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-   -   [ICEM] Annoying mesh holes on an aircraft (http://www.cfd-online.com/Forums/ansys-meshing/98038-annoying-mesh-holes-aircraft.html)

Santos-Dumont March 1, 2012 15:17

Annoying mesh holes on an aircraft
 
Hi there

I'm currently working on a project of a 2-seater ultralight (http://imageshack.us/photo/my-images/685/buselec.jpg/). I'm trying to make some calculations but meshing puts me in trouble.


I've been trying to do it with blocking but I let go because the task was obviously too difficult for me.

So my idea was to use the same procedure as I did with Gambit. Create the volume with CATIA, export to STP. Then in ICEM make some surface merging to clean the unnecessary edges and surfaces and then mesh using Tri Elements and something like a size function...

It's very frustrating because I want to suceed in doing that with ICEM but...

1) Surface merging do not work. So I have to keep every surfaces generated by CATIA which seems less than ideal.


But whatever, I create new parts for my boundary and for the aircraft. I do a global size for the aircraft surfaces only, and a more refined one on the wings, horizontal tail, nose cone and prop. Then I do the volume mesh without problems.

http://imageshack.us/photo/my-images/843/29338367.jpg/

2) Meshing is nice, fast and the mesh looks great, on that point ICEM is way better than GAMBIT. But in some zones I get some holes which I can't figure out how to get rid of ! Look closely on the propeller and horizontal tail.

http://imageshack.us/photo/my-images/577/10447806.jpg/

http://imageshack.us/photo/my-images/13/92755498.jpg/

I have some uncovered faces problem that I fix using the mesh repair tool and I eventually manage to export to Fluent with all the boundaries working. I also tried the convert 12 TET to 1 Hex once and it worked nicely.


3) When exporting to Fluent I get that message that says that a shadow wall is created and it includes like one element randomly picked on the aircraft...

Still, I made some Fluent calculations that were nice but I still have this hole problems on the airfoils trailing edge and on the propeller. So I tried every meshing pethod but none have worked. When meshing the surface only the mesh was great everywhere without holes. But when meshing the volume even with the "use existing mesh" option and the aircraft selected the holes appeared after volume meshing.

Am I doing something wrong ? I followed the procedure that I found with tutorials but it doesn't work...

Santos-Dumont March 1, 2012 15:19

I finally managed to get the prism layer to work. I'm actually amazed by the result. This new feature is very useful to solve the boundary layer without too much expense.

http://imageshack.us/f/33/buselecprism.jpg/

But still, I get a semi-empty prop. I tried to remesh the surface (see picture below) and to remesh the entire volume while using the already computed mesh on the aircraft surface but I get multiple errors (Misoriented faces) and the result is not usable.

http://imageshack.us/f/526/91260081.jpg/


Any idea ? That sounds like a simple thing to fix but I can't figure out how to do it...

Thanks
Charles

Santos-Dumont March 2, 2012 09:13

Please, nobody have anything on this ?

I tried the prop only but that didn't work. I made all build topology and geometry cleanup I could but nothing worked.... I even tried to export only the propeller from Catia and I had the exact same problem...
Actually I see that the meshes of lower and upper part of the prop and wings tend to join at the trailing edge. That explains why the mesh doesn't reach the trailing edge...


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