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March 14, 2006, 22:58 |
Hi,
Can someone tell me und
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#1 |
Senior Member
Pei-Ying Hsieh
Join Date: Mar 2009
Posts: 317
Rep Power: 18 |
Hi,
Can someone tell me under what condiction should momentumPredictor be set to yes? Thanks! Pei |
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March 15, 2006, 05:35 |
As far as I understand, in the
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#2 |
Member
Pierre Le Fur
Join Date: Mar 2009
Location: UK
Posts: 60
Rep Power: 17 |
As far as I understand, in the pressure-velocity algorithm for two-phase flows in Foam does not need the momentum equation to be solved, so in general momentumPredictor should be set to no, especially for "challenging" test cases (i.e if there is problems with convergence or sharp volume fractio gradient). In this case the momentum equation is only constructed and used to obtain fluxes and solve the pressure equation. On the other hand solving the momentum eqaution might speed up convergence in non-challenging steady-state calculations.
Hope that helps Pierre |
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March 15, 2006, 14:54 |
Thanks Pierre!
How about tu
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#3 |
Senior Member
Pei-Ying Hsieh
Join Date: Mar 2009
Posts: 317
Rep Power: 18 |
Thanks Pierre!
How about turbFoam? Pei |
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March 16, 2006, 14:07 |
TurbFoam uses the standard PIS
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#4 |
Member
Pierre Le Fur
Join Date: Mar 2009
Location: UK
Posts: 60
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TurbFoam uses the standard PISO algorithm, momentum equation is always solved. it can be used for unsteady or steady cases.
Pierre, |
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January 22, 2009, 05:53 |
Hi together,
for me it is n
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#5 |
New Member
Marc Wattenberg
Join Date: Mar 2009
Posts: 3
Rep Power: 17 |
Hi together,
for me it is not clear where the velocity field is coming from when the momentum equation is not solved. perhaps it is a stupid question but for the moment a need a hint thanks marc |
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January 22, 2009, 06:32 |
U = U* - grad(p)/A
where U*
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#6 |
Senior Member
Eugene de Villiers
Join Date: Mar 2009
Posts: 725
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U = U* - grad(p)/A
where U* = H/A i.e. U is solved explicitly after the pressure equation. |
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January 22, 2009, 11:25 |
Hi Marc,
It depends on the
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#7 |
Senior Member
Hrvoje Jasak
Join Date: Mar 2009
Location: London, England
Posts: 1,906
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Hi Marc,
It depends on the importance of the laplacian in the momentum equation: if you have important diffusivity in the momentum, you should solve the momentum equation implicitly. Enjoy, Hrv
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Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk |
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March 16, 2010, 04:16 |
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#8 |
Senior Member
Claus Meister
Join Date: Aug 2009
Location: Wiesbaden, Germany
Posts: 241
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Hey Foamers,
I read your posts. Could anybody tell me where to find a direct statement about this, i.e. no long text. Friends referred me to Ferziger. But I cannot find the right page. Cheers |
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March 16, 2010, 07:27 |
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#9 |
Senior Member
Sandy Lee
Join Date: Mar 2009
Posts: 213
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I want to know too. I guess, if we set no, maybe it is slow to get convergence to some cases, but they will get the same results, right? Who can give some light?
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March 17, 2010, 02:10 |
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#10 |
Senior Member
matej forman
Join Date: Mar 2009
Location: Brno, Czech Republic
Posts: 182
Rep Power: 17 |
Dear Claus,
Ferzinger , Peric, Comput. Methods for Fluid Dynamics is very good book and I guess you should read it all anyway. But not to waste your time, have a look at chapter 7.5 as a start. Also these slides from stanford I googled my appeal:http://www.stanford.edu/class/me469b...mpressible.pdf As a good quote from this site sais: "Two weeks of playing with a CFD code will save you one afternoon of reading". (sorry, I forgot the author). good luck matej |
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