CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Main CFD Forum

Negative temperature

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

Reply
 
LinkBack Thread Tools Display Modes
Old   October 27, 2003, 04:34
Default Negative temperature
  #1
Oleg Melnik
Guest
 
Posts: n/a
Dear All! I need some help. I try to calculate shock tube problem when the high pressure chamber is filled with gas-particle dispersion. I use Mac-Cormack method with implicit account of interaction terms.

When I've used isothermal approach everything worked fine. When I've added energy equation I got negative temperatures and pressures after the shock wave at the beginning. Later on proper shock wave forms. Additionally I need very small CFL numbers ~ 0.05 whereas for isothermal case 0.2-0.3 was good. I am trying to simulate high pressure drops 20-40 MPa.

Any suggestions?

Oleg
  Reply With Quote

Old   October 28, 2003, 13:37
Default Re: Negative temperature
  #2
T. Pallidum
Guest
 
Posts: n/a
What kind of artificial viscosity are you using?
  Reply With Quote

Old   October 29, 2003, 05:08
Default Re: Negative temperature
  #3
Oleg Melnik
Guest
 
Posts: n/a
I use the term eps*(V_i+1 - 2*V_i + V_i-1) in momentum equation and play with eps. V is gas velocity.

Oleg
  Reply With Quote

Old   October 29, 2003, 12:18
Default Re: Negative temperature
  #4
Oleg Melnik
Guest
 
Posts: n/a
The problem is solved now. I've added TVD to Mac-Cormack method and temperature behaves properly.

Now there is one more issue. I have a closed end of the high pressure chamber. The material of the wall is metal with high conductivity. The behaviour of the pressure at the wall (which we measure) strongly depends on temperature BC. I've tried constant temperature and adiabatic wall. The real one should be in between. Could you help me with a proper BC for the temperature?

Best regards,

Oleg
  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
channelFoam for a 3D pipe AlmostSurelyRob OpenFOAM 3 June 24, 2011 13:06
BlockMesh FOAM warning gaottino OpenFOAM Native Meshers: blockMesh 7 July 19, 2010 14:11
help,why the negative energy source does'nt make the temperature decrease, thank you! hunter FLUENT 6 May 12, 2010 17:39
Axisymmetrical mesh Rasmus Gjesing (Gjesing) OpenFOAM Native Meshers: blockMesh 10 April 2, 2007 14:00


All times are GMT -4. The time now is 06:02.