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Vipac Engineers & Scientists Ltd

Vipac Engineers & Scientists Ltd. COMPUTATIONAL FLUID DYNAMICS Simulation of Turbulent Flows and Pollutant Dispersion Around Groups of Buildings . presented by Dr. Neihad Al-Khalidy Specialist Consultant Fluid and Thermal Technologies. Background .

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Vipac Engineers & Scientists Ltd

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  1. Vipac Engineers & Scientists Ltd COMPUTATIONAL FLUID DYNAMICSSimulation of Turbulent Flows and Pollutant Dispersion Around Groups of Buildings presented by Dr. Neihad Al-Khalidy Specialist Consultant Fluid and Thermal Technologies

  2. Background • The analysis of flow and dispersion of pollutants around buildings is important from an environmental point of view • Examine pollutant problem under different scenarios based on a detailed fluid flow Analysis

  3. Strategy CFD Model Construction Wind data Data Flow Simulation Pollutant Dispersion Prediction Pollutant sources Probability Analysis Recommend modifications to the duct heights, dimensions or velocities to achieve the recommended criteria Compliance with Occupational Health & Safety Commission limits at human height levels and living area

  4. Geometry – Proposed Building

  5. Geometry – Surrounding buildings

  6. Geometry – Surrounding buildings

  7. Boundary Condition - Wind Data • Still wind condition • Windy condition • At the upwind free boundary inlet velocity profiles were derived from the Australian Wind Code AS1170.2

  8. Boundary Condition - pollutant Data • The maximum pollution emission rate at each stack is 450 l/s • The maximum mass flowrate of Xylene fume is 1200 l/s at each of the two ducts through the roof located near the plant room • A pollution concentration of unity is assumed at the pollutant sources • The pollutants were assumed to be slightly heavier than air at the sources

  9. CFD Modelling • Phonics Software • Navier-Stokes equations for continuity, momentum, energy and species concentration • Steady-state • Incompressible

  10. CFD Modelling • Standard K-є model • 680000 unstructured grid cells • A Hybrid numerical approach to discretise the convective term in the governing equations. • SIMPLE algorithm for the pressure – velocity coupling. • Relaxation parameter to stabilize the solution processes • convergence 20-32 hours CPU

  11. Sensitivity Analysis

  12. CFD Flow Results South-Westerly Wind Conditions

  13. CFD Flow Results South-Westerly Wind Conditions

  14. CFD Pollutant Dispersion Results • concentration profile in a horizontal section at the chest level. • Downwash effect

  15. CFD Pollutant Dispersion Results • concentration profiles in a horizontal section at the 15 m elevation • Thepollutant dispersed to a wider region andthe concentration is increased to 1.7% source concentration.

  16. CFD Pollutant Dispersion Results • concentration profiles in a horizontal section Through the outlet of the stack • The pollution concentrations seen to increase to 3% source concentration near the roof of the building.

  17. CFD Pollutant Dispersion Results • Concentration Profile- Iso-surface of 1%Source Concentration – Pollutant Slightly Heavier Than Air

  18. CFD Pollutant Dispersion Results • Concentration Profile- Iso-surface of 1%Source Concentration – Pollutant of a Similar Density Than That of Air Was Used

  19. CFD Flow Results North-Easterly Wind Conditions

  20. CFD Pollutant Dispersion Results • Concentration Profile in Horizontal Section at 1.5 m Elevation

  21. CFD Pollutant Dispersion Results • Concentration Profile in Horizontal Section at 15 m Elevation

  22. CFD Pollutant Dispersion Results • North-Easterly Wind Condition

  23. CFD Pollutant Dispersion Results • Calm Wind Condition – near the roof of the building

  24. Conclusions • ð Flow fields and pollutant dispersal around a number of buildings to the east and west of a proposed building have been predicted using computational fluid dynamics analysis. • ð The flow characteristics are seen to be captured well by the two equation k-ε model. The pollutant concentrations were predicted at the chest level and at a range of elevations during near calm wind and windy conditions. • ðThe CFD analysis has offered a comprehensive range of outputincluding velocity distribution, pressure profile and turbulence levels. Subsequent testing of the modified duct system has validated the approach using CFD analytical tools. • ð The CFD results will be validated against the measurement data when the proposed building is completed and operated

  25. Vipac Engineers & Scientists Ltd • Phone: 1300 7 VIPAC • www.vipac.com.au

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