# [GAMBIT] [and others..] How would you mesh this geometry?

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April 19, 2013, 10:15
[and others..] How would you mesh this geometry?
#1
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Daniele
Join Date: Oct 2010
Location: Italy
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Hi everybody!
I'm helping a member of this forum in meshing a geometry; it is a small cilinder with an impeller.
We would like to have a structured hexa mesh, and we would like to know how you would mesh it and or split the geometry.
As you can see from the attached pictures, high skewness cells are generated near the semicircle.
Inner cylinder (which has small semicircles) is the rotor (walls), outer cylinder is rotating fluid.
What do you think?

Thank you,
Daniele
Attached Images
 11.PNG (31.1 KB, 42 views) 12.PNG (45.2 KB, 48 views)

April 19, 2013, 11:27
#2
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Daniele
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4 blocks approach?
Attached Images
 4block.png (5.6 KB, 27 views)

April 19, 2013, 17:19
#3
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Sijal
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Quote:
 4 blocks approach?
Yes. It is perfect idea.

I am also working on the similar case. Attaching blocking https://dl.dropboxusercontent.com/u/...tank_Jamal.zip

 April 20, 2013, 02:00 #4 Senior Member     Daniele Join Date: Oct 2010 Location: Italy Posts: 998 Rep Power: 18 Thank you Far for your answer, basically I was using the same approach as yours, but in gambit Looking at your picture, what do you think, in your experience, of sudden change in size of adjacent cells?Near the rotor walls I can see a change in size near 10 times: can this affect convergence? Daniele jamalf64 likes this.

 April 20, 2013, 02:07 #5 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,358 Blog Entries: 6 Rep Power: 45 Yes you are correct, spacing jump is large and needs to be corrected. In fact this blocking is not final and still few operation are needed. Like making ogrid in remaining two drilled holes or blades. O-grid is also needed outside these drilled holes to make the mesh of high quality. My intention to upload blocking at this stage is to invite forum fellows to try further and improve this version. Meanwhile as I get time I will improve it but it may take two to three days. At the moment mim quality is 0.2 in the holes where o-grid is not implemented otherwise mesh is of higher quality. The problem with bottom - up approach is considerable effort in making vertices, edges, faces and volumes which is avoided in ICEM CFD. Moreover ICEM is flexible in sense that we can change location of any vertex, edge and face at any time to make the quality better without deleting everything and starting over. Edit: O-grid at bottom is implemented and can be seen in attached pics. ghost82 and jamalf64 like this. Last edited by Far; April 20, 2013 at 02:24. Reason: Attaching images

 April 20, 2013, 02:35 #6 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,358 Blog Entries: 6 Rep Power: 45 Daniele: I would suggest that put a boundary layer in drilled holes and mesh with tetra to control the quality. Other portions (except drilled holes) may be meshed with full hexa. jamalf64 likes this.

April 20, 2013, 10:32
#7
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Daniele
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Quote:
 Originally Posted by Far Daniele: I would suggest that put a boundary layer in drilled holes and mesh with tetra to control the quality. Other portions (except drilled holes) may be meshed with full hexa.
Yes, of course!
Thanks

April 20, 2013, 10:35
#8
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Sijal
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Quote:
 Originally Posted by ghost82 Yes, of course! Thanks

April 20, 2013, 10:45
#9
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Daniele
Join Date: Oct 2010
Location: Italy
Posts: 998
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Quote:
I would really enjoy the "icem world"; I have to install it and try; I remember when I opened the first time gambit and all was new to me; but after some time I was able to understand the most of the functions.
I need only time to look at icem and move on..gambit is good in my opinion, but it is a bit old and new software is coming on with new features.

Daniele

 April 20, 2013, 10:48 #10 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,358 Blog Entries: 6 Rep Power: 45 Yes. Gambit is good software. I have used it for seven years. It has very good features.

 April 22, 2013, 01:23 #11 Super Moderator     Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 3,243 Rep Power: 34 Regarding the sudden change of size, I would try to attach a size function (type meshed) with fine entities as source. Gambit should smooth the mesh in this area. Far's option is also a good alternative. ghost82 likes this. __________________ In memory of my friend Hervé: CFD engineer & freerider

April 22, 2013, 12:09
#12
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Jamal Foroozesh
Join Date: Oct 2012
Location: Iran
Posts: 141
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Quote:
 Originally Posted by ghost82 Hi everybody! I'm helping a member of this forum in meshing a geometry; it is a small cilinder with an impeller. We would like to have a structured hexa mesh, and we would like to know how you would mesh it and or split the geometry. As you can see from the attached pictures, high skewness cells are generated near the semicircle. Inner cylinder (which has small semicircles) is the rotor (walls), outer cylinder is rotating fluid. What do you think? Thank you, Daniele
Hi dear Daniele
a question: How do you create this volume? (The volume that has been mesh in right hand picture)

Best Regards

 April 23, 2013, 02:25 #13 Senior Member     Daniele Join Date: Oct 2010 Location: Italy Posts: 998 Rep Power: 18 Hi, in gambit, under edges, project the rotor curved lines on the external face (minimum distance), with the split face option enabled. Then create all the remaining faces to create the volume. If you want to follow the "4 blocks approach", then split the edge of the upper face and create a small square, create the edges and then split the face with edges. Change if necessary vertex types (under face mesh in gambit) to have the faces mappable and mesh them with hex->map. A mappable face has 4 'end vertex'. Mesh one of the "vertical" edges of the volume and mesh it with the cooper scheme. Daniele jamalf64 likes this. Last edited by ghost82; April 23, 2013 at 04:50.

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