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

In this paper, the aeroelastic model of a 3-D box wing configuration is derived using a semi-analytical approach and its aeroelastic behavior is studied. Modeling and aeroelastic analysis of box wings were carried out in previous published papers by 2-D models or professional software. Here, the box wing structure is considered as two front and rear wings connected by a winglet and plunge and pitch motions are considered for each wing. The winglet is modeled by two longitudinal and torsional linear springs. The governing equations are extracted via Hamilton's variational principle. In order to apply the aerodynamic force and moment, Wagner unsteady model is considered. For the purpose of model validation, the box wing flutter speed and frequency are compared with MSC NASTRAN software results and good agreement is reported. The effects of different design parameters such as sweep angles and the winglet rigidity on the stability boundary 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 BWA stability boundary.