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Old   February 20, 2013, 09:53
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That solved the problem! Far, you're the man.
That was Broly not FAR !!!
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New to ICEM CFD, try this document --> http://goo.gl/G2gkE
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Old   February 20, 2013, 09:55
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Old   February 21, 2013, 10:06
Default Volume orientations
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Well, returning to the initial topic of this thread, some days ago I got negative volumes due to bad quality elements, I though it was just on the blade tip but it resulted to be all over the blade surface.

I've done all the blocking again to make it simpler, I've moved vertices to avoid complicated shapes, etc. but I still get many negative volumes (pictures 1 and 2).

I've tried the block check options: run-check/fix and fix inverted blocks and nothing changed.

I've converted the mesh into unstructured, checked the mesh and a message says:
"1078 problems were found for volume orientations"
I choose to fix them
"208 elements could not be fixed"
"208 elements could not be fixed -- probably the element quality is too bad."

Then a message appears about multiple edge (picture 3) and I choose to ignore.

Then another message appears about non-manifold edges (picture 4) and I choose to fix (441 out of 2644 could not be fixed).
And that's it.

How can I improve those 208 elements quality to avoid the volume orientation issue? as I guess volume orientation is the cause of negative volumes.


What should I try next? Any ideas?
Attached Images
File Type: jpg negative_volumes_blade.jpg (51.1 KB, 26 views)
File Type: jpg volumes_from_-0.001_to_-0.00075.jpg (58.6 KB, 24 views)
File Type: png Diagnostics_multiple_edge.png (19.3 KB, 15 views)
File Type: png non_manifold_vertex.png (22.5 KB, 13 views)
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Old   February 21, 2013, 10:14
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That looks like to be an association issue. But you should share your .tin and .blk file so we could have a look.

For your record, multiple edge is a possible problem.
But if you have 3 or more surfaces which intersect at the same curve, this curve would be considered as a multiple edge. So that's not a problem.
But if you have 2 surfaces which intersect at the same curve, this curve should NOT be considered as a multiple edge, otherwise, there is a problem.

Non manifold vertices often means nodes which are not connected to other nodes ..
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Old   February 21, 2013, 10:37
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That looks like to be an association issue. But you should share your .tin and .blk file so we could have a look.
Geometry is not mine, so I'm not allowed to share it now.

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But if you have 3 or more surfaces which intersect at the same curve, this curve would be considered as a multiple edge. So that's not a problem.
I don't have 3 or more surfaces intersecting in a curve.

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But if you have 2 surfaces which intersect at the same curve, this curve should NOT be considered as a multiple edge, otherwise, there is a problem.
I have many pairs of surfaces intersecting in the same curve. How can I know that these curves are multiple edges? How can I change them to single edge?

Merci bien pour l'aide!
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Old   February 21, 2013, 10:43
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On the tree menu, right click on curve -> color by count :

Yellow means that the curve is in contact with one surface.
Red means that the curve is in contact with 2 surfaces.
Blue means that the curve is in contact with 3 or more surfaces.

That colors means something if you have done a build topology. Otherwise, all your curves would be colored by yellow.

Are you sure you have associated all your edge with the right curve ?
Zoom more around the blade, make picture with the mesh.
Do the same without, only with curve and with the option "show association" activated.
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Old   February 21, 2013, 10:55
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Here you are some pics:
Attached Images
File Type: jpg low_blade_mesh.jpg (61.9 KB, 34 views)
File Type: jpg edges_curves_low_blade.jpg (63.7 KB, 30 views)
File Type: jpg balde_mesh.jpg (54.2 KB, 27 views)
File Type: jpg blade_curves_and_edges.jpg (29.1 KB, 24 views)
File Type: jpg blade_curve-edge_no_surface.jpg (36.9 KB, 24 views)
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Old   February 21, 2013, 11:03
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It's really hard to help you without the project files ..
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Old   February 21, 2013, 11:06
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I know, I'm sorry. I'm gonna ask if I can upload the files but that won't be until tomorrow. I'll keep posting.

Thanks a lot.
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Old   February 21, 2013, 11:09
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That is wind turbine ?
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Old   February 21, 2013, 12:48
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That is wind turbine ?
Yes, it's a wind turbine, a 120 sector with periodic boundary conditions to use a rotating SRF in Fluent.
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Old   February 22, 2013, 04:17
Default Curves colored by count
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Quote:
Originally Posted by BrolY View Post
On the tree menu, right click on curve -> color by count :

Yellow means that the curve is in contact with one surface.
Red means that the curve is in contact with 2 surfaces.
Blue means that the curve is in contact with 3 or more surfaces.
You can see the counts by color in the pics. I have blue, red, green and yellow curves in the sector and prism around the blade. And green and yellow coincident curves in the blade. What does green mean?

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Originally Posted by BrolY View Post
That colors means something if you have done a build topology. Otherwise, all your curves would be colored by yellow.
What is to build a topology? I've created geometry and blocking for the prism around the blade, and then imported a sub-topology for the rest of the domain.

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Originally Posted by BrolY View Post
Are you sure you have associated all your edge with the right curve ?
I've found many extra curves, I guess I have to delete them and leave just one curve, and then associate that only curve to each edge. Right?

I'm very sorry I cannot upload geometry and blocking files.

Thanks a lot for your effort guys!
Attached Images
File Type: jpg curves_sector_colored_by_count.jpg (40.9 KB, 17 views)
File Type: png balde_tip_curves_colored_by_count.png (13.3 KB, 16 views)
File Type: jpg low_blade_curves_colored_by_count.jpg (38.9 KB, 17 views)
File Type: jpg blade_colored_by_count.jpg (16.3 KB, 16 views)
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Old   February 22, 2013, 04:20
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Originally Posted by Bollonga View Post
What is to build a topology? I've created geometry and blocking for the prism around the blade, and then imported a sub-topology for the rest of the domain.
How do you import the sub-topo? How does sub-topo work and what is the advantage of using it?
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Old   February 22, 2013, 04:27
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How do you import the sub-topo? How does sub-topo work and what is the advantage of using it?
I started working just with the prism around the blade, to make it easier to remesh as it is a smaller domain. I did the rest of the domain in another project, so when I wanted to merged both blocking files I had to use sub topologies.
On the tree menu, on topologies, right click and save, it is saved as a blocking file. Then in the other project I had to import that file.

I asked for info about that in this thread: Merge blocking
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Old   February 22, 2013, 04:33
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What is difference between making a single blocking and using suptopo? How do you make sure that at interface you have similar features for both blocking files?
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Old   February 22, 2013, 04:40
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What is difference between making a single blocking and using suptopo? How do you make sure that at interface you have similar features for both blocking files?
I'm not sure about that, I just wanted to find a way to import some blocks into a file with many blocks. I think I have to apply the merge option to get just one blocking.
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Old   February 22, 2013, 10:50
Default Unattached, single and double edges
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I've been cleaning the geometry, deleting all redundant curves and points, and making some reading from icem help manual, and I've realized that I have many unattached curves even if it's supposed to be a two surfaces intersection, is that a problem?
The same happens with single and double edges. There are just two multiple edges (blue).

I attach some pictures of unattached (green, picture 1), single (yellow, picture 2) and double curves (red, picture 3), a general view of surfaces (picture 3) and a picture with surfaces in grey scale where you can see the double and multiple curves (picture 5).

The domain is a 120 cylinder sector with inlet, outlet, two symmetry curved faces and two flat periodic faces. Then there's a prism around the blade with several surfaces.

Please, ask me any required info. Thank you very much!
Attached Images
File Type: jpg unattached_curves.jpg (31.8 KB, 16 views)
File Type: jpg single_curves.jpg (19.5 KB, 13 views)
File Type: jpg double_curves.jpg (15.9 KB, 14 views)
File Type: jpg general_view_surfaces.jpg (26.6 KB, 13 views)
File Type: png multiple_double_curves.png (13.9 KB, 12 views)
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Old   February 22, 2013, 10:55
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Quote:
Originally Posted by Bollonga View Post

Please, ask me any required info. Thank you very much!
Quote:
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It's really hard to help you without the project files ..
Already asked by Broly


This topic has been discussed in very much detail by Simon. Search on forum.
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Old   February 25, 2013, 06:49
Default Negative volumes in a simpler case
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Well, I've found that same problem in a way more simple case. It's a 3D flat plate inside a prismatic domain. Even if blocking is very simple, after specifying the bunching in all edges (I don't use to specify surface mesh parameters, are they really necessary?) and pre-meshing, many tiny negative volumes appear (see picture), of the order of 7e-13 and smaller (see histogram in the picture)

I guess this issue has something to do with the blade one, so I'd really appreciate any help, as I'm running out of time...

As it is hard to be helped without .prj .tin nor .blk files I upload them so it's easier to be helped.

Thanks you all, guys!
Attached Images
File Type: jpg Plate_negative_volumes_-7e-13.jpg (51.4 KB, 14 views)
Attached Files
File Type: zip 3D_plate.zip (15.8 KB, 10 views)
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Old   February 25, 2013, 09:21
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Originally Posted by Bollonga View Post
Well, I've found that same problem in a way more simple case. It's a 3D flat plate inside a prismatic domain. Even if blocking is very simple, after specifying the bunching in all edges (I don't use to specify surface mesh parameters, are they really necessary?) and pre-meshing, many tiny negative volumes appear (see picture), of the order of 7e-13 and smaller (see histogram in the picture)

I guess this issue has something to do with the blade one, so I'd really appreciate any help, as I'm running out of time...

As it is hard to be helped without .prj .tin nor .blk files I upload them so it's easier to be helped.

Thanks you all, guys!
Well, I've managed to resolved the issue in this simpler case. It was just reducing the bunching in some edges and negative volumes dissappeared.

So my questions are:
How can bunching generate negative volumes?
If an edge has too much nodes it seems to end up in negative volumes. Isn't it a limitation of the size of the mesh?

Thanks
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