Application of Transient Aerodynamics to the Structural Nonlinear Flutter Problem

A method is presented for the transient, time domain solution of the structural nonlinear flutter problem. Excellent agreement between the linear standard reduced frequency and transient flutter solutions is obtained for both a simplified two-degree-of-freedom system with Theodorsen two-dimensional incompressible unsteady aerodynamics and a multiple-degree-of-freedom system with three-dimensional compressible unsteady aerodynamics. The transient solution is then utilized to develop an approach for precisely including the effects of structural nonlinearities. This approach provides the capability of using the same detailed structural and aerodynamic models for both linear and nonlinear analyses.