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

Rotational Periodic Boundary Conditions

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   February 1, 2012, 11:37
Default Rotational Periodic Boundary Conditions
  #1
New Member
 
Join Date: Dec 2009
Location: Italy
Posts: 23
Rep Power: 16
SerSe is on a distinguished road
Dear all,

I have two simple questions regarding rotational periodic boundary conditions. The model is a 6-holes nozzle inside a cylindrical pipe - I am modelling a 60° sector with 3D tetrahedral elements.

1. Shall the axis of rotation be the x axis in Fluent?
2. Shall the two opposite faces defining the 60° sector be coupled in one part, so to apply only one PERIODIC boundary condition? I am using ICEM for geometry + mesh + boundary conditions.

I made some trials, but Fluent gives undefined error during calculation of first iteration.

Thank you very much!

Sergio
SerSe is offline   Reply With Quote

Old   February 1, 2012, 13:31
Default
  #2
New Member
 
Join Date: Mar 2011
Posts: 7
Rep Power: 15
dynamics is on a distinguished road
Hi,
1. Shall the axis of rotation be the x axis in Fluent?
Yes, you can

2. Shall the two opposite faces defining the 60° sector be coupled in one part, so to apply only one PERIODIC boundary condition? I am using ICEM for geometry + mesh + boundary conditions.

If the two periodic boundaries are in separate parts, the periodicity can be defined in ICEM by first defining the axis and angle in 'Mesh -> Global mesh setup -> Define periodicity'
Then 'Blocking -> Edit block -> Periodic vertices' selected the periodic pairs. After creating all the periodic vertices, in the display control tree, activate Faces and verify by right clicking on Faces -> Periodic Faces.
All the periodic faces should appear 'red'.

If this is done, Fluent automatically shows only one periodic boundary on which rotational periodicity have to be specified.
dynamics is offline   Reply With Quote

Old   February 2, 2012, 04:57
Default
  #3
New Member
 
Join Date: Dec 2009
Location: Italy
Posts: 23
Rep Power: 16
SerSe is on a distinguished road
Hello!

1. I understand it is not mandatory to use the x axis as axis of rotation (for instance, in 2D axisymmetric problems, the axis of revolution has to be the x axis)

2. I've checked my models with the Mesh -> Periodicity from the display control tree. If the two opposite faces defining the 60° sector are coupled in one part, there is no periodicity relation though I created the mesh with Global Mesh setup parameters. If the two opposite faces belong to two different parts, I see the periodicity relation (the opposite nodes are linked by straight green lines). I apply then the periodic BC to the parts in ICEM.

Now, when Fluent reads the mesh file of the correct ICEM model, one periodic part is OK, for the other the following message appears:

"Skipping zone periodic_sh (not referenced by grid)"

and the part gets deleted. Is this normal? I guess Fluent couples the two parts, one as periodic and the other as shadow...

The fact is that the simulation does not run, I don't know if due to wrong periodic BC or to the use of multispecies+density-based solver+periodic BC (I have read somewhere that periodic BCs cannot be used by density-based solver when chemical species are activated). Might you help?

Thank you very much!

Sergio
SerSe is offline   Reply With Quote

Old   February 3, 2012, 11:50
Default
  #4
New Member
 
Join Date: Mar 2011
Posts: 7
Rep Power: 15
dynamics is on a distinguished road
Hi,
Have you created "periodic pairs" of the vertices on periodic faces in ICEM?
Regards
dynamics is offline   Reply With Quote

Old   February 3, 2012, 12:59
Default
  #5
New Member
 
Join Date: Dec 2009
Location: Italy
Posts: 23
Rep Power: 16
SerSe is on a distinguished road
Helllo,

I don't need to create periodic pairs of vertices as the mesh is made of tetras. The ICEM model with two parts (each with one periodic face) is working fine. The simulation does not run with the density-based solver or with the coupled pressure-based solver, while it runs well with the segregated pressure-based solver. Energy, species and turbulence are activated, fluids have properties changing with temperature.

Residuals go as low as 10^-5, more iterations do not decrease their values. How to get 10^-6? Should I increase under-relaxation factors?

Thank you very much!

Sergio
SerSe 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
periodic boundary conditions fro pressure Salem Main CFD Forum 21 April 10, 2013 01:44
Periodic boundary conditions in 3D Eulerian granular flow simulations dsm FLUENT 4 March 2, 2012 20:04
Problem with using periodic boundary conditions Sun FLUENT 0 January 14, 2011 10:47
Urgent: periodic boundary conditions ck1973 FLUENT 3 July 5, 2006 12:32
How to apply a periodic boundary conditions ck1973 FLUENT 2 July 4, 2006 02:27


All times are GMT -4. The time now is 04:49.