[beluiz93]

Hello all,


I'm having a hard time calculating the viscous dissipation term in my flow field. Basically what I'm doing is multiplying the shear stress tensor times the strain rate tensor.


This is my expression:



ViscousDiss_lead
{
type swakExpression;
valueType cellZone;
zoneName controlvolume35by25_lead;
variables
(
"viscousdiss_lead=0.002*(pow(grad(U).xx,2)) + 0.001*(pow((grad(U).xy+grad(U).yx),2)) + 0.002*(pow(grad(U).yy,2));"
);
accumulations ( integrate );
expression "viscousdiss_lead";
verbose true;
writeStartTime no;
autoInterpolate true;
warnAutoInterpolate false;
autowrite true;
}



And the error I get:


--> FOAM FATAL ERROR:
Parser Error for driver CellZoneValueExpressionDriver at "1.1-4" :"field grad not existing or of wrong type"
"grad(U)"
^^^^
--|



I've seen other posts somewhat related to this but it seems it's not working when we try to use grad(U). I'm aware of snGrad but I can't use this one since what I want it's an integral of that in a specific cellZone. Any ideas on how to proceed?


Thanks in advance!


Bernardo

[beluiz93]

I managed to get a workaround if a replace grad(U) to gradU (rename it) but since this field is obtained in of4.1, I needed to change my patchField from extrapolatedCalculated to calculated and then it works...


Is it possible to use of4.1 with swak4foam?


Thanks again in advance!