Computing Streamwise Turbulent HeatFlux

deji · May 28, 2011, 11:06

Hey there Foamers, I would like to confirm my understanding of calculating the streamwise turbulent heatflux, uT:

If I know Urms and Trms, can I take the product

uT= UrmsTrms ??

Thanks.

Thomas Baumann · May 30, 2011, 06:49

Hallo,

you can't do this:
you have to define the vectorfield
u*T, and get the mean-values out of this product and so get from this your rms values.

deji · May 30, 2011, 11:22

Thanks for the reply. I have checked, but it seems OpenFOAM fieldAverage does not have the capability of averaging u'T',v'T'. Is that so? Thanks much in advance.

Deji

Thomas Baumann · June 1, 2011, 06:29

Hi,

I would rewrite the solver and get an output similar to:

volVectorField UT
(
IOobject
(
"UT",
runTime.timeName(),
mesh,
IOobject::MUST_READ,
IOobject::AUTO_WRITE
),
U*T
);

and than in the controlDict:

functions
{
fieldAverage
{
type fieldAverage;
functionObjectLibs ("libfieldFunctionObjects.so");
enabled true;
outputControl outputTime;
fields
(
UT
{
mean on;
prime2Mean on;
base time;
}
);
}
}

Regards Thomas

deji · June 1, 2011, 12:32

Thank you very much Thomas.

Best regards,
Deji

May 28, 2011, 11:06	Computing Streamwise Turbulent HeatFlux	#1
deji Senior Member n/a Join Date: Sep 2009 Posts: 199 Rep Power: 18	Hey there Foamers, I would like to confirm my understanding of calculating the streamwise turbulent heatflux, uT: If I know Urms and Trms, can I take the product uT= UrmsTrms ?? Thanks.

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May 30, 2011, 06:49		#2
Thomas Baumann Senior Member Join Date: Apr 2009 Location: Karlsruhe, Germany Posts: 104 Rep Power: 18	Hallo, you can't do this: you have to define the vectorfield u*T, and get the mean-values out of this product and so get from this your rms values.

May 30, 2011, 11:22		#3
deji Senior Member n/a Join Date: Sep 2009 Posts: 199 Rep Power: 18	Thanks for the reply. I have checked, but it seems OpenFOAM fieldAverage does not have the capability of averaging u'T',v'T'. Is that so? Thanks much in advance. Deji

June 1, 2011, 06:29		#4
Thomas Baumann Senior Member Join Date: Apr 2009 Location: Karlsruhe, Germany Posts: 104 Rep Power: 18	Hi, I would rewrite the solver and get an output similar to: volVectorField UT ( IOobject ( "UT", runTime.timeName(), mesh, IOobject::MUST_READ, IOobject::AUTO_WRITE ), U*T ); and than in the controlDict: functions { fieldAverage { type fieldAverage; functionObjectLibs ("libfieldFunctionObjects.so"); enabled true; outputControl outputTime; fields ( UT { mean on; prime2Mean on; base time; } ); } } Regards Thomas

June 1, 2011, 12:32		#5
deji Senior Member n/a Join Date: Sep 2009 Posts: 199 Rep Power: 18	Thank you very much Thomas. Best regards, Deji