CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Mesh Generation & Pre-Processing Software > Pointwise & Gridgen

Domain "collapses"

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

Like Tree1Likes
  • 1 Post By cnsidero

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   March 10, 2013, 10:33
Default Domain "collapses"
  #1
Senior Member
 
Lefteris
Join Date: Oct 2011
Location: UK
Posts: 337
Rep Power: 15
Aeronautics El. K. is on a distinguished road
Hello everyone!

I have one more question and I'd really appreciate it if someone could help.

When I use 4 connectors to assemble an unstructured domain, the mesh that is created is as if it has collapsed inwards. I attach a picture of the resulting domain.
It would be nice if I understood why this is happening and how to fix it.

Update
-------
I think I found the solution by reading this post:
http://www.cfd-online.com/Forums/poi...-question.html

I selected the database lines and then I selected
Create --> Coons Patch --> Generate Surfaces --> OK

and afterwards I assembled the domain and it seems ok...
Attached Images
File Type: png domain.png (13.5 KB, 14 views)
__________________
Lefteris


Last edited by Aeronautics El. K.; March 10, 2013 at 11:46.
Aeronautics El. K. is offline   Reply With Quote

Old   March 10, 2013, 12:59
Default
  #2
Senior Member
 
Chris Sideroff
Join Date: Mar 2009
Location: Ottawa, ON, CAN
Posts: 434
Rep Power: 22
cnsidero is on a distinguished road
Good to see you found that post. I didn't give much of an explanation though.

Creating unstructured domains from curved connectors _without_ underlying geometry will result in the initialized points being created like you saw because the algorithm it uses for unconstrained domains is a very simple interpolation of the boundary points.

This however is not the case for unconstrained structured domains which uses transfinite interpolation (TFI) and will do a much better job at creating the internal point locations such that it better represents the curvature of the bounding connectors. In fact, the structured domain TFI creates domains in a similar manner to how b-spline surface geometry is created.

The moral is for unstructured domains with curved bounding connectors you need to create an underlying database surface by which it can constrain it's internal points otherwise you end up with what you saw.

-Chris

Quote:
Originally Posted by Aeronautics El. K. View Post
Hello everyone!

I have one more question and I'd really appreciate it if someone could help.

When I use 4 connectors to assemble an unstructured domain, the mesh that is created is as if it has collapsed inwards. I attach a picture of the resulting domain.
It would be nice if I understood why this is happening and how to fix it.

Update
-------
I think I found the solution by reading this post:
http://www.cfd-online.com/Forums/poi...-question.html

I selected the database lines and then I selected
Create --> Coons Patch --> Generate Surfaces --> OK

and afterwards I assembled the domain and it seems ok...
Hybrid likes this.
cnsidero is offline   Reply With Quote

Old   March 10, 2013, 14:15
Default
  #3
Senior Member
 
Lefteris
Join Date: Oct 2011
Location: UK
Posts: 337
Rep Power: 15
Aeronautics El. K. is on a distinguished road
Chris, thank you so much for the answer and the thorough explanation.
I had, in fact, nocited while experimenting with the software's features that - as you said - this is happening only with the unstructured domains while the structured ones are perfect. Now, I found out how to do it properly and thanks to you, I know the underlying theory as well! I appreciate your help!

Quote:
Originally Posted by cnsidero View Post
Good to see you found that post. I didn't give much of an explanation though.

Creating unstructured domains from curved connectors _without_ underlying geometry will result in the initialized points being created like you saw because the algorithm it uses for unconstrained domains is a very simple interpolation of the boundary points.

This however is not the case for unconstrained structured domains which uses transfinite interpolation (TFI) and will do a much better job at creating the internal point locations such that it better represents the curvature of the bounding connectors. In fact, the structured domain TFI creates domains in a similar manner to how b-spline surface geometry is created.

The moral is for unstructured domains with curved bounding connectors you need to create an underlying database surface by which it can constrain it's internal points otherwise you end up with what you saw.

-Chris
__________________
Lefteris

Aeronautics El. K. 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
Domain Imbalance HMR CFX 5 October 10, 2016 06:57
Domain format problem on airfoil flow simulation andrenonaka CFX 14 December 7, 2015 01:42
domain imbalance for enrgy equation happy CFX 14 September 6, 2012 02:54
CFX domain comparison Kiat110616 CFX 4 April 3, 2011 23:43
CFX Solver Memory Error mike CFX 1 March 19, 2008 08:22


All times are GMT -4. The time now is 07:40.