Numerical study of the dynamic behavior of cylinders with nonlinear support exposed to flow

Vortex-induced vibrations may cause chaotic behavior in offshore structures. Chaos reduces the life of these structures by causing fatigue. In this research, assuming a nonlinear support, the dynamic behavior of these structures has been investigated. The support nonlinearity was changed by using different types of springs. The displacement and lift force signals were obtained by simultaneously solving the two-dimensional Reynolds averaged Navier-Stokes equations and the cylinder motion equation. Then, chaos detection tests were applied to the signals. The results show that the behavior of the system consists of two branches. The second branch's amplitude is multiple times the amplitude of the first branch. At the starting point of the second branch, the cylinder behavior and the lift force are chaotic. As the support nonlinearity increases, the length of the second branch decreases, but the degree of chaotic behavior of the cylinder and the lift force increases.