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Turbulance Model- how they ensure closure of RANS Model.

Posted May 13, 2013 at 07:11 by K_RAMAKRISHNAN

In CFD simulations involving turbulence we are focused on predicting the effect of the turbulent flow rather then the actual fluid flow. Example we are not worried about the eddies which happen on a microsecond timescale but are rather focused on the effect that turbulence will have on flow parameters.

In RANS Model we introduce extra variables like u', v', p' in the flow equations. Many different types of turbulence models provide additional equations which must be satisfied my flow...
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Help using FLUENT in batch mode: script in the Journal file

Posted April 29, 2013 at 11:11 by diamondx

danobis, here is a working example of a journal files (.jou), when you see a ";", it means i'm asking fluent to skip that command:

/file/read-case-data /home/maghazlani/Analysis/intake_test_3-1-23000.cas
;/define/operating-conditions/operating-pressure 0
;/define/models/solver/density-based yes
;/define/models/energy yes
;/define/models/viscous/kw yes
;/define/boundary-conditions/modify-zones/zone-type 11 pressure-inlet
;/define/materials/change-create...
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Rating: 4 votes, 3.25 average.

Decomposition methods in parallel

Posted April 23, 2013 at 01:05 by Tushar@cfd (Blogs: OpenFOAM)
Updated March 27, 2015 at 06:51 by Tushar@cfd (Minor corrections)

OpenFOAM has four methods of decomposition:
(1) simple
(2) hierarchical
(3) scotch
(4) manual

"Scotch decomposition requires no geometric input from the user and attempts to minimise the number of processor boundaries."(for more information refer OpenFOAM website)

We tried to compare "simple" and "scotch" methods. These methods were verified for a test case using similar processor inputs:

Both...
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2D-empty vs pseudo 2D upd. results

Posted April 18, 2013 at 02:53 by skeptik (CFD notes)
Updated April 18, 2013 at 03:15 by skeptik

Pseudo 2D results is here on the graph
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Cx is predicted very well, so let's make a comparation with 2D results

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The difference is really big on supercritical angles, the PISO's results on 2D tetra meshes were also bad and quite similar to the 2D hexa's results.

So, it's better to use PISO with symmPlane or slip BC on domain's sides

#OpenFoam #2Dairfoil
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2D-empty vs pseudo 2D - symmPlane

Posted April 15, 2013 at 04:35 by skeptik (CFD notes)

It seems there is big difference in case with 1-cell thick domain where we set empty BC compare to case with 5-cells or 3 - cells thick where we set symmPlane

for SST and NACA23012 we have (17 and 15 grad angle of attack)

Click image for larger version

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So when we use PISO, it would be better to use 5 or 3 -cells thick domain.
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