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Old   April 19, 2016, 08:57
Default Implementation of new transportModel
Johannes Martens
Join Date: Jun 2015
Posts: 41
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Hi all,

I am currently trying to implement a new transport model describing non-newtonian behaviour according to the formula (attached file BloodViscosity.PNG) with the functions (attached file BloodViscosity_Functions.PNG).



I created the file structure for the transportModel as described in and took care of the division by the strainRate() similar to the implementation as it is done in the crossPowerLaw transportModel, which comes with the OpenFOAM compilation.

Foam::viscosityModels::generalizedPowerLaw::calcNu () const
(nuInf_ + deltaNu_*exp(-(scalar(1) + strainRate()/a_)*exp(-b_/max(strainRate(), 1/dimensionedScalar("VGREAT", dimTime, VGREAT) ) ) ) )
* pow(max(strainRate()/one_, dimensionedScalar("VSMALL", dimless, VSMALL)),
(nInf_ - deltaN_*exp(-(scalar(1) + strainRate()/c_)*exp(-d_/max(strainRate(), 1/dimensionedScalar("VGREAT", dimTime, VGREAT) ) ) ) ) - 1.0);


The library is compiled fine with wmake libso and the inclusion in the controlDict works fine, too. If I then start a simulation run, the calculations work fine until after a couple of timesteps the core is dumped. Either the bounding k explodes or the time step continuity error becomes too large.
This happens with a custom solver (based on pisoFoam) as well as with pisoFoam itself.
I guess the implementation of the formula is somehow bogus, but I don't know how I could do this more elegantly.
Or possibly the boundary conditions for k and nuSgs are chosen wrong? However, this seems weird to me, because the same BCs work fine in the Newtonian case.
Can anybody give me a hint to a direction, where I should be looking for an improvement? Or maybe someone sees a clear mistake in the code above, which I am missing?

Thanks a lot to anyone looking into this!

Best regards
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