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Modification of CFD code to model the atmospheric boundary layer Modelling atmospheric stability in EllipSys3D T. Koblitz A. Bechmann A. Sogachev N. N. Sørensen
Modification of CFD code to model the atmospheric boundary layer
Modelling atmospheric stability in EllipSys3D
T. Koblitz
A. Bechmann
A. Sogachev
N. N. Sørensen
Risø DTU, Technical University of DenmarkRisø DTU, Technical University of Denmark
Atmospheric stability
2
Chimney plume under stable and unstable conditions
13-july-2011ICWE13, Amsterdam, Netherlands
Source: kindly been provided by Dr. Torben Mikkelsen, Risø DTU and Dr. Thomas Ellermann, National Environmental Research Institute
stable unstable
Risø DTU, Technical University of DenmarkRisø DTU, Technical University of Denmark
Atmospheric stability
Why: Influence on the wind field
Source: Kaimal and Finnigan 1994,Wallace and Hobbs 2006
heat flux
heat flux
3
Flat terrain
Source: Kaimal and Finnigan 1994,Wallace and Hobbs 2006
13-july-2011ICWE13, Amsterdam, Netherlands
Risø DTU, Technical University of DenmarkRisø DTU, Technical University of Denmark
Atmospheric stability
Why: Influence on the wind field
Complex terrain
4
unstableneutralstable
13-july-2011ICWE13, Amsterdam, Netherlands
Risø DTU, Technical University of DenmarkRisø DTU, Technical University of Denmark
Contents
Atmosperic stability
• Why Influence on the wind profile
• How Momentum, Temperature, Turbulence equations
• Results Test Case I neutral ABL
Test Case II diurnal cycle in the ABL
5 13-july-2011ICWE13, Amsterdam, Netherlands
Risø DTU, Technical University of DenmarkRisø DTU, Technical University of Denmark
EllipSys3D:
• in-house Risø/DTU CFD code
• flow solver developed for flow over terrain (by N.N. Sørensen)
• development during the last ~20 years at Risø DTU
Governing equations:
• Momentum
• Coriolis forcing
• Temperature
Atmospheric stability
How: Implementation into Ellipsys3D
6 13-july-2011ICWE13, Amsterdam, Netherlands
Risø DTU, Technical University of DenmarkRisø DTU, Technical University of Denmark
Atmospheric stability
• Turbulence(k-ε)
• coefficient Cε3
• length-scale limiter
• ambient turbulence values
How: Implementation into Ellipsys3D
7 13-july-2011ICWE13, Amsterdam, Netherlands
Risø DTU, Technical University of DenmarkRisø DTU, Technical University of Denmark
Test Case I
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Neutral ABL simulationcompared against Cabauw site, Netherlands & Sogachev (2006)
13-july-2011ICWE13, Amsterdam, Netherlands
Risø DTU, Technical University of DenmarkRisø DTU, Technical University of Denmark
Test Case II
Transient simulation of diurnal cycle in the ABL
Numerics
• boundary conditions :
bottom: rough wall, T(t)
top: symmetry
vertical: cyclic
• computational domain:
12 x 12 x 3 km
32 x 32 x 128 grid points
9
Mellor & Yamada (1974)
13-july-2011ICWE13, Amsterdam, Netherlands
Risø DTU, Technical University of DenmarkRisø DTU, Technical University of Denmark
Results
Transient simulation of diurnal cycle in the ABL
10 13-july-2011ICWE13, Amsterdam, Netherlands
Risø DTU, Technical University of DenmarkRisø DTU, Technical University of Denmark
Results
Transient simulation of diurnal cycle in the ABL
11 13-july-2011ICWE13, Amsterdam, Netherlands
Risø DTU, Technical University of DenmarkRisø DTU, Technical University of Denmark
Results
Transient simulation of diurnal cycle in the ABL
12 13-july-2011ICWE13, Amsterdam, Netherlands
Risø DTU, Technical University of DenmarkRisø DTU, Technical University of Denmark
Results
Transient simulation of diurnal cycle in the ABL
13 13-july-2011ICWE13, Amsterdam, Netherlands
Risø DTU, Technical University of DenmarkRisø DTU, Technical University of Denmark
Results
Transient simulation of diurnal cycle in the ABL
14 13-july-2011ICWE13, Amsterdam, Netherlands
Risø DTU, Technical University of DenmarkRisø DTU, Technical University of Denmark
Conclusions / Future Work
AusblickRückblickFuture Work
• validation against flat terrain field data (e.g. Høvsøre)
• non-neutral flow over complex terrain
• validation against complex terrain field experiments
(e.g. Benekanahalli hill, India)
AusblickRückblickConclusions
• modifications implemented and validated
• diurnal flow pattern reproduced (qualitative comparison)
15 13-july-2011ICWE13, Amsterdam, Netherlands
Risø DTU, Technical University of DenmarkRisø DTU, Technical University of Denmark
Thank you for your attention!
13-july-2011ICWE13, Amsterdam, Netherlands
