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July 30, 2013, 08:58 |
LES for 2D case?
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#1 |
Member
X Meng
Join Date: Jun 2012
Location: Scotland
Posts: 89
Rep Power: 13 |
Dear Foamers,
When I use LES model for a 2D case, it suggests that 'LES is not strictly applicable.....' So, it means it is not ok to use LES for 2D case? A little bit confused. |
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July 30, 2013, 15:51 |
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#2 |
Senior Member
Nima Samkhaniani
Join Date: Sep 2009
Location: Tehran, Iran
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it can be used numerically, but when i asked an expert in turbulence it says using LES for 2D cases is non-sense as it LES using spatial filter
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July 30, 2013, 15:57 |
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#3 |
Super Moderator
Alex
Join Date: Jun 2012
Location: Germany
Posts: 3,400
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Two-dimensional turbulence has different physical behavior than three-dimensional turbulence.
That is why LES on a 2-dim. domain should not be used to obtain reliable results for 3-dim. flows. |
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July 31, 2013, 02:58 |
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#4 |
Member
X Meng
Join Date: Jun 2012
Location: Scotland
Posts: 89
Rep Power: 13 |
Emmm, I am using a 2D case to test my own developed solver, coz 3D case is bloody time-waste, if put too many grid inside the layer Y+<30.
I mean, is it a possible way to confirm the LES model's working well? |
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July 31, 2013, 05:42 |
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#5 |
Super Moderator
Alex
Join Date: Jun 2012
Location: Germany
Posts: 3,400
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If you are comparing your results to the results from another 2D LES solver, you should be fine.
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July 31, 2013, 07:59 |
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#6 |
Senior Member
Lieven
Join Date: Dec 2011
Location: Leuven, Belgium
Posts: 299
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Hi Xiangyin,
Both Alex and Nima are correct. You need to make a distinction between validating your implementation and validating your model. * If you purely want to validate your solver (so the numerical implementation), you can compare your results with other solvers. * However, if you want to validate it, doing a 2D LES is basically pure non-sense. Turbulence is by definition a 3D effect. As soons as you neglect this, you will probably end up with pure rubbish. Cheers, Lieven |
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July 31, 2013, 09:21 |
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#7 |
Member
X Meng
Join Date: Jun 2012
Location: Scotland
Posts: 89
Rep Power: 13 |
Thank you guys! That's really what I want to know.
My plan is to make sure every step is OK before using real 3D running, otherwise it is too long to try something in setup. Thanks again! |
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April 26, 2020, 04:03 |
Why 2D pitzDaily with "LES" in tutorials?
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#8 | |
Senior Member
Ali Shayegh
Join Date: Oct 2015
Posts: 130
Rep Power: 10 |
Quote:
Why OpenFOAM contains 2D pitzDaily with LES in Code:
tutorials/incompressible/pisoFoam/LES/pitaDaily Obviously it does not need to validate implementation, on the other hand, based on your saying, it is completely rubbish! Then why? |
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April 26, 2020, 08:14 |
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#9 |
Senior Member
Herpes Free Engineer
Join Date: Sep 2019
Location: The Home Under The Ground with the Lost Boys
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OpenFOAM tutorials are neither validation nor verification, but only a set of illustrations of the functionalities of OpenFOAM, so that users can fetch parts useful to them.
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April 26, 2020, 09:09 |
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#10 |
Senior Member
Ali Shayegh
Join Date: Oct 2015
Posts: 130
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By the way, I don't think they put a wrong case just for illustration purposes; Existing a 2D LES case somehow depicts the allowability of using LES with 2D geometries, at least in some situations.
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April 26, 2020, 10:13 |
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#11 |
Senior Member
Herpes Free Engineer
Join Date: Sep 2019
Location: The Home Under The Ground with the Lost Boys
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turbulence is by definition a three-dimensional phenomenon, except for some simplified cases of atmospheric flows; therefore, 2D LES is almost always nonsense since any vortex stretching mechanism is theoretically nonexistent in the governing equations (note: I do not refer to statistically independency or homogeneity). accordingly, they have definitely put the tutorial as an illustration, in my opinion.
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The OpenFOAM community is the biggest contributor to OpenFOAM: User guide/Wiki-1/Wiki-2/Code guide/Code Wiki/Journal Nilsson/Guerrero/Holzinger/Holzmann/Nagy/Santos/Nozaki/Jasak/Primer Governance Bugs/Features: OpenFOAM (ESI-OpenCFD-Trademark) Bugs/Features: FOAM-Extend (Wikki-FSB) Bugs: OpenFOAM.org How to create a MWE New: Forkable OpenFOAM mirror |
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April 26, 2020, 11:19 |
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#12 |
New Member
Join Date: Apr 2020
Posts: 3
Rep Power: 6 |
Hi
Your guids and helps are so good, I use them Thank you very much. |
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