Effect of structural parameters on the synchronization characteristics in a stall-induced aeroelastic system

Abstract

This study focuses on discerning the role of structural parameters on the bifurcation characteristics and the underlying synchronization mechanism in an aeroelastic system undergoing nonlinear stall behaviour. To that end, wind tunnel experiments are performed on a NACA 0012 airfoil capable of undergoing bending (plunging) and torsional (pitching) oscillations under scenarios involving nonlinear aerodynamic loads, i.e., dynamic stall conditions. Flow conditions under both deterministic/sterile flows and fluctuating/stochastic flows are fostered. The structure possesses continuous or polynomial-type stiffness nonlinearities and therefore is an aeroelastic experiment involving both structural and aerodynamic nonlinearities. We discern the bifurcation routes for a range of key structural parameters, such as frequency ratio, static imbalance, and the extent of structural nonlinearity. In addition to interesting and atypical routes to stall-induced instabilities, we systematically demonstrate the role of modal interactions – via a synchronization analysis – over the manifestation of these instabilities. To the best of the authors’ knowledge, this is perhaps the first study to document the role of multiple structural parameters on a stall-induced aeroelastic system and in turn cast the physical mechanism behind these dynamical transitions through the framework of synchronization.