CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

Pressure losses in a 3d pipe with RANS

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   January 27, 2009, 05:13
Default Hello, I am running a simpl
  #1
Member
 
Rosario Russo
Join Date: Mar 2009
Location: Trieste, Italy
Posts: 56
Rep Power: 17
ariorus is on a distinguished road
Hello,

I am running a simple 3d pipe (the section changes from inlet to outlet, from a square section to a circular section).
I am obtaining bad results: the pressure loss seems too large, compared with the same case run by cfx.

I have tested different Reynolds number and the results are correct only in laminar flow.
The problem seems somehow correlated with the turbulent model but there are problems also at the outlet where there is a sudden change in pressure as it is showed in the attached picture.
.

I thought that the problem was due to the too short pipe length (the velocity field is still changing at the outlet section), but looking at the picture reporting velocity the changing at outlet seems very slow..


I have tried different discretization schemes, different turbulent models but nothing changes.

By the way the computation converges without problems and the y+ are fairly at maximum around 40.
I'm attaching here also the screenshots of other fields.

In cfx with the same geometry, the same mesh(even if the mesh is not strictly the same since cfx uses value at grid nodes) the same turbulent model and the same values at inlet for turbulent quantities, the pressure variation at outlet is smooth and the pressure loss from inlet to outlet is lower. The grid is made by tetra and prisms at the walls. Checking the mesh by checkMesh everything is fine.

I used fixedValue for velocity and zeroGradient for pressure at inlet, and fixedValue for pressure and zeroGradient for velocity at outlet.

I have also tried to use OutletInlet boundary condition at the outlet for pressure and inletOutlet for velocity (and turbulent quantities) but it didn't help.

Did anybody have ever had similar problems?
Am I missing something obvious?




ariorus is offline   Reply With Quote

Old   January 27, 2009, 05:26
Default http://www.cfd-online.com/Open
  #2
Member
 
Rosario Russo
Join Date: Mar 2009
Location: Trieste, Italy
Posts: 56
Rep Power: 17
ariorus is on a distinguished road

ariorus is offline   Reply With Quote

Old   January 27, 2009, 05:28
Default http://www.cfd-online.com/Open
  #3
Member
 
Rosario Russo
Join Date: Mar 2009
Location: Trieste, Italy
Posts: 56
Rep Power: 17
ariorus is on a distinguished road

ariorus is offline   Reply With Quote

Old   January 27, 2009, 05:30
Default http://www.cfd-online.com/Open
  #4
Member
 
Rosario Russo
Join Date: Mar 2009
Location: Trieste, Italy
Posts: 56
Rep Power: 17
ariorus is on a distinguished road

ariorus is offline   Reply With Quote

Old   January 27, 2009, 05:32
Default http://www.cfd-online.com/Open
  #5
Member
 
Rosario Russo
Join Date: Mar 2009
Location: Trieste, Italy
Posts: 56
Rep Power: 17
ariorus is on a distinguished road

ariorus is offline   Reply With Quote

Old   January 27, 2009, 05:34
Default http://www.cfd-online.com/Open
  #6
Member
 
Rosario Russo
Join Date: Mar 2009
Location: Trieste, Italy
Posts: 56
Rep Power: 17
ariorus is on a distinguished road

ariorus is offline   Reply With Quote

Old   January 29, 2009, 07:58
Default Problem solved. It was my f
  #7
Member
 
Rosario Russo
Join Date: Mar 2009
Location: Trieste, Italy
Posts: 56
Rep Power: 17
ariorus is on a distinguished road
Problem solved.

It was my fault of course... :-P
I had compiled some customized BCs and must have touched something I didn't want...
I recovered the original version and now everyhing seems ok.
ariorus 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
pressure losses in pipes lottie FLUENT 3 February 5, 2007 13:33
pressure losses modelisation Alex CFX 2 March 17, 2006 06:08
pressure losses Olivier Macchion CFX 5 December 13, 2002 05:43
resistance & pressure losses Jan CFX 0 May 14, 2002 08:33
Pressure losses René CFX 11 April 12, 2002 09:55


All times are GMT -4. The time now is 15:56.