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Fluid flow through a sinusoidal fracture, mass is not conserved.

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Old   May 12, 2019, 20:05
Smile Fluid flow through a sinusoidal fracture, mass is not conserved.
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Wanxin He
Join Date: May 2019
Location: Irvine
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Hi all,
I'm now using SimpleFoam to simulate the laminar incompressible flow through a roughness geometry inside ( Sinusoidal fracture), I give it pressure difference at inlet and outlet along y direction (inlet:30 pa; outlet:0 ) to lead the flow happen. However, after 5000 iterations it still not converged. the residual of Ux keep flipping at around 0.0001 although residual of Uy,Uz and Pressure drop very quickly at around 200 iterations(reach 1e-8).
At first I suspect the the residual is calculated after normalization, because Ux is very small, so I add additional pressure different along x direction (front: 5 pa, back:0 ) to make Ux bigger, and it works within my expectation. However, when do the mass conservation check, flux near inlet and outlet is very large and oscillates. inflow and outflow to an element is not equal. But in smooth wall case all are running well.
Can anyone help me to find what is going wrong? Appreciate!
The attachments are my domain geometry, mesh, and residual plot.
Attached Images
File Type: png generalgeometry.png (33.6 KB, 15 views)
File Type: png detail_dense.png (179.8 KB, 14 views)
File Type: png Sinusoidal wall.png (48.7 KB, 15 views)
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Old   May 12, 2019, 20:15
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Wanxin He
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Here are my BCs for p and U:

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
{
inlet
{
type zeroGradient;
}

outlet
{
type zeroGradient;
}

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

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

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

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

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


// ************************************************** *********************** //

P:

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

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

internalField uniform 0;

boundaryField
{
upperWall
{
type zeroGradient;
}

lowerWall
{
type zeroGradient;
}

reactiveWall
{
type zeroGradient;
}

inlet
{
type fixedValue;
value uniform 30;
}

outlet
{
type fixedValue;
value uniform 0;
}

front
{
type zeroGradient;
}

back
{
type zeroGradient;
}

}

// ************************************************** *********************** //
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Old   September 29, 2022, 22:10
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Hi Vicky,

I am curious how did you generate the wavy wall geometry in OpenFoam? Because I am working on a droplet impact case where the surface is sine wave shape... And I try use spline under edges but did not work... If you do not mind, could you give some hints on it?

Thanks a lot.

Cheers,
Chris
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