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HEX or TET - Which One is better choice?

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Old   July 17, 2008, 12:27
Default HEX or TET - Which One is better choice?
  #1
MAB
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Hi generally speeaking ..is there preference in between these meshes. which mesh is best option for better results and for less computer time.
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Old   July 17, 2008, 12:51
Default Re: HEX or TET - Which One is better choice?
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Rogerio Fernandes Brito
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less computer time = HEX better results = none of them, both have the same results easier to build = TET worst to build = HEX

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Old   July 17, 2008, 15:33
Default Re: HEX or TET - Which One is better choice?
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MAB
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great .. Thanks
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Old   July 20, 2008, 12:45
Default Re: HEX or TET - Which One is better choice?
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Charles
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My theory ... build a quick tetra mesh to get it running in order to keep the boss or client off your back. While it is running, build a good hexa mesh to get the real answers ....

Alternatively: If it's only going to be one run for a given geometry, go tetra. If you are going to run one mesh many times, go hexa.

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Old   July 20, 2008, 22:51
Default Re: HEX or TET - Which One is better choice?
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Jerry Tanner
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Hexa mesh has a 99% chance beating tet mesh.Generally,tet mesh-> quick results -> bad quality.
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Old   July 21, 2008, 05:10
Default Re: HEX or TET - Which One is better choice?
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MAB
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hi... it seems that i dont have ICEM in my CFX . do i need ICEM to build hex mesh ?
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Old   July 21, 2008, 06:36
Default Re: HEX or TET - Which One is better choice?
  #7
Charles
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AFAIK hexa meshing is not part of the standard CFX-mesh. So to get it you need some additional meshing tool that can do hexa meshes. Icem is probably the most powerful and versatile hexa (and tetra) meshing program out there, but it is rather pricey. If you want to consider less expensive alternatives, Gridgen is one option, Gridpro is another. Within the Ansys stable, if you have access to Fluent, Gambit can also do useful hexa meshes.

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Old   July 21, 2008, 22:29
Default Re: HEX or TET - Which One is better choice?
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Glenn Horrocks
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Hi,

You cannot generate hex meshes with CFX-Mesh. You can with either ICEM-Hexa (additional license required) or Simulation in workbench (you might already have this, decompose the geometry into hex shapes and use mapped and swept meshing). You can also do basic hex meshing in ICEM but it is very basic and manual.

Glenn Horrocks
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Old   July 22, 2008, 09:13
Default Re: HEX or TET - Which One is better choice?
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Rogerio Fernandes Brito
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"...Gridgen is one option, Gridpro is another...." Is there a free version? I would like to test these softwares.
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Old   July 22, 2008, 09:42
Default Re: HEX or TET - Which One is better choice?
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Rogerio Fernandes Brito
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"My theory ... build a quick tetra mesh to get it running in order to keep the boss or client off your back..."

If u have a lot of memory and good processors...

I did a test using tetra and i spent 10 hours. For about the same mesh using hexahedrical mesh, i spent only 3 minutes, using a PC with one processor and only 512 MB of RAM memory!
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Old   July 22, 2008, 10:05
Default Re: HEX or TET - Which One is better choice?
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Charles
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Ah, but you are dealing with quite a simple geometry then. I've just been doing exactly this experiment in Star-CCM+, using a hexa mesh from Gridgen, a CCM trim mesh and a CCM poly mesh. For a simple, un-tapered wing in isolation there is no contest. You could create a top quality hexa mesh in less time than it took CCM to build a poly mesh automagically. The hexa mesh was 1/3 if the size, more accurate and ran more quickly. Now take a full configuration, non mid-winged, H-tailed aircraft with big antennae and things, and do the same experiment ..... Suddenly the unstructured option looks a lot more competitive.

But there is no reason not to have loads of memory and powerful processors, they are cheap compared to man-hours.

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Old   July 22, 2008, 10:07
Default Re: HEX or TET - Which One is better choice?
  #12
Charles
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Gridgen (Pointwise) will let you have a free version to test for a few weeks if you ask nicely. For simple geometries it makes structured grids of exquisite quality. For more complicated geometry it does a nice job of hybrid meshing, which is not really an Icem strength.
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Old   July 22, 2008, 10:38
Default Re: HEX or TET - Which One is better choice?
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Rogerio Fernandes Brito
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a simple geometry = yeah! but boring to build the hexa mesh studied problem = too difficult
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Old   July 22, 2008, 10:39
Default Re: HEX or TET - Which One is better choice?
  #14
Rogerio Fernandes Brito
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cool! are you uisng this software?
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Old   July 23, 2008, 04:38
Default Re: HEX or TET - Which One is better choice?
  #15
Mihail
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It's look very interesting: "I did a test using tetra and i spent 10 hours. For about the same mesh using hexahedrical mesh, i spent only 3 minutes, using a PC with one processor and only 512 MB of RAM memory!" Can you give more details about thise case?

Regards!
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Old   July 23, 2008, 07:48
Default Re: HEX or TET - Which One is better choice?
  #16
Rogerio Fernandes Brito
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Send me your e-mail and i will send you the project in ICEM CFD. Itīs a too simple geometry.

My e-mail is rogeriobrito2007@hotmail.com or Skype: rogeriofbrito
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Old   July 25, 2008, 02:40
Default Re: HEX or TET - Which One is better choice?
  #17
Mihail
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Can sombody explaine me why hex mesh requirement more resources when tetra. I meam CPU resources? As I understand in cfx polihedral mesh?
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