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 Attesz February 17, 2010 08:39

Periodic compressor geom&mesh

Hi all,

I'm doing a centrifugal compressor simulation. To speed up the simulation, I want to use only a blade passage instead of the whole geometry. To get this, I have to slice the geom to a periodic piece. What is the recommend way?
1. Slice between the blades, so I get a geometry bounded by periodic boundary conditions with a blade in the middle, or
2. Slice at the centroid of the blade, so I get a clear blade passage, bounded by blade walls.

I found examples for the type 1., but the second one seems to be good too.

Attesz

 PSYMN February 22, 2010 13:06

Tip Gap?

Both ways have merit…

The rule of thumb I generally use has to do with the tip gap…

If I have no tip gap, then I tend to model the passage. It gives me more freedom from periodicity constraints because only the flow ahead of and behind the blade needs to be periodic. The space between is very forgiving and I can more easily all sorts of interesting configurations (y-block, etc) for high lift blades because I don’t need to keep the element count the same along the blade.

On the other hand, If I must model the tip gap, then I model the blade (with periodicity between blades). This allows me to take advantage of the periodic smoother which will have much more flexibility to adjust the mesh between the blades because there is more room to move.

 Attesz March 3, 2010 06:44

Thanks for your answer, I chose the first type, because of the tip gap.

Best Regards,
Attesz

 Attesz March 4, 2010 10:18

periodic mesh

Hi,

I want to use 1:1 periodic interface in centrifugal compressor. Could you tell me the instructions, how to create a 1:1 mesh on the periodic interface surfaces? I'm using ICEM V11 tetra.

Thank you very much,
Attesz

 PSYMN March 4, 2010 10:38

I get asked this question periodically, but you could just look in the help

Type periodic into the help search engine ;) I shouldn't make it so easy that you don't just look in the help first.

There are tutorials and documentation.

But it is easy to do. Just go into the Global Mesh params (first button on the mesh tab), and then select the Global Periodicity settings (last ICON in the Global Params DEZ). Once inside, it should be pretty clear.

Tetra uses this as it is,

Hexa uses this as a starting point (to set the periodicity settings), but then you still need to "Make Verts Periodic" in the blocking tab.

 Attesz March 5, 2010 13:53

Yes, I've found that in help, there was not too much information :confused: I thought it's not so easy as you write it. However, thanks! :)

Regards,
Attesz

 PSYMN March 5, 2010 17:58

I think users think it will be difficult because they are expecting to need to select periodic faces, etc. but all it wants is the angle of rotation and a point and vector for the axis... It figures out the rest.

I usually do still put my periodic faces into different parts, but that is just for the BOCOs or Periodicity check and is not required by the mesher.

 Attesz March 11, 2010 07:09

Thanks Psymn for your answer, it's really simple. But I have 3 domains in geometry, and they are all periodic, but have all different periodic angle: 72deg, 60deg and 120deg. In this case, how can I set the periodicity for each domain, or is it impossible?

Thanks again!
Regards,
Attesz

 PSYMN March 11, 2010 20:09

Sorry, its a global function.

Nope, because the periodic setting is global, only one section can be done at a time...

We are thinking about adding a "match face" command that would essentially allow you to set identical mesh on any pair of surfaces even if they aren't periodic, but we are not there yet.

 PSYMN March 11, 2010 20:12

Work around.

Work around...

If you want to trick it, you can mesh it without periodicty, then copy/rotate the surface mesh from one periodic face to the other... Then run the merge meshes => Make Consistent option...

This will make the volume mesh consistent with the new volume mesh...

If you have some experience with ICEM CFD mesh editing, it is pretty doable, but if you are new... Then I suggest you just break the model up into three sections and run periodic on each one.

Simon

 Attesz March 12, 2010 11:33

The first option that you suggested, sounds better. I've a bit more than half-year experience in tet-meshing with ICEM, so I think I can make it. Otherwise, I will do the other way..

Thank you for your kind assistance :)

Best regards,
Attesz

 Attesz April 7, 2010 09:50

Hi all,

I have a little problem in Icem v12.1. Previously I used quick delanuay volume mesh type in tetra mesh. Now I try to change to advancing front, but this method removes the surface mesh on the interfaces. I have a compressor stage, and between the stages there are interfaces, as a single planar surface. Should I use duplicate surfaces? Why removes this method the surface mesh from the interfaces?

Regards,
Attesz

 PSYMN April 21, 2010 18:10

Try Delaunay with TGlib AF in 12.1

The Advancing front mesher is my least favorite. It has lots of issues like this. If you have access to 12.1, try the Delaunay with AF (Advancing Front) TGlib (TGrid Libraries) turned on. You can set the growth ratio low and it is much better than the old Advancing front mesher. It is also smart enough not to mess up your internal walls or other existing mesh.

Simon

 Attesz April 22, 2010 02:51

Thanks Simon, I've 12.1 now, I'lll try it!

Attesz

 akj October 15, 2011 10:33

hey m also dng d same kind of problem. can u plz guide me how to mesh the periodic section....

 akj October 15, 2011 10:42

plz help me i wana do meshing of a compressor blade its a periodic section or we can say a fluid flow profile up to there i hav completed and nw i want to mesh it and i want to do a unstructured mesh as structured mesh takes more computational time so plz help me and tell me how to proceed if ur having any tutorials related to that and if u can send me i will be very thankful to u....my email id is anil.jazzya@gmail.com

 shahid nadeem June 5, 2014 08:54

Periodic

Is it possible to make periodic in ANSYS Meshing and please tell me what is the exact need to make body periodic. how should i cut the body and how should i do the mesh and which tip you are talking about

thank You

 FJSJ June 6, 2014 05:21

Hi Shahid,

take a look to this thread:

[ICEM] How define periodicity correctly in ICEM

It can be useful for you :)

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