CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > CFX

Questions in the residual and SST model

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   June 1, 2020, 07:24
Smile Questions in the residual and SST model
  #1
M29
New Member
 
Sumin Park
Join Date: Jul 2019
Posts: 26
Rep Power: 6
M29 is on a distinguished road
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!!
Attached Images
File Type: png K-216.png (23.9 KB, 18 views)
File Type: png K-217.png (21.6 KB, 14 views)
M29 is offline   Reply With Quote

Old   June 1, 2020, 19:03
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,703
Rep Power: 143
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
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).
__________________
Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.
ghorrocks is offline   Reply With Quote

Old   June 2, 2020, 03:04
Default
  #3
M29
New Member
 
Sumin Park
Join Date: Jul 2019
Posts: 26
Rep Power: 6
M29 is on a distinguished road
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?
M29 is offline   Reply With Quote

Old   June 2, 2020, 07:25
Default
  #4
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,703
Rep Power: 143
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
That is possible. It could also have read in the wall boundary scale values from a previous run as an initial condition.
__________________
Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.
ghorrocks is offline   Reply With Quote

Old   June 2, 2020, 07:45
Default
  #5
Senior Member
 
Join Date: Jun 2009
Posts: 1,804
Rep Power: 32
Opaque will become famous soon enough
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
__________________
Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.
Opaque is offline   Reply With Quote

Old   June 3, 2020, 22:10
Default
  #6
M29
New Member
 
Sumin Park
Join Date: Jul 2019
Posts: 26
Rep Power: 6
M29 is on a distinguished road
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"?
M29 is offline   Reply With Quote

Old   June 3, 2020, 22:11
Default
  #7
M29
New Member
 
Sumin Park
Join Date: Jul 2019
Posts: 26
Rep Power: 6
M29 is on a distinguished road
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.
M29 is offline   Reply With Quote

Reply

Tags
cfx 14, turbulence analysis


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
transsonic nozzle with rhoSimpleFoam Unseen OpenFOAM Running, Solving & CFD 8 July 1, 2022 06:54
k-omega SST blew up after first few iterations Jinjolee OpenFOAM 4 May 12, 2019 11:51
NACA 2412 airfoil fail with SST but works with k-Epsilon. What I'm doing wrong? CsabiH OpenFOAM 3 April 30, 2019 08:35
SimpleFoam crashes after restarting simulation fedez91 OpenFOAM Running, Solving & CFD 18 September 4, 2016 08:59
Omega goes infinity callumso OpenFOAM Running, Solving & CFD 5 October 2, 2013 07:52


All times are GMT -4. The time now is 03:52.