Effect of grid size and initial conditions on vortex-induced vibration of a circular cylinder

A direct-forcing immersed boundary (DFIB) method was used with an in-house parallelized C++ code to simulate the vortex-induced vibration (VIV) of a one-degree-of-freedom (1-DOF) elastically mounted circular cylinder in the laminar and turbulent flow regimes. The continuity and Navier-Stokes equations were solved numerically together with the equation of motion to study the VIV response of the cylinder in 3-D. The results were analysed and compared with published literature. The importance of conducting a grid independence study at multiple points inside the lock-in (synchronization) region for VIV simulations has been ascertained through detailed comparisons of coarser and finer grids in each of the flow regimes. In addition, for laminar flows, the effect of the grid on the evolution of the vibration response in the lock-in region was discussed. For turbulent flows, the effect of different initial conditions on VIV amplitude was studied, and a hysteresis phenomenon was observed in the initial and upper branches of the lock-in region. The need for multiple calculation methods of vibration amplitudes in turbulent flows was highlighted.