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-   -   [Pointwise] structured mesh (http://www.cfd-online.com/Forums/pointwise/108692-pointwise-structured-mesh.html)

James_ October 30, 2012 14:28

[Pointwise] structured mesh
 
Hello,

I'm new user of Pointwise software. Pointwise seems to be powerful and intuitive tool for meshing. I've decided to use this software for meshing very simple geometry (straight pipe).
You can download project: http://www.filefactory.com/file/1ai7lxpen9pp/n/ex2_7z
This project is very similar to tutorial "Transition Duct" provided by Pointwise
I loaded geometry file in format .x_b and I started meshing.
I 've some weird problems:

1. I can't create structured mesh at the inlet and outlet (red mesh in project), but I can create unstructured mesh. Can someone explain me why? I 've chosen 5 conectors and option "Assemble Domains" but it doesn't work.

2. I wanted to create mesh inside the pipe. First I've created block ("blk-2" in my project) and then I clicked on "Initalize" button, but inside the pipe there is no cell mesh.

Thank you in advance for your help.


Best regards,
James

cnsidero November 1, 2012 16:41

2 Attachment(s)
Quote:

Originally Posted by James_ (Post 389331)
1. I can't create structured mesh at the inlet and outlet (red mesh in project), but I can create unstructured mesh. Can someone explain me why? I 've chosen 5 conectors and option "Assemble Domains" but it doesn't work.

By definition a structured domain has 4 edges and opposing edges must have the same number of points. If the edges were named, in sequential order, A, B, C and D. Edges A and C must have same # of points and B and D must have same # of points.

Within Pointwise you may choose to define each of the edges with more than one connector, meaning it is possible to assemble a structured domain, as in your case, with 5 connectors. However, in your case, the number of points used will not allow the assembly (this part is obvious).

The number of points of your 5 connectors starting with the longest one on the symmetry plane moving clockwise is: 20, 5, 6, 6, 6. If instead you change the number of points for each of the 5 as: 11, 6, 6, 6, 6 it will assemble. So:

Edge A uses the 11 pt connector
Edge B uses the first 6 pt connector
Edge C uses the second and third 6 pt connectors
Edge D uses the fourth 6 pt connector

Clearly edges B and C match. A has 11 points. Even though edge C has two 6 pt connectors for a total of 12, two points are at the same location - where the connectors join - so only one is counted. The general formula for computing total points on an edge is:

(sum of all connector points) - (number of connectors - 1) = edge points

In your case:

(6 + 6) - (2-1) = 11

e2-struct-init.png illustrates the result using the above numbers.

I would go another step further and smooth this domain with the solver to improve the quality (see e2-struct-solve.png).

Quote:

2. I wanted to create mesh inside the pipe. First I've created block ("blk-2" in my project) and then I clicked on "Initalize" button, but inside the pipe there is no cell mesh.
I looked at your mesh and the unstructured block "blk-2" does in fact have cells. Pointwise won't display volume elements unless you examine the block using the tools in the Examine menu. Basically I don't see anything wrong here other than you can't see them by default.


Hope that helps, Chris

cnsidero November 1, 2012 16:46

A quick follow on to my first one. The same logic applies to structured blocks, except blocks have 6 faces instead of 4 edges. Opposing faces must have the same number of points and topological arrangement.

James_ November 1, 2012 18:05

Thank you very much Chris:)

You've been very helpful:)You made my life easier:)

cnsidero November 1, 2012 22:15

No problem. Happy to help.


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