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-   -   [GAMBIT] Boundary layer meshing problems (http://www.cfd-online.com/Forums/ansys-meshing/84432-boundary-layer-meshing-problems.html)

gambiss January 29, 2011 11:03

Boundary layer meshing problems
 
Hi

I am having trouble making a boundary layer around an aerofoil as I want a y+ as 1 so structure mesh at first (1% of the chord) then unstructure out from that (modelling a VAWT turbine with three blades).

Does anyone have any suggestion how to do this, as when I try it boundary layer function does go around the blade, and just make lines across it.

Thanks

-mAx- January 31, 2011 02:31

first mesh edges from your airfoil

gambiss January 31, 2011 13:49

Cheers. Now when I try to mesh, I either get error: boundary layer is to high, then when I reduce it says: that mesh is not possible without interference.

I have taken off the auto smooth default. Is their anything else I should do?

Thanks

-mAx- February 1, 2011 01:52

can you post a picture with the BL you try to attach

gambiss February 6, 2011 15:12

Still having problems, is this a fault of my meshed edge or? An gambit error, as some times it seems to work with out hassle... and see that other people are having simular problem...

https://picasaweb.google.com/1157392...56072322986802
https://picasaweb.google.com/1157392...56075170157810
https://picasaweb.google.com/1157392...56075170157810

Thanks for you help in advance!

-mAx- February 7, 2011 02:19

if you deselect the trailing edge in the BL-surface list, does the error remain?

gambiss February 7, 2011 07:01

If you mean, not creating a boundary layer around the trailing edge then no, this doesn't work either!

But unsure of what you mean!

-mAx- February 7, 2011 07:54

no I mean, don't pick the trailing edge, when you select edges where the BL will be attached.
Does the error remain?
Quote:

Originally Posted by gambiss (Post 292989)
Now when I try to mesh, I either get error: boundary layer is to high, then when I reduce it says: that mesh is not possible without interference. Thanks


gambiss February 7, 2011 08:08

Yes, now it will mesh, is there any way to get it create a boundary layer around the whole blade?

Thanks!

-mAx- February 8, 2011 01:58

ok that means the error comes from this edge.
Try to add more nodes on this edge.
If it don't help, try to merge the edge with the 2 others (both sides), and perturb nodes distribution

gambiss February 8, 2011 05:42

I've managed to Mesh it now, but, it is really skewed next to the blade, is this just from the position of the nodes and is the only way to solve this adjusting them?

Or is there a simpler way!?

Thanks for all you help, I really appreciate it!

-mAx- February 8, 2011 05:51

post a picture

gambiss February 8, 2011 06:01

https://picasaweb.google.com/1157392...56384960415330

https://picasaweb.google.com/1157392...56392982700834

-mAx- February 8, 2011 06:04

something is weird.
Can you provide me the dbs file?

gambiss February 8, 2011 06:59

http://www.fileswap.com/dl/eQjBziUI/...again.zip.html

-mAx- February 8, 2011 08:30

3 Attachment(s)
ok I kept the parameters from your BL and your SF.
But first, you absolutely need to split your domain into several smallest surfaces.
Indeed you have 3 airfoils, so I would isolate each airfoil with a split (circle in my example)
Then Gambit will have less difficulty to mesh surfaces, especially when you impose a thin BL.
So I meshed one airfoil with this method (you choosed tri), but here you can easily mesh it with hexa.
I would mesh it with hexa ,then you can have more control on the aspect ratio between last cell layer from your BL and cells outside the BL.
Attachment 6404Attachment 6405Attachment 6403

gambiss February 8, 2011 10:18

Okay, thanks for that! I will reduce my surfaces...

But- I can only select hexa in volume meshing? How do I do it for 2D? :?

-mAx- February 8, 2011 10:52

quad or map

gambiss February 9, 2011 07:31

Hmm, I've meshing the blades seperately but I still get the same skewed BL around them... :(

-mAx- February 9, 2011 07:58

with quad or tri?
As you saw, with tri I didn't have any problem
post pictures


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