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fvc::ddt(alphac) equals zero

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Old   August 3, 2017, 03:10
Default fvc::ddt(alphac) equals zero
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Dongyue Li
Join Date: Jun 2012
Location: Torino, Italy
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Hello guys,

Below is the pressure equation In MPPICInterFoam:
fvScalarMatrix p_rghEqn
            fvm::laplacian(Dp, p_rgh)
            fvc::ddt(alphac) + fvc::div(alphacf*phiHbyA)

//Info << fvc::ddt(alphac);
The problem is that fvc::ddt(alphac) is zero all the time. After commenting out this term, the solver gives the same result.

Below is from Jasak:
HTML Code:
Thus, if you try to evaluate the ddt the way it is written, it will recognise that the field does not have the oldTime() level stored and will use the current value to initialise it. Basically, fvc::ddt(magSqr(U)) will always give you zero, which is wrong.
One reason is that the alphac is so small, but it should not be zero. I am not sure ifs a bug.
Im the translator of OpenFOAM User Guide Chinese Edition! But always newbie on CFD.
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