Modeling and Flutter Analysis of a 3D Box-Wing using Wagner Unsteady Aerodynamic Model

In this paper, a three dimensional model of a box wing configuration is derived by a semi-analytical approach and the aeroelastic behavior is studied. So far, the flutter characteristics have been studied on the typical wing sections or via a whole lot more time and cost in the professional software. The winglet is modeled by two longitudinal and torsional springs and in order to simulate the effect of the winglet on the dynamic behavior, two ends of the springs are placed on the elastic axis of the sections. The governing equations are extracted via Hamilton's principle and in order to apply the aerodynamic forces, Wagner unsteady model is considered. To transform the linear partial integro-differential equations into a set of ordinary differential equations, mathematical techniques are employed. For the purpose of validation, the flutter values of the box wing are obtained by MSC NASTRAN and the proposed numerical procedure. The effects of the sweep angles and the winglet rigidity on the flutter are investigated. The results reveal that increasing the sweep angles and the chord ratio, enhances the flutter speed, remarkably. Furthermore, increasing the torsional rigidity of the winglet is more significant than the longitudinal rigidity on the flutter.