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-   -   Meshing doubt (http://www.cfd-online.com/Forums/ansys-meshing/75696-meshing-doubt.html)

arjit May 3, 2010 09:12

Meshing doubt
 
Hi guys!

Can I get accurate results of CFD of a 3D wing (finite) if I dont use a boundary layer, but instead, a very fine unstructured mesh near the boundary.. growing towards the exterior?

Thanks!

arjit May 3, 2010 09:17

contd..
 
One of the tutorials that I found online was this:
[http://hmf.enseeiht.fr/travaux/CD010...nual/index.htm

Do you think I can get accurate results with such a setup?

h.m lee May 3, 2010 11:22

depends your turbulence model.

Chris D May 3, 2010 18:33

If you use an unstructured mesh, you'll need more gridpoints to resolve the boundary layer than you would need if you used structured. This is because hexes can tolerate more stretching than tets. Just out of curiosity, why do you want to use unstructured instead of structured?

arjit May 4, 2010 04:22

Re:
 
Thanks for the reply Chris!

I had initially gone in for a structured BL with a structured mesh.

However, for the geometry that I am currently meshing, structured meshing doesn't seem to be appropriate, I have to use unstructured mesh.

Is a structured BL compatible with an unstructured mesh?
If so, how?

Thanks again!

PSYMN June 8, 2010 20:15

Tetra Prism.
 
If your geometry is complicated and you would rather go with tetras than hexas, that is fine, but you should insert inflation layers (prism layers) to capture the viscous boundary layer. You could do it with just tetras, but you would need so many that it wouldn't be practical. prisms allow you to have the higher number of elements perpendicular to the wall, and growing in a way that efficiently captures the velocity profile, but without increasing the node count isotropically...

A tetra prism mesh is considered standard these days and is a fully unstructured mesh.

h.m lee June 9, 2010 11:16

Quote:

Originally Posted by arjit (Post 257445)
Thanks for the reply Chris!

I had initially gone in for a structured BL with a structured mesh.

However, for the geometry that I am currently meshing, structured meshing doesn't seem to be appropriate, I have to use unstructured mesh.

Is a structured BL compatible with an unstructured mesh?
If so, how?

Thanks again!

Yes, Prism is prepare specially for BL.:)
And maybe you mean you want to use hybrid mesh. You can use Hexa-8 in BL, that likes structured mesh. Its efficient is more than 2 times than Penta-6( Prism). And Tetra-4 in far field.


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