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Solving the momentum equation

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Old   January 10, 2008, 11:39
Default Hi all! I have a simple que
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msg30
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Hi all!

I have a simple question, which may be a bit dumb but I cannot see immediately the answer. May be a case of "sitting too many hours in front of the PC" syndrom but I try it anyway:

When I look at the output from a transient icoFOAM for example we see that FOAM solves (in 2D say) first the U-momentum equation, then the V-momentum equation and then the respective PISO correctors. Correct so far? Or am I missled by the output on the screen?

I further assume that the scheme is implicit.

If the above is correct then you have to iterate over the U-V momentum equations using ADI for example, in order to get the change of V into U and vice versa, or? Or solve a coupled system of the moemtum equations. Otherwise it would not be explicit anymore and possibly not correct at all.

Am I missing something? Guess I am. Looking forward to the discussion!

Kind regards,

Markus

PS: Would it be possible to get FOAM 1.5 into the svn? Maybe on a "here it is but do not dare to email if something does not work yet" basis? That would be really great! Keep up the good work!
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Old   January 10, 2008, 17:54
Default I meant to write "Otherwise it
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msg30
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I meant to write "Otherwise it would not be implicit anymore and possibly not correct at all." of course ...

Cheers,

Markus
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Old   January 11, 2008, 08:24
Default Dear Markus, Having a look
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Patricio Bohorquez
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Dear Markus,

Having a look at icoFoam solver:

http://openfoamwiki.net/index.php/IcoFoam

you will realize that UEqn is constructed using a complete implicit method (fvm:: is employed to discretize all the differential operators).

These momentum equations are solved together with the continuity equation using a PISO loop (see, for instance, the comment by Hrv that follows

http://www.cfd-online.com/OpenFOAM_D...html#POST17984

or references in the Wiki cited above). Therefore, the Implicitly Discretized Fluid Flow Equations are not solved with a block-coupled approach, but this does not mean that icoFoam is not implicit anymore.

Does that make sense?

Best wishes,
Patricio
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