Numerical simulation and wind tunnel experiments on the effect of a cubic building on the flow and pollutant diffusion under stable stratification

Abstract

The renormalization group k-ε turbulence model was adopted to simulate the effect of a cubic building on the flow structure and pollutant dispersion at different bulk Richardson numbers (Rib). The simulation results were compared with the corresponding results of wind tunnel experiments. The computational fluid dynamics numerical simulation results are in good agreement with the wind tunnel test results; as Rib increases, the stationary point on the windward side of the building gradually moves upward, and the top recirculation zone gradually moves towards the leeward edge of the building. The length of the windward cavity zone of the building changes little when Rib increases from 0.057 to 0.21; when Rib increases from 0.21 to 0.52, the length of the windward cavity zone of the building increases slightly; and when Rib is increased to 1.13, the length of the windward cavity zone of the building decreases greatly. Near Rib = 0.21, the flow field structure is transformed from the dominant turbulent convection field structure to similar laminar flow, where mean advection plays a more important role than does turbulent diffusion because of the very weak turbulence. The effects of different stable stratification on the diffusion of pollutants in the near field of the building are different. As Rib increases, the vertical distribution range of the plume gradually decreases, the maximum value of the concentration gradually increases, and the maximum concentration range near the emission source gradually moves from upwind to downwind of the emission source.