- **OpenFOAM Running, Solving & CFD**
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- - **Solving the momentum equation**
(*https://www.cfd-online.com/Forums/openfoam-solving/59236-solving-momentum-equation.html*)

Hi all!
I have a simple queHi 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! |

I meant to write "Otherwise itI meant to write "Otherwise it would not be implicit anymore and possibly not correct at all." of course ...
Cheers, Markus |

Dear Markus,
Having a look 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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