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Wrong treatment of time derivatives in matrices (Jasak Presentation)

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Old   February 1, 2017, 16:44
Default Wrong treatment of time derivatives in matrices (Jasak Presentation)
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Tobias Holzmann
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Dear community,

today I got an interesting presentation that was held last year Hrvoje Jasak with the title Pressure-Velocity Coupling in FOAM - Consistent Derivation for Steady and Transient Flow Solvers. Here it is described that the included time term in the matrices:

Code:
fvVectorMatrix UEqn
(
    fvm::ddt(U)
    ...
)
lead to wrong or lets say time-step depended results. Therefore, I came across this problem again (already forgot it). At the moment I did not read everything but I will do that. It seems that the included ddt term makes troubles in both, transient and steady-state solvers and therefore the ddtCorr() function takes care of removing the troubles somehow.

Can someone provide some information about that and does anyone know if this will be re-implemented in a correct and consistent way in future like Jasak suggested? However, there is one question left because based on the fact that the developers introduced the ddtCorr() function, they know that there is a problem (more or less), so why do they patch it instead of fix it. Maybe there is some special meaning of doing it in that way or there is no other possible way (but again, Jasak demonstrated it).

In addition I want ask kindly if this ddtCorr is related to the Rhie Chow Interpolation because something is mentioned here: DdtPhiCorr However, here it is said that this stuff is consistent while Jasak mentioned in his presentation, that it is not consistent. In addition I will check out the paper that is mentioned in the above mentioned thread.

Thanks in advance.
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