Instability Mechanisms of Skewed Circular Cylinders

Quasi-steady hypotheses have been often adopted to model wind forces on moving cylinders in cross-flow and to study instability conditions of spring-supported rigid cylinders. Recently, much attention has been paid to the experimental study of inclined and/or yawed circular cylinders detecting peculiar dynamical phenomena such as galloping-like instability but, at the present state-of-the-art, no mathematical model is able to recognize or predict satisfactorily this behaviour. The present paper presents a generalization of the quasi-steady theory for the definition of the aeroelastic forces on yawed and inclined circular cylinders. The proposed two degree-of-freedom model is able to replicate experimental behaviours observed during a series of recent wind-tunnel tests, and to predict the galloping-like instability phenomena.