• wing
• transonic
• instability
• flutter
• dynamic
• buffet
• aeroelastic

This thesis concerns the study of planform influence on the dynamic instability of wings in the transonic regime. A comparison between a traditional swept wing and a curved planform wing was carried out by means of Fluid structure interaction analyses (also known as 2-ways FSI ) performed with ANSYS Workbench Rel.15 commercial software. Preliminary CFD analyses were executed on the rigid models of the two wings in order to compare their aerodynamic performances for cruise Flight conditions (h = 10000 m, M = 0:85). These analyses confirmed that, under the assumption of rigid models, the in-plane curvature of the wing reduces the aerodynamic drag in the transonic regime where the non-uniform distribution of the sweep angle of the curved wing leads to a reduction of the wave drag effects. Detailed FEM models of the two half-wings (skin, stringer, ribs and spars) were modelled by means of CATIA V5 R20 and ANSYS Mechanical, also taking into account fuel, engines and gravity effects. Modal analyses were carried out to study the distribution of the structure natural frequencies and the shape of the associated normal modes. These analyses allowed to adjust the first torsion frequency of clamped half wing by means of a fictitious distribution of moment of inertia (applied at the tip of the two wings) and to properly set the structural damping. The corresponding CFD models were generated by means of ICEM CFD where fully hexahedral meshes were obtained to be suitably used in ANSYS Fluent. The FSI analyses were carried out by coupling the mechanical solver, ANSYS Mechanical APDL, with the CFD solver, ANSYS Fluent. The results of these analyses confirm that, for a curved planform wing, the dynamic instability condition occurs at higher flight speed if compared to a traditional swept wing with similar profiles, aspect ratio, angle of sweep at root, similar structural layout, and similar mass. A curved wing lifting system could thus improve the performance of future aircraft.