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Two different nonlinear aeroelastic tool sets, SHARPy and the Modal Rotation Method (MRM), have been employed to predict and design a wind tunnel flutter test campaign of a very flexible wing, the Pazy Wing, as part of the 3rd Aeroelastic Prediction Workshop. The first method, SHARPy, uses geometrically exact beams coupled with an Unsteady Vortex Lattice, which is linearised about a deformed configuration, reduced by means of Krylov subspaces and analysed to compute the stability boundaries of the wing. The MRM is based on structural modal data, from either beam models or finite element models, coupled with a doublet-lattice aerodynamic model from ZAERO of the straight wing configuration. The excellent agreement between numerical and experimental data for structural-only and static aeroelastic analyses paves the way for predicting the stability boundaries of the Pre-Pazy wing with sufficient confidence for the safe design of a flutter wind tunnel test campaign.

The stability boundaries of a very flexible wing are sought to inform a wind-tunnel flutter test campaign. The objective is twofold: to identify via simulation the relevant physical processes to be explored while ensuring safe and non-destructive experiments, and to provide a benchmark case for which computational models and test data are freely available. Analyses have been independently carried out using two geometrically nonlinear structural models coupled with potential flow aerodynamics. The models are based on a prototype of the wing for which static load and aeroelastic tests are available, and the experimental results have been successfully reproduced numerically. The wing displays strong geometrically nonlinear effects with static deformations as high as 50% of its span. This results in substantial changes to its structural dynamics, which display several mode crossings that cause the flutter mechanisms to change as a function of deformation. Stability characteristics depend on both the free-stream velocity and the angle of attack. A fast drop of the flutter speed is observed as the wing deforms as the angle of attack is increased, while a large stable region is observed for wing displacements over 25%. The corresponding wind tunnel dynamic tests have validated these predictions.

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