Simulating Turbulent Air Flows In Central London And Studying Effect Of Tall Buildings

We present work associated with the implementation of a validated street-canyon/neighbourhood model that can help
assess the air quality within existing building and neighbourhood designs and suggest modifications & improvements
in order to produce sustainable, safer, healthier, and more comfortable urban environments. The work was motivated
by both the increasing number of tall buildings in central London (“skyscrapers”) and also the recent plans of placing
combined heat and power plants (CHPs) within the urban environment. The Large Eddy Simulation (LES) work was
initiated after a series of wind tunnel experiments were carried out at the Enflo wind tunnel (University of Surrey) in
order to assess the effect of emissions from Combined and Heat Power plants (CHPs) on top of one of the buildings.
A series of scenarios were tested in the wind tunnel and mean concentrations and their fluctuations were measured.
The LES models were set-up representing the wind tunnel geometries as well as wind conditions. The novel LES
methodology implemented uses an unstructured, adaptive mesh and an anisotropic eddy viscosity tensor for the subgrid
scales (based on the anisotropic mesh). The comparisons of the complex turbulent air flows and concentrations
between model results and wind tunnel data show a good correlation – less than 20% error between predictions and
measured data. We also looked at the effect of tall buildings on the surrounding complex air flows and dispersion of
pollutants, using as prime examples the “Walkie-Talkie” building and the Shard skyscraper in central London, UK.
Interesting simulation air flow results and dispersion for the “Walkie-Talkie” building are presented.
Key words: air pollution, urban environment, wind tunnel experiments.