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-   -   icoPoly8ThermoPhysics limits density below 2 kg/m3 (http://www.cfd-online.com/Forums/openfoam/98685-icopoly8thermophysics-limits-density-below-2-kg-m3.html)

smajer March 16, 2012 05:28

icoPoly8ThermoPhysics limits density below 2 kg/m3
 
Hello all,

I am trying to use chtMultiRegionSimpleFoam with liquid (water). Since it is important to take in account buoyant forces I have specified thermophysical properties as:
thermoType hRhoThermo<pureMixture<icoPoly8ThermoPhysics>>;

Unfortunately, it seems that a density is limited to 2 kg/m3.

To demonstrate this, I have changed the thermophysicalProperties file in multiRegionHeater case (tutorial for chtMultiRegionSimpleFoam).
For density (in this case constant, but it is just to demonstrate the problem) lower then 2 solver is using the value from thermophysicalProperties file. For density above 2 solver is fixing density to 2.
--------------
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.1.x |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "constant/topAir";
object thermophysicalProperties;
}

thermoType hRhoThermo<pureMixture<icoPoly8ThermoPhysics>>;

mixture
{
specie
{
nMoles 1;
molWeight 28.9;
}
equationOfState
{
// rhoCoeffs<8> ( 1.999 0 0 0 0 0 0 0 ); //If you use this, density is constant but lower then 2
rhoCoeffs<8> ( 2.1 0 0 0 0 0 0 0 ); //If you use this, density is constant and always 2 (it is same even if you put other coefficients for polynom)
}
thermodynamics
{
Hf 0;
Sf 0;
CpCoeffs<8> ( 1000 0 0 0 0 0 0 0 );
}
transport
{
muCoeffs<8> ( 1.8e-05 0 0 0 0 0 0 0 );
kappaCoeffs<8> ( 0.0242 0 0 0 0 0 0 0 );
Pr 0.7;
}
}

// ************************************************** *********************** //

---------------


Why is that so? In OF documentation (http://www.openfoam.com/features/thermophysical.php) we can find this statement:
"icoPolynomial - Incompressible polynomial equation of state, e.g. for liquids"

Can someone explain this?

Best regards,

Sinisa

Aurelien Thinat March 16, 2012 06:41

Hi,

Check out your fvSolution file. You may have limited the density value range.

smajer March 16, 2012 07:11

Well, that was quick and efficient!!
Thank you very much!!
That was the problem. I searched everything before posting here, but I didn't notice that density is limited in fvSolution.

Once again,

thanks!

Sinisa


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