Gas dispersion in atmospheric boundary layers · 2018. 3. 13. · CO2 concentration at 80m 0 20 40...
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Gas dispersion in atmospheric boundary layers HENRY PLISCHKA University Rostock, Chair of Modelling and Simulation 23. Februar 2018 c 2018 UNIVERSITÄT ROSTOCK | CHAIR OF MODELLING AND SIMULATION 0 / 12
Transcript of Gas dispersion in atmospheric boundary layers · 2018. 3. 13. · CO2 concentration at 80m 0 20 40...
Gas dispersion in atmosphericboundary layers
HENRY PLISCHKAUniversity Rostock, Chair of Modelling and Simulation
23. Februar 2018 c© 2018 UNIVERSITÄT ROSTOCK | CHAIR OF MODELLING AND SIMULATION 0 / 12
Motivation
• Simulation of gas dispersion in urban enviromentwith OpenFOAM
• Prediction e.g. for toxic and flamable gases
• Very complex underground
• Area upstream of dispersion should be resolved
• Reduce inlet length (synthetic turbulence at inlet)
• No precurser or recycling needed (lesscomputational costs)
∗
∗Copyright 2016 by Julia Boldt
23. Februar 2018 c© 2018 UNIVERSITÄT ROSTOCK | CHAIR OF MODELLING AND SIMULATION 1 / 12
Description of solver
• Using rhoReactingBuoyantFoam solver
• Conservation equations∂ρ
∂t+∇ ·
(ρU
)= 0 (1)
∂ρU
∂t+∇ ·
(ρUU
)= −∇p +∇ · (τeff ) + ρg (2)
∂ρYi
∂t+∇ ·
(ρUYi
)= +∇ ·
(µeff∇Yi
)+ Sy (3)
∂ρh
∂t+∇ ·
(ρUh
)+∂ρK
∂t+∇ ·
(ρUK
)= −∇ ·
(αeff∇h
)+ Sh (4)
• With additional initialization of p_rgh field
• Little changes in pressure correction for stability reasons
23. Februar 2018 c© 2018 UNIVERSITÄT ROSTOCK | CHAIR OF MODELLING AND SIMULATION 2 / 12
Description of first test case
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100 m80 m
60 m40 m
20 m
Vent locationu∞
†Jennifer Wen u. a. “Dispersion of carbon dioxide from vertical vent and horizontal releases—a numerical study”. In: Proceedings of the Institution of Mechanical Engineers, PartE: Journal of Process Mechanical Engineering 227.2 (2013), S. 125–139.
23. Februar 2018 c© 2018 UNIVERSITÄT ROSTOCK | CHAIR OF MODELLING AND SIMULATION 3 / 12
Description of first test case
†
• Dispersion of CO2 from jet (20 s inflow)
• Pure CO2 at the outlet
• Vent with D = 50 mm at 3 m height
• Pressure in CO2 vessel 151 bar
• Wind velocity at 2 m height≈ 1,8 m/s
• Measurements of CO2 concentrationdownstream at 1m height
∗Wen u. a., “Dispersion of carbon dioxide from vertical vent and horizontal releases—a numerical study”.
23. Februar 2018 c© 2018 UNIVERSITÄT ROSTOCK | CHAIR OF MODELLING AND SIMULATION 4 / 12
Description of simulation
• Profiles for T, U, CO2-fraction in 13 m above pipe (from †)
3 m
13 m
4 mInlet simulation
pipe
0.050.000.050.100.150.200.250.300.35
CO
2 in %
CO2 concentration
10
0
10
20
30
40
50
U in m
/s
velocity
0.0 0.5 1.0 1.5 2.0r in m
160
180
200
220
240
260
280
T in K
temperature
∗Wen u. a., “Dispersion of carbon dioxide from vertical vent and horizontal releases—a numerical study”.
23. Februar 2018 c© 2018 UNIVERSITÄT ROSTOCK | CHAIR OF MODELLING AND SIMULATION 5 / 12
Description of simulation
• RANS with constant atmospheric boundary layer profile (z0 = 0.01, suggested in †)
• Domain 190 m x 120 m x 150 m
• Mesh size 1M to 10M cells
†Wen u. a., “Dispersion of carbon dioxide from vertical vent and horizontal releases—a numerical study”.
23. Februar 2018 c© 2018 UNIVERSITÄT ROSTOCK | CHAIR OF MODELLING AND SIMULATION 6 / 12
Contour of CO2 concentration=1%
23. Februar 2018 c© 2018 UNIVERSITÄT ROSTOCK | CHAIR OF MODELLING AND SIMULATION 7 / 12
CO2 concentration at 80 m
0 20 40 60 80 100
time in s
−0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2C
O2
in%
exp 80 mfiates 2016this work
‡
• Good agreement with measurements
• Maximum is slightly overpredicted, second peak not occurs
‡Juliane Fiates u. a. “An alternative CFD tool for gas dispersion modelling of heavy gas”. In: Journal of Loss Prevention in the Process Industries 44 (2016), S. 583–593.
23. Februar 2018 c© 2018 UNIVERSITÄT ROSTOCK | CHAIR OF MODELLING AND SIMULATION 8 / 12
CO2 concentration at 100 m
0 20 40 60 80 100
time in s
0.0
0.5
1.0
1.5
2.0
CO
2in
%exp 100 mfiates 2016this work
‡
• Good agreement with increasing time of CO2
• Overpredicted maximum, second peak is only indicated
‡Fiates u. a., “An alternative CFD tool for gas dispersion modelling of heavy gas”.
23. Februar 2018 c© 2018 UNIVERSITÄT ROSTOCK | CHAIR OF MODELLING AND SIMULATION 9 / 12
Difficulties
In this comparison• Fluctuation in wind speed and direction
In general:• Measurements in the field are not repeatable• RANS fluctuactions are completely modelled• Modelling of highly rough walls is still subject of
research
⇒ Using high quality wind tunnel measurements fordifferent urban enviroments
⇒ Long time intervals for statistical analysis ofturbulence and gas occurrence
†
†
†Wen u. a., “Dispersion of carbon dioxide from vertical vent and horizontal releases—a numerical study”.
23. Februar 2018 c© 2018 UNIVERSITÄT ROSTOCK | CHAIR OF MODELLING AND SIMULATION 10 / 12
Outlook
• Verify the LeMoS-Inflow-Generator for urban athmospheric boundary layer (currentlyworking on this, using measurements of Michelstadt experiment)
⇒ Reproduce urban atmospheric boundary layer with LES simulation in free terrain (wallfunction or porous media at the bottom, periodic BC)
⇒ Verify turbulence properties
⇒ Extract U-profiles, length scales L and reynolds stresses R
⇒ Inflow-Generator in same domain
⇒ Validate turbulent boundary layer
• Dispersion simulation with Inflow-Generatorin urban enviroment
23. Februar 2018 c© 2018 UNIVERSITÄT ROSTOCK | CHAIR OF MODELLING AND SIMULATION 11 / 12
End
Thank you for your attention!
23. Februar 2018 c© 2018 UNIVERSITÄT ROSTOCK | CHAIR OF MODELLING AND SIMULATION 12 / 12
