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-   -   [ICEM] Translational periodicity (http://www.cfd-online.com/Forums/ansys-meshing/124882-translational-periodicity.html)

c120613 October 15, 2013 04:50

Translational periodicity
 
1 Attachment(s)
Hi All, I am new in ICEMCFD and I am trying to understand how to make a translational periodicity of blocks. My problem is to get exactly the same blocks and the same edges on a turbine blade cascade as shown in the attached file. So far I found only the rotational periodicity. Kind Regards

FJSJ October 15, 2013 06:46

Hi Domenico,

you can find all the options about this tools in Blocking -> Transform Blocks

:)

c120613 October 15, 2013 08:18

model is not currently 3-d
 
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Hello Javi, many thanks for your reply. I actually have set up the translational periodicity in global mesh setup > set up periodicity, the condition translational periodic by defining the offset in the x,y, and z. After that I followed what you said and by looking in the manual I though to defined a part made by the blade and all of the blocking system placed around the blade itself as shown in Figure attached to this message. By doing that, however, the edges at the boundary of the whole blocking region selected became white. As I do what you suggested to me, on the background I got the message saying "model is not currently 3-d" and the copying is not carried out. Do you have idea about what happened? Many thanks in advance and your help has become quite significant so far. Kind Regards Domenico P.S. if you which to reply we can carry on to talk here or on a chat if you want.

c120613 October 15, 2013 08:26

How to fix the periodicity of the edges
 
Hi All, I was actually wondering how to define the periodicity of the edges. Is there a manner to do that? I saw that the vertices can get this property. I need this property if you imagine to split up an edge in different part to transform it in a spline. Actually it is the case of the periodic edge which occur between two adjacent blades of the cascade. Many thanks in advance Domenico

FJSJ October 15, 2013 10:58

Hi Domenico,

can you share your project? Itīs easier if we have the real problem to work on it.

c120613 October 16, 2013 06:09

blocking edges problem
 
1 Attachment(s)
Hi, I used to define and split a edge as a spline and by having two control points. as shown in the attached file. In particular, the line is that which has to be periodic between two adjacent blades. My idea is to create the blocking for one blade and then make a translational periodicity. Therefore I need to create the upper edge periodic. How this can be done? What I did on the system shown in Fig was to made the vertices periodic, but as a consequence the mesh does not follow the upper edge. Another problem that I got is that by mistake I deleted a block which should have been just attached to the blade (see upper surface). How can I get this block back? (I am quite new in ICEM) Many thanks in advance Domenico

PSYMN October 16, 2013 20:27

If you make the verts periodic, the edge between them becomes periodic...

In 3D, if you make 4 verts periodic, the face between them becomes periodic.


If you delete a block, it really just moves into "VORFN". You can turn on the VORFN part and move it back to FLUID (or what ever the rest of your blocking is called).

c120613 October 17, 2013 06:59

2 Attachment(s)
Actually if the edge is a spline, this does not become periodic when the vertices become periodic. Regarding the VORFN, indeed, it has been very helpful. Apart from that, I got another issue at the moment. which is explained here below: Do you guys have an idea how I can fix this problem too. Many thanks in advance Domenico __________________________________________________ ____ I am quite new in ICEM and at the moment I got issues when I create blocks if they are transformed from 2D to 3D. In the 2D prospective what I did it was to create several blocks and in particular that around a blade of a cascade. Then, after having developed the blocks in the third dimension and having made associations to the curves and surfaces I can start to see the mesh around the blade itself (see attached figure). Then, I applied the periodicity to get a blade cascade (with the command: Transform blocks -> Copy periodic blocking). However, I got a couple of issues at the moment when I do that: -although I choose to apply the periodicity only for the parts made by blocking system around the single blade itself, any other geometric entities and surrounded blocking are also copied; - also, by doing the periodicity, the associations for all of other blades are relative to the original blades (see attached figure). Is it a problem of the definition of the part? Since the periodicity command asks the definition of a part I tried the following two conditions: 1. I created one part which consists of the blocks that surround the original blade. 2. I created one part which consists of the blocks and blade that surround the original blade. Both of these conditions gave me the same problem of associations. Do you have any idea about what I should do? Many thanks in advance Domenico __________________________________________________ ______________

dengemunzur December 2, 2014 05:05

Hi to All,

I am trying to obtain mesh for an axial turbine for a linear cascade. I defined "translational periodicity". My question is that do I have to create periodic vertices? if I create periodic vertices, I think it will be more difficult to obtain a good mesh since it takes the flexibility to change the location of vertices seperately?
is it enough just to define periodicity without creating periodic vertices for the simulation?

Kind Regards

PSYMN December 2, 2014 09:49

Yes, if you want the mesh to be periodic, you need to define periodic verts...

However, if your solver is able to define periodicity without periodic mesh, then you can get away without it.

However, you don't need to make the vertex periodic with a pair on the same index... If you are having trouble with skewness, you can do what is called "shifted periodic". Search CFD-online for that term and you will find the instructions.

dengemunzur December 3, 2014 19:16

Thanks for your answer Simon,

The information you gave was very helpful. I noticed "shifted periodic" in the video but havent been used, thus I am not familiar, but I think I may use because of the skewness.

Thanks again

Kind Regards


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