Aeroelastic modelling of aircraft empennage buffet

Abstract

The airframes of high performance aircraft, such as the F/A-18, have suffered from aeroelastic tail buffet problem for many years. This problem is inherent to vortical flows used to generate lift at high angles of attack as they tend to break down causing empennage severe dynamic loading and its premature fatigue failures. The challenges associated with the empennage buffet problem vary from prediction of the nonlinear separated vortical flows about complex configurations to the coupled interaction between the flow and the dynamic response of the tail structure. The paper describes he development and validation of aeroelastic model for the prediction of empennage buffet due to bursting vortices. The multidisciplinary problem of tail buffeting is solved accurately in time using an unsteady vortex model for prediction of aerodynamic loads and coupled aeroelastic equations for the bending and torsional deflections of the tail which are resolved using the Galerkin method. A dynamic aeroelastic analysis of empennage buffet is performed for a generic delta-wing, twin vertical-tail configuration at high angles of attack. Results of flow simulation indicated that the aeroelastic model is able to predict major unsteady features of the vortex induced buffet loads and the resulting coupled fluid-structure interaction.