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Error when using Boussinesq Model

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Old   July 29, 2014, 08:54
Question Error when using Boussinesq Model
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Julian
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Hello everybody,

I am simulating a simple pipe flow with a heated pin in it with forced and natural convection. When I run the Solver with the full buoyancy model (variable density) everything is fine. But when I try to use the boussinesq model (constant density, but a value for the thermal expansivity) i get this error:

Error detected by routine PEEKR
CDANAM = ../../HEATM/TFC/SIGMA/VALUE
CRESLT = NONE

Current Directory : /FLOW/PHYSICS/ZN1/FL1/TURBM/BUOYTURB

+--------------------------------------------------------------------+
| ERROR #001100279 has occurred in subroutine ErrAction. |
| Message: |
| Stopped in routine MEMERR |
| |
| |
| |
| |
| |
+--------------------------------------------------------------------+

I think maybe a value 'Sigma' is missing, but I dont know how I can fix it. Did anyone have a similar Problem or any idea how to fix it?

Thank you, CFDJ
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Old   July 29, 2014, 15:43
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If you are more specific on the details of the turbulence model, perhaps someone here can help you.

For example,
  • What turbulence model are you using ?
  • Did you activate the Buoyance Turbulence sub-model ? Which option ?
  • Did you set the Turbulent Schmidt Number for Buoyancy Turbulence ?
  • What release of ANSYS CFX are you running ?

For example, the Buoyancy tutorial provided assumes laminar flow. You can change it to turbulence flow, and apply similar settings and see if it works for you.
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Old   July 30, 2014, 02:47
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Hi,

thank you for your reply. I thought maybe the error code whould be enough, but here are some further informations:

-I'm using the SST Model, however I've already tried others - same error
-I use Production and Dissipation option with a turbulente Schmidt Number of 0.9 and a Dissipation Coefficient of 1. I also tried to run the simulation with no buoyance sub model - still same error
-I'm using CFX 15.0

thank you for your help
CFDJ
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Old   July 30, 2014, 06:08
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If you turn buoyancy off entirely (not just the buoyancy turbulence stuff) do you get the error?
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Old   July 30, 2014, 07:07
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Hi,

when I choose the 'Non Buoyant' option, I don't get the error. My values, wenn I choose the 'Buoyant' option are:

x = 0 m s^-2
y = 0 m s^-2
z = -9.81 m s^-2

Ref. Temp : 572.15K

Ref. Location : Automatic
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Old   July 30, 2014, 07:13
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In that case the error is most likely in the way you have set up your materials. What materials are you using?
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Old   July 30, 2014, 07:20
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Actually I want to work with a liquid metal. But if I run the simulation using the predefined 'Water' Material, I still get the error.
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Old   July 30, 2014, 07:43
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The error message is cryptic and I cannot be sure what it is getting at. But I suspect you are missing an essential material property associated with the Buoyancy turbulence model.
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Old   July 30, 2014, 07:56
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You might be right, but it's confusing that it doesn't work, even if i choose the predefinded Materials like 'Water' or 'Air at 25 C', which also use the Boussinesq Model. I didn't change them. Is it possible that something written in these materials is wrong?
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Old   July 30, 2014, 08:00
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Sometimes I get additionaly this Error in an extra Window:

No data source for Workspace, cannot monitor Solver data.
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Old   July 30, 2014, 08:09
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What do you mean "something written in these materials is wrong?". Something is wrong in your model, that is why you are getting the error. But I can assure you many people have done buoyancy simulations in CFX before (me, for instance) and it worked just fine for us.

I very rarely run CFX inside workbench. It just adds another layer of things to go wrong (as you just found out). So I run CFX in stand alone mode - except in the rare cases when you need workbench to drive parameters or do FSI or something like that.
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Old   July 30, 2014, 08:25
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I also use stand alone mode. The additional window is just an error-window.

And I know that my model is wrong, but if I use the Libary Material Water and there is still an Error, then the Error can't arise from the Material setup, or am I wrong?
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Old   July 30, 2014, 18:34
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Can you post your CCL?
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Old   July 31, 2014, 02:47
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I think I have found the problem.
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Old   July 31, 2014, 02:58
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I defined a function for the turbulent Prandtl Number, making it variable. This caused the error, when I tried to use the Boussinesq Model. Now that I know where the error comes from I can try to fix it. Thank you for your support!
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Old   February 3, 2021, 08:41
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Hi @CFDJ, I am facing exactly the same problem (variable turbulent Prandtl number for a mixed convection case). I also noticed that the variable Prandtl number works fine for a non-buoyant case, but not when the buoyancy is activated. Did you manage to make a mixed convection case run, i.e., with buoyancy effects?
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