[hrvig]

Dear all,

I modelling fully developed flow in a pipe having streamwise periodic dimensions. I am to investigate heat transfer and pressure drop characteristics. The momentum equation is corrected using the fvOptions:

momentumSource
{
type pressureGradientExplicitSource;
active true;
selectionMode all;

pressureGradientExplicitSourceCoeffs
{
fieldNames (U);
Ubar ( 0 0 35 );
}
}

which works just fine for the velocity alone. I want to obtain a fully developed thermal boundary layer as well. I found the channelFoam.C fine which contains an example of how the velocity can be updated:

// Correct driving force for a constant mass flow rate

// Extract the velocity in the flow direction
dimensionedScalar magUbarStar =
(flowDirection & U)().weightedAverage(mesh.V());

// Calculate the pressure gradient increment needed to
// adjust the average flow-rate to the correct value
dimensionedScalar gragPplus =
(magUbar - magUbarStar)/rAU.weightedAverage(mesh.V());

U += flowDirection*rAU*gragPplus;

gradP += gragPplus;

Info<< "Uncorrected Ubar = " << magUbarStar.value() << tab
<< "pressure gradient = " << gradP.value() << endl;

As I am quite new to C++ programming (still learning), I am having a hard to correct the temperature. I am using a modified simpleFoam solver which includes the temperature as a passive scalar:

while (simple.loop())
{
Info<< "Time = " << runTime.timeName() << nl << endl;

// --- Pressure-velocity SIMPLE corrector
{
#include "UEqn.H"
#include "pEqn.H"
}

turbulence->correct();

fvScalarMatrix TEqn
(
fvm::ddt(T)
+ fvm::div(phi, T)
- fvm::laplacian(DT, T)
);

TEqn.solve();

runTime.write();

Info<< "ExecutionTime = " << runTime.elapsedCpuTime() << " s"
<< " ClockTime = " << runTime.elapsedClockTime() << " s"
<< nl << endl;
}

Can anyone give hints on how to make the temperature scalar periodic to obtain a constant area average temperature field at the inlet of my geometry?

Best,
Jakob

[hrvig]

Did anyone make the temperature distribution cyclic using the fvOptions functionality of OpenFOAM 2.2?
The temperature can be considered as a passive scalar and therefore the energy equation is not solved.

For the velocity I added a source term to the momentum equation using

momentumSource
{
type pressureGradientExplicitSource;
active true;
selectionMode all;

pressureGradientExplicitSourceCoeffs
{
fieldNames (U);
Ubar ( 0 0 35 );
}
}

What about the temperature if I want to set the upstream mean temperature? I use constant wall temperature.

Best,
Jakob

[wyldckat]

Greetings Jakob,

I've moved your 2nd post from another thread: http://www.cfd-online.com/Forums/ope...m-2-2-2-a.html - because it was a bit out of context back there. Technically, the answer to your second post is: the "fvOption" "pressureGradientSource" only changes the pressure and flow fields, it does not affect directly all other fields.

As for your question from both posts, it seems you've managed to solve this issue, according to what you wrote on this thread: http://www.cfd-online.com/Forums/ope...tml#post539477 - posts #8 and onward

Best regards,
Bruno

[hrvig]

Hi Bruno,

Sorry for bring unclear. What I actually wanted to do was to use the new fvOptions to change a passive scalar field. I found options such as "scalarcodedsource" which I guess could do what I needed.

Anyway, I guess modifying the solver directly is still the way to go in most cases.

Best,
Jakob

[CI8]

I have the same need. Have you solved this issue?

[agustinvo]

Hello

what you can do is to use a semiImplicitSource, but first you need to know your heat flux, so you can get an idea of the input power. If you are working without density and specific heat capacity, then divide your heat source value by them, and use it in your fvOptions.

I hope that it would be helpful.

PS: hello Edoardo

[CI8]

Hi agustinvo, thanks! Let's continue on the other discussion:

Heat source using fvOptions in laplacianFoam

Ps. Ciao Agustin!!!