Fully Coupled Aeroelastic Analyses of Wing Flutter towards Application to Complex Aircraft Configurations

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Abstract
Aeroelastic instabilities are some of the critical issues affecting the reliability and safety of military and commercial aircraft. In this study, a coupled computational fluid dynamics and computational structural dynamics (CFD-CSD) capability was developed for transonic aeroelasticity analysis in the time domain. To expedite application of the CFD solver for aeroelastic simulations, a morphing technique was developed for mesh deformation in CFD, eliminating successive calling for a grid generator. The CFD solution was then tightly coupled with CSD by a fully implicit method. The three-dimensional (3D) CSD solver is a finite element model solving 3D elasticity equations using second-order tetrahedron elements. The coupling between aerodynamic loads and elastic deflections is developed based on spline matrices using radial basis functions. The results from the coupled CFD-CSD simulations for a two-dimensional (2D) rigid airfoil and the 3D elastic AGARD 445.6 wing are in reasonable agreement with the experimental and computational data available in the public domain. Also, the results reported in this paper highlight the importance of viscous effects for Mach numbers at and above the transonic dip, thereby highlighting the necessity to use a Navier-Stokes-based CFD solution as opposed to Euler. It is shown that the use of 3D elasticity enables the consideration of complex aircraft configurations such as with underwing stores, which can then be coupled in aircraft flutter simulations and sensitivity studies.

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