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ANALYSIS OF NUMERICALLY MODELLED LOCAL CONCENTRATION GRADIENTS IN STREET CANYONS: IMPLICATIONS FOR AIR QUALITY MONITORING J.M. Crowther 1, D. Mumovic 2,

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Presentation on theme: "ANALYSIS OF NUMERICALLY MODELLED LOCAL CONCENTRATION GRADIENTS IN STREET CANYONS: IMPLICATIONS FOR AIR QUALITY MONITORING J.M. Crowther 1, D. Mumovic 2,"— Presentation transcript:

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 1.A single street canyon 2.A staggered cross-road 3.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 U i = mean velocity, u i = turbulence velocity P = pressure, = density, μ = dynamic viscosity t = turbulent viscosity

7 Pollutant Transport Equations Turbulence Contribution to the Pollutant Flux Conservation of Pollutants 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 k =0.7914, =0.7914, C 1 =1.42, C 2 =1.68, C = o = 4.38, = 0.012

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 Standard k- model Single Street Canyon Pollutant Dispersion Case 1

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

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

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

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

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, 5 th Canyon

30 Local Concentration Gradients

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


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