Uncertainties Quantification in Flutter Prediction of a Wind Tunnel Model Exhibiting Large Displacements

Abstract

This study is a follow up on our contribution to {AIAA SciTech 2021}; the most relevant additions is the account of the wind tunnel campaign in which five different specimen of the PAZY wing were manufactured and tested along with an improved mathematical model, namely, a structurally and aerodynamically non-linear mathematical model based on the software SHARPy. The wind tunnel measurements have shown a relatively large scatter of quantities of interest such as natural frequencies and flutter speed. We believe that the most important causes are related to the buckling of the foil under aerodynamic loading. CFD analysis suggests that this may trigger an early transition of the boundary layer and avoid or reduce the laminar separation bubble - very evident on NACA0018 at similarly low Reynolds. As a consequence, the lift curve slope as well as the aerodynamic moment slope may significantly differ among specimen. Based on wind tunnel results, a more realistic propagation of uncertainties is carried out, showing updated confidence intervals for flutter speed and frequency. Results are only applicable to the materials and manufacturing techniques we used.