Large Eddy Simulation Study on Flow Fields and Aerodynamic Performance on a Square Cylinder with Four Surface Ribs

Abstract

At a Reynolds number of Re = 2.2 × 10⁴, large eddy simulation (LES) was employed to investigate the flow field structure, vortex dynamics, wind pressure distribution, and variations in aerodynamic force coefficients for square cylinders fitted with vertical and horizontal ribs of different rib heights (d). The aerodynamic performance of the ribbed cylinders was also evaluated. The results indicate that under time-averaged flow conditions, vertical ribs exhibit a more pronounced interference effect on the square cylinder. The incoming flow separates in an arc-shaped pattern after impinging on the windward ribs, leading to a gradual elongation of the wake vortex. The instantaneous flow fields corresponding to the maximum and minimum lift coefficients show opposite trends for the two rib configurations. Under transient vorticity conditions when the vertical rib height ratio d/D reaches 0.10 and the lift coefficient approaches zero, a large-scale vortex forms in the wake region. A notable difference in aerodynamic coefficients is observed between horizontal and vertical ribs, with horizontal ribs generally producing higher values. This finding suggests that the arrangement of vertical ribs significantly influences the wind load effects on buildings.