CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   ANSYS Meshing & Geometry (http://www.cfd-online.com/Forums/ansys-meshing/)
-   -   [ICEM] Hexa Prism layer NOT USING hexa (Blocking tab) (http://www.cfd-online.com/Forums/ansys-meshing/90182-hexa-prism-layer-not-using-hexa-blocking-tab.html)

la7low July 3, 2011 19:29

Hexa Prism layer NOT USING hexa (Blocking tab)
 
3 Attachment(s)
Hi Everyone,

could someone tell me how to create hexa prism layers (rextangular bricks) or quad elements extruded to a hexahedral elements (distorted bricks)? Ive always used blocking method before but now I must use volume/surface/prism meshing methods on a 3d geometry...

I have another question: how to create such a mesh on a 3d wing (again not using blocking) as depicted there (http://www.cfd-online.com/Forums/ans...tml#post258691) on the 4th pic?

How can you tell the prims mesher to just stop at a point without stair stepping? For me either you tell Icem prism generator to do stair stepping and you give up the boundary layer resolution (middle picture) there or you uncheck stair stepping getting crap like that on the left and right pictures.

Any help would be greatly appreciated!

PSYMN July 5, 2011 09:30

The problem is that if you don't stair step, but transition directly to tetras, you have very thin pyramids right up against the tetras and the tetra quality is very poor. If you want to do that, you can force a remesh by selecting those pyramids (and a few tetras attached) and remeshing them with tetras (Edit Mesh => Remesh => Subset).

I recommend a 4th option... Try the trailing edge baffle (as you did on your 3rd image), but with stair stepping... This will taper off the prism layer along the baffle.

To take it one step further, you could actually transition the initial height along the baffle. To do this, make sure you don't set an initial height on the baffle its self, but rather set the height on the curves. On the wing trailing edge side, set the small initial height that you set on the wing. On the other end of the baffle, set a larger height that will allow for easier transition to the volume...

la7low July 5, 2011 12:18

3 Attachment(s)
Quote:

Originally Posted by PSYMN (Post 314776)
I recommend a 4th option... Try the trailing edge baffle (as you did on your 3rd image), but with stair stepping... This will taper off the prism layer along the baffle.

To take it one step further, you could actually transition the initial height along the baffle. To do this, make sure you don't set an initial height on the baffle its self, but rather set the height on the curves. On the wing trailing edge side, set the small initial height that you set on the wing. On the other end of the baffle, set a larger height that will allow for easier transition to the volume...

I could make this (1st picture). My probem with this idea is that it does stair stepping at the free tip too as seen on the 2nd picture below. It would be important to maintain the resolution of the boundary layer there.

So I rather liked your first suggestion to remove the prisms and then remesh it:

Quote:

Originally Posted by PSYMN (Post 314776)
The problem is that if you don't stair step, but transition directly to tetras, you have very thin pyramids right up against the tetras and the tetra quality is very poor. If you want to do that, you can force a remesh by selecting those pyramids (and a few tetras attached) and remeshing them with tetras (Edit Mesh => Remesh => Subset).

I assume you were referring to Edit Mesh => Repair Mesh => Remesh Elements . Is that right at the first place? I could not use that tool. First of all, how to select the pyramids and some surrounding tetras? I could put all pyramids to a subset by turning on the visibility of Pyramids under Mesh-Volumes, then by right-clicking Subsets => Create I could put the visible pyramids to a subset. But how to add some nearby tetras to it?
Then I went Edit Mesh => Repair Mesh => Remesh Elements. There I opted for the followings:
Mesh type: Tetra
Elements: the subset I created (without tetras nearby)
Part: Inherited
Surface Projection/ Ignore Projection was left unckeched
Unfortunately, the pyramids were barely replaced by tetras (look at 3rd picture)...What should I do different?
Thanks for the help!

la7low July 8, 2011 01:43

Success but further questions..
 
1 Attachment(s)
I could make it, see picture below. I even scripted it and have a question about the "ic_uns_subset_add_pick_polygon" command. Its arguments are: "what name poly vect from_names partial convex etype [""]".

What is "vect"? I could not figure it out and Programmer's Guide only says: "Add elements in a screen polygon area to the subset, what can be one of edge, node, element, or a list of one or more of 0d, 1d, 2d, 3d."

In addition, I still welcome suggestions on how to extrude Autoblock surface mesh to layers containing hexa (topic title)? For me the prism layers always die prematurely when starting off with all quad surfaces...

Thanks for the help so far!

PSYMN July 11, 2011 15:49

Vect is probably the screen view vector...

The polygon select assumes that you are viewing the polygon from a particular orientation (normal to the screen), and so needs a direction vector...

mingersai January 29, 2012 00:50

Quote:

Originally Posted by la7low (Post 315253)
I could make it, see picture below. I even scripted it and have a question about the "ic_uns_subset_add_pick_polygon" command. Its arguments are: "what name poly vect from_names partial convex etype [""]".

What is "vect"? I could not figure it out and Programmer's Guide only says: "Add elements in a screen polygon area to the subset, what can be one of edge, node, element, or a list of one or more of 0d, 1d, 2d, 3d."

In addition, I still welcome suggestions on how to extrude Autoblock surface mesh to layers containing hexa (topic title)? For me the prism layers always die prematurely when starting off with all quad surfaces...

Thanks for the help so far!

Would you please tell me how you did this?


All times are GMT -4. The time now is 16:57.