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

Why is the pressure larger than the total pressure

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   November 9, 2012, 04:41
Default Why is the pressure larger than the total pressure
  #1
New Member
 
Join Date: Apr 2011
Posts: 8
Rep Power: 14
greatwall is on a distinguished road
I am simulating a gas flow through a rotating multi-channels with CFX, both the inlet and outlet are the Opening boundary condition. While the inlet has a reletive pressure of 4atm, and the outlet of 2atm, rotation speed is 10000r/min. When I look the result of my computation, at the inlet plane, the pressure is larger than the total pressure, how could this happened?
greatwall is offline   Reply With Quote

Old   November 9, 2012, 05:30
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,665
Rep Power: 143
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
Can you show some images of what you are seeing?
ghorrocks is offline   Reply With Quote

Old   November 9, 2012, 06:07
Default
  #3
New Member
 
Join Date: Apr 2011
Posts: 8
Rep Power: 14
greatwall is on a distinguished road


[IMG]
These are the inlets, the range of the contour is local, from the picture we can see that the pressure is larger than the total pressure in the inlets plane, I don't know why.

Last edited by greatwall; November 9, 2012 at 06:12. Reason: the pictures didnot show well
greatwall is offline   Reply With Quote

Old   November 9, 2012, 06:09
Default
  #4
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,665
Rep Power: 143
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
Sorry, I do not download files from other websites. Please post them as attachments to this post (using "Go Advanced").
ghorrocks is offline   Reply With Quote

Old   November 9, 2012, 06:12
Default
  #5
New Member
 
Join Date: Apr 2011
Posts: 8
Rep Power: 14
greatwall is on a distinguished road
[IMG]http://b323.photo.store.qq.com/psb?/V13rxVKa3rhjqK/dwmy9NgB8guQ2FZrPtVmGUFOOzoOhbMyE*ps3QsggBA!/b/dGl*isCnAAAA&bo=hAOAAQAAAAADACM![/IMG]
greatwall is offline   Reply With Quote

Old   November 9, 2012, 06:24
Default
  #6
New Member
 
Join Date: Apr 2011
Posts: 8
Rep Power: 14
greatwall is on a distinguished road
1.jpg

2.jpg
greatwall is offline   Reply With Quote

Old   November 9, 2012, 06:36
Default
  #7
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,665
Rep Power: 143
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
We will need to see a bit more of the geometry to make any sense of it. Can you post an image which shows what the flow is actually doing?

Also, is this boundary on a rotating frame of reference? Multiphase? Does it have reverse flow?
ghorrocks is offline   Reply With Quote

Old   November 9, 2012, 06:51
Default
  #8
New Member
 
Join Date: Apr 2011
Posts: 8
Rep Power: 14
greatwall is on a distinguished road
This boundary is on a rotating frame of reference, no multiphase. The geometry is a turbine blade internal cooling channel, in the computation, the trailing edges did have reverse flow.
3.jpg
greatwall is offline   Reply With Quote

Old   November 9, 2012, 16:22
Default
  #9
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,665
Rep Power: 143
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
Where is the axis of rotation for the domain?
ghorrocks is offline   Reply With Quote

Old   November 9, 2012, 21:36
Default
  #10
New Member
 
Join Date: Apr 2011
Posts: 8
Rep Power: 14
greatwall is on a distinguished road
The axis of the rotation is on the negative y direction
greatwall is offline   Reply With Quote

Old   November 11, 2012, 06:10
Default
  #11
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,665
Rep Power: 143
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
I see. I cannot explain what you are seeing.

What does the total pressure in the stationary frame of reference look like?
ghorrocks is offline   Reply With Quote

Old   November 12, 2012, 21:49
Default
  #12
New Member
 
Join Date: Apr 2011
Posts: 8
Rep Power: 14
greatwall is on a distinguished road
The problem has been solved. Thank you! When I put the total pressure in the stationary frame of reference, the result is correct.
greatwall is offline   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
Total pressure in rel frame and total pressure Salut CFX 14 May 8, 2023 03:29
Does star cd takes reference pressure? monica Siemens 1 April 19, 2007 12:26
Neumann pressure BC and velocity field Antech Main CFD Forum 0 April 25, 2006 03:15
total pressure in CFX Atit Koonsrisuk CFX 0 January 1, 2005 06:46
Total pressure to static pressure ratio roadracer Siemens 1 April 17, 2003 06:31


All times are GMT -4. The time now is 01:12.