The role of flow separation in the forces on a circular cylinder with one or two control rods

Abstract Direct numerical simulations were conducted to investigate the effects of one or two control rods on vortex-shedding suppression for a circular cylinder at Re = 3900. Compared with a single cylinder, the control rods alter the near-wake flow via interactions between the wake of the main cylinder and the rods. For the single control rod configuration, the rod suppresses the development of one shear layer and induces a Coanda effect, causing the cylinder’s shear layer to reattach to it. Subsequent coupled vortex shedding from both bodies injects a jet-like flow into the wake, amplifying vortex oscillations and enhancing flow fluctuations. In the two control rods configuration, a large-angle jet generated by one rod impedes vortex formation behind the main cylinder, reducing oscillation amplitudes and effectively suppressing lift and drag force fluctuations.