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Development of a coupled fluid/structure aeroelastic solver with applications to vortex breakdown-induced twin tail buffeting
Simulation of tail buffet is studied for several delta wing-vertical tail configurations. Flow conditions are chosen such that the wing primary-vortex cores experience vortex breakdown and the resulting turbulent wake flow impinges on the vertical tail. The dimensions and material properties of the vertical tails are chosen such that the deflections are large enough to insure interaction with the flow, and the natural frequencies are high enough to facilitate a practical computational solution. This multi-disciplinary problem is solved sequentially for the fluid flow, the elastic deformations and the grid displacements. The flow is simulated by time accurately solving the laminar, unsteady, compressible, Navier-Stokes equations using an implicit, upwind, flux-difference splitting, finite volume scheme. The elastic vibrations of the tail are modeled by coupled bending and torsion beam equations. These equations are solved accurately in time using the Galerkin method and a five-stage, Runge-Kutta-Verner scheme. The grid for the fluid dynamics calculations is continuously deformed using interpolation functions to smoothly disperse the displacements throughout the computational domain. Tail buffet problems are solved for single tail cases, twin F/A-18 tail cases and twin highly swept generic tail cases. The use of an apex flap for buffet control is also computationally studied. The results demonstrate the effects of inertial structural coupling, Reynolds number, aft fuselage geometry and spanwise tail location on the tail buffet loads and response. Favorable comparisons with experimental data indicate that the present aeroelastic method is well suited to providing qualitative insight into the tail buffet problem, as well as quantitative data for refined long duration simulations.