New nonlinear coupled model for modeling the vortex-induced vibrations of flexibly supported circular cylinders

The oscillation of a cylinder, which is excited by steady fluid flow, is investigated. Regarding the nonlinearity of real practical structures like marine risers and the stay cable of a long-span bridge, the dynamic behavior of a circular cylinder is described using two nonlinear equations, and the aerodynamic force performance of the wake flow is expressed by the wake oscillator equation. Unlike previous studies, in the present investigation, attention is focused on coupling the wake oscillator equations, considering quadratic terms. Following this approach, the cylinder’s mixed in-line and crossflow vortex-induced vibrations (VIV) are accurately modeled. Experimental coefficients are corrected using previous credible experimental studies and the effects of changing coefficients of the VIV parameters are studied in the sub-critical Reynolds number range of about 2×10³–5×10⁴. The oscillating amplitude calculated by the present model is close to that of the experiment. The present model has a lower relative error compared to the previous model. The model presented can predict the lock-in range with greater accuracy for bluff bodies near the plate than previous models. Moreover, the present model successfully predicts the moving trajectories of a circular cylinder under VIV in a figure-of-eight shape.