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Electric Field normal to a Surface

Posted 19 sept. 2019, 00:42 UTC−4 Electromagnetics, General, Parameters, Variables, & Functions Version 5.4 1 Reply

Sebastian Rodriguez
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Hi! I have a surface with an inclination of 9 degrees in an axisymmetric system of coordinates. I know that using -Vr and -Vz I get the electric field according to r and z. However, I want to get the electric field that is normal to my surface. How can I calculate this? Thank you very much!

1 Reply Last Post 19 sept. 2019, 09:37 UTC−4
Jeff Hiller COMSOL Employee

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Posted: 5 years ago 19 sept. 2019, 09:37 UTC−4
Updated: 5 years ago 20 sept. 2019, 14:50 UTC−4

Hello Sebastian,

In a 2D axisymmetric geometry, the r and z components of the normal vector are nr and nz. On external boundaries, the normal vector points outward. On internal boundaries, if there are any in your geometry, you can use an "arrow line" plot to see which way the normal vector points.

You can use nr and nz in your potprocessing to plot , the scalar product of V with the normal vector, or any other expression of interest to you. But then again, if the boundary in question is a straight line, as it sounds from your post, nr and nz are easily expressed analytically in terms of the cosine and sine of 9 degrees, so in that case you don't even have to use the nr and nz notations.

Jeff

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Jeff Hiller
Hello Sebastian, In a 2D axisymmetric geometry, the r and z components of the normal vector are nr and nz. On external boundaries, the normal vector points outward. On internal boundaries, if there are any in your geometry, you can use an "arrow line" plot to see which way the normal vector points. You can use nr and nz in your potprocessing to plot V.n = Vr*nr+Vz*nz, the scalar product of V with the normal vector, or any other expression of interest to you. But then again, if the boundary in question is a straight line, as it sounds from your post, nr and nz are easily expressed analytically in terms of the cosine and sine of 9 degrees, so in that case you don't even have to use the nr and nz notations. Jeff

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