COMPUTATIONAL MODELLINGDr Marina Neophytou

University of Cambridge, Department of Engineering

Scope: Test the appropriateness and validity

of models of different levels of complexity and improvement

•Simple rules of thumb•Operational models(e.g UDM, ASUDM, ESUDM,

OSPM, ADMS-URBAN)•Computational Fluid Dynamics (CFD) models (e.g. RANS, LES)

Models:

Themes: •Urban Air Quality•Accidental releases of hazardous materials

Purposes: •Prediction/forecasting•Design of mitigation strategies

A. FIELD CAMPAIGN

Location Distance from

source (m)

Measured average

concentration (ppqv)

Estimated maximum

concentration (ppqv)

Westminster Council House

120 490 2200

Bickenhall Mansions

200 185 830

End of York Street

190 10 900

Thornton Place 60 1590 8800

Some concluding remarks:

•Measurements and estimates are consistent•Significant variations over the 30 minute (long)period (possibly due to wind meandering)

Rule of Thumb: C ~ 10 Q U-1 x-2

York StreetLibrary

Bickenhall Street

WestminsterCouncil House

Thornton Place

Bickenhall Mansions

x

3

65

4

A. FIELD CAMPAIGN

Source-Receptor Positions

B. SCALE-VARIANT MODELLING

•Address urban dispersion in terms of different processes occurring at different scales

•On what basis one could define different scales is an open issue

•One way is through physically meaningful scales such as:

•Regional •City

•Subdistricts•Neighbourhood• Street-canyons

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