CFD simulation for the buoyancy flows and pollutant dispersion through different scale urban areas

摘要

There exist many difficulties for CFD application and model validation in simulating multiscale problems. In this paper, a coupled CFD model used to study the multiscale problems on the flow and dispersion passing neighborhood scale - street scale - indoor scale models was validated by wind-tunnel measurements with Richardson numbers (Ri) equal to 0 and 0.85. The basic flow, heat and pollutant transfer are solved with the 3-D steady RANS equations. The compared results show that the CFD model can predict the general flow structures and the buoyancy effects. For the two cases, the standard k-ε model (SKE) with standard wall functions (SWFs) can better predict the flow and temperature fields. For Case 1, the turbulence model can determine the flow structure, however, which significantly depends on the wall functions when Ri = 0.85 (Case 2). Furthermore, it is found that only when Re_H ≥ 7.57E+03, the wind-tunnel results are independent on the street Re_H to present the realistic cases meaningfully, meanwhile the IAQ is mainly determined by the street Ri.