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Assigning linear increasing Potential to wire array

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I'm completely new to Comsol, so maybe my problem might look simple to you, but I couldn't find a solution on my own yet. So I hope for your help.

I'm trying to build up a field-cage with an array of 100 wires and i want to assign a linear increasing potential to the wires.



In the attached file I have an example-geometry, simplified by using only 6 wires for the vertical wire-array. I manually created 6 potentials and assigned them, manually too, to these wires. (top and bottom array are no problem, as those are on the same potential)

Unfortunatly, I need about 100 wires in my real geometry.
Do I really have to create 100 Potentials and manually apply them to the wires? Or is there a smarter way, something similar to creating the wires using an array...

Thanks in advance for any help


4 Replies Last Post Jun 25, 2015, 5:18 p.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago Nov 1, 2011, 4:47 a.m. EDT
Hi

to make your model simpler you could replace the coils by "points" (use range() definitions for X&Y to make multiple points in one call).

Then I would use more air around to avoid lateral surface effects, except if you have a conducting box surrounding everything.

To avoid making 100 points and selecting them all, try to use symmetry, you should be able to reduce to the half, no ?

Its always the same, either you use brute force, systematically, and take some time to solve, or you think more, with the risk that you oversimplify and get something wrong because you have made a wrong assumption

--
Good luck
Ivar
Hi to make your model simpler you could replace the coils by "points" (use range() definitions for X&Y to make multiple points in one call). Then I would use more air around to avoid lateral surface effects, except if you have a conducting box surrounding everything. To avoid making 100 points and selecting them all, try to use symmetry, you should be able to reduce to the half, no ? Its always the same, either you use brute force, systematically, and take some time to solve, or you think more, with the risk that you oversimplify and get something wrong because you have made a wrong assumption -- Good luck Ivar

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Posted: 1 decade ago Nov 2, 2011, 9:50 a.m. EDT
I think you got me wrong (or maybe I got you wrong...):

a) I don't want to simplify my modell, it is already simplified, as especially top and bottom grid in the real experiment are not axial symmetric. The time my computer needs to computze the result is not too important.
b) The File I posted is just an example to illustrate my problem. (i.e. there will be no air at all, but noble gas and there will be a steel vessel around which is on ground potential)
c) I already used axial symmetry, further symmetries will not be available in the complete simulation

The wires are not "coils" in the electromagnetic sense (creating a B-field). What I want to create is a very homogenous electric field to drift electrons. I am interested in the size of inhomogenities, therefore I don't want to simplify too much.

What I want to do is reduce the time I need to apply the different potentials to the wires (only vertical part), especially if I change size and number of wires, to see the influence. So I am looking for a technique to apply a voltage to the wires that depends on the position of the wire in the cylinder , something like U(z)...
I need for example the lowest wire to be at 0V, the next at 100V, the third at 200V and so on and I hoped there was a technique to do this automatically



I think you got me wrong (or maybe I got you wrong...): a) I don't want to simplify my modell, it is already simplified, as especially top and bottom grid in the real experiment are not axial symmetric. The time my computer needs to computze the result is not too important. b) The File I posted is just an example to illustrate my problem. (i.e. there will be no air at all, but noble gas and there will be a steel vessel around which is on ground potential) c) I already used axial symmetry, further symmetries will not be available in the complete simulation The wires are not "coils" in the electromagnetic sense (creating a B-field). What I want to create is a very homogenous electric field to drift electrons. I am interested in the size of inhomogenities, therefore I don't want to simplify too much. What I want to do is reduce the time I need to apply the different potentials to the wires (only vertical part), especially if I change size and number of wires, to see the influence. So I am looking for a technique to apply a voltage to the wires that depends on the position of the wire in the cylinder , something like U(z)... I need for example the lowest wire to be at 0V, the next at 100V, the third at 200V and so on and I hoped there was a technique to do this automatically

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Posted: 1 decade ago Nov 2, 2011, 10:24 a.m. EDT
Maybe comsol with matlab can do it, I guess.
Maybe comsol with matlab can do it, I guess.

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Posted: 9 years ago Jun 25, 2015, 5:18 p.m. EDT
I am having the same issue, I am trying to design a field cage to create a uniform electric field, and it is too time consuming to manual set every field wire potential. I talked to someone at comsol and they said to use "box" by right clicking Definitions and going to selections. Then make a box containing the array, and assign a potential function to it. He said to use a piece wise function but I still haven't figured out how to set that up yet.
I am having the same issue, I am trying to design a field cage to create a uniform electric field, and it is too time consuming to manual set every field wire potential. I talked to someone at comsol and they said to use "box" by right clicking Definitions and going to selections. Then make a box containing the array, and assign a potential function to it. He said to use a piece wise function but I still haven't figured out how to set that up yet.

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