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icoFoam backward facing step tutorial problem

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Old   January 25, 2015, 15:51
Default icoFoam backward facing step tutorial problem
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Isa
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Hi,

My setup for icoFoam is as follows:

Mesh configuration:
Mesh configuration

The checkMesh.log.

fvSchemes
fvSolution

So what happened was, when I decreased my time step, my solution changes.

The following files are my U_magnitude at end time:
deltaT = 5e-3
deltaT = 5e-4
deltaT = 5e-5
deltaT = 5e-6

So by intuition, shouldn't all files have the same values?

Thank you for your help.

Last edited by isa982; January 26, 2015 at 04:39.
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Old   January 25, 2015, 16:33
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Bruno Santos
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Greetings Isa,

What about the Courant Number for each simulation? What values did you get?

Best regards,
Bruno
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Old   January 26, 2015, 04:26
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The largest Courant number for all cases is not more than 0.4.
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Old   January 26, 2015, 16:21
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Hi Isa,

I'm guessing here, but I think you're seeing something similar to this case: http://www.cfd-online.com/Forums/ope...tml#post446350

The problem is that the mesh refinement you have at the inlet is creating a distortion in the fluid flow. You should have a uniform mesh, if you want good results.

Have a look at this blog post of mine for more ideas: OpenFOAM: Interesting cases of bad meshes and bad initial conditions

Best regards,
Bruno
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Old   January 26, 2015, 18:07
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Hi Bruno,

I think the boundary conditions might be the problem. So far I have tested several cases using large and uniform mesh and they all converge.

I am going to try smaller meshes and see what happens.

Thank you very much for your help.
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Old   January 27, 2015, 04:51
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Quote:
Originally Posted by isa982 View Post
Hi,

My setup for icoFoam is as follows:

Mesh configuration:
Mesh configuration

The checkMesh.log.

fvSchemes
fvSolution

So what happened was, when I decreased my time step, my solution changes.

The following files are my U_magnitude at end time:
deltaT = 5e-3
deltaT = 5e-4
deltaT = 5e-5
deltaT = 5e-6

So by intuition, shouldn't all files have the same values?

Thank you for your help.
Hello isa,

I have solved this backward step tutorial and validated with Available experimental data.

If you want to have a look on my set up files then I can share it with you. you may inbox me your email add.
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