Experimental Characterization of Flutter and LCO of a Very Flexible Wing

The present study presents intermediate results obtained in a wind tunnel campaign aimed at characterising the LCO of the PAZY wing, a wind tunnel model designed to exhibit large elastic deflections. The measurements carried out at “La Sapienza” wind tunnel allowed a complete identification of the flutter mechanism at various angles of attack: operational modal analysis (OMA) methods made possible this experimental characterization of the flutter and LCO conditions of the PAZY wing model because these methods allow the estimate of the natural frequencies, damping ratios, and mode shapes, at the different wind tunnel speeds and angles of attack. This allowed an accurate tracking of the evolution of the aeroelastic poles as a function of the airflow speed. The results confirmed that the flutter mechanism involves the second bending and the first torsional modes and that the flutter speed is strongly affected by the aeroelastic-static deflection of the wing. Measurements carried out at ZHAW wind tunnel showed qualitatively similar LCO, whereas additional experiments are necessary to complete the modes identification and still outstanding at time of submission. The stability boundaries observed in the two wind tunnels are also in good agreement between each other and with the analytical model the authors developed for the Third Aeroelastic Workshop in January 2023.