Aerodynamic damping models for vortex-induced vibration of a rectangular 4:1 cylinder: Comparison of modeling schemes

Accurate modeling of vortex-induced force acting on a structure is of great significance to precisely evaluate its vortex-induced vibration (VIV). This paper systematically compares the capabilities of five aerodynamic damping models in simulating the VIV amplitudes of a line-like structure at various mass-damping conditions. These models are categorized into two types. Scanlan's model, the polynomial model, and the describing function-based model, as the first type, can be utilized to calculate the VIV amplitudes in the entire lock-in range. The second type, including Larsen's model and a newly-developed aerodynamic envelope model, that is designed to directly obtain the peak VIV amplitude. The relationships between aerodynamic damping of the aeroelastic systems and aerodynamic parameters of five models are established to convenience the identification of aerodynamic parameters. The aerodynamic parameters can be either identified based on the VIV decay-to-resonance and/or grow-to-resonance displacement signals at a single mass-damping condition, or based on the VIV steady amplitudes at various mass-damping conditions. Numerical examples involving the VIV analyses of a rigid rectangular 4:1 cylinder and two flexible cylinders are presented to compare the predictive capabilities of various models. The polynomial model and the describing function-based model can satisfactorily predict the VIV amplitudes at various mass-damping conditions, while the predicative capabilities of Scanlan's model, Larsen's model, and the aerodynamic envelope model may be comparatively lower. The underlying reasons for the different levels of accuracy of various models are discussed. Furthermore, it is demonstrated the mode shape correction factor of a flexible cylinder may be dependent not only on the mode shape, but also on other parameters such as the mechanical damping level.