Abstract: Flow and dispersion of gases emitted by vents located on its roof was simulated using the k-ε(RNG)and the LES turbulence model in different wind direction,and numerical results were compared with wind-tunnel tests.The result of simulation shows that numerical simulation can better simulate flow field structure around the building,especially the downwind horseshoe vortex,upwind face stagnation location,roof-top vortex and reattachment lengths were reproduced almost exactly by all turbulence models,etc.The result of concentration shows that for an oblique wind angle,the differences among the predicted concentrations of the turbulence models are small on the roof and behind the cube.This tendency is contrary to that for a 90° wind angle.It was confirmed that the prediction accuracy of the velocity field strongly affected that of the concentration field.Analysis shows that numerical simulation results are in good agreement with the wind tunnel tests in the windward side and the roof-top backflow of the building.However,numerical simulation results are slightly higher than ones from wind tunnel tests in the rear cavity.As a whole,compared with wind tunnel tests,the LES model can better simulate the flow field and concentration field around the cube.In general,in order to estimate the environmental impact of building effectively,it is necessary to combine wind tunnel test with numerical simulation.