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[ANSYS Meshing] Creating a good mesh on difficult geometry

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Old   November 20, 2014, 10:52
Default Creating a good mesh on difficult geometry
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Jip Krens
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Dear all,

For my Bachelors Thesis I'm analyzing a complex burner. I use the Ansys workbench / Fluent for this, and the last month I've been busy getting comfortable with the program. This forum has been really helpful with that.

At this point however I'm stuck with creating a good quality mesh in the workbench. The burner is a cylinder with a diameter of around 1 meter and a length of 2 meter. There is one inlet with pre-mixed combustion and one inlet for extra air. Inside the cylinder a conical liner is placed.

The liner is the problem: It's 1,20 meter long, but only 2 mm thick.

Whats the best way to create a good mesh for this geometry? I've been trying for over a week and can't seem to get it right.

Best regards,
Jip Krens
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Old   November 21, 2014, 04:47
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Try meshing it by yourself & tell what problems you are getting.
Some tips:
1. Simplify the geometry
2. Take only a sector or half or quarter section of the geometry.
3. Go for unstructured mesh first.
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Old   November 21, 2014, 08:02
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Dear shivasluzz,

Thanks for your reaction. I created a mesh with simpeler geometry (I left out the holes from the liner) and could create a good geometry this way. However, the most important part of my analysis is the mixture of air and fuel thru these holes in the liner.

I managed to create one mesh with the total geometry, but this mesh had 3,2 million elements, and the academic version of Fluent only supports 500,000 elements.

What do you mean by going for the unstructured mesh first?
I could post a photo of the geometry if that helps?

Thanks again,
Jip
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Old   November 21, 2014, 08:17
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Hope you are aware that there are two types of mesh 1. Structured mesh (Hex elements)
2. Unstructured mesh (tet elements)

If you want to reduce the number of elements then go for structured mesh. But it's time consuming.

Ok post the post
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Old   November 21, 2014, 08:29
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Dear shivasluzz,

The pictures are attached. The first picture is the burner room, the second one the liner which is placed inside the burner room.

Best regards,
Jip
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File Type: jpg Schermafbeelding 2014-11-21 om 13.23.34.jpg (42.4 KB, 92 views)
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Old   November 21, 2014, 09:03
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First follow this simple method.
(hope you have already created the fluid model)
1. Insert "method" by right clicking on the 'mesh' in the tree view.
2. Set method to "multizone"
3. Generate mesh
4. Increase or decrease the "releavnce centre" in mesh detail to make the mesh finer or coarser.
Try this and tell me
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Old   November 21, 2014, 09:36
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I tried the multizone method, but got the following two errors:
- The mesher has an unhandled exception. Running out of memory may be the cause.
- The mesh generation was not successful.

Is there a way to solve this?
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Old   November 21, 2014, 09:47
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Decrease the "relevance centre" and try again.
If that also not works, then decompose your body into several bodies (1 part & many bodies under it) in design modeller. Split in such a way that each body is sweepable. For your geometry, split the main cylinder into 3 (before, after and at the location of liner), also split all the small cylinder which are created in the holes & etc.,
Now in the meshing software, right click on mesh & click "show sweepable" body. It should show many selectable bodies and then insert method, select "sweep" as your option.. Then mesh it!
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Old   November 21, 2014, 09:50
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shivasluzz, thanks again for your reply, I will try the sweep method aswell.

I get what you mean by splitting the main cylinder in 3 parts, but what do you mean by splitting the small cylinder / holes?

Thanks!
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Old   November 21, 2014, 11:32
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What I meant to say is.. If we make fluid model for your geometry, then we will get cylinders in the place of holes of liner rite.. That's wat I told..
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Old   January 12, 2017, 18:25
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Hi all

I have an important question that will assist me with my final year project.

I am looking into solid particle erosion in pipes and would like to know how i can obtain a good quality mesh for a straight pipe (19.25 in in length and 2.25 inch in outer diameter) on ANSYS Fluent.

Thank you very much
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