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How to applying surface roughness in Openfoam damBreak? |
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April 4, 2018, 20:50 |
How to applying surface roughness in Openfoam damBreak?
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#1 |
New Member
Jesse Cheung
Join Date: Apr 2018
Posts: 18
Rep Power: 8 |
Hello, I am a new OpenFOAM user and currently working on how the effect of surface roughness affecting the impact introduced by dam break.
As a result, I am building a model through using the damBreak in OpenFoam Tutorial. Is there any way to introduce surface roughness into damBreak? sincerely, Jesse |
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April 4, 2018, 21:49 |
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#2 |
Senior Member
Pablo Higuera
Join Date: Jan 2011
Location: Auckland
Posts: 627
Rep Power: 19 |
Hi Jesse,
you need to run the case with a turbulence model and specify nutkRoughWallFunction for nut. Ks is the equivalent grain roughness (Nikuradse) and Cs is a roughness constant, check the details here: https://cpp.openfoam.org/v3/a01666.html#details All this is put into play in the damBreakWithObstacle tutorial. Best, Pablo |
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April 4, 2018, 22:44 |
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#3 | |
New Member
Jesse Cheung
Join Date: Apr 2018
Posts: 18
Rep Power: 8 |
Quote:
However, I still not quite sure how to run the case with a turbulence model and specify nutkRoughWallFunction for nut. Do you mind elaborate more? Many thanks! Jesse |
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April 5, 2018, 07:01 |
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#4 | ||
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Jesse Cheung
Join Date: Apr 2018
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Quote:
Does it mean all I need to do is to change the value of Ks and Cs (in bold text) nut file in file 0 in order to control the surface roughness? Quote:
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April 5, 2018, 07:19 |
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#5 |
Senior Member
Pablo Higuera
Join Date: Jan 2011
Location: Auckland
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Exactly, select the appropriate values for your case and check damBreakWithObstacle tutorial if you can't make it work at first.
Pablo |
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April 5, 2018, 07:22 |
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#6 |
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Jesse Cheung
Join Date: Apr 2018
Posts: 18
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Many thanks for your help!
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April 5, 2018, 09:41 |
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#7 | ||
New Member
Jesse Cheung
Join Date: Apr 2018
Posts: 18
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Quote:
int the nut file, do i need to include those 'faces' as zeroGradient? see the following quote Quote:
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December 19, 2018, 17:19 |
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#8 |
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Nicola D'Ettole
Join Date: Nov 2018
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For velocity , pressure, k, epslion i have to use rough functions ?
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January 16, 2020, 19:15 |
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#9 |
New Member
Join Date: Nov 2019
Posts: 24
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Hello. The nutkRoughWallFunction requires 3 entries:
Ks Cs value What does it mean "value"? For example In the dam break with obstacle tutorial the entries are: Ks uniform 0.0001; Cs uniform 0.5; value uniform 5e-07; What does it mean value uniform 5e-07? Also what does value $internalField means? Sorry for the stupid question but I cannot find valid documentation. Thank you. |
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January 19, 2020, 09:18 |
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#10 |
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Michael Alletto
Join Date: Jun 2018
Location: Bremen
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I'm not sure if the value is really required. It is written to the file since the nutwallfunctions are derived from the fidedValue boundary condition.
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January 20, 2020, 02:08 |
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#11 | |
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Quote:
I am quite sure that a value is needed because if i delete that line the code does not run and gives me error. It could be that the value is uninfluential when using the nutkwallfunctions but how can i be sure about it? Where can i find official reference about this function?? Thank you |
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January 20, 2020, 05:36 |
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#12 |
Senior Member
Michael Alletto
Join Date: Jun 2018
Location: Bremen
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You find some reference here:
https://www.openfoam.com/documentati...8H_source.html https://www.openfoam.com/documentati...8C_source.html some good explanation about wall functions in general (read the chapter standard wall function): http://www.tfd.chalmers.se/~lada/pos..._report_WF.pdf wall functions in openfaom http://www.tfd.chalmers.se/~hani/kur...nfoamFinal.pdf Unfortunately the nutkroughwallfunction is not described. But the only difference to the nutkwallfunction is the assumed velocity profile in the first cell adjacent to the wall. Hope this helps Best Michael |
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January 22, 2020, 00:01 |
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#13 |
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Excellent! Thank you!
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October 13, 2020, 06:14 |
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#14 | |
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Feng
Join Date: Apr 2017
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Quote:
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dambreak, openfoam, roughness, surface |
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