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

Periodic Boundary Condition problem, help

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

Reply
 
LinkBack Thread Tools Display Modes
Old   October 28, 2001, 14:09
Default Periodic Boundary Condition problem, help
  #1
arhgang
Guest
 
Posts: n/a
Hi,

While model flow around a missle projectile with 4 wrap-around fins(Alpha=0, Farfield flow is parallel to missle axis), i use 1/4 circumferential domain in the Gambit model.

I tried to specify periodic BC to the two side faces of the quarter domain, but errors occured when export mesh.

errors: periodic boundary condition on face face.8 is incorrect and will not be written into neutral file.

BTW, cannot use Symmetry BC here, since it's wraparound fins rather than 4 cross fins.

the relation of two side faces, i think, are one's in = another's out, so i tried periodic BC.

How to correct this error? or any else way?

thanx.
  Reply With Quote

Old   October 29, 2001, 03:10
Default Re: Periodic Boundary Condition problem, help
  #2
kim
Guest
 
Posts: n/a
Did you hardlinked the meshes on the periodic faces ? Did you assign the periodic BC for both faces in pair ? These are the necessary conditions for correct export of mesh.
  Reply With Quote

Old   October 29, 2001, 04:51
Default Re: Periodic Boundary Condition problem, help
  #3
arhgang
Guest
 
Posts: n/a
thank u i really hadn't used hardlink, then i'll try, though dunno how to hardlink.

| ( 0

| )
  Reply With Quote

Old   October 29, 2001, 11:06
Default Re: Periodic Boundary Condition problem, help
  #4
Lanre
Guest
 
Posts: n/a
Go to the Mesh Faces tool pad and click on the hard link (the first button on the left, lower row). For rotationally periodic faces like the ones you describe, make sure you check the "reverse orientation" box.
  Reply With Quote

Old   October 30, 2001, 05:14
Default Re: Periodic Boundary Condition problem, help
  #5
arhgang
Guest
 
Posts: n/a
thank u, OK now.

I set rotational periodic BC and Delta.P=0 in Fluent? Right?

  Reply With Quote

Old   October 30, 2001, 11:20
Default Re: Periodic Boundary Condition problem, help
  #6
arhgang
Guest
 
Posts: n/a
because the whole calculation domain was decomposed into several volumes, so each side was built up by 3 conplane conjoint faces.

I set 3 pairs of faces as hardlinked. so 3 periodic BC created.

periodic.4 periodic.5 periodic.6

then two conjoint edge was defined as Axis BC, now problem came, --axis bc cannot be exported with mesh! Gambit reported that no entity was related with the edges.

when build case in fluent, no axis bc was seen in BC selections.(rotaional periodic BC need axis, right?)

why? i have no idea.
  Reply With Quote

Old   October 31, 2001, 05:08
Default Re: Periodic Boundary Condition problem, help
  #7
kim
Guest
 
Posts: n/a
You do not have to set any axis BC. You just mark rotational in periodic BC panel. Rotation speed and axis of rotation is set in fluid panel and wall panel.
  Reply With Quote

Old   October 31, 2001, 08:22
Default Re: Periodic Boundary Condition problem, help
  #8
arhgang
Guest
 
Posts: n/a
thank u, Kim and Lanre

You remind me sth. deep in my mind. At first I was about to simulate a stationary missle, that is, only X-direction wind exist and the body keep stationary. So I can set in fluid BC pannel as:

Rotation-Axis Direction: (1,0,0)

Motion-Type:Stationary now if i want to simulate a rotating missle(Alpha=0, Phi=2rad/s), then i shall set here:

Rotation-Axis Direction: (1,0,0)

Motion-Type:Moving Mesh

Rotational Velocity Speed: 2 rad/s

Translational Velocity: (0,0,0)

and the mesh is the same as mentioned above.

am i right?

  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
Periodic boundary condition Arif FLUENT 2 January 17, 2014 07:48
Problem with assigned inlet velocity profile as a boundary condition Ozgur_ FLUENT 2 August 3, 2012 05:54
problem about periodic boundary condition in Fluent winnawinna FLUENT 0 December 29, 2010 00:32
Import problem ARC Open Source Meshers: Gmsh, Netgen, CGNS, ... 0 February 27, 2010 11:56
Transient outlet boundary condition problem jwillie2000 CFX 1 December 7, 2009 18:07


All times are GMT -4. The time now is 22:14.