Investigation of the branching behaviour of a freely vibrating circular cylinder at low Reynolds numbers

In this study fluid flow around a freely vibrating cylinder is analyzed using an in-house code based on the finite difference method. Mass ratios between m* = 2 and 150 are considered, the Reynolds number is fixed at Re = 300 and the reduced velocity is varied from U* = 2.5 to 7.5. The results indicated that an amplitude increment observed in the lower end of the lock-in domain corresponds to the upper branch, which has not been found before for low-Reynolds number flows. In the upper branch P+S asymmetric vortex structure was observed while in the initial and lower branches 2S wake mode formed which agree with the data in the literature.