[Gerrit]

Hi,

I am solving a case with buoyantSimpleFoam. It is a small heated wire in a pipe that is laying horizontal (see picture attached). So inlet and outlet are on the same level.
Although my simulations run, I am still not sure about the pressure definitions.

1. As far as I know the pressures are related by this:

PHP Code:

p = p_rgh + rho*g*z 


I am simulating a gas and my pipe is only 6 mm in diameter, wouldn't that lead to:

PHP Code:

p=p_rgh 


2. How do I handle this if I have a pressure of for example 2 bar at outlet?

What I did until now is to define my p file like always:

   
  dimensions      [1 -1 -2 0 0 0 0];

 internalField   uniform 2e5;

   inlet
    {
        type            zeroGradient;
    }
    outlet
    {
        type            fixedValue;
        value           uniform 2e5;
    }
     "(wall1|wall2|wire)"
    {
        type            zeroGradient;
    }
    "(bottom|top)"
    {
        type            empty;
    }

and the p_rgh like this:

dimensions      [1 -1 -2 0 0 0 0];    

internalField   uniform 2e5;

boundaryField
{
    inlet
    {
        type            zeroGradient;
    }
    outlet
    {
        type            fixedValue;
        value           uniform 2e5;
    }

    "(wall1|wall2|wire)"
    {
        type            fixedFluxPressure;
        gradient        uniform 0;
        value           uniform 2e5;
    }

    "(bottom|top)"
    {
        type            empty;
    }
}

Especially in the p_rgh I am not sure, if my definitions are correct. Does it make sense to use zeroGradient at inlet for this?

Can someone give a comment on this please?

Thank you!

Best
Gerrit

[Gerrit]

Hi,

I continued on the case and found a tutorial called circuitBoardCooling. I copied the boundaries from there it now I think it makes somehow sense:

p:

dimensions      [1 -1 -2 0 0 0 0];

internalField   uniform 237233.6;

boundaryField
{
    inlet
    {
        type            zeroGradient;
    }
    outlet
    {
        type            fixedValue;
        value           uniform 237233.6;
    }
     "(wall1|wall2|wire)"
    {
        type            zeroGradient;
    }
    "(bottom|top)"
    {
        type            empty;
    }

}

and p_rgh

dimensions      [1 -1 -2 0 0 0 0];    

internalField   uniform 237233.6;

boundaryField
{
    inlet
    {
        type            zeroGradient;
    }
    outlet
    {
        type            fixedValue;
        value           uniform 237233.6;
    }

    "(wall1|wall2|wire)"
    {
        type            fixedFluxPressure;
        gradient        uniform 0;
        value           uniform 237233.6;
    }

    "(bottom|top)"
    {
        type            empty;
    }
}

I am still a little bit uncertain about the value itself. From my point of view it should be similar to the incompressible cases, where the pressure p is the static pressure. From that point of view I could set it to 0, right?

Best