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-   -   trailing edge negative volumes (http://www.cfd-online.com/Forums/ansys-meshing/84061-trailing-edge-negative-volumes.html)

Nick R January 19, 2011 07:46

trailing edge negative volumes
 
2 Attachment(s)
Hi guys,


I'm trying to mesh an airfoil with a sinusoidal leading edge using a simple blocking scheme with an O-ring. No matter how I move things around I always get negative volumes especially toward the trailing edge (see the images) I tried to get rid of the wedge behind the foil but didn't make much of a difference.
I'm quite a rookie and don't know how to fix these simple things. I'd very much appreciate your help.
Also any ideas about the blocking scheme for a wavy leading edge would be appreciated.
Nick

PSYMN January 30, 2011 18:12

3 Attachment(s)
I can't see exactly what the problem is, but negative volumes mean that your blocking is probably tangled... Your verts may actually be crossing. Perhaps your upper edge is projected to the lower curve and vice versa?

Perhaps a CGrid blocking would be better than an OGrid.

As for the waving leading edge, with Hexa, you should focus on the topology, not the actual shape. A bent pipe is still a pipe, a wavey wing is still basically a wing. You don't need to block for those curves, just block as a normal wing and associate with the surface. The mesh will follow and interpolate nicely...

Here are some pics...

First the side blocking of the CGRID...
Attachment 6266

Then, since this model had a sharp trailing edge, I split behind the wing and collapse the trailing edge block...
Attachment 6267

A few more steps and here is roughly done... Note this is just a single wedge block associated with the more interesting airfoil. No extra blocking was done to capture the wavy leading edge.
Attachment 6268

The thing about hexa is to have fun with it... ;)

Nick R February 2, 2011 03:05

Simon!

This is really cool and sort of like what I made. How did you create the foil? I use Solid Edge. Is there a more efficient way? I had difficulty with creating the surfaces.
Thanks again.


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