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Old   June 1, 2020, 08:24
Smile Questions in the residual and SST model
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M29
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Sumin Park
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Hello! I'm graduate student in Republic of Korea.

I'm analyzing the Dry Cask to cool down the spent fuel using CFX.

I set up the SST model and now the calculation is on going.

But in the residual monitor in CFX solver, there are some problems.

First, I don't know why the "wall boundary and scale" is empty.

Second, In the Turbulence residual, the value of RMS K-TurbKE was reach to 10^-100. I wonder whether there is no problem or not.

I attached two figures about those.

Please teach me the meaning of two situations.

In addition to those, I want to know the criterion of y plus in the SST model.

Please give me advice.

Thank you!!
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File Type: png K-217.png (21.6 KB, 10 views)
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Old   June 1, 2020, 20:03
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Once the wall boundary scale converges it stops calculating that equation. So the display is blank for the iterations it is not calculated for.

If a residual reaches 1E-100 it means that there is effectively zero happening in that equation. So I suspect it means the value of that equation is zero everywhere (or close to it), which means either the equation is not required (as it is doing nothing) or your setup is wrong (and the equation is not working properly).
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Old   June 2, 2020, 04:04
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Quote:
Originally Posted by ghorrocks View Post
Once the wall boundary scale converges it stops calculating that equation. So the display is blank for the iterations it is not calculated for.

If a residual reaches 1E-100 it means that there is effectively zero happening in that equation. So I suspect it means the value of that equation is zero everywhere (or close to it), which means either the equation is not required (as it is doing nothing) or your setup is wrong (and the equation is not working properly).
Thanks for your answer!

So, Can i understand that because the "wall boundary scale" is converged just first iteration, so it looks like empty?
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Old   June 2, 2020, 08:25
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That is possible. It could also have read in the wall boundary scale values from a previous run as an initial condition.
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Old   June 2, 2020, 08:45
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Your setup has multiple disconnected domains, and I assume it is somehow incorrect.

Have you created the appropriate domain interfaces to allow the flow to pass through?

Are you running with Beta Features on? Did you remove the "Constant Domain Physics" setting?

Something is off
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Old   June 3, 2020, 23:10
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Quote:
Originally Posted by Opaque View Post
Your setup has multiple disconnected domains, and I assume it is somehow incorrect.

Have you created the appropriate domain interfaces to allow the flow to pass through?

Are you running with Beta Features on? Did you remove the "Constant Domain Physics" setting?

Something is off
Thank you for your answer.

Actually, I solved my simulation using laminar(turbulence-none) first. So, I think the connection between domains is correct.

I use the Beta Features to set up the different fluid in domains.

Finally, I don't check the "Constant Domain Physics" setting.

The solver is running. So, if the solver is finished, I will check that.

The problems that i faced with come from the "Beta physics"?
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Old   June 3, 2020, 23:11
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Quote:
Originally Posted by ghorrocks View Post
That is possible. It could also have read in the wall boundary scale values from a previous run as an initial condition.
Thank you!! Your answer was really helpful.
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