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overpressure room

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Old   July 23, 2018, 05:26
Default overpressure room
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Aurélien Mingot
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Hi

I have a little question with the buoyantBoussinesqSimplefoam solver. I run a simulation for a room with supply and extract system air. But It works only when supply flow=extract flow otherwise I have continuity error message. I would like to know if we can simulate an overpressure room even if buoyantBoussinesq is for incompressible flow. I would like to know if it possible without using potentialfoam.

I have for p
zeroGradient ( supply qnd extract)
for U
flowRateInletVelocity ( supply)
flowRateOutletVelocity ( extract)
for p-rgh
fixedFluxPressure
uniform 0 (supply and extract )

Thanks a lot
Aurélien
Have a nice day
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Old   July 23, 2018, 06:45
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Peter Baskovich
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Hello,
You are going to have numerical issues because the problem is constrained.
Typically we setup cases with Dirichlet-Neumann partitioning, this means if you specify the value at one patch, you must specify the gradient at the alternate patch.
See: BC common combinations
Typically we would used a "fixed" velocity inlet and a "fixed" pressure outlet.
The alternate patches get a zeroGradient condition to avoid over constraint.
Try:
Inlet
U flowRateInletVelocity
p fixedFluxPressure

Outlet
U fluxCorrectedVelocity
p fixedMean (or just fixedValue 0, if it's unstable)

These should work if there is no circulation across the patches (no inflow on an outlet etc)
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Old   July 23, 2018, 09:57
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Aurélien Mingot
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Thanks for your answer !
So I understand now that I have to use a fixed velocity inlet with fixed pressure outlet or a fixed velocity outlet and a fixed pressure inlet, that's it ?

I tried with your parameters but I have continuity errors again. I probably made mistake in my files.
Quote:
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: plus |
| \\ / A nd | Web: www.OpenFOAM.com |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volScalarField;
object p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [0 2 -2 0 0 0 0];

internalField uniform 0;

boundaryField
{
ceiling
{
type zeroGradient;
}

doors
{
type zeroGradient;
}

exposedwalls
{
type zeroGradient;
}
floor
{
type zeroGradient;
}

indoorwalls
{
type zeroGradient;
}

kitchenExtract
{
type fixedValue;
value uniform 0;
}
supply
{
type fixedFluxPressure;
value uniform 20;
}

wetrommsExtract1
{
type fixedValue;
value uniform 0;
}
wetrommsExtract2
{
type fixedValue;
value uniform 0;
}
wetrommsExtract3
{
type fixedValue;
value uniform 0;
}
windows
{
type zeroGradient;
}
}

// ************************************************** *********************** //
here is my p file is it set up correctly ?

and here my U file
Quote:
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: plus |
| \\ / A nd | Web: www.OpenFOAM.com |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volVectorField;
object U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [0 1 -1 0 0 0 0];

internalField uniform (0 0 0);

boundaryField
{
ceiling
{
type noSlip;
}

doors
{
type noSlip;
}

exposedwalls
{
type noSlip;
}
floor
{
type noSlip;
}

indoorwalls
{
type noSlip;
}

kitchenExtract
{
type fluxCorrectedVelocity;
phi phi;
rho rho;

}
supply
{
type flowRateInletVelocity;
volumetricFlowRate constant 0.7;
value uniform (0 0 0);
}

wetroomsExtract1
{
type fluxCorrectedVelocity;
phi phi;
rho rho;
}
wetroomsExtract2
{
type fluxCorrectedVelocity;
phi phi;
rho rho;
}
wetroomsExtract3
{
type fluxCorrectedVelocity;
phi phi;
rho rho;
}
windows
{
type noSlip;
}
}

// ************************************************** *********************** //
perhaps the error comes from others files but with continuity errors it should be U and p the problem.

Thanks for your link I will have a look now
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