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

Shock wave Capture in a C-D Nozzle

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

Reply
 
LinkBack Thread Tools Display Modes
Old   April 13, 2013, 19:12
Post Shock wave Capture in a C-D Nozzle
  #1
F C
New Member
 
Farzad
Join Date: Apr 2013
Posts: 3
Rep Power: 4
F C is on a distinguished road
I have been assigned the Sajben Transonic Diffuser, in which I am attempting to solve in Ansys CFX as a 2D case in Ansys 14.5, so far I have been unable to capture the shock wave which occurs in the nozzle.

Below is the link to the studies which can be found at the bottom of the page
http://www.grc.nasa.gov/WWW/wind/val.../transdif.html

With my set up I am running Similar conditions to the the studies

Inlet Velocity: 300m/s (~0.9 Mach)
Inlet Temperature: 500R (277.78K)
Inlet Pressure: 19.58 psia (134.999 kPa)
Outlet Pressure: 14.1 psia ( 97.21 kPa) This pressure is reported to create a strong shock wave

Turbulence Model: SST
Heat Transfer: Total Energy

I am currently using a structured mesh which is approximately the same density that is used by the studies, however I think this may not be dense enough to capture the shock wave.

I am now using a Transient Simulation which is working much better and getting me close but in regards to the convergence of the simulations, they get very close to the simulation criteria, 1E-05 in my case however heat transfer generally just floats right above this value which stops it fully converging.

I am currently thinking that it may be due to my mesh being too coarse, and I am now attempting a finer mesh but it may be a while before I obtain results!

Any help is appreciated

Many Thanks

Farzad
Attached Images
File Type: jpg Heat Transfer.jpg (46.6 KB, 56 views)

Last edited by F C; April 14, 2013 at 05:57.
F C is offline   Reply With Quote

Old   April 14, 2013, 07:21
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,646
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
This FAQ is written for the zillions of posts whch ask this question on steady state simulations: http://www.cfd-online.com/Wiki/Ansys...gence_criteria

Most of the comments are relevant to your transient simulation.

Have you checked that you require convergence to this tolerance? I bet you will find that you do not need to converge this tightly for a transient simulation, and then your problem will disappear.
ghorrocks is offline   Reply With Quote

Old   October 1, 2013, 14:39
Default
  #3
Member
 
Hesam Moghaddam
Join Date: Mar 2012
Posts: 49
Rep Power: 5
hesamking is on a distinguished road
Farzad Jan,
How did you give both pressure and velocity at the inlet?
Do you mean you set either pressure or velocity in the initialization setting and
specified the other one at the inlet?
By the way, looking at the problem it seems that you can solve it as subsonic. why did you use Total energy?
have you been able to solve it?
thanks,
hesamking is offline   Reply With Quote

Old   November 29, 2013, 03:23
Default
  #4
New Member
 
Antony V.J
Join Date: Nov 2013
Location: India
Posts: 2
Rep Power: 0
amalthevj is on a distinguished road
Hello Farzad,

I am trying for a simulation just like yours,if you have problem in getting shocks,try the back up results from steady state analysis and of course in my view mesh should be fine enough for it.Then try using inlet conditions as mass flow rate as it's more robust in CFX..You can give pressure inlet conditions,but in most of the cases ,while running solver it shows message"Wall has been placed at portion of inlet".Its not weird,it do generate results.but i don't know how much its accurate......
amalthevj is offline   Reply With Quote

Reply

Tags
converging-diverging, shock wave, transonic

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
help - Running Converging Diverging Nozzle with a shock wave Daco FLUENT 0 September 3, 2012 08:23
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
Question about the shock wave in CFX software nucharin Main CFD Forum 1 January 25, 2005 09:26
Shock wave in Nozzle Mohammad Main CFD Forum 0 May 16, 2002 11:33


All times are GMT -4. The time now is 03:27.