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Old   August 9, 2021, 10:39
Default Checkerboarding problem_simpleFoam
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Hello Everyone,
I am working on very simple steady state solution (2D) of a channel flow using simpleFoam and having single cell along the flow direction (x).
I have used periodic boundary condition for inlet and outlet, noSlip (for U) for the walls. I have tried different available fvSchemes.
However, getting checkerboarding issue with p, Uy and Uz.
Any suggestions to eliminate the issue will be highly appreciated. Thanks.

Subho
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Old   August 9, 2021, 11:18
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First: Periodic b.c. often lead to problems. You are in 2D. It may be much better stacking some of the geometries and avoid periodicity in b.c.
Second: Checkerboarding is an issue of Mesh, may be combined with schemes. Try using a finer mesh.
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Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950)
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Old   August 9, 2021, 12:18
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Many thanks for your reply Uwe. In my case, I have restrict to a 2D simulation. I have used fine mesh.

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Old   August 9, 2021, 23:58
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In most cases, the main question is not
How may I get my simulation running
but
How do I change my real world problem into a simulation.

> I have restrict to a 2D simulation

Normally, there are no such restrictions. We have to select the simulation which gives the most reliable results. Often, this is the simplest one.

If you want to stay your simulation, I recommend using more stable schemes and relaxation.
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Old   August 13, 2021, 10:17
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Hello Uwe,
Thanks for your reply. I am using the following schemes
Code:
ddtSchemes
{
    default         steadyState;
}

gradSchemes
{
    default 		Gauss linear; //cellLimited Gauss linear 1;
}

divSchemes
{
    default				none;
	div(phi,U)  		bounded Gauss limitedLinearV 1;//bounded Gauss linearUpwind grad(U);
    div(phi,k)      	bounded Gauss limitedLinear 1;
    div(phi,epsilon) 	bounded Gauss limitedLinear 1;
	div((nuEff*dev2(T(grad(U))))) Gauss linear;
    div((nu*dev2(T(grad(U))))) Gauss linear;//For LRR, SSG
	div(phi,R)      	bounded Gauss limitedLinear 1; //For LRR, SSG
    div(R)          	Gauss linear; //For LRR, SSG
}

laplacianSchemes
{
    //default         Gauss linear corrected;
	default 		Gauss linear orthogonal;
}

interpolationSchemes
{
    default 		linear;
	//interpolate(U) 	linear;
}

snGradSchemes
{
    //default         corrected;
	default 		orthogonal;
}

fluxRequired
{
	default	no;
	p;
}

wallDist
{
	method			meshWave;
}
Relaxation:
for p 0.3 and for rest 0.7. I have also tried with lower/higher relaxations.
But no noticeable improvements.

Subhojit

Quote:
Originally Posted by piu58 View Post
In most cases, the main question is not
How may I get my simulation running
but
How do I change my real world problem into a simulation.

> I have restrict to a 2D simulation

Normally, there are no such restrictions. We have to select the simulation which gives the most reliable results. Often, this is the simplest one.

If you want to stay your simulation, I recommend using more stable schemes and relaxation.
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checkerboarding, simplefoam convergence, steady state

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