Large-eddy simulation of approaching-flow stratification on dispersion over arrays of buildings

Abstract

The study investigates thermal stratification effects of approach flows on dispersion in urban environments. This is in some ways analogous to a well developed non-neutral flow (e.g. through a large urban area) approaching a neighborhoodscale urban region, where the effect of the local heat transfer was assumed less important. A generic urban-type geometry, i.e. a group of staggered cubes, was
taken as the first test case. The DAPPLE site, which was about a one-km2 region near the intersection of Marylebone Road and Gloucester Place in central London, was taken as the second test case. Only weakly unstable conditions (i.e.
bulk Richardson number Rb >= ?0.2) of approach flows were considered, with adiabatic boundary conditions at the ground and building surfaces. A number of numerical experiments including with various Rb were performed. The modelled mean concentration for Rb = ?0.1 gave the best agreement with the field data at all DAPPLE stations. This suggests that stratification effects on dispersion in
weakly unstable conditions (e.g. in London) are not negligible.

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Identifiers

ORCID for Zheng-Tong Xie: orcid.org/0000-0002-8119-7532

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