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

2D Laminar Pipe Flow(Urgent)

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

Reply
 
LinkBack Thread Tools Display Modes
Old   January 6, 2006, 13:17
Default 2D Laminar Pipe Flow(Urgent)
  #1
tnpmember
Guest
 
Posts: n/a
Hi All I m facing problem to simulate a circular pipe with laminar flow in CFX.I m taking 45 deg section of pipe and trying to model laminar flow.I am imposing inlet,outlet and two syymetry boundary conditions on circumference along with a wall on top. I dont know why solver is giving an error in symmetry plane not in strict parellel.Can anybody suggest how to overcome and is it possible to define a symmetry axis in CFX.Because i doing it in ICEM but its not visible in CFX. Please help.

regards

kirti
  Reply With Quote

Old   January 6, 2006, 13:25
Default Re: 2D Laminar Pipe Flow(Urgent) *NM*
  #2
tnpmember
Guest
 
Posts: n/a
  Reply With Quote

Old   January 6, 2006, 14:52
Default Re: 2D Laminar Pipe Flow(Urgent)
  #3
tuks
Guest
 
Posts: n/a
Hi friend, Are you really using 45 deg section? Then it should work. Sometimes you may get problem because two symmetric planes are merging(having common) onto one line(centre) and according to definition of the symmetry plane vector's can't cross it. That means for one symmetry plane vectors are parallel but for other it may cross it which is not allowed by definition of symmetry. I think the error also indicates same.. but anyway

Try with 180, 90 and less than 45 deg sections and see what happenes.. if problem persists, generate geometry accurately you may be able to solve the problem.

Regards
  Reply With Quote

Old   January 7, 2006, 11:14
Default Re: 2D Laminar Pipe Flow(Urgent)
  #4
Jeff
Guest
 
Posts: n/a
Two things to check:

1. Make sure you're doing a build topology in ICEM (under Repair Geometry) to get the edges on the ends of the pipe. If you don't, you may get elements that "round off" the sharp edges and result in faces that don't lie in the symmetry plane. This happens because there's no hard curve on which to constrain the element edges. You can see these type of defects in the mesh by zooming in and visually inspecting the sharp corners of the mesh looking for round off elements.

2. Slight bumps in the mesh surface on the symmetry plane can result in element faces which have a normal that is more than 5 degrees off normal of the symmetry plane. There's an expert parameter in CFX that allows you to set the tolerance (in degrees) for symmetry faces. Set this to something like 15 or 20 degrees and see if this fixes the problem.

Jeff
  Reply With Quote

Old   January 7, 2006, 11:42
Default Re: 2D Laminar Pipe Flow(Urgent)
  #5
tnpmember
Guest
 
Posts: n/a
Hi jeff Thanks for your help.I have some queries as i am new to all this stuffs. should i take a radius at the end of pipe?or i can model it with sharp corner. What about the boundary conditions.Should i take periodic type bc or simple symmetry would be enough. Please reply

regards
  Reply With Quote

Old   January 7, 2006, 15:59
Default Re: 2D Laminar Pipe Flow(Urgent)
  #6
Jeff
Guest
 
Posts: n/a
If it's the inlet or outlet, you probably want a sharp corner at the end of the pipe.

If there is any swirl component to the flow, you want periodic, i.e. what goes out one face comes in the other. However if flow is all in the axial direction use plain symmetry.

Jeff
  Reply With Quote

Old   January 9, 2006, 05:40
Default Re: 2D Laminar Pipe Flow(Urgent)
  #7
tnpmember
Guest
 
Posts: n/a
Hi jeff how can i define a symmetry axis in CFX.However if i am taking radius at the end it is running well but i want the velocity exactly at the centre of pipe. Should i use expert control parameter?How can i use them? kindly reply

regards
  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
Laminar Circular pipe flow problem GLee CFX 6 September 15, 2011 10:57
Boundary conditions of laminar flow in pipe alireza.glz OpenFOAM 2 July 26, 2011 08:56
laminar pipe flow with buoyantSimpleRadiationFoam and janafThermo crashes Fabian OpenFOAM 1 September 29, 2010 11:38
Laminar field as initial state for turbulent two phase pipe flow kjetil OpenFOAM Running, Solving & CFD 3 July 21, 2009 09:15
Terrible Mistake In Fluid Dynamics History Abhi Main CFD Forum 12 July 8, 2002 09:11


All times are GMT -4. The time now is 15:47.