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Electric field norm - what is it?

Posted 17 nov 2014, 08:21 GMT-5 Electromagnetics, RF & Microwave Engineering 5 Replies

Emily Young
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This may be a stupid question, but I am brand new to COMSOL so please be patient with me.

When I'm processing results, say plotting 2D surface plots, COMSOL provides a list of expressions it can evaluate. But how do I know what these are exactly? What, for example, is being plotted when I select emw.normE (electric field norm). Is that the electric field magnitude of the component normal to the surface? Or some 'normalised' electric field?

Is there somewhere I can view the equations for what is being plotted?

Any help appreciated.
5 Replies Last Post 28 ott 2016, 11:55 GMT-4
Mohammad Amin Nazirzadeh
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Posted: 10 years ago 17 nov 2014, 09:32 GMT-5
Here norm means the amplitude of the electric field:

normE = sqrt(Ex ^ 2 + Ey ^ 2 + Ez ^ 2)

* This is the norm of E field matrix
Here norm means the amplitude of the electric field: normE = sqrt(Ex ^ 2 + Ey ^ 2 + Ez ^ 2) * This is the norm of E field matrix
Emily Young
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Posted: 10 years ago 17 nov 2014, 09:37 GMT-5

Here norm means the amplitude of the electric field:

normE = sqrt(Ex ^ 2 + Ey ^ 2 + Ez ^ 2)

* This is the norm of E field matrix


Ok, thanks. Where did you find that information? Is it in the help somewhere?
[QUOTE] Here norm means the amplitude of the electric field: normE = sqrt(Ex ^ 2 + Ey ^ 2 + Ez ^ 2) * This is the norm of E field matrix [/QUOTE] Ok, thanks. Where did you find that information? Is it in the help somewhere?
Dennis Brown
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Posted: 10 years ago 17 nov 2014, 12:26 GMT-5
This is not 100% accurate. This is a response from support about this question that I asked a couple years ago. Please note that the p.119 reference may not be 100% valid for the latest versions of the s/w.


The variable normE is defined by the expression
sqrt(realdot(Ex,Ex)+realdot(Ey,Ey)+realdot(Ez,Ez)), where the operator
realdot(a,b) treats complex numbers a and b as if they were real-valued
vectors of length 2 and returns their dot product (like a shorthand form of
real(a*conj(b)), except in respect to its partial derivatives). More
information on the realdot() operator can be found in the COMSOL
Multiphysics User's Guide on p. 119 (this user's guide can be found within
the software via Help > Documentation, but I have also included a copy of
this in a link below for your convenience).



Here norm means the amplitude of the electric field:

normE = sqrt(Ex ^ 2 + Ey ^ 2 + Ez ^ 2)

* This is the norm of E field matrix


This is not 100% accurate. This is a response from support about this question that I asked a couple years ago. Please note that the p.119 reference may not be 100% valid for the latest versions of the s/w. The variable normE is defined by the expression sqrt(realdot(Ex,Ex)+realdot(Ey,Ey)+realdot(Ez,Ez)), where the operator realdot(a,b) treats complex numbers a and b as if they were real-valued vectors of length 2 and returns their dot product (like a shorthand form of real(a*conj(b)), except in respect to its partial derivatives). More information on the realdot() operator can be found in the COMSOL Multiphysics User's Guide on p. 119 (this user's guide can be found within the software via Help > Documentation, but I have also included a copy of this in a link below for your convenience). [QUOTE] Here norm means the amplitude of the electric field: normE = sqrt(Ex ^ 2 + Ey ^ 2 + Ez ^ 2) * This is the norm of E field matrix [/QUOTE]
Henrik Sönnerlind COMSOL Employee

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Posted: 10 years ago 18 nov 2014, 02:16 GMT-5
Hi,

You can always see the expressions defining a variable in Equation View.

Switch on Equation View using the icon with an 'eye' at the top of the Model Builder window. You will then get a subnode 'Equation view' under each node in the physics part of the model tree. There you can see (and modify!) the definitions of all variables created by that feature.

Note that the definition of a variable may not be the same for all study types. So you may have to look in Equation View after a certain study step had been run (or do a 'Get Initial Value' for the intended study step).

Regards,
Henrik
Hi, You can always see the expressions defining a variable in Equation View. Switch on Equation View using the icon with an 'eye' at the top of the Model Builder window. You will then get a subnode 'Equation view' under each node in the physics part of the model tree. There you can see (and modify!) the definitions of all variables created by that feature. Note that the definition of a variable may not be the same for all study types. So you may have to look in Equation View after a certain study step had been run (or do a 'Get Initial Value' for the intended study step). Regards, Henrik
WRS433
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Posted: 8 years ago 28 ott 2016, 11:55 GMT-4
Ok, I'm digging up an old thread here, but I have a follow-up question. I've actually started a new thread on this topic as well for magnetic materials, so sorry for the repeat.

I understand that the expression for normE is:

sqrt(realdot(es.Ex,es.Ex)+realdot(es.Ey,es.Ey)+realdot(es.Ez,es.Ez))

according to equation view, and this agrees in the volume of domains. However, this does not seem to be the case on the boundary of electrically polarized domains or on the boundary of domains with relative permittivity!=1. The analogy holds for magnetic materials as well.

Thanks,
-Matt
Ok, I'm digging up an old thread here, but I have a follow-up question. I've actually started a new thread on this topic as well for magnetic materials, so sorry for the repeat. I understand that the expression for normE is: sqrt(realdot(es.Ex,es.Ex)+realdot(es.Ey,es.Ey)+realdot(es.Ez,es.Ez)) according to equation view, and this agrees in the volume of domains. However, this does not seem to be the case on the boundary of electrically polarized domains or on the boundary of domains with relative permittivity!=1. The analogy holds for magnetic materials as well. Thanks, -Matt

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