Effects of facade rib arrangement on aerodynamic characteristics and flow structure of a square cylinder

Ribs on building facade can reduce wind loads acting on high-rise buildings and modify the corresponding flow structures. The present study investigates the effect of vertical ribs with different arrangements on the flow field and aerodynamic characteristics of a square cylinder under uniform flow by using LES. The results show that the windward face ribs and downstream ribs of sidewall can obviously affect the behavior of the separated shear layer by introducing the local recirculation. The upstream ribs of sidewall and leeward face ribs, however, show insignificant effect on the flow filed and aerodynamic force. The multi-location combination of ribs generally exhibits better aerodynamic performance than the single-location ribs. The optimal combination can significantly modify the shear layer flow, and reduce the surface pressure, mean drag force and fluctuating lift force. The fourface-ribs arrangement is the most practical arrangement with considering real application. By using this arrangement, the mean drag and fluctuating lift force can be reduced up to 38% and 70%, respectively. The nearfacade flow becomes more complicated with more local re-circulations when model is equipped with densely arranged ribs. Correspondingly, the wake vortex is obviously shortened accompanying with increase of wind force. The space in between the ribs is also found to be an essential factor for modifying the flow structure and wind load acting on the structure.