CFD Online URL
[Sponsors]
Home > Forums > ANSYS Meshing & Geometry

[ICEM] Specifying Periodic Vertices Causes Strange Problem

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

Reply
 
LinkBack Thread Tools Display Modes
Old   September 2, 2010, 16:59
Default Specifying Periodic Vertices Causes Strange Problem
  #1
Senior Member
 
Joshua Counsil
Join Date: Jul 2009
Location: Halifax, Nova Scotia, Canada
Posts: 366
Rep Power: 8
Josh is on a distinguished road
Hi all -

I'm encountering a strange problem when I try to create periodic sides on a 3D airfoil.

I have a working, complete 2D mesh that ran successfully (shown below).



I want to create a 3D mesh with periodic sides. The span length is 100.85531 mm. First, I went into the Global Mesh Setup and defined a translational periodicity with the z (span) offset as 100.85531. I then extruded my 2D blocking scheme to 3D using a z translation of 100.85531.



So far, so good. The problem arises when I begin specifying my periodic vertices. The vertices in the outer boundaries (inlet, farfield, outlet) don't seem to cause problems. The inner vertices (around the airfoil), however, seem to cause the mesh to extrude itself in the opposite direction desired (see below). The first picture shows the proper extrusion.



The next pictures show the problem areas.













Is my strategy incorrect? Any suggestions?

Thanks!

Josh
Josh is offline   Reply With Quote

Old   October 15, 2010, 16:26
Default
  #2
New Member
 
Grant
Join Date: Apr 2009
Posts: 3
Rep Power: 7
grantom is on a distinguished road
Are you specifying the airfoil vertices as periodic? If so, don't do that. The airfoil surface is not periodic, only outer boundaries.

Grant
grantom is offline   Reply With Quote

Old   October 16, 2010, 05:36
Default Order...
  #3
Senior Member
 
PSYMN's Avatar
 
Simon Pereira
Join Date: Mar 2009
Location: Ann Arbor, MI
Posts: 2,660
Blog Entries: 1
Rep Power: 34
PSYMN has a spectacular aura aboutPSYMN has a spectacular aura about
When making verts periodic, you must be consistent with the order of selection. Go back and make sure that when you do it again, you always pick the lower k index first and then the higher K index next (or vice versa), but never change the oder during the selection of periodic pairs.

I think this hassle has been improved in more recent versions you could alternate without the problem.
PSYMN is offline   Reply With Quote

Old   October 16, 2010, 21:21
Default
  #4
Senior Member
 
Joshua Counsil
Join Date: Jul 2009
Location: Halifax, Nova Scotia, Canada
Posts: 366
Rep Power: 8
Josh is on a distinguished road
Thanks for the suggestions, guys. I'm swamped this week with a different problem but will return to this topic at a later time with updates.
Josh is offline   Reply With Quote

Old   July 15, 2011, 08:41
Default
  #5
Senior Member
 
Joshua Counsil
Join Date: Jul 2009
Location: Halifax, Nova Scotia, Canada
Posts: 366
Rep Power: 8
Josh is on a distinguished road
It's been a long time, but I've finally returned to this problem (and, unsurprisingly, I haven't yet solved it!).

As I mentioned previously, I have a working 2D mesh. Let me just ask this to start: What's the best way to proceed from there in order to make a 0.1c (10% chord-lengths, which for a 1 meter chord is 0.1 m) span mesh with 11 nodes (10 elements) in the spanwise direction? As far as I know, there are 2 methods:

1) Mesh > Part Mesh Setup > Define Translational Periodicity > [0 0 -0.1];
Blocking > Create Block > 2D to 3D > Method: Translate > Define new part: Solid > Distance [0 0 -0.1];
Blocking > Edit Block > Periodic Vertices > (set periodic vertices);
Blocking > Pre-Mesh Params > Edge Params > (define spanwise edge and parallel edges as 11 nodes deep)

2) Mesh > Part Mesh Setup > Define Translational Periodicity > [0 0 -0.1];
Edit Mesh > Extrude Mesh > (select all elements, 10 layers, 0.01 spacing);
Edit Mesh > Repair Mesh > Make/Remove Periodic > Make Periodic > (choose individual nodes)

Method 1 fails at step 2. When I extrude the block to 3D and observe the new pre-mesh, only certain parts are extruded.

Method 2 produces the correct spanwise mesh, but now I have 78,000 nodes. I can't specify the periodicity of each node pair.

How would you suggest I go about this?
Josh is offline   Reply With Quote

Old   July 19, 2011, 17:09
Default
  #6
Senior Member
 
Joshua Counsil
Join Date: Jul 2009
Location: Halifax, Nova Scotia, Canada
Posts: 366
Rep Power: 8
Josh is on a distinguished road
I believe I've solved my problem. I used method 2 from the above post but neglected the periodic steps. I simply extruded my 2D mesh to 3D, created new parts for the 3D boundaries, and exported the mesh to CFX. It seems that specifying periodicity in ICEM is only required when the periodic interfaces are not directly aligned 1:1, e.g., in a turbine cascade. In my case, the periodic interfaces (the side boundaries) are directly aligned.

Hope this helps others.
Josh is offline   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
A Strange Problem in making Parallel (Ansys/CFX 12) a.sarami CFX 13 October 7, 2010 02:33
problem in meshing a periodic boundary dumas FLUENT 4 March 8, 2006 11:54
Periodic Boundary Condition problem, help arhgang FLUENT 7 October 31, 2001 08:22
MRF problem you FLUENT 1 May 16, 2001 00:09
Problem with periodic boundary layers Phil FLUENT 15 October 2, 2000 15:56


All times are GMT -4. The time now is 01:19.