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Compressible model producing unknown "boundary" near patch interfaces

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Old   March 24, 2020, 14:19
Default Compressible model producing unknown "boundary" near patch interfaces
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Hi all,

I have been attempting to model high-speed compressible lubrication in a bearing but have been struggling to get viable results. The model is simplified to a wedge geometry where the inlet is twice the height of the outlet. I have been able to get an incompressible model working using icoFoam, and have attached an image of it to show the approximate results for pressure I am aiming to achieve with a compressible model. (Flow is from left to right)

The problem comes when trying to model the case with a compressible solver. I chose rhoCentralFoam to use in my case. After running the simulation with boundary conditions that mimic the incompressible case, I arrived at results where the boundary conditions were not necessarily satisfied. I have attached 2 images showing the pressure solution for the compressible case. I am unsure as to why those pressure jumps are occurring near the patch boundaries (especially near the outlet) when the boundary condition for those patches is that they should be at a fixed value of the ambient pressure.

Any insight as to why this is occurring would be much appreciated. Thanks!
Attached Images
File Type: png Incompressible.png (59.3 KB, 3 views)
File Type: png Compressible1.png (130.3 KB, 4 views)
File Type: png Compressible2.png (66.1 KB, 3 views)
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Old   March 24, 2020, 14:32
Default Initial Conditions
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Here are the initial T, U, and p files for the compressible simulation:

T:
Code:
internalField   uniform 400;

boundaryField
{
    top
    {
        type            fixedGradient;
	gradient	uniform 100;
    }

    inlet
    {
        type            fixedValue;
        value           uniform 400;
    }

    outlet
    {
        type            zeroGradient;
    }

    bottom
    {
        type            fixedGradient;
	gradient	uniform 100;
    }

    frontAndBack
    {
        type            zeroGradient;
    }
}
U:
Code:
internalField   uniform (0 0 0);

boundaryField
{
    top
    {
        type            noSlip;
    }

    inlet
    {
        type            zeroGradient;
    }

    outlet
    {
        type            zeroGradient;
    }

    bottom
    {
        type            movingWallVelocity;
	value		uniform (170 0 0);
    }

    frontAndBack
    {
        type            zeroGradient;
    }
}
p:
Code:
internalField   uniform 100000;

boundaryField
{
    top
    {
        type            zeroGradient;
    }

    inlet
    {
        type            fixedValue;
        value           uniform 100000;
    }

    outlet
    {
        type            fixedValue;
	value		uniform 100000;
    }

    bottom
    {
        type            zeroGradient;
    }

    frontAndBack
    {
        type            fixedValue;
	value		uniform 100000;
    }
}
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