Aeroelastic Analysis of Highly Flexible Wings with Linearized Frequency-Domain Aerodynamics

Abstract

Aeroelastic flutter analysis of configurations with geometric structural nonlinearities typically is done with time-domain analysis. The results from this process are computationally expensive and can yield cumbersome results that may be difficult to manage and interpret. Compared to time-domain methods, frequency-domain flutter analysis can provide additional insight into the characteristics of a flutter instability. By linearizing the aeroelastic problem about the nonlinear equilibrium state, this work applies frequency-domain aeroelastic analysis to the Pazy wing, the subject of the Large Deformation Working Group in the Aeroelastic Prediction Workshop. Generalized aerodynamic forces (GAFs) are computed with both a doublet-lattice method and a computational fluid dynamics solver at a range of reduced frequencies as well as a range of dynamic pressures to account for the dependence of the mode shapes on the nonlinear equilibrium state. These GAFs are used in a flutter solver, which is modified to handle the nonlinear dependence of the stiffness matrix and GAFs on the dynamic pressure. The hump mode flutter mechanism predicted by the linear doublet-lattice method is found to underpredict the severity of the instability, relative to the computational fluid dynamics-based tool, though the overall static and dynamic aeroelastic mechanisms predicted by the two fidelities are similar.