Slit Effectiveness Analysis on the Lift Fluctuation Caused by Low-Speed Laminar Flow over a Circular Cylinder

Low-speed laminar flow over a slotted circular cylinder was numerically studied to investigate the slit effectiveness on the vortex shedding suppression and also determine the suppression mechanism physically. The base flow is two dimensional and characterized by Re = 150. The base slit was cut along the cylinder diameter in parallel to the upcoming flow. The effect of the slit width was studied and compared with previous reported results. Obtained results showed that the lift suppression increased with the slit-width increment so that there was no optimum slit width at this particular flow regime. Considering the strength of the structure, the slit with width of 20% of the cylinder diameter approximately suppresses the lift fluctuation completely and decreases the mean drag coefficient by 5%. Computed results showed that the slit induced additional stagnation points on the surface of the cylinder, which made the primary separation bubbles remain attached to the cylinder. These attached separation bubbles form a stable near-wake and a milder periodic vortex shedding at the far-wake regions. Additionally, other slit configurations were proposed and studied to confirm the proposed physical theorem. (C) 2021 American Society of Civil Engineers.