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Residual fluctuation, cylinder internal flow

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Old   September 2, 2014, 16:11
Default Residual fluctuation, cylinder internal flow
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Muhammad Waqas
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Hello everyone,

I am doing simulation for internal laminar flow in a cylinder and I am using simple foam. I got the required results that match with analytical solution.
But I have a problem in my residual curve. I get some fluctuation in residual curve (figure is attached), although my results are fine. I want to ask, does this fluctuation matters or not as I get in my case. I mean, the residual curve should be smooth or not. Thank you

My fvScheme is as follows

divSchemes
{
default none;
div(phi,U) Gauss upwind;
div(phi,k) Gauss upwind;
div(phi,epsilon) Gauss upwind;
div(phi,R) Gauss upwind;
div(R) Gauss upwind;
div(phi,nuTilda) Gauss upwind;
div((nuEff*dev(T(grad(U))))) Gauss linear;
}
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File Type: png Residual.png (7.0 KB, 20 views)
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Old   September 3, 2014, 07:05
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joegi
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Residuals are not your solution. Your solution is the quantity of interest.

Did you get a good agreement with the analytical solution using this numerical scheme?
Because you are using a first order scheme, and they are highly diffusive.

From your residuals I can see that maybe you were changing some parameter in the numerical scheme, and that is reflected in the jumps in the residuals.


jg
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Old   September 3, 2014, 07:18
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Muhammad Waqas
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hello Joegi

Yes I am getting good agreement with analytical solution and I didn't change any parameter while solution was running. But I was getting these peaks in residual.

What other fcScheme I can try ??

Thank you
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