Study on the incorporation and application of the aerodynamicalurban canopy scheme

An aerodynamical urban canopy scheme is incorporated into the fine town boundary layer model. The scheme contains drag effect of urban buildings on flow and effect of building morphology on urban turbulent activity and momentum transfer. The incorporated model is evaluated by simulation results of two different building aerodynamical scheme in southeast region of Beijing area, which are building drag scheme and aerodynamical urban canopy scheme. The conclusions are drawn by the comparisons between the simulation results of the wind speed and the observations of the automatic weather stations in the urban areas: the simulated results of incorporated model are more in reasonable agreement with the observations than that of building drag scheme, and the diurnal trend of that is more agreement with observations. The model incorporated with the aerodynamical urban canopy scheme is better to simulate the wind field on the urban areas.The conclusions are drawn by the comparisons between the simulation results of the building drag scheme and the aerodynamical urban canopy scheme in a real town: the simulated wind speed with the aerodynamical canopy scheme on the town areas is always lower than that on the surrounding rural areas, but that with the other scheme is not so. The simulated results describe the dynamical effect of the buildings on the turbulent activity, and the simulated turbulent kinetic energy distribution is consistent with the real distribution.The effect of the building height variation in the town on the wind field and turbulence is also simulated, and the results are as followings: the increase of the building height results in the decrease of the horizontal wind speed on the town areas, and the wind speed at the bottom of the higher building is larger than that of the lower building. The turbulent kinetic energy on the town areas ascends, that in the bottom of the high building is lower and ascends with the height in the canopy layer. The vertical diffusion coefficient increases as the building height ascends. The pollution concentration on the town areas with higher buildings is lower on the emission level, and that is lower on the surface and is higher on the upper level of the downstream rural areas.