1. COMPUTATIONAL MODELLING Dr 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

2. A. FIELD CAMPAIGN Location Distance from source (m) Measured average concentration (ppqv) Estimated maximum concentration (ppqv) Westminster Council House 1204902200 Bickenhall Mansions 200185830 End of York Street 19010900 Thornton Place6015908800 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

3. York Street Library Bickenhall Street Westminster Council House Thornton Place Bickenhall Mansions x 3 6 5 4 A. FIELD CAMPAIGN Source-Receptor Positions

4. 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

5. An example:A source apportionment study for Central London