CFD Online Discussion Forums - Unstable Outlet Boundary Condition

Hello there,

Could someone please advise me about the problem I am facing as seen in the attached images?

There is clearly an error in the setting of the outlet boundary condition that is causing instability at the end of my simulation. It is ok for the majority for run. This error is also causing a general increase in overall pressure within the domain.

My geometry is a sufficient distance from the outlet.

Thanks,

See below my boundary conditions:

Velocity:

Code:



dimensions      [0 1 -1 0 0 0 0];



internalField   uniform (3.5 0 0);



boundaryField

{

inlet

{

        type            freestream;

        freestreamValue $internalField;

}



    outlet

    {

        type            freestream;

        freestreamValue $internalField;

    }



    ".*foil.*"

    {

        type            movingWallVelocity;

        value           uniform (0 0 0);

    }







"AMI.*"

{

    type  cyclicAMI;

    value   $internalField;

}



    top

    {

        type            slip;

    }



    bottom

    {

        type            slip;

    }



    "front.*"

    {

        type            slip;

    }



    "back.*"

    {

        type            slip;

    }

}

Pressure:

Code:

dimensions      [0 2 -2 0 0 0 0];



internalField   uniform 0;



boundaryField

{

    inlet

    {

        type            freestream;

        freestreamValue $internalField;

    }



    outlet

    {

        type            freestream;

        freestreamValue $internalField;

    }



    ".*foil.*"

    {

        type            zeroGradient;

    }

   

    top

    {

        type            slip;

    }



    bottom

    {

        type            slip;

    }



    "front.*"

    {

        type            slip;



    }



    "back.*"

    {

        type            slip;

    }



"AMI.*"

{

    type  cyclicAMI;

    value   $internalField;

}





}