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False diffusion in Lid driven cavity

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Old   May 13, 2020, 17:47
Default False diffusion in Lid driven cavity
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Mudit Mehta
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Please Help!!! Hello, Can someone please explain how a false diffusion will look like in Lid driven cavity problem. (Reynolds number = 100)
I am using first order upwind scheme for the discretization of convective terms in steady state navier stokes equation and using SIMPLE method.
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Old   May 13, 2020, 18:32
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Originally Posted by Mudit2208 View Post
Please Help!!! Hello, Can someone please explain how a false diffusion will look like in Lid driven cavity problem. (Reynolds number = 100)
I am using first order upwind scheme for the discretization of convective terms in steady state navier stokes equation and using SIMPLE method.



You are working on a test-case that has no analytical solution. we already discussed such issue. The numerical diffusion can act as if you are solving the lid-driven cavity at a smaller Re. But that is locally determined by the cfl value. For the steady case you need to consider the grid size.
However, your question is not well stated.
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Old   May 13, 2020, 18:38
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The grid size i have taken is 65x65 and 21x21. I have generated u, v, p countours, streamlines, u velocity along vertical geometric centre of cavity and v velocity along horizontal centre of cavity. Can we look at false diffusion from here?
I have values to compare from ghia et. al. of u velocity along vertical line and v velocity along horizontal line.
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Old   May 13, 2020, 18:41
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The grid size i have taken is 65x65 and 21x21. I have generated u, v, p countours, streamlines, u velocity along vertical geometric centre of cavity and v velocity along horizontal centre of cavity. Can we look at false diffusion from here?
I have values to compare from ghia et. al. of u velocity along vertical line and v velocity along horizontal line.

You can only perform a grid refinement study and report the velocity profiles at each grid.
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Old   May 13, 2020, 18:42
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Okay. Thank you so much
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