This numerical study uses a two-dimensional finite volume method (FVM) to simulate the vortex-induced vibrations (VIVs) of an elastically mounted cylinder wrapped by a porous layer. The flow is incompressible, and the effects of mass ratio ( \(2\le {m}^{*}\le 10\) ), damping ratio ( \(0.01\le \xi \le 0.1\) ), and aspect ratio \((0.75\le {A}_{r}\le 1.5)\) on the lift force, pressure coefficients, and vibration response of a cylinder with constant Darcy number are investigated at Re = 150. Afterward, the dynamic response of the porous-coated cylinder with successive Darcy reduction is studied over a range of reduced velocities \((4\le {U}_{r}\le 14)\) for the first time to investigate the influence of gradual migration of suspended marine particles on the streamlines, flow wake, pressure contours, pressure coefficients, hydrodynamic forces, and vibration response of a vertically oscillating cylinder. According to the results, the influence of gradual Darcy reduction on \({{C}_{L}}_{rms}\) is significant at \({U}_{r}\) = 4 and 5 and reaches its maximum at \({U}_{r}\) = 6, where \({{C}_{L}}_{rms}\) increases by more than 100%. When the reduced velocity is increased from \({U}_{r}\) = 4, the effect of successive Darcy reduction on \({A}^{*}\) becomes more significant at some critical values of reduced velocity and shows a 70% increase at \({U}_{r}\) = 6. Moreover, \({f}^{*}\) slightly increases for all reduced velocities when the Darcy number decreases over successive periods. In this study, this successive Darcy reduction has an impact similar to that of the lock-in region. The normalized response frequency approaches one at \({6\le U}_{r}\le 8\) and creates a desynchronization regime to fully suppress the vibration amplitude at reduced velocities higher than those of the lock-in area. Moreover, when the cylinder undergoes high-amplitude oscillations, the effect of successive Darcy reduction on the flow wake increases the width of the lock-in region, where galloping (2P) occurs during the transition from the initial branch to the upper regime.
