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-   -   orthogonality in gambit (http://www.cfd-online.com/Forums/fluent/41342-orthogonality-gambit.html)

kohi June 10, 2006 03:33

orthogonality in gambit
 
Hi all,

How to generate orthogonal mesh in boundaries using the gambit software.

thank all.

ivanbuz May 13, 2009 14:03

I also want to know
 
I am trying to generate orthogonal mesh around an airfoil using GAMBIT. After a lot of attempts and search online, I am almost convinced that Gambit cannot do it.

I will be glad if anyone can confirm this or show how to do it.

martingariepy May 13, 2009 14:20

I think youre right, Gambit can't do it. You will have to use ICEM CFD. You can try my little trick to mesh at 90 degrees, I'm using the boundary layer as a guide for the meshing, and the BL is always perpendicular to your wall. Hope it's help

Ralf Schmidt May 14, 2009 04:26

Hi!

Gambit ca create an orthogonal mesh... but it might be very tricky...

A BL mesh is NOT ALWAYS orthogonal to the surface!! If you have walls that are non orthogonal, and the BL is attached to these walls, the BL might align to these walls.

You can create an orthogonal mesh via premeshing the edges that are opposite to each other. In the mesh edges option, select both edges and mesh them together.

I grant, if you have an irregular shape inside your domain, a purely orthogonal mesh is impossible in gambit. BUT... how should this look like? I cannot imagine a purely orthogonal mesh on a curved surface.....

Best wishes
Ralf

ivanbuz May 15, 2009 18:40

Thanks to Martin and Ralf, but I am a little confused.

To Martin, BL can not guarantee orthogonal mesh in the boundary layer. Unfortunately I do not have a license for ICEM CFD.

To Ralf, do you mean to LINK the two edges by "In the mesh edges option, select both edges and mesh them together.”

Some one told me GridGen by Pointwise Inc will do it, but I am not sure and I don't have a license. :(

Ralf Schmidt May 16, 2009 04:59

Hi!

yes, thats what i am talking about - select both parallel lines and select "soft link -> form" (this is standard setting).

Take care, that both lines are aligned in the same direction (the little red arrow shown)

You can post a picture of your geometry here. We can give you advice if and how to create an orthogonal mesh...

Best wishes
Ralf

ivanbuz May 18, 2009 17:03

Thanks, Ralf,

I am not sure if linking the two edges (the upper edge and the lower edge of the airfoil) will help to generate orthogonal mesh around the airfoil. These two edges are not parallel, they are connected.

The geometry of the airfoil NACA4412 and the mesh I have right now is here

http://www.cfd-online.com/Forums/mem...rfoil-mesh.jpg

alikami May 26, 2009 00:17

Orthognality
 
I think you make two contours.
1. Aerofoil
2. Offset aerofoil by a distance in which grid should remail orthognal.
make sure the offset distance is not very large.
the mesh inside this two curves will be nearly orthognal.
rest of the mesh between the outer boundary and offseted contour wont be orthognal
ali


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