Discussion Forum

Here's three ideas. You can either: (1) type it all in (like you said), (2) create a MatLab script to do it for you if you are comfortable with that, or (3) you can create some kind of clever stepped potential function to apply to all the rings, such that the potential (function) depends on position (but in steps), and (not coincidentally) happens to yield the correct potentials on each and every ring. All three options require work. Good luck.

Here's three ideas. You can either: (1) type it all in (like you said), (2) create a MatLab script to do it for you if you are comfortable with that, or (3) you can create some kind of clever stepped potential function to apply to all the rings, such that the potential (function) depends on position (but in steps), and (not coincidentally) happens to yield the correct potentials on each and every ring. All three options require work. Good luck.

Thank you for your reply.

If I use a potential function that depends on position then the geometry of the rings are not accounted for, right? In that case I could use a solid block with a continious potential distribution. Or am I missing something?

Re: "If I use a potential function that depends on position then the geometry of the rings are not accounted for, right? In that case I could use a solid block with a continious potential distribution. Or am I missing something?"

Well, first of all, I am assuming that any particular ring is an equipotential. Right? Second, your function, which should be defined as a user-defined function, can be written in terms of (x,y,z). But you should assign it only to the rings (as boundary conditions), not to the entire computational space! Your definition of the rings defines their geometry. For example: Suppose the function of (x,y,z) that you create returns a value of 7 volts whenever x is between 23.1 and 23.5 meters. Then, if you assign this function as the potential on all your rings, then for any single ring that happens to be positioned such that its entire surface fits between x=23.1 and x=23.5, its potential will be set = 7 volts. Ok? Again, you are not setting a potential to fill a volume here. You are simply defining a function and then using that function to define the boundary conditions on your actual rings (i.e., in place of typing in all the 120 different potentials by hand, on those ring surfaces). If, for example, all your rings are separated along x, then this doesn't even have to be a function of (x,y,z). It could be simply a function of x.

Re: "If I use a potential function that depends on position then the geometry of the rings are not accounted for, right? In that case I could use a solid block with a continious potential distribution. Or am I missing something?"

Well, first of all, I am assuming that any particular ring is an equipotential. Right? Second, your function, which should be defined as a user-defined function, can be written in terms of (x,y,z). But you should assign it only to the rings (as boundary conditions), not to the entire computational space! Your definition of the rings defines their geometry. For example: Suppose the function of (x,y,z) that you create returns a value of 7 volts whenever x is between 23.1 and 23.5 meters. Then, if you assign this function as the potential on all your rings, then for any single ring that happens to be positioned such that its entire surface fits between x=23.1 and x=23.5, its potential will be set = 7 volts. Ok? Again, you are not setting a potential to fill a volume here. You are simply defining a function and then using that function to define the boundary conditions on your actual rings (i.e., in place of typing in all the 120 different potentials by hand, on those ring surfaces). If, for example, all your rings are separated along x, then this doesn't even have to be a function of (x,y,z). It could be simply a function of x.

That does make sense, if I use a function that outputs discrete values at desired locations of the rings and multiply it by the object density (1 for ring, 0 for space). Still wonder how that works practically, but I guess I have a starting point now. Thank you.

You don't have to multiply it by the object density or some other trick like that. You don't have to apply the function to anything except the rings in the first place. Create a potential boundary condition and select the surfaces of the rings. Then assign the potential to that boundary condition. And the potential that you assign should be the function we've been talking about. That's it. The only tricky part is writing the function down.

You don't have to multiply it by the object density or some other trick like that. You don't have to apply the function to anything except the rings in the first place. Create a potential boundary condition and select the surfaces of the rings. Then assign the potential to that boundary condition. And the potential that you assign should be the function we've been talking about. That's it. The only tricky part is writing the function down.

Yes I figured out, if I only select the ring boundaries it only applies to the rings and in that case it works obviously. It al seems to work just as mentioned.

Thank you.