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

Shock Capturing in a Con-Di Nozzle.

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

Reply
 
LinkBack Thread Tools Display Modes
Old   December 22, 2004, 19:30
Default Shock Capturing in a Con-Di Nozzle.
  #1
Meriem Allouache
Guest
 
Posts: n/a
Hi, I am trying to find an alternative/similar dissipation term to the Jamesn's Scheme in order to remove the non-physical expansion shock at convergent part of the nozzle. Some terms were tried but wiggles in the tip of the Shock are still there!

Any suggestions/ references or Advice from your experience is appreciated.

Thanks for your time.
  Reply With Quote

Old   December 23, 2004, 11:33
Default Re: Shock Capturing in a Con-Di Nozzle.
  #2
Biga
Guest
 
Posts: n/a
Hi!

Are you sure there is an expansion shock with Jameson scheme? I'm not quite sure this artificial dissipation scheme would give you answers just like that... Could you please give more detail of your code and of your numerical settings? =D

From our experience here, you removed wiggles near shock waves with upwind schemes, just like the upwind-biased CUSP scheme, or the Roe scheme (both second order). First-order Roe scheme gave us expansion shocks, but Jameson's explicitly-added AD not.

Looking forward for more details...

PS.: Are you from Bristol? I got a friend that graduated there... and I've been there once too!
  Reply With Quote

Old   December 23, 2004, 16:30
Default Re: Shock Capturing in a Con-Di Nozzle.
  #3
Meriem Allouache
Guest
 
Posts: n/a
Hi, Thanks for the reply.

>Are you sure there is an expansion shock with Jameson scheme

No, I am trying to experiment a different/new disspation term

More details about my work are as follows:

1- I am coding Maccormack's Scheme (Second order accurate...) for a Con-Di Nozzle using a conservative approach. The typical input values for the code cause a Shock wave at the divergent part.

> From our experience here, you removed wiggles near shock waves with upwind schemes,

My aim is to add an artificial viscosity to stabilise the solution.

Hope this helps.

Looking for you reply!

Meriem.A.

  Reply With Quote

Old   December 27, 2004, 06:49
Default Re: Shock Capturing in a Con-Di Nozzle.
  #4
Biga
Guest
 
Posts: n/a
Hi, Meriem!

Ok! So there's no shock expansion, only shock wave, correct?

Maybe a shock-wave in the Div portion of your nozzle is correct, depending on your total pressure/exit static pressure ratio. A suggestion is that you should use the quasi-1-D relations to verify if you should really expect a shock wave in there or not. Other numerical schemes give you the same shock wave?

Which MacCormack scheme are you using? The 1969 one, based on predictor-corrector steps? MacCormack claims that this scheme does not require addition of artificial dissipation since it is a Lax-Wendroff-type scheme (which should be self-stabilising). However, I've never seen anyone who implemented it and did not have to use a little amount of artificial dissipation...

If there's any other information you would like to add...

Best regards, Biga
  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
How to visualise the shock wave in a laval nozzle? xck1986 OpenFOAM 1 January 20, 2011 05:31
Con-Div Nozzle Shock structure problem padmanathan FLUENT 2 November 16, 2010 04:37
Shock in nozzle - dangerous? Christian Main CFD Forum 1 May 8, 2006 12:48
compressible flow in a counterflow nozzle d.vamsidhar FLUENT 0 November 24, 2005 02:45
Shock capturing Dr B.M. Smith (Smith) OpenFOAM Running, Solving & CFD 1 December 10, 2004 06:40


All times are GMT -4. The time now is 01:02.