# Solving the momentum equation

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 January 10, 2008, 11:39 Hi all! I have a simple que #1 msg30 Guest   Posts: n/a 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!

 January 10, 2008, 17:54 I meant to write "Otherwise it #2 msg30 Guest   Posts: n/a I meant to write "Otherwise it would not be implicit anymore and possibly not correct at all." of course ... Cheers, Markus

 January 11, 2008, 08:24 Dear Markus, Having a look #3 Member   Patricio Bohorquez Join Date: Mar 2009 Location: Jaén, Spain Posts: 95 Rep Power: 10 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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