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Help 4 Setting amount of 'Fixed Current' in 2D simulation
Posted Jul 7, 2009, 1:54 a.m. EDT 2 Replies
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I am a new COMSOL user, and just wondering when I have a current source or input port in the system how to set the amount of current for the simulation?
or when you have a port with 'Fixed Current Density', the unit (A/m^2) doesn't make sense in 2D simulation.
could anybody help me for setting the exact amount of current sources?
2. As output port I had to use ground to get the proper results. Is it the right way or there is another way to define an output port, while the reference of potential (ground) is somewhere else in the geometry with '0' current sink?
2 Replies Last Post Jul 19, 2009, 10:14 p.m. EDT
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Posted:
2 decades ago
Hello
Well your 2D object has a certain "thickness" d see the Subdomain Settings, and the boundary a ceratain length, for me this is your "Area". You have to keep your physics consistent.
If you do not know your Boundary length, use COMSOL to calculate it by selecting the boundary and a "Options - Integration Coupling Variable - Boundary Variables" and give a name such as "Length_1" and integrate the value "1" along ds, this gives you the total length of the boundary you have selected.
Then you can define your current as a Con stant as "I_1" "2[mA]" and you use "I_1/(Length_1*d_emdc)" as your current denisty entry. now if you are using another physics adapt the name of it "d_emc" or "d_emes" or "d_emqa" ... You may also give directly the current denisty when you know it, but do not forget to change it too if you change the thickness or boundaries of your model.
Now usig the "Port" approach, I understand that COMSOL looks after some of these variable and surface calculations for you. I havnt used them enough myself to really understand your question. And I have no "current denisty on my "ports". "Ports" was introduced one or a few versions ago, to speed up and minimise the formulas you need to type.
I suggest you run a few of the examples, re-read the doc, attend a training course, and always try a few simple cases you know and can analyse by hand, and if not sufficient then be more explicit in your questions.
Good luck
Well your 2D object has a certain "thickness" d see the Subdomain Settings, and the boundary a ceratain length, for me this is your "Area". You have to keep your physics consistent.
If you do not know your Boundary length, use COMSOL to calculate it by selecting the boundary and a "Options - Integration Coupling Variable - Boundary Variables" and give a name such as "Length_1" and integrate the value "1" along ds, this gives you the total length of the boundary you have selected.
Then you can define your current as a Con stant as "I_1" "2[mA]" and you use "I_1/(Length_1*d_emdc)" as your current denisty entry. now if you are using another physics adapt the name of it "d_emc" or "d_emes" or "d_emqa" ... You may also give directly the current denisty when you know it, but do not forget to change it too if you change the thickness or boundaries of your model.
Now usig the "Port" approach, I understand that COMSOL looks after some of these variable and surface calculations for you. I havnt used them enough myself to really understand your question. And I have no "current denisty on my "ports". "Ports" was introduced one or a few versions ago, to speed up and minimise the formulas you need to type.
I suggest you run a few of the examples, re-read the doc, attend a training course, and always try a few simple cases you know and can analyse by hand, and if not sufficient then be more explicit in your questions.
Good luck
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Posted:
2 decades ago
Thanks a lot for the comments