Numerical studies on aerodynamic forces and flow control regimes of square cylinder with four surface ribs

Abstract

Façade ribs attached to building surface are effective in mitigating wind-induced effects. In this paper, LES approach is adopted to explore the impact of four surface ribs on aerodynamic forces and flow structure around a square cylinder with width D. ANSYS Fluent is used to carry out the simulations at Re=2.2 × 104, the standard sub-grid scale (SGS) model is used. Simulation results indicate that small vortices formed near ribs can remarkably suppress flow separation, and reduce the shear layer's curvature and periodic flapping. Facade ribs accelerate the vortex shedding process, and clearly reduce the wake vortices’ intensity. The change of the flow field clearly mitigates surface pressure with increase in rib extension depth dr, resulting in a clear reduction in wind forces. When the depth dr is greater than 0.06D, the variation trends of drag coefficient C¯D and lift coefficient C’L are relatively complex with change of rib location br. This is due to the significant changes of flow patterns with different rib configurations. The maximum reduction rates of C¯D and C’L are 61% and 82%. It is found that extension of rib dr from around 0.08D to 0.1D with distance to the corner br from about 0.16D to 0.2D may show the best performance in reducing wind load.