[dEntropy]

hi,

me = noob
me = that guy who has spent days searching
me = that guy who prefers comsol over openFoam


preliminaries: i'm trying to solve an incompressible flow problem with a simple Newtonian fluid. I am using a fairly simple geometry, though the fluid dynamics are anything but simple. I know the Re, so i am setting the inlet as a uniform fixed value and trying to get output from potentialFoam...for use in my pimpleFoam simulation.

I do not know the pressure, but i can at least set the outlet as a uniform fixed value = 0, or zerogradient.

I have absolutely no idea what value to set for pressure inlet. None!

ideas?


p:

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

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

internalField   uniform 0;

boundaryField
{
    

    inlet-1
    {
        type            zeroGradient;
    }

    inlet-2
    {
        type            zeroGradient;
    }

    outlet-1
    {
        type            zeroGradient;
    }

    outlet-2
    {
        type            zeroGradient;
    }
   
    

    walls
    {
        type            fixedValue;
        value           uniform 0;
    }
}

U:

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

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

internalField   uniform (0 0 0);

boundaryField
{
    
    outlet-1
    {
        type            zeroGradient;
    }

    outlet-2
    {
        type            zeroGradient;
    }

    

    inlet-1
    {
        type            uniformFixedValue;
        uniformValue    constant (1 0 0);
    }

    inlet-2
    {
        type            uniformFixedValue;
        uniformValue    constant (1 0 0);
    }
    

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

[AshwaniAssam]

What happens you use these boundary conditions. I mean to say as per the p file, you are using zero gradient for the pressure do you get the result with this. It should be working.

[dEntropy]

i've since set the pressure outlet to fixed value = 0.

i think the solvers and schemes are equally as important, and i've recently found ones that work well.

[alexB]

Hi mike,

perhaps pressureInletOutletVelocity ( http://cfd.direct/openfoam/user-guide/boundaries/ ) would fit to your problem but I don't know what you are planning with the inlet and outlet.

Perhaps you should look which tutorial ( http://www.rapidof.com/wp-content/up...rialsGuide.pdf ) could fit to your problem best and adapt it for your needs.

regards
Alex

[dEntropy]

hi Alex,

so, I've just set the pressure inlets as zeroGradient boundaries and the outlets as fixed value = 0.

i was using the velocity inlets as surfaceNormalFixedValue and the velocity outlets as zeroGradients.


i have since been working towards explicitly solving for the square duct velocity profile and applying that as the inlet condition. otherwise, i need to run potentialFoam or my actual pisoFoam run with long inlet channels before I get a fully developed profile.

[alexB]

Hi mike,

I am not that much in potentialFOAM, pisoFOAM and the corresponding boundary conditions.

I hope someone else could help you better.

regards
Alex