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Low-Re Boundary Conditions for K-omega SST (aerodynamics) |
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April 29, 2020, 11:30 |
Low-Re Boundary Conditions for K-omega SST (aerodynamics)
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#1 |
New Member
Andrea Stedile
Join Date: Feb 2020
Posts: 11
Rep Power: 6 |
Hi all,
Noob here, having a simple question. Let's take the Motorbike tutorial, that is included in OpenFOAM: Code:
/opt/openfoam7/tutorials/incompressible/simpleFoam/motorBike I have already seen this post, but it is quite old and I am not sure if it is still valid: k-omega SST and wall functions in OpenFOAM-1.5-dev I will include for your convenience the code of the k, nut, omega, p, U.orig files. k Code:
#include "include/initialConditions" dimensions [0 2 -2 0 0 0 0]; internalField uniform $turbulentKE; boundaryField { //- Set patchGroups for constraint patches #includeEtc "caseDicts/setConstraintTypes" //- Define inlet conditions #include "include/fixedInlet" outlet { type inletOutlet; inletValue $internalField; value $internalField; } lowerWall { type kqRWallFunction; value $internalField; } motorBikeGroup { type kqRWallFunction; value $internalField; } #include "include/frontBackUpperPatches" } Code:
boundaryField { //- Set patchGroups for constraint patches #includeEtc "caseDicts/setConstraintTypes" frontAndBack { type calculated; value uniform 0; } inlet { type calculated; value uniform 0; } outlet { type calculated; value uniform 0; } lowerWall { type nutkWallFunction; value uniform 0; } upperWall { type calculated; value uniform 0; } motorBikeGroup { type nutkWallFunction; value uniform 0; } } Code:
#include "include/initialConditions" dimensions [0 0 -1 0 0 0 0]; internalField uniform $turbulentOmega; boundaryField { //- Set patchGroups for constraint patches #includeEtc "caseDicts/setConstraintTypes" #include "include/fixedInlet" outlet { type inletOutlet; inletValue $internalField; value $internalField; } lowerWall { type omegaWallFunction; value $internalField; } motorBikeGroup { type omegaWallFunction; value $internalField; } #include "include/frontBackUpperPatches" } Code:
#include "include/initialConditions" dimensions [0 2 -2 0 0 0 0]; internalField uniform $pressure; boundaryField { //- Set patchGroups for constraint patches #includeEtc "caseDicts/setConstraintTypes" inlet { type zeroGradient; } outlet { type fixedValue; value $internalField; } lowerWall { type zeroGradient; } motorBikeGroup { type zeroGradient; } #include "include/frontBackUpperPatches" } Code:
#include "include/initialConditions" dimensions [0 1 -1 0 0 0 0]; internalField uniform $flowVelocity; boundaryField { //- Set patchGroups for constraint patches #includeEtc "caseDicts/setConstraintTypes" #include "include/fixedInlet" outlet { type inletOutlet; inletValue uniform (0 0 0); value $internalField; } lowerWall { type fixedValue; value $internalField; } motorBikeGroup { type noSlip; } #include "include/frontBackUpperPatches" } |
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April 29, 2020, 21:22 |
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#2 |
New Member
Bssam
Join Date: Nov 2019
Posts: 19
Rep Power: 7 |
I assume that the boundary layer is already refined so that y+<1. If not then try to refine the boundary layer using the command:
refineWallLayer 'patchNmae' 0.5 Then type omegaWallFunction; value $internalField; automatically switches to a low Re in case y+<1 and it resolve the boundary layer without using any wall function and switches to wall function when y+ is large. No need to modify anything |
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April 30, 2020, 07:04 |
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#3 | ||
New Member
Andrea Stedile
Join Date: Feb 2020
Posts: 11
Rep Power: 6 |
Bassam, thanks for your answer.
Quote:
Quote:
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May 1, 2020, 00:05 |
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#4 |
New Member
Bssam
Join Date: Nov 2019
Posts: 19
Rep Power: 7 |
For omega wall function I am sure! You can revise the theory behind this wall function which switch automatically.
However, the k and nut should be: kLowReWallFunction nutLowReWallFunction I just realised that they were not a LowRe Please revise page 27 from this report that support my claims: A Thorough Description Of How Wall Functions Are Implemented In OpenFOAM - Chalmers |
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May 1, 2020, 09:39 |
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#5 |
New Member
Andrea Stedile
Join Date: Feb 2020
Posts: 11
Rep Power: 6 |
Thank you very much for your help and time, I will modify accordingly!
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May 2, 2020, 18:02 |
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#6 |
New Member
Bssam
Join Date: Nov 2019
Posts: 19
Rep Power: 7 |
So did it work with you? I tried the approach in another case and compared the results to experiment which was satisfactory
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May 3, 2020, 07:16 |
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#7 |
New Member
Andrea Stedile
Join Date: Feb 2020
Posts: 11
Rep Power: 6 |
Hi, right now I am trying to replicate in OpenFOAM a Simscale case that investigates the Ahmed body, using the boundary conditions that you suggested. I will get back to you as soon as possible and send you the outcomes when the solver will be done; it will take ~ 1 day because the mesh is pretty fine (18M cells and I am using a server with 8 cores only). Thank you again for your dedication
https://www.simscale.com/projects/gs...ni/ahmed_body/ |
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May 3, 2020, 10:50 |
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#8 |
New Member
Bssam
Join Date: Nov 2019
Posts: 19
Rep Power: 7 |
Wow 18M that definitely needs a cluster computer to handle the case. All the best in your simulations!
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Tags |
boundary conditions, boundary layer, k-omega sst, low-re, yplus |
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