[AnjaMiehe]

Hello Dirk,

Thanks for your answer. I am using the code by Fabian Rösler and I have read the paper by him as well as the paper for the d'Arcy Term and the techniques for the energy equation.
However, I still have problems with the additional source terms in the concentration equation. Would you share some code? The ideas I had in coding do compile but do I do get errors on solving.
Regards, Anja

[dzi]

hi anja,
i observed that the solution is very sensible to the diffusion coefficient (->instable if too high). In principle it works like described above with the governing eqn for the concentration, where the source term for cLiq is given by the change of alpha.

{
dAlpha = alpha - alpha.oldTime();
cTmp = - dAlpha * cLiq * k / runTime.deltaT();
fvScalarMatrix liqSegEqn
(
fvm::ddt(cLliq)
+ fvm::div(phi, cLiq)
- alpha * fvm::laplacian(DLiq, cLiq)
== cTmp
);

pLiqSegEqn.solve();
};

As mentioned, there is still a error for the total bilance over time evolution which I could not fix yet.

best dirk

Originally Posted by AnjaMiehe

Hello Dirk,

Thanks for your answer. I am using the code by Fabian Rösler and I have read the paper by him as well as the paper for the d'Arcy Term and the techniques for the energy equation.
However, I still have problems with the additional source terms in the concentration equation. Would you share some code? The ideas I had in coding do compile but do I do get errors on solving.
Regards, Anja

[dzi]

Hi,
I fond another strange behaviour of this solver. If I use it for the mirrored problem (i.e. the solidification goes form left to right) the solution changes.
because laplacian(DLiq, cLiq) gives either positive or negative values, depending on the direction. But why?
Idea: use the abs value of it, but this wont compile.

How can I write:
alpha * fvm::laplacian(DLiq, cLiq)
as
mag(alpha * fvm::laplacian(DLiq, cLiq)) or similar?

Here the solver again:

{
dAlpha = alpha - alpha.oldTime();
cTmp = - dAlpha * cLiq * k / runTime.deltaT();
fvScalarMatrix liqSegEqn
(
fvm::ddt(cLliq)
+ fvm::div(phi, cLiq)
- alpha * fvm::laplacian(DLiq, cLiq) // <- this term acts as source or as sink, depending on the direction of solidifiaction
== cTmp
);
liqSegEqn.solve();
};

The other problem: "large" diffusion coefficients for DLiq(>1e-6) end in no usable, funny patterns for the concentration - also for smaller timesteps.
What else could I adjust?
Thanks for any hint.
dirk