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-   -   [GAMBIT] 2D ellipse in rectangular domain (https://www.cfd-online.com/Forums/ansys-meshing/73003-gambit-2d-ellipse-rectangular-domain.html)

 rieuk February 24, 2010 03:08

[GAMBIT] 2D ellipse in rectangular domain

2 Attachment(s)
Hi guys, I'm wondering how to create the mesh in Gambit as shown in the figures attached. Particularly how to get the curvilinear grid lines from the surface of the ellipse to the outer circle.

Creating nodes on the ellipse and the circle then meshing them simply creates nodes following straight lines from the circle to the ellipse resulting in skewed cells on the ellipse surface.

 -mAx- February 26, 2010 02:27

try to attach a Boundary Layer on the ellipse with lot's of layers

 rieuk February 26, 2010 03:46

Thanks for the reply, but creating a boundary layer on the ellipse simply creates nodes coming out in straight lines.

I need some kind of way to create intermediate mesh lines between the ellipse and circle to gradually release the ellipse into the circle.

I've asked a lot of people who were supposedly very good using GAMBIT and noone has any idea of what I'm talking about much less what I want to achieve.

 -mAx- February 26, 2010 04:54

1 Attachment(s)
ok you don't want normal lines...
Then you have to enforce gambit meshing your domain with curved lines.
You have to plit your domain with those curved lines.
In the pictures you can see my splits (blue lines), but maybe it is not what you want...

 rieuk February 26, 2010 06:38

Hey Max, thanks for having a go at it and yea I can see your blue splits (4 of them) - interesting approach and I might go with it. However it doesn't exactly apply the condition that the grid lines come out from the ellipse exactly normal at every point which the mesh in the original pics I posted seem to do...

 -mAx- February 26, 2010 07:46

My splits are done at random. Splitting with right ellipses-arcs, and at the right locations, will give you more accurate grid lines.
Also you may split your domain with another ellipse (bigger and surrounding your initila ellipse --> like a transition between your first ellipse and you circle). It will be more accurate.
Anyway you cannot expect meshing your domain on the fly without any splits.

 dreft October 7, 2010 07:55

I´m meshing a elipse like you , but I need a Boundary layer ,did you use the boundary layer¿?How do you mesh it ¿?

 rieuk October 7, 2010 08:46

I used the technique suggested by -MaX-. It's not exactly a conformal mesh but it works very well if you do it carefully. No I didn't use any 'boundary layer' but my mesh was naturally highly resolved in the boundary layer...

 dreft October 7, 2010 08:52

and how did you mesh the part between the elipse and the circle¿?
I did a succesive ratio =1 and the same intervals in the elipse than in the circle.I thought that if the number of intervals grow up , maybe the boundary layer will be ok,but i´m not sure.