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-   -   [GAMBIT] create faces inside geometry (https://www.cfd-online.com/Forums/ansys-meshing/88966-create-faces-inside-geometry.html)

 Lilly May 31, 2011 09:04

create faces inside geometry

1 Attachment(s)
Hello everybody,

due to several things I want to do, I have to generate faces close to the bifurcation of my geometry perpendicular to the flow direction (see pic). I tried to do this using Gambit, but wasn’t successful till now. I also tried to create the centerline of my geometry using another software and import it to Gambit, but failed too.(I thought I could maybe create this faces easier using such a centerline.) Does anybody have an idea or knows a software to create such faces?
Lilly

 hittie May 31, 2011 15:58

try to make a surface splitting the edges respect to a point (you need to know the exact coordinates ) and then make the surface making the edges between two vertex and after make the surface using the edges.

 -mAx- June 1, 2011 01:34

*if your volume is still real, you can work with planes, and split your volume with planes

*if your volume is virtual, then :
-split the edges at specific locations
- split surfaces with 2 vertices > gambit will create an edge which will split your surface
- Create surface from generated edges
- split volume with created surface

 Lilly June 1, 2011 07:29

What’s the best way to create such an edge there (where I added the red bars)? I should have mentioned that my geometry is a virtual one. Is there any trick to place vertices or edges at this special position? I already tried to use the Display Grid option, but I wasn’t successful due to my complex geometry with odd orientation… Do you have any idea, what I could do?
Lilly

 -mAx- June 1, 2011 08:10

use edges projection on surface

 Lilly June 15, 2011 08:46

1 Attachment(s)
Thank you -mAx-!
I tried to use the edge projection on the surface by revolving a vertex around the geometry (using the centerline as axis) and projecting this edge on the surface of my geometry afterwards (I attached a pic). Unfortunately I always get two different error messages "could not facet edge because of bad input values" and "Projection of edge on face cannot create unique or correct edge". I guess this is due to my uneven surface made of triangles.
Does anybody have an idea how to solve this problem?
Lilly

 -mAx- June 16, 2011 02:07

The problem you have is that you only have one surface (except top surfaces)
That means you don't have any edge for further work.
Did you import your surface from cad, or did you build it?

 Lilly June 16, 2011 04:21

Thank you -mAx-!
I was reconstructing it using 3dSlicer and processed and smoothed it using vmtk and MeshLab. Afterwards I imported it to Gambit as a stl file. Is there a way to process the surface afterwards?

 -mAx- June 16, 2011 04:25

from 3dSlicer are you able to export stl,iges, step, parasolid file (any format which you can import in Gambit)?

 Lilly June 16, 2011 13:16

I only have the option to export it as Poly Data (*.vtk), XML Poly Data (*.vtp) and *.stl :(

 -mAx- June 17, 2011 10:29

2 Attachment(s)
ok the problem is that STL isn t a cad format, but a surface mesh (never used this format).
If you have a cad-tool with which you can split your surface, you can try to import some stl files, and then in gambit you can reconnect them.
Advantage will be that connection will be generated at edges (in this case it will be extrimity from each stl import).
Else you can try to convert your surface from non-real to real, but it take some time (without guarantee it will work). I canceled since I don't have so much time.
If it is successfull you can split surfaces with plane.
But anyway you can mesh your domain on the fly with tetra-hexcore and apply an BL.
Attachment 8079 Attachment 8080

 Lilly June 23, 2011 08:34

Sorry for the late reply and thank you for all your help and efforts, -mAx-!
You posted a lot of helpful suggestions! I already tried to convert the non-real geometry to a real one, but wasn't succesful.
But I will try to merge/reconnect the imported branches and I will test the tetra-hexcore mesh now. These are really good ideas!
Thanks a million!

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