by a modified p-k method with damping iteration and implications of the second order of damping term are also drawn. Linear unsteady aerodynamics computed by panel method in the frequency domain or by linearized frequency-domain CFD results are assumed. To adapt the standard p-k method to the dependence of matrix A on damping, it is suggested to include the damping iteration in addition to the reduced-frequency iteration in the solution algorithm of the standard p-k method. The generalized mass, stiffness, and aerodynamic matrices are obtained from ZAERO output file. The comparison of the flutter characteristics between the modified p-k method and the g method show a good agreement between these methods. The V-g and V-f diagrams seem to be almost identical between both approaches. Source


Gu Y.,Northwestern Polytechnical University | Gu Y.,Institute of Structural Dynamics and Control | Yang Z.,Northwestern Polytechnical University | Yang Z.,Institute of Structural Dynamics and Control
Journal of Aircraft | Year: 2012

This chapter examines the application of pattern search in worst-case flutter solution. The aeroelastic model with purely real valued uncertainties is reviewed, and the promising pattern search algorithm is introduced and applied to solve this type of optimization problem by taking the worst- or best-case flutter speed or aeroelastic damping or frequency as the objective function and taking the structured uncertainty operators as design variables. It is a valuable feature of the present approach because such correlation may enhance the confidence on the results especially when there lacks available validation methods. It should be noted that, as the number of design variables increases about five times compared with the last case, the CPU time cost is still within 10s for computing the lower and upper bounds of damping/frequency for each branch at a given airspeed, while the iterations required are typically within 350 and the objective function evaluation count is about 3000. Source

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