## Periodicity and regulated heat

General discussions about how to formulate a script for FlexPDE.

### Periodicity and regulated heat

Hi,

two questions referring to the example in the attachment:

1. If I uncomment the periodic(x,-y) line in Region 1 I get an error that reads "Error: Multiple Periodic Images of Point" which I understand and which I think is correct but if you want to build an infinite grid that should somehow be possible.

2. Assume I want to regulate the heat Q in Region 5 such that a certain temperature is reached (without using surface boundary conditions), how could I implement this? Do I have to manipulate the Q Definition in Region 5 in an empiric way or do I need some definitions in the Constraints section?

BTW: Version 6.5 professional is running on linux.

Kind Regards,
dag
Attachments
Block_einzel.pde
dag

Posts: 19
Joined: Thu Jan 23, 2014 7:25 am

### Re: Periodicity and regulated heat

Update:

I tried to solve the adaptive heat problem with constraints, which did not work and this approach seems strange to me since you try to manipulate conservation in some kind. The other idea was to use a second pde which is used as a resistance heating but I did not now how to formulate said problem.
Now I use python and export report to achive this. The idea is to export the relevant properties, read them in and manipulate the flex script in such way that the temperature converges to a certain value.
dag

Posts: 19
Joined: Thu Jan 23, 2014 7:25 am

### Re: Periodicity and regulated heat

The specific cause of the diagnostic you are seeing ("Multiple Periodic Images") is an implementation constraint in version 6. Any point in the mesh can be mirrored at only one other point in the mesh (this restriction has been removed in version 7). You need to break one of your boundaries and insert a short piece with NATURAL(.)=0 so that each joint is imaged in only one place. See the example "Samples|Usage|Periodicity|Two-Way_Periodic.pde".

However, you have not followed the rules of construction for extruded figures.
Read again the article "Extrusions in 3D" in the Technical Notes section of the Help Index.
In particular, your first three regions are actually the same region, so the third one stated over-writes and hides the first two.
REGIONS are subdivisions of the projection (X,Y) plane, and are extruded through the Z dimension. These extruded regions can then be divided into layers.
moderator

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Joined: Tue Jan 11, 2011 1:45 pm

### Re: Periodicity and regulated heat

Thanks for the tip about breaking the boundaries at special points. I'm afraid I cannot use v7 since we do not have a licence for that but breaking boundaries should do it.

I know that the first two are partially overwritten with the limited region as stated in http://www.pdesolutions.com/help/usage_ ... egion.html since the x-y size of the elements are exactly the same but only exist in the specified layers. It could that I am missing the point of your concerns but this is a layered (sandwiched) setup where the R1, R2 and R3 have exactly the same size in x-y space and only the z-extrusion and the z-coordinates are different respectively. I could have defined R3 over the whole z-domain and formulated the script as seen at the end of the post. This should result in exactly the same geometry IF I am not mistaken.

REGION 1 "R1"
k = k_pu
Q = 0
START(-x1,-x1)
periodic(x,-y)
LINE TO (x1,-x1)
line TO (x1,x1)
nobc(Temp)
line TO (-x1,x1)
periodic(-x,y)
line TO CLOSE

Limited REGION 2 "R2"
Layer "L3"
k = k_specimen
Q = 0
START(-x1,-x1)
LINE TO (x1,-x1) TO (x1,x1) TO (-x1,x1) TO CLOSE

Limited REGION 3 "R3"
k = k_cu
Q = 0
Layer "L4"
START(-x1,-x1)
LINE TO (x1,-x1) TO (x1,x1) TO (-x1,x1) TO CLOSE
dag

Posts: 19
Joined: Thu Jan 23, 2014 7:25 am

### Re: Periodicity and regulated heat

After re-reading the Extrusion in 3D again I now know what you wanted to tell me

REGION 1 "R1"
Layer "L0" k = k_pu Q = 0
Layer "L1" k = k_pu Q = 0
Layer "L2" k = k_pu Q = 0
Layer "L3" k = k_specimen Q = 0
Layer "L4" k = k_cu Q = 0
START(-x1,-x1)
!periodic(x,-y)
LINE TO (x1,-x1)
line to (x1,x1)
nobc(Temp)
line to (-x1,x1)
periodic(-x,y)
line TO CLOSE

is the way to do it. Both scripts return exactly the same numbers, but it simplifies it A LOT. Thanks again.

Final Question: Is there a command line parameter to stop this warning:
dag

Posts: 19
Joined: Thu Jan 23, 2014 7:25 am

### Re: Periodicity and regulated heat

Yes, you can turn off the automatic check for updates by modifying the "flexpde6.ini" file in the "flexpde6user" folder.

Change the line
[UPDATECHECK] 1
to
[UPDATECHECK] 0

This has been added to the Preferences panel of version 7 so you do not need to manually change the ini file in that case.
moderator

Posts: 722
Joined: Tue Jan 11, 2011 1:45 pm