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Saikiran March 17, 2011 08:27

Blocking and OGrid
4 Attachment(s)
Hello everyone.....I have to do an analysis for combustion modeling of butane brazing torch. I have the model for meshing but it looks quite difficult for me to start with blocking.Can someone give idea where to start with??

The funnel like structure at one end is modeled to capture the flame and circular faces of the two cylinders intersecting orthogonally are inlets for air.
Images of geometry are attached.
Thank you........

BrolY March 18, 2011 06:13

First of all, you should create one o-grid for your inner tube. Then split the O-grid everytime you have a change in the direction of the tube, and associate your edges AND points on the curves. It's important to "fix" your O -grid to avoid problems when you add others o-grids inside the 1st o-grid.
I guess your issue is located at the air inlets ? Create 2 splits to there, and use the extrude face options to capture the air inlets.
Also, another issue is located on pictures 2 : you may have have to creates 2 or 3 inner o-grids because to capture the geometry.

Try that by yourselves, and come back with a try to see what it looks like ;) I can help you if you need.

Saikiran March 19, 2011 09:40

3 Attachment(s)
Thanx for your instructions BroIY. I have followed your instructions.I have two issues:
1. The mesh near the surface of the inner tube looks fine but inside the cross it's messed up.
2. And the two intersecting cylinders. How to tacklet that one??
Pics of the same are attached
Thank you.

BrolY March 21, 2011 10:55

1 Attachment(s)
I attached the files of my project: .tin and .blk
I changed a few your geometry by adding new points and curves which help to fix the blocking. Here are the steps to create this mesh :
1) create an O-grid and cut it every time the section of the tube changes.
2) remove the blocks of the grid (but keep the inner one) which are located between the butane_inlet and right after the air_inlet (when the section of the tube drops)
3) associate all your points and curves
4) cut your block twice, before and after the air_inlet. Then extrude the face of the blocks (blocking -> create block -> extrude face with the option extrude along curve) to the air-inlet. Associate.
5) Create an o-grid between the butane_inlet and right after the air-inlet (when the section of the drops) and select the face of the butane_inlet and air_inlet for the ogrid
6) about the cross with the small tude inside, just cut your blocks in this area twice in the horizontale direction, and twice in the verticale direction. Associate, and delete the blocks which are not in the fluid

It should work well ;)
I recommand you to try that by yourself, and just use my project as an example. Post some pictures if you are jamed !
Have fun ;)

Saikiran March 22, 2011 05:16

Thank you BroIY. I finished it. :)

Saikiran April 3, 2011 11:58

1 Attachment(s)
HELLO BroIY...your tips were helpful but i found some bad elements near the corners(on the cross) and i'm unable to initialize OGrid by selecting blocks and faces(ICEM gives an error). The picture is attached with the post.

BrolY April 4, 2011 03:40

Once you created the two first O-grid,associate curves with edges (that's why I added some curves in your model, so you can associate your edges). Then, split your blocks around the cross (and only those blocks, do not propagate your splits) before doing the last O-grid.
Associate the curves (and points) you have splitted with the edges. Thanks to the splitting you've done for the cross, you can associate the 4 inner edges to the small curves of your small inner tube. Delete the blocks that you don't need and, at the end, you can do the last O-grid inside the small tube of the cross.

Saikiran April 4, 2011 06:29

1 Attachment(s)
Hey BroIY...I'm sorry...should have written the other way. My intention was to improve the mesh at the corners for which i have tried to use OGrid and it wasn't working. The model which u have shared with me also has some elements with high skewness factor(If i increase the number of nodes for an edge). I'm not pointing out anything.Just wanted to know.

Can give some general guidelines for improving the mesh quality??

nitinbansal184 October 2, 2012 08:11

Try Edge alignment,
Or try creating new Ogrid
Or try increasing number of nodes on edges with low quality mesh

energy382 October 2, 2012 09:13

:D:D this thread is 1,5 years old.

don't think, he's still busy with that project

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