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

Shock Induced Seperation

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   March 21, 2006, 13:34
Default Shock Induced Seperation
  #1
Nick
Guest
 
Posts: n/a
Has anybody had any experience with predicting shock induced seperation from a wall. We know that it is not happening in reality but our predictions do not tie up with this. We are using 2nd order descritization with standard K-e. We have tried various things mainly , changing the surrounding conditions but to no avail.

Cheers, Nick

  Reply With Quote

Old   March 21, 2006, 22:19
Default Re: Shock Induced Seperation
  #2
Ahmed
Guest
 
Posts: n/a
It is not clear to me what you really mean? Whether you are asking about a shock wave formed as a result of a separation Or separation results as a result of a shock wave. Both cases are physically possible provided the conditions are the proper ones. A separation bubble can cause a shock wave if the flow is supersonic. A shock wave is formed when a supersonic flow is deflected (perturbed) whether that perturbation is caused by a boundary layer, by a mechanical means,.........etc. Separation is caused by adverse pressure gradients. So what is your geometry and flow conditions, so one can try to engage in a useful discussion Good Luck
  Reply With Quote

Old   March 22, 2006, 05:16
Default Re: Shock Induced Seperation
  #3
Nick
Guest
 
Posts: n/a
Sorry for being vague, but I can't go into depth about the geometry. Its certainly a high mach number flow seperating as a result of the shock wave, (extremely unfaourable pressure gradient resulting in reverese flow within the boundary layer) Needless to say with a first order scheme it remains attached but switch on up to 2nd order and the flow jumps right off the surface. we're looking at a jet attached to a surface, with peak mach numbers of the order of 2.

  Reply With Quote

Old   March 22, 2006, 19:55
Default Re: Shock Induced Seperation
  #4
Ahmed
Guest
 
Posts: n/a
I normally start analysis using first order upwind schemes then I switch to second order (Just to save computing time), in simple language I never trust final results based on first order schemes, I do not know if that will help you. A jet attached to a surface, have you considered the so called The Coanda Effect? The Mach number reaching the value of 2, this might be the result of Thermodynamics, The speed of sound is a function of temperature, so check the thermodynamics of your problem. One more point:- For Your results based on first order schemes, Plot both the Entropy generation and the vorticity generation. Does the Entropy plot Satisfies the Second Law of Thermodynamics? Good Luck
  Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
HLL Riemann Shock Tube Matlab Problem Luke F Main CFD Forum 2 May 20, 2016 03:10
Shock Fitting Craig FLUENT 1 April 24, 2008 18:06
Will compression waves overtake a moving shock? GRA Main CFD Forum 2 October 19, 2006 01:24
Shock capturing Dr B.M. Smith (Smith) OpenFOAM Running, Solving & CFD 1 December 10, 2004 06:40
shock wave induced separation Pao Main CFD Forum 2 June 12, 2003 11:52


All times are GMT -4. The time now is 05:48.