Aerodynamic damping model in vortex-induced vibrations for wind engineering applications

Abstract

The paper addresses the modelling of aeroelastic forces in vortex-induced vibrations (VIV) and aims to provide a suitable model to predict cross-wind oscillations of circular structures. The Van der Pol and Rayleigh oscillators – non-linear physical systems, which attain limit cycles under self-induced vibrations – are often applied in literature to describe the aeroelastic force. Among VIV models, the paper focuses on the model developed by Vickery and Basu (1983). In the paper, the quadrature component of the force as a function of the oscillation amplitude in lock-in is investigated through forced-vibration wind tunnel experiments on a circular cylinder. In presence of aeroelastic interaction, the positive quadrature component corresponds to energy transferred to the structure, which then acts as negative aerodynamic damping. The experiments reveal an amplitude-dependent behaviour of the aerodynamic damping with positive curvature. The experimental curve can be applied as modification of the Vickery and Basu model and used to predict the oscillation of circular structures under vortex-excitation. In the paper, it is applied to the response of a cantilever beam. The prediction is validated through free-vibration wind tunnel experiments. The consistency of results is promising.