Modeling of downburst outflows and wind pressures on a high-rise building under different terrain conditions

Abstract This study investigates the characteristics of downburst outflows and wind pressures on a tall building under different terrain conditions. The rough terrain exposure was explicitly modelling by arranging the roughness elements on the ground and the impinging jet (IJ) model were experimentally adopted to reproduce the spatial velocity distribution of the downburst-like winds. Also, large-eddy simulations (LES) using both the IJ model and Cooling Source (CS) model were performed to elucidate the characteristics of microburst flow fields over rough grounds and visualize the flow structures. To experimentally measure the aerodynamic loadings on the squared tall building, the rigid model using the SMPSS (synchronous multiple-pressure scanning system) was mounted on the ground for wind pressure measurements on the building surfaces under different terrain exposures including a homogeneously flat surface and two rough ones. The results were found that rough terrain played a retarding role on the microburst-like winds in the inner core regions near the ground and its drag effects gradually decreased in the outburst regions with the radial separation distance from the center of the impinging jet. The height of maximum radial velocity increased with rougher terrain conditions, but the maximum wind speed was reduced to some extent. The mean pressure distribution patterns on the windward surface were significantly influenced by rough terrains due to significant differences among the vertical profiles of radial velocity component under different terrain exposures. The maximum pressure fluctuations on the tested model were found to occur further downstream from the center of microburst winds. The outcomes of this study are of great use to improve the understanding of the effects of terrain roughness on downburst winds and the corresponding aerodynamic loads on tall buildings.