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July 28, 2016, 14:45 |
Setting atmopheric boundary layer
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#1 |
Member
Almond Wong
Join Date: May 2016
Posts: 68
Rep Power: 9 |
Hi,
I am trying to understand how to set up an atm boundary layer. I came across 2 threads that i felt were relevant. However, I would like to clarify something. Following this thread: http://www.cfd-online.com/Forums/ope...ary-layer.html. nutRoughWallFunction was used. Supporting that is this thread: http://www.cfd-online.com/Forums/ope...ocumented.html which detailed the specification to be: Code:
{ type nutRoughWallFunction::Ks; value uniform 0.001; type nutRoughWallFunction::Cs; value uniform 0.5; } Code:
{ type nutkAtmRoughWallFunction; z0 $z0; value uniform 0.0; } 1) which is the "more correct" function to depict an ABL? 2) How are Ks and Cs specified through nutkAtmRoughWallFunction or are they somehow accounted for? |
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July 28, 2016, 17:02 |
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#2 |
Member
Almond Wong
Join Date: May 2016
Posts: 68
Rep Power: 9 |
If I were to simulate flow over a city (reasonably defined) using the nutkAtmRoughWallFunction, do I have to define z0 as per required as 2.0 or leave it out as it is already accounted for by the geometry?
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April 12, 2019, 18:31 |
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#3 |
Member
Andrew O. Winter
Join Date: Aug 2015
Location: Seattle, WA, USA
Posts: 78
Rep Power: 10 |
It seems to me that there is a more appropriate set of functions to use for simulating atmospheric boundary layer behavior. I'm working on trying out the BCs for U, k, and epsilon as defined according to https://www.openfoam.com/documentati...daryLayer.html.
Additionally, there is a different nut BC that can be used to go along with these U, k, and epsilon BCs, which can be read about at https://www.openfoam.com/documentati...8H_source.html. To address your question about z0, you have to set it to something non-zero for the equations to work out since it is used in the denominator of some of them. Thus I think setting it to the "physically correct" value according to the type of terrain roughness you're trying to model even if you're explicitly including those objects is the way to go. |
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August 4, 2022, 11:04 |
wall-functions for the ABL
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#4 |
New Member
Juan Carlos
Join Date: Aug 2022
Posts: 1
Rep Power: 0 |
Hi everyone!
Even though it has been six years ago, I think the next link (from Chalmers University) might be helpful for anyone looking for more answers: http://www.tfd.chalmers.se/~hani/kur..._Segersson.pdf I hope, it helps. Sincerely, Juan |
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