Aerodynamic damping in vortex resonance from aeroelastic wind tunnel tests on a stack

Abstract

The paper investigates the negative aerodynamic damping of circular cylinders in vortex-induced vibrations and compares the results of two different types of wind tunnel experiments. Firstly, forced-vibration wind tunnel tests on a rigid sectional model allow measuring the aerodynamic damping directly from the experiments. This is because the aerodynamic damping is related to the phase shift between the force and the imposed motion. They also offer the advantage of a systematic investigation for different velocity ratios and a constant oscillation amplitude. Secondly, aeroelastic experiments on a cantilevered cylinder with distributed elasticity free to oscillate under the wind action are performed. These experiments do not impose the motion from the outside and therefore, the physical nature of the vortex-induced vibration can develop without any further constraint to the motion. However, these tests do not explicitly reveal the relationship between the load and response. Nevertheless, the aerodynamic damping can still be evaluated, if a mathematical model to describe the relationship between load and response is assumed. The cross-check of aerodynamic damping values obtained from the two experimental approaches not only gives evidence of the reliability of the proposed aerodynamic damping model, but also proves the effectiveness of the Vickery&Basu spectral model to predict vortex-induced vibrations.