CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM Running, Solving & CFD

Temperature field error in compressible LES

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   August 21, 2013, 03:42
Default Temperature field error in compressible LES
  #1
New Member
 
Join Date: Jul 2011
Posts: 4
Rep Power: 5
aljo is on a distinguished road
Dear Foamers,

I encountered a serious problem in a high speed gas jet simulation (LES) with sprayFoam.

The jet velocity is 177 m/s with random perturbations added. The temperature at the inlet is set to 600K (!!). The velocity field (attachment) and pressure field are looking good. For the RANS simulation I get reasonable temperature profiles. For the LES (smagorinsky) the temperature in the field remains constant with a non-smooth transition.
Chemistry and so on are switched off.
I tried various fvSchemes (upwind, linear, ..). Also the transsonic option.
My guess is that it has something to do with the thermodynamic settings (same as for aachenBomb-Tutorial).

The only post I found that is dealing with a similar problem is

Problems with temperature jump at the boundary

Can anyone give me a hint of how to solve this problem

Best regards

Aljoscha
aljo is offline   Reply With Quote

Old   August 22, 2013, 04:12
Default
  #2
Member
 
cosimo bianchini
Join Date: Mar 2009
Location: Florence, Tuscany, Italy
Posts: 88
Rep Power: 8
cosimobianchini is on a distinguished road
Send a message via Skype™ to cosimobianchini
Can you explain better what is plotted in the first two pictures (please provide scales)?
Can you provide a picture of the mesh for picture 2?

Quote:
For the LES (smagorinsky) the temperature in the field remains constant with a non-smooth transition.
Can you explain better what you expect and why?
__________________
Cosimo Bianchini

Energy Engineering Department "S. Stecco"
University of Florence
Via di S.Marta, 3
50139 Florence - ITALY
Tel: +39 055 4796575
Fax: +39 055 4796342
Mob: +39 320 9460153
e-mail: cosimo.bianchini@htc.de.unifi.it
URL: www.htc.de.unifi.it
cosimobianchini is offline   Reply With Quote

Old   August 22, 2013, 10:39
Default
  #3
New Member
 
Join Date: Jul 2011
Posts: 4
Rep Power: 5
aljo is on a distinguished road
Hello!

Some more information about the case:
The jet diameter is 2.2 mm and the cell size at the outlet is about 0.05 mm. An o-block mesh has been used. For the contours the non-interpolated values have been plotted. So it is visible that the mesh is relatively fine at the inlet (velocity field).
The temperature field however is not so so well resolved. I would have expected a temperature field similar to the gas velocity field. The strangest thing is, that the temperature field is static for all time steps.

Hope the case is clear now

Regards
Aljoscha
aljo is offline   Reply With Quote

Old   August 23, 2013, 03:40
Default
  #4
Member
 
cosimo bianchini
Join Date: Mar 2009
Location: Florence, Tuscany, Italy
Posts: 88
Rep Power: 8
cosimobianchini is on a distinguished road
Send a message via Skype™ to cosimobianchini
From what you say I guess that first picture is velocity and second is temperature on the same cutting plane of the same mesh. In this case I agree with you temperature field looks wired.

If temperature field is the same at every iteration it might be that your fvSolution file is set so that energy is not actually solved.
Can you plot your fvSolution dictionary and a log of few iterations?
Also what solver are you using?
Try to use constant transport properties first (mu and Prandtl) instead of Sutherland as I'm not sure in which cases the formula implemented to estimate alpha (thermal diffusion coefficient) provides reasonable results.
Regards,
Cosimo
__________________
Cosimo Bianchini

Energy Engineering Department "S. Stecco"
University of Florence
Via di S.Marta, 3
50139 Florence - ITALY
Tel: +39 055 4796575
Fax: +39 055 4796342
Mob: +39 320 9460153
e-mail: cosimo.bianchini@htc.de.unifi.it
URL: www.htc.de.unifi.it
cosimobianchini is offline   Reply With Quote

Old   December 10, 2013, 04:30
Default Problem solved
  #5
New Member
 
Join Date: Jul 2011
Posts: 4
Rep Power: 5
aljo is on a distinguished road
Dear Foamers,

I was able to solve this problem a while ago. It seems to be important for this specific chase to initialise the flow field with a streamwise velocity component u_field>5 m/s (u_jet = 240 m/s). If u_field is in the order of 1 the jet cannot develop well.
Still I think the core is somewhat short in comparison with fluent 13.0.0 .

Aljo
aljo is offline   Reply With Quote

Reply

Thread Tools
Display Modes

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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Calculation of the Governing Equations Mihail CFX 7 September 7, 2014 06:27
Field Function relating to temperature. Please Help kj878 STAR-CCM+ 12 February 8, 2012 17:13
Internal field temperature decreases after each iteration (Combustion Modeling) germinal OpenFOAM Running, Solving & CFD 1 November 29, 2010 14:16
give me some advice about compressible LES. Bin Li Main CFD Forum 3 September 19, 2003 13:01
Question concering about validating Temperature field ghlee Main CFD Forum 1 December 1, 1998 13:36


All times are GMT -4. The time now is 16:31.