Vortex Shedding Modes of a Vertical Plate in Close Proximity to a Smooth Wall at Low Reynolds Number

A series of two-dimensional numerical simulations were performed by solving the Navier–Stokes equations to investigate the flow past a vertical plate in close proximity to a smooth wall at a fixed Reynolds number of Re = 150. The effects of the gap ratio G/L, defined as the wall-to-plate distance over the plate length, were systematically examined in the range of 0.0 to 4.0. The results revealed that the drag and lift coefficients varied significantly when the gap ratio was less than 1.0, whereas they remained relatively stable for larger gap ratios. As the gap ratio increased, the wake transitioned from no vortex shedding to periodic shedding, and the influence of the lower wall on the wake progressively diminished. Further analysis of the wake vortex structures identified six distinct vortex shedding modes within the parameter range considered. When the gap ratio is sufficiently large (G/L ≥ 2.5), the wake pattern evolves into a Kármán vortex street resembling that of an unbounded flow.