The wind environment around tall buildings in a central business district (CBD) was numerically investigated.The district covers an area of～4.0 km2 and features a high density of tall buildings.In this study,only buildings taller than 20 m were considered,resulting in 173 tall buildings in the analysis.The numerical investigation was realized using the commercial computational fluid dynamics code FLUENT with the realizable k-ε turbulence model.Special efforts were made to maintain inflow boundary conditions throughout the computational domain.The reliability of the numerical method was validated using results from an experimental investigation conducted in the core area of the CBD (～1.5 km2).Experimental and numerical investigations of wind speed ratios at the center of the three tallest buildings in the CBD agree within an uncertainty factor of 2.0.Both the experimental and numerical results show that wind speed ratios in the wind field with exposure category D are higher than those from the wind field with exposure category B.Based on the above validation work,the wind environment around tall buildings in the whole CBD was then investigated by numerical simulation.Common flow phenomena and patts,such as stagnation points,shielding effects,separation flow,and channeling flow,were identified around the tall buildings.The pedestrianlevel wind environment around tall buildings in the CBD was further evaluated using nearby meteorological wind data.The evaluation results show that some pedestrian activities,such as sitting at the center of the three tallest buildings,are unadvisable when the wind blows from the south-east.