janafThermo error T=0
Dear all!
I implemented a combustion model into chtMultiRegionFoam using the janafThermo<equationOfState> (hsPsiMixtureThermo<veryInhomogeneousMixture<suthe rlandTransport<specieThermo<janafThermo<perfectGas >>>>>). Any time when I apply the solidWallMixedTemperatureCoupled BC to couple the solid and fluid regions I get the following error: Code:
> FOAM FATAL ERROR: (1) The error disappears when any other BC than solidWallMixedTemperatureCoupled is applied at the solidfluid interface. (2) I checked the values of the solidfluid interface and internal temperatures and all of them are greater than zero. (3) The error happens at the first time the code enters the sensible enthalpy (hs) equation. (4) The problem appears no matter the combustion model is en or disabled. Does anybody have made similar experience or have any idea what the problem could be? I greatly appreciat your comments! Best regards, Aram 
it looks like the error relates to lower bound of JANAF table. try with manually changing the lower bound from 200 K to much lower value of about 50 K. initialize the T field above this value. probably this may fix it.

hi chandra,
thanks for your comment! I tried to set the the lower temperature to e.g. 50K but the problem persists. From somewhere the checkTfunction gets a Tvalue equal to zero, but only when the mentioned BC is used; I couldn t figure out yet where or how T=0K occurs but I ll keep on digging. regards, aram 
Have you already tried the new Janaf model?

hi!
i played arround with the initial temperatures of the fluid and solid regions and observed the following: the "solidWallMixedTemperatureCoupled" BC is of type "mixedFvPatchScalarField", switching between "fixedValue" (if heat flux is outgoing) and "fixedGradient" (when flux is incoming) for the T. I figured out that the above mentioned error message from JANAF happens at the moment one of the fluid patches on the solidfluid intreface is set to "fixedGradient" (no error if all patches ar set to "fixedValue"!). hence, I thought the problem depends on the sign of the heat flux or the Tgradient at the interface (as it governs the switching of the mixed BC) and used a "fixedGradient" BC with different signs of "gradient" for T on the fluid side. no error message was outputed, neither for a positive nor a negative Tgradient. therefore the problem is with the mixed BC in combination with JANAF. I ll keep on digging and report. @cedric: thanks a lot for the hint! I ll have a look at the new JANAF model. regards, aram 
hi all!
finally i found the problem. when using the solidWallMixedTemperatureCoupled BC a mixedEnthalpyFvPatchScalarField is used to calculate the BC for hs when entering the hsequation. there a refValue() for hs is determined as follows (see mixedEnthalpyFvPatchScalarField.C): refValue() = thermo.hs(Tw.refValue(), patchi); Tw is the temeperature field evaluated by the solidWallMixedTemperatureCoupled BC, where the Tw.refValue() is calculated as (see solidWallMixedTemperatureCoupledFvPatchScalarField .C): Code:
// if outgoing flux use fixed value, else fixed gradient. best regards, aram ps: should this be reported as a bug???? 
very nice troubleshooting!!!:)

All times are GMT 4. The time now is 07:29. 