J.M. Crowther 1 , D. Mumovic 2 , Z. Stevanovic 3

1. ANALYSIS OF NUMERICALLY MODELLED LOCAL CONCENTRATION GRADIENTS IN STREET CANYONS: IMPLICATIONS FOR AIR QUALITY MONITORING J.M. Crowther 1, D. Mumovic 2, Z. Stevanovic 3 1 School of the Built and Natural Environment, Glasgow Caledonian University 2 The Bartlett, Faculty of the Built Environment, University College, London 3 Institute of Nuclear Sciences, University of Belgrade

2. Objectives of this study • To analyse numerically modelled, local concentration gradients in street canyons • To make recommendations for the positioning of air quality monitoring stations

3. Cases Studied • A single street canyon • A staggered cross-road • An idealised complex configuration of several street canyons

4. Methodology • PHOENICS with different turbulence models: • Standard k-epsilon • Renormalisation group k- model • Chen-Kim modification of k- model • Two-scale k-

5. Validation • Comparison with air quality data collected for Glasgow city Council, Scotland • Wind tunnel data from the University of Hamburg, Germany

6. Incompressible, Steady-state Navier Stokes equations k = turbulence kinetic energy per unit mass Ui = mean velocity, ui = turbulence velocity P = pressure,  = density, μ = dynamic viscosity t = turbulent viscosity

7. Pollutant Transport Equations Conservation of Pollutants Turbulence Contribution to the Pollutant Flux D = Laminar Diffusivity, C = Turbulent Schmidt No.

8. General Transport Equation Property  with source S and diffusivity 

9. Standard k- Turbulence Model k=1.0, =1.314, C1=1.44, C2=1.92, C= 0.09

10. RNG k- Turbulence Model o= 4.38,  = 0.012 k=0.7914, =0.7914, C1=1.42, C2=1.68, C= 0.0845

11. Chen-Kim k- Turbulence Model k= 0.75, =1.15, C1 =1.15, C2 =1.9, C3 = 0.25, C= 0.09

12. Two-scale k-ε Turbulence model

13. Two-Scale k- Turbulence Model Parameters

14. Case 1: Single Street Canyon • Hope Street, Glasgow • Three-dimensional: wind direction at normal incidence • Ref. Mumovic & Crowther, 2002 • Four different turbulence models • Longitudinal single vortex

15. Case 1 Standard k- model Single Street Canyon Pollutant Dispersion

16. Case 1 RNG k- model Single Street Canyon Pollutant Dispersion

17. Case 1 Chen-Kim k- model Single Street Canyon Pollutant Dispersion

18. Case 1 Two-Scale k- model Single Street Canyon Pollutant Dispersion

19. Case 1 Single Street Canyon Comparison of a wind- tunnel study (Pavageau & Schatzmann, 1999) with the RNG turbulence model

20. Case 2: Staggered Cross-Road • University of Hamburg wind-tunnel test • Ref Mumovic, Crowther & Stevanovic, 2003a • Ref. Mumovic, Crowther & Stevanovic, 2003c

21. Case 2 Staggered cross-road

22. Case 2 Staggered cross-road, Section B-B

23. Case 2 Staggered cross-road, Section A-A

24. Case 3: Complex Configuration of Street canyons • Wind-tunnel study University of Hamburg • Ref. Crowther, Mumovic & Stevanovic, 2003a, b

25. Experimental Geometry

26. Model Grid for Wind-Tunnel Simulation

27. Case 3 Complex configuration of street canyons: vertical plane at centre of 5th cavity

28. Case 3: Concentration distribution in the mid-height horizontal cross-section of the 5th cavity

29. Experimental Concentration Contours: Horizontal Cross-Section, Mid-Height, 5th Canyon

30. Local Concentration Gradients

31. Practicality of Location Suitable Location Local Concentration Gradients Level of Turbulence Factors for Location of Monitoring Equipment