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Problem with boundary layer - noSlip condition not being respected - OpenFOAM

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Old   July 11, 2019, 17:38
Default Problem with boundary layer - noSlip condition not being respected - OpenFOAM
  #1
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Vitor Heitor Cardoso
Join Date: Jan 2019
Location: Rio de Janeiro
Posts: 10
Rep Power: 2
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Dear community,

I've been running a few validation tests comparing numerical methods (FVM, FEM, FDM) for flow through parallel plates. I have the the following setups, which are also attached:

- Flow: Laminar, developed, incompressible;
- Flow through parallel plates -> Length = 1 mm, Height = 0,250 mm, thickness = 20 micrometers)
- Fluid: Water (rho = 1000kg/m, mu = 0,001 Pa.s -> nu = 1e-6 m/s)
- Pressure-Driven Flow: Inlet Pressure: 1 Pa ( 0,001 Pa/rho)

When I run the simulation, I have very promissing results in a global analysis. However, when I analyze the behavior of the flow next to the walls, I realize the "noSlip" condition is not being respected.

Does anyone knows what could be resulting this behavior? I was studying about y+ and stuff but I have low understanding about it so far, but I thought y+ stuff were influential only on turbulent flow (I might be terribly wrong).

(I'm sorry for the attachments on the text, but I couldnt upload the files)

Thanks in advance.

Best Regards,
Vitor

#-------------------------- Attached Files---------------------------------------------#


p Dictionary

object p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField uniform 0;

boundaryField
{
Inlet
{
type fixedValue;
value uniform 0.001;
}

Outlet
{
type fixedValue;
value uniform 0;
}

TopWall
{
type zeroGradient;
}

BottomWall
{
type zeroGradient;
}

FrontAndBack
{
type zeroGradient;
}
}
--------------------------------------------------------------------------------------------------------

U dictionary

object U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [0 1 -1 0 0 0 0];
internalField uniform (0 0 0);


boundaryField
{
Inlet
{
type pressureInletVelocity;
value uniform (0 0 0);
}

Outlet
{
type zeroGradient;

}

TopWall
{
type noSlip;

}

BottomWall
{
type noSlip;

}

FrontAndBack
{
type noSlip;
}
}
---------------------------------------------------------------------------------------------------------------

fvSchemes

object fvSchemes;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

ddtSchemes
{
default steadyState;
}

gradSchemes
{
default Gauss linear;
grad(p) Gauss linear;
}

divSchemes
{
default none;
div(phi,U) bounded Gauss linearUpwind grad(U);
div(phi,k) bounded Gauss limitedLinear 1;
div(phi,epsilon) bounded Gauss limitedLinear 1;
div(phi,omega) bounded Gauss limitedLinear 1;
div(phi,v2) bounded Gauss limitedLinear 1;
div((nuEff*dev2(T(grad(U))))) Gauss linear;
div(nonlinearStress) Gauss linear;
}

laplacianSchemes
{
default Gauss linear corrected;
}

interpolationSchemes
{
default linear;
}

snGradSchemes
{
default corrected;
}

fluxRequired
{
default no;
p;
}

wallDist
{
method meshWave;
}

----------------------------------------------------------------------------

fvSolution


solvers
{
p
{
solver PCG;
preconditioner DIC;
tolerance 1e-07;
relTol 0.1;
//smoother GaussSeidel;
}

"(U|k|epsilon|omega|f|v2)"
{
solver smoothSolver;
smoother symGaussSeidel;
tolerance 1e-07;
relTol 0.1;

}
}

SIMPLE
{
nNonOrthogonalCorrectors 0;
consistent yes;

residualControl
{
p 1e-5;
Ux 1e-5;
Uy 1e-5;
"(k|epsilon|omega|f|v2)" 1e-3;
}
}

relaxationFactors
{
equations
{
U 0.9; // 0.9 is more stable but 0.95 more convergent
".*" 0.9; // 0.9 is more stable but 0.95 more convergent
}
}

-------------------------------------------------------------------------------------------------------------------------------------

checkMesh Results:

Checking geometry...
Overall domain bounding box (0 0 0) (0.001 0.00025 2e-05)
Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
Mesh has 3 solution (non-empty) directions (1 1 1)
Boundary openness (1.59928e-17 2.1878e-17 -1.73529e-18) OK.
Max cell openness = 2.2343e-16 OK.
Max aspect ratio = 2.95283 OK.
Minimum face area = 1.07169e-12. Maximum face area = 6.31543e-12. Face area magnitudes OK.
Min volume = 1.78608e-18. Max volume = 7.55579e-18. Total volume = 5e-12. Cell volumes OK.
Mesh non-orthogonality Max: 39.3315 average: 9.2241
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 0.465947 OK.
Coupled point location match (average 0) OK.

Mesh OK.

End
Attached Images
File Type: png U-Z.png (15.4 KB, 7 views)
File Type: png u-Y.png (14.5 KB, 6 views)
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Old   August 14, 2019, 06:14
Default
  #2
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anonymous
Join Date: Jan 2016
Posts: 286
Rep Power: 7
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Hi!

It is respected, since noSlip creates a BC as a fixedValue Zero.
You see weird results because you are using the paraFoam -builtin versoin, which can't understand that noSlip BC. If you build your paraFoam properly, it should be good. Check the extension if it is .foam (not correct), or .OpenFOAM (correct).



If you set FixedValue (0 0 0), you can read that case properly with paraview too.
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