[jeanpinto24|]

When changing the geometry of the cavity (solver icoFoam) case to a box with a cylindrical inlet and outlet like the attached image, I get the following error:

https://drive.google.com/open?id=0B8...1F1U1JkUko1cDQ

-> FOAM FATAL ERROR:
Continuity error can not be removed by adjusting the outflow.
Please check the velocity boundary conditions and / or run potentialFoam to initialise the outflow.
Total flux: 0.284255
Specified mass inflow: 1246.79
Specified mass outflow: 0
Adjustable mass outflow: 0


From function adjustPhi (surfaceScalarField &, const volVectorField &, volScalarField &)
In file cfdTools / general / adjustPhi / adjustPhi.C at line 118.

The entrance is by the lower cylinder.

I attach the files 0 / U and 0 / p:

FoamFile
{
version 2.0;
format ascii;
class volVectorField;
object U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField uniform (0 0 0);

boundaryField
{
inlet
{
type fixedValue;
value uniform (0 0 1);
}

exit
{
type fixedValue;
value uniform (0 0 0);
}

walls
{
type fixedValue;
value uniform (0 0 0);
}
}





FoamFile
{
version 2.0;
format ascii;
class volScalarField;
object p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField uniform 0;

boundaryField
{
inlet
{
type zeroGradient;
}

exit
{
type zeroGradient;
}

walls
{
type zeroGradient;
}
}

[wouter]

hello jeanpinto24|,
setting all inputs and outputs to a fixed value does not work with incompressible flows.
So either set the input or the output and leave the other for example zero gradient.

hope this helps
Wouter

[jeanpinto24|]

If the speed at the input can not have a fixed value, how is the input speed defined for the control volume? (Which in my case has a fixed value in the input).

Jean.

[Diro7]

Hi,

you can of course set a fixed velocity on the inlet, but you can't set another one at the outlet. icoFoam is a solver for incompressible fluid flows, so total volumetric flow rate must be conserved.

If you set a velocity on the inlet, the actual value at the outlet will be determined by the solution. Also, your inlet and outlet sections seem to be equal, so fixing different velocities at inlet and outlet is totally unphysical!

The usual choice is to set zeroGradient at the outlet, so fixing the gradient the actual value can be determined according the inlet value.

The same holds for pressure: it's common to set a fixedValue at the outlet (typically 0, since the fluid is incompressible only pressure differences matter) and zeroGradient at the inlet.

Andrea

[jeanpinto24|]

Hello Andrea,

Thank you for your thoughts on this case. According to your advice, make a change of the file 0 / U as follows (It is correct that the two cylinders have equal geometry):

FoamFile
{
Version 2.0;
Format ascii;
Class volVectorField;
Object U;
}
// * * * * * * * * * * * * * *

Dimensions [0 1 -1 0 0 0 0];

InternalField uniform (0 0 0);

BoundaryField
{
Inlet
{
Type fixedValue;
Value uniform (0 0 1);
}

Exit
{
Type zeroGradient;
}

Walls
{
Type zeroGradient;
}
}

I kept the file 0 / p:

FoamFile
{
Version 2.0;
Format ascii;
Class volScalarField;
Object p;
}
// * * * * * * * * * * * * * *

Dimensions [0 2 -2 0 0 0 0];

InternalField uniform 0;

BoundaryField
{
Inlet
{
Type zeroGradient;
}

Exit
{
Type zeroGradient;
}

Walls
{
Type zeroGradient;
}
}

I am waiting for the results of the simulation.

Jean.

[jeanpinto24|]

https://drive.google.com/file/d/0B89...phdU9FbXc/view

[wouter]

hello jeanpinto24|,

now you have set the wall as an outlet. fixed value for the wall of U=(0,0,0) because there is no flow through the wall.

Hope this helps
Wouter

[jeanpinto24|]

Hi wouter

I will now change from solver of icoFoam to buoyantBoussinesqPimpleFoam, I have the doubt to apply the Contour condition of Temperature, I would do it as follows:

FoamFile
{
Version 2.0;
Format ascii;
Class VolScalarField;
Object T;
}
// * * * * * * * * * * * * *

Dimensions [0 0 0 1 0 0 0];

InternalField uniform 300;

BoundaryField
{
Inlet
{
Type fixedValue;
Value uniform 500;
}
Exit
{
Type zeroGradient;
}
Walls
{
Type fixedValue;
Value uniform 300;
}
}

Is the procedure for the temperature contour condition correct?