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Detailed numerical modeling of local atmospheric dispersion in an idealized urban area

Detailed numerical modeling of local atmospheric dispersion in an idealized urban area. M. Milliez, S. Panzarella, B. Carissimo CEREA Research and Teaching Center for Atmospheric Environment Chatou/Marne-la-Vallée, FRANCE. Outline. Objectives The Mercure model

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Detailed numerical modeling of local atmospheric dispersion in an idealized urban area

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  1. Detailed numerical modeling of local atmospheric dispersion in an idealized urban area M. Milliez, S. Panzarella, B. Carissimo CEREA Research and Teaching Center for Atmospheric Environment Chatou/Marne-la-Vallée, FRANCE

  2. Outline • Objectives • The Mercure model • Simulation results evaluated with two experiments: • Hydraulic simulation of the MUST array (R.W.Macdonald, C.E.Ejim, 2002) : results and comparison • MUST: Mock Urban Setting Test (C.A.Biltoft et al., 2001) : results and preliminary comparison • Perspectives Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  3. Objectives • Investigate flows and pollution dispersion in an urban environment: analyses of flow properties and concentration fields. • In order to: • Study the impact on population and environment on a local scale • Describe the average building effects (in terms of porosity, drag and turbulence) on flow and concentration fields Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  4. The Mercure model • Developed by EDF and CEREA • 3-D model adapted to atmospheric flow and dispersion simulation • Core of the model: CFD model Code_Saturne (EDF) which can handle complex geometry and complex physics • Unstructured grid, finite volumes • Simulations: • Eulerian approach • Full scale, fine resolution, complex terrain, thermal effects • Large scale meteo. conditions taken into account • k- turbulence closure model • porosity/drag option Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  5. Hydraulic simulation of the MUST array • Report “Flow and Dispersion Data from a Hydraulic Simulation of the MUST array”, R.W. Macdonald, C.E. Ejim,2002, University of Waterloo, Canada • Hydraulic flume with an upstream region to simulate of a turbulent ABL flow in neutral stability conditions. • Experiments: • 1:50 scale • Array of 10x4 obstacles (200mm long, 50mm wide, 50 mm high) • Use of heat as a tracer Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  6. Hydraulic simulation of the MUST array • continuous release: • several locations upstream and within the array • 3 different flow direction: 0 deg, 30 deg, 45 deg Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  7. z0=0.3m Simulations with the Mercure model • Boundary conditions: • Upstream : • Dowstream: gradients = 0 • Mesh: ~900 000 elements • Horizontal grid = 0.5 m x 0.5m • Stretched vertical grid = 0.5m -> 1.6 m Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  8. Simulations with the Mercure model • 0 ° • 30 ° • 45 ° Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  9. Comparisions Wind 0 °, source upstream • U • TKE Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  10. Comparisions: concentration Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  11. Comparisions: concentration Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  12. The Mock Urban Setting Test • C.A. Biltoft, et al. Report and data, 2001. • Near full scale experiment in the U.S. Army Dugway Proving Ground (Utah), conducted for the DTRA (Defense Thread Reduction Agency ) • Objectives : acquire meteo. and dispersion data set • overcome the scaling limitations of laboratories simulations. • Neutral gas releases in a field of containers. • Array of 10x12 obstacles (12.9 m long, 2.42 m wide, 2.54 m high) Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  13. The Mock Urban Setting Test • Releases for different meteorological conditions in several locations within the array • 63 continous releases of duration of ~15 min • Data: preanalyses and statistics Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  14. The Mock Urban Setting Test N Pneumatic Mast 32-m Tower (digiPIDs at 1-, 2-, 4-, 6-, 8-,10-, 16-m levels) Line4 h=1.6 m Line5 Line3 h=1.6 m Line2 h=1.6 m Line1 h=1.6 m simulated release point: Hs=0.15 m 30° simulated wind Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  15. Simulations with the Mercure model • Mesh: ~800 000 hexahedral elements • Dimensions: 240 m x 233 m x 32m • Horizontal grid : lower levels ~4 m 0.6 to 1m ~2 m ~0.3 m • Stretched vertical grid ~4 m Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  16. Simulations with the Mercure model • Boundary conditions: • Upstream :wind profile in a stable atmosphere • L=100 • Z0=0.1m • Wind bearing: 28 ° • u~3m/s (z=8m) • Dowstream: gradients = 0 • Top : symetry and free slip Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  17. Simulations with the Mercure model Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  18. Simulations with the Mercure model Y=86 m Y=146 m Y=106 m Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  19. Simulations with the Mercure model • Y=86 m • Y=106 m • Y=146 m Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  20. 2 1 3 First comparisons: wind speed Row 5 Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  21. 2 1 3 First comparisons: TKE Row 5 Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  22. 2 1 3 First comparisons: concentration Row 5 Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  23. First comparisons Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  24. Conclusions • Water flume simulations: • Satisfactory results for wind, turbulence and C at 0° • Differences in side wall effects at 30°, 45°  comparison not conclusive • MUST simulations: • first results : encouraging comparison • further analyses needed ( inflow profile …) Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  25. Perspectives • More analyses / comparisons with the MUST experiment • Future thesis work = take into account heat fluxes and radiative transfers with buildings Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  26. Acknowledgments • Rob Macdonald, University of Waterloo (CA) • water flume experimental data and analysis • Defense Threat Reduction Agency (USA) • MUST field experiment database • B. Carissimo was supported during his sabbatical leave by the Comprehensive Atmospheric Modeling Program (CAMP) at George Mason University (USA) Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  27. Thank you Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

  28. Simulation with the Mercure model Maya Milliez NATO ADVANCED STUDY INSTITUTE, Kyiv, May 2004

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