|
[Sponsors] |
April 18, 2016, 10:52 |
Advice about turbulence models?
|
#1 |
New Member
Join Date: Feb 2016
Posts: 28
Rep Power: 10 |
Hi everyone!
I am looking for advice about turbulence models in OpenFoam. I have tried three turbulence models (k-omega SST, k-epsilon, Spalart-Allmaras) for the same case (study of the wind load on a building). At the beginning, I used the k-omega SST model but results were not enough accurate. So I tried the k-epsilon model but the calculation did not seem to converge. With the Spalart-Allmaras, model results are ridiculous. The stagnation pressure is approximately 50% higher than expected. The geometry is complex so it is really difficult to create a good mesh using snappyHexMesh. I know that differences between turbulence models could be due to the mesh, but it seems I cannot improve the quality of the mesh with snappyHexMesh. I cannot show the mesh or the geometry, it is for an industrial case. Regards, mqsim |
|
April 25, 2016, 19:24 |
|
#2 |
New Member
anas
Join Date: Jun 2015
Posts: 18
Rep Power: 11 |
Hi mqsim,
You are comparing 3 different turbulence models. k-omega is accurate but requirs yplus ~ 1. The standard k-epsilon is not that accurate but usually it converge easier. On the other hand Spalart-Allmaras is not that accurate since it is a one equation model. I suggest to check your yplus. Then compare the results obatined with k-omega (with yplus ~1) with that obtained by realizableKE model. All the best and success. |
|
April 26, 2016, 05:10 |
|
#3 |
New Member
Join Date: Feb 2016
Posts: 28
Rep Power: 10 |
Hi anas,
Thank you for your answer. I am not sure to understand what means "yplus". Is it the size of the mesh in the y direction? mqsim |
|
April 26, 2016, 13:55 |
|
#4 |
New Member
anas
Join Date: Jun 2015
Posts: 18
Rep Power: 11 |
||
April 27, 2016, 05:36 |
|
#5 |
New Member
Join Date: Feb 2016
Posts: 28
Rep Power: 10 |
Thank you Anas! Hopefully it will help me to improve my models.
|
|
April 27, 2016, 08:02 |
|
#6 |
Super Moderator
Tobias Holzmann
Join Date: Oct 2010
Location: Bad Wörishofen
Posts: 2,711
Blog Entries: 6
Rep Power: 52 |
I just want to mention that
kEpsilon vs kOmega: kEpsilon is more accurate far away from walls kOmega is more accurate at walls Therefore the kOmega-SST model was introduced which at least blends both models
__________________
Keep foaming, Tobias Holzmann |
|
April 27, 2016, 08:50 |
|
#7 |
New Member
Join Date: Feb 2016
Posts: 28
Rep Power: 10 |
Thank you Tobi for your answer, it is really useful to me!
|
|
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
PANS turbulence models | HelioVillanueva | OpenFOAM Programming & Development | 39 | June 23, 2024 08:13 |
Only two turbulence options available in CFX Pre | Jack001 | CFX | 5 | March 30, 2016 03:47 |
Y plus for various turbulence models | taram | CFX | 8 | December 16, 2013 12:44 |
Are there more FLUENT Turbulence Models? | Travis | FLUENT | 3 | December 30, 2008 02:45 |
Turbulence models become invalid at Re=2000~5000? | liweif | FLUENT | 9 | August 27, 2007 12:55 |