MERGING CFD AND ATMOSPHERIC MODELING CAPABILITIES TO SIMULATE AIRFLOWS AND DISPERSION IN URBAN AREAS

摘要

The objective was to simulate airflows over an urban area where weather variations are significant. First, a three-dimensional atmospheric model, HOTMAC, was improved so that airflows not only in complex terrain, but also around buildings were simulated. A horizontal grid spacing of 10 m or smaller was required to simulate separations and re-circulations of airflows around buildings. On the other hand, the computational domain should be large enough to include major topographic features, which have significant influences on local circulations. To accommodate both requirements, we nested two computation domains of fine horizontal grid spacing of 40 m and 10 m inside the outer domain, where horizontal grid spacing was 160 m. As far as we are concerned, this was the first successful simulation where a single model was used to simulate simultaneously mesoscale and CFD scale circulations.