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Vipac Engineers Scientists Ltd

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Vipac Engineers Scientists Ltd

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    1. Vipac Engineers & Scientists Ltd

    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

    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 The CFD study was undertaken to estimate the pollution concentrations during near calm and windy conditions: ð      Wind Load Condition: An estimate of average wind velocity was determined for two prevailing wind conditions namely, southwest and northeast winds. At the upwind free boundary inlet velocity profiles were derived from the Australian Wind Code AS1170.2 [3]. Surrounding terrain was classified as Category 2 to the east and the west of the proposed building. A profile velocity inlet was provided 300 m to the west and east of the building and more than 250 m to the south and north of the building. At the downwind and upper free boundaries constant pressure boundary conditions were applied. The fume flow being released continuously from the stacks. ð      Near Calm Air Condition: A magnitude of wind speed of 1 km/hr was chosen to represent the calm condition. In this study only the east condition is investigated. A pressure boundary condition of zero referenced to ambient static pressure is applied downstream to the west of the proposed building with a fume flow being released continuously from the stacks. The CFD study was undertaken to estimate the pollution concentrations during near calm and windy conditions: ð      Wind Load Condition: An estimate of average wind velocity was determined for two prevailing wind conditions namely, southwest and northeast winds. At the upwind free boundary inlet velocity profiles were derived from the Australian Wind Code AS1170.2 [3]. Surrounding terrain was classified as Category 2 to the east and the west of the proposed building. A profile velocity inlet was provided 300 m to the west and east of the building and more than 250 m to the south and north of the building. At the downwind and upper free boundaries constant pressure boundary conditions were applied. The fume flow being released continuously from the stacks. ð      Near Calm Air Condition: A magnitude of wind speed of 1 km/hr was chosen to represent the calm condition. In this study only the east condition is investigated. A pressure boundary condition of zero referenced to ambient static pressure is applied downstream to the west of the proposed building with a fume flow being released continuously from the stacks.

    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 The following pollution emission rates obtained from Bestec were included in the 3-dimensional analysis during windy and near calm wind conditions: ð   The maximum pollution emission rate at each stack is 450 l/s. The mechanical engineering drawing suggests locating 18 stacks through the roof of a number of selected areas ð   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 ð   A pollution concentration of unity is assumed at the pollutant sources (i.e. exhaust stacks and ducts). The contaminant at the source is modelled as a one variable called CO with a concentration of unity at the sources ð   In the absence of other data the pollutants were assumed to be slightly heavier than air at the sources. However, one of the cases (south-westerly winds condition, was repeated using pollutants of a similar density than that of air The following pollution emission rates obtained from Bestec were included in the 3-dimensional analysis during windy and near calm wind conditions: ð   The maximum pollution emission rate at each stack is 450 l/s. The mechanical engineering drawing suggests locating 18 stacks through the roof of a number of selected areas ð   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 ð   A pollution concentration of unity is assumed at the pollutant sources (i.e. exhaust stacks and ducts). The contaminant at the source is modelled as a one variable called CO with a concentration of unity at the sources ð   In the absence of other data the pollutants were assumed to be slightly heavier than air at the sources. However, one of the cases (south-westerly winds condition, was repeated using pollutants of a similar density than that of air

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

    10. CFD Modelling Standard K-? 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 In general, summer and midseason winds occur from southwest at noon. The following results are presented for a typical day in May at noon where the average velocity at 1.5 m is 5 m/s. In this study inlet velocity profiles were derived from the Australian Wind Code AS1170.2. (velocity vector) and (velocity colour contours) show a plan view of the flow field 1.5 m above the ground level (typical chest level). Flow characteristic is seen to be captured well by the CFD model and the following can be concluded: ð      The flow around the proposed and neighbouring buildings generates an expected boundary layer profile ð      The flow is accelerated near the corners as expected A stagnation region is located immediately downstream of the proposed building and a number of neighbouring buildings. This is related to wind direction and angle of attack relative to the local building orientation In general, summer and midseason winds occur from southwest at noon. The following results are presented for a typical day in May at noon where the average velocity at 1.5 m is 5 m/s. In this study inlet velocity profiles were derived from the Australian Wind Code AS1170.2. (velocity vector) and (velocity colour contours) show a plan view of the flow field 1.5 m above the ground level (typical chest level). Flow characteristic is seen to be captured well by the CFD model and the following can be concluded: ð      The flow around the proposed and neighbouring buildings generates an expected boundary layer profile ð      The flow is accelerated near the corners as expected A stagnation region is located immediately downstream of the proposed building and a number of neighbouring buildings. This is related to wind direction and angle of attack relative to the local building orientation

    13. CFD Flow Results

    14. CFD Pollutant Dispersion Results concentration profile in a horizontal section at the chest level. Downwash effect A source of pollution with a concentration of unity was defined at the exhaust stacks. The total fume flow being released continuously from the stacks is 10500 L/min [4]. The concentration profiles for the windward and leeward side of the buildings are given in Figures 5 to 8. Figure 5 shows the concentration profiles in a horizontal section at the chest level. One can see that the pollutants are affected by the downwash flow and also transported away from the proposed building to the east side of Frome road due to the strong southwesterly winds (see also Figure 7). The concentration profiles are plotted on a scale between 0 to 1%. Pollutants with 1% source concentration are seen to accumulate near the dead zones created by buildings to the east of Frome Road. A source of pollution with a concentration of unity was defined at the exhaust stacks. The total fume flow being released continuously from the stacks is 10500 L/min [4]. The concentration profiles for the windward and leeward side of the buildings are given in Figures 5 to 8. Figure 5 shows the concentration profiles in a horizontal section at the chest level. One can see that the pollutants are affected by the downwash flow and also transported away from the proposed building to the east side of Frome road due to the strong southwesterly winds (see also Figure 7). The concentration profiles are plotted on a scale between 0 to 1%. Pollutants with 1% source concentration are seen to accumulate near the dead zones created by buildings to the east of Frome Road.

    15. CFD Pollutant Dispersion Results concentration profiles in a horizontal section at the 15 m elevation The pollutant dispersed to a wider region and the concentration is increased to 1.7% source concentration. A source of pollution with a concentration of unity was defined at the exhaust stacks. The total fume flow being released continuously from the stacks is 10500 L/min [4]. The concentration profiles for the windward and leeward side of the buildings are given in Figures 5 to 8. Figure 5 shows the concentration profiles in a horizontal section at the chest level. One can see that the pollutants are affected by the downwash flow and also transported away from the proposed building to the east side of Frome road due to the strong southwesterly winds (see also Figure 7). The concentration profiles are plotted on a scale between 0 to 1%. Pollutants with 1% source concentration are seen to accumulate near the dead zones created by buildings to the east of Frome Road. A source of pollution with a concentration of unity was defined at the exhaust stacks. The total fume flow being released continuously from the stacks is 10500 L/min [4]. The concentration profiles for the windward and leeward side of the buildings are given in Figures 5 to 8. Figure 5 shows the concentration profiles in a horizontal section at the chest level. One can see that the pollutants are affected by the downwash flow and also transported away from the proposed building to the east side of Frome road due to the strong southwesterly winds (see also Figure 7). The concentration profiles are plotted on a scale between 0 to 1%. Pollutants with 1% source concentration are seen to accumulate near the dead zones created by buildings to the east of Frome Road.

    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. In Figure 7 the outlets of the stacks is at the plane section. The pollution concentrations seen to increase to 3% source concentration near the roof of the building to the east of the proposed building.In Figure 7 the outlets of the stacks is at the plane section. The pollution concentrations seen to increase to 3% source concentration near the roof of the building to the east of the proposed building.

    17. CFD Pollutant Dispersion Results Concentration Profile- Iso-surface of 1% Source Concentration – Pollutant Slightly Heavier Than Air In Figure 7 the outlets of the stacks is at the plane section. The pollution concentrations seen to increase to 3% source concentration near the roof of the building to the east of the proposed building.In Figure 7 the outlets of the stacks is at the plane section. The pollution concentrations seen to increase to 3% source concentration near the roof of the building to the east of the proposed building.

    18. CFD Pollutant Dispersion Results Concentration Profile- Iso-surface of 1% Source Concentration – Pollutant of a Similar Density Than That of Air Was Used In Figure 7 the outlets of the stacks is at the plane section. The pollution concentrations seen to increase to 3% source concentration near the roof of the building to the east of the proposed building.In Figure 7 the outlets of the stacks is at the plane section. The pollution concentrations seen to increase to 3% source concentration near the roof of the building to the east of the proposed building.

    19. CFD Flow Results In general, summer and midseason winds occur from southwest at noon. The following results are presented for a typical day in May at noon where the average velocity at 1.5 m is 5 m/s. In this study inlet velocity profiles were derived from the Australian Wind Code AS1170.2. (velocity vector) and (velocity colour contours) show a plan view of the flow field 1.5 m above the ground level (typical chest level). Flow characteristic is seen to be captured well by the CFD model and the following can be concluded: ð      The flow around the proposed and neighbouring buildings generates an expected boundary layer profile ð      The flow is accelerated near the corners as expected A stagnation region is located immediately downstream of the proposed building and a number of neighbouring buildings. This is related to wind direction and angle of attack relative to the local building orientation In general, summer and midseason winds occur from southwest at noon. The following results are presented for a typical day in May at noon where the average velocity at 1.5 m is 5 m/s. In this study inlet velocity profiles were derived from the Australian Wind Code AS1170.2. (velocity vector) and (velocity colour contours) show a plan view of the flow field 1.5 m above the ground level (typical chest level). Flow characteristic is seen to be captured well by the CFD model and the following can be concluded: ð      The flow around the proposed and neighbouring buildings generates an expected boundary layer profile ð      The flow is accelerated near the corners as expected A stagnation region is located immediately downstream of the proposed building and a number of neighbouring buildings. This is related to wind direction and angle of attack relative to the local building orientation

    20. CFD Pollutant Dispersion Results Concentration Profile in Horizontal Section at 1.5 m Elevation In Figure 7 the outlets of the stacks is at the plane section. The pollution concentrations seen to increase to 3% source concentration near the roof of the building to the east of the proposed building.In Figure 7 the outlets of the stacks is at the plane section. The pollution concentrations seen to increase to 3% source concentration near the roof of the building to the east of the proposed building.

    21. CFD Pollutant Dispersion Results Concentration Profile in Horizontal Section at 15 m Elevation In Figure 7 the outlets of the stacks is at the plane section. The pollution concentrations seen to increase to 3% source concentration near the roof of the building to the east of the proposed building.In Figure 7 the outlets of the stacks is at the plane section. The pollution concentrations seen to increase to 3% source concentration near the roof of the building to the east of the proposed building.

    22. CFD Pollutant Dispersion Results North-Easterly Wind Condition In Figure 7 the outlets of the stacks is at the plane section. The pollution concentrations seen to increase to 3% source concentration near the roof of the building to the east of the proposed building.In Figure 7 the outlets of the stacks is at the plane section. The pollution concentrations seen to increase to 3% source concentration near the roof of the building to the east of the proposed building.

    23. CFD Pollutant Dispersion Results Calm Wind Condition – near the roof of the building In Figure 7 the outlets of the stacks is at the plane section. The pollution concentrations seen to increase to 3% source concentration near the roof of the building to the east of the proposed building.In Figure 7 the outlets of the stacks is at the plane section. The pollution concentrations seen to increase to 3% source concentration near the roof of the building to the east of the proposed 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-e model. The pollutant concentrations were predicted at the chest level and at a range of elevations during near calm wind and windy conditions. ð The CFD analysis has offered a comprehensive range of output including 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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