Elmer Discussion Forum

In the Tutorial no. 14 "Magnetic field induced by harmonic current in a wire" are two bugs:

1. Equation 14.3 states how to calculate B for a given wire radius. In the Text it is written that R is 0.01m, but to get the mentioned result of B = 0.037T, the radius R is 0.001 m.

Looking at the grid of the wire (wire.grd), this must be correct, because to get a field strength of 1 V/m at the given U = 0.01V, the wire must have a length of 10 mm and the wire is longer than its radius.

So just a simple typo, but it was confusing for me. I hope this can be fixed.

2. When performing the tutorial to its end one gets as result a maximal imaginary B of 0.052 T (while Re(B) = 0.011). In the tutorial text, it is written that Im(B) would be 0.524 T. This would be a factor 10 too high. So I think also here there I think the fix is to correct the tutorial text.

Good catch! Something to include in the next update for the tutorials.

Thanks, Rich.

Rich_B wrote: ↑09 Feb 2023, 23:23 Good catch! Something to include in the next update for the tutorials.

I downloaded the latest tutorial from February 9th. The mentioned issued have not yet been fixed. I could do this but don't know where to submit a PR for the docs.

Hello Uwe,

I'm working on fixing the tutorial.

Point 1, yes, the radius should be 1 millimeter, 0.001 meters.

Point 2, I'm coming up with an imaginary B of 0.0052 T. I added a Saveline solver, and that's the result at the surface of the wire at radius = 0.001 meters.

Some of the manuals (including the tutorials) are available on Github:

viewtopic.php?t=7207

Rich.

Attached is the ElmerGUI project, with the Saveline solver addition.

The included csv file has the saveline results, plot ' 4: coordinate 1' versus ' 19: magnetic flux density im 2' for the result.

I've seen that Paraview can also generate a line result, but don't know how to actually do that. It would be interesting to compare the two methods.

Rich.

Rich_B wrote: ↑13 Feb 2023, 16:15 Point 2, I'm coming up with an imaginary B of 0.0052 T. I added a Saveline solver, and that's the result at the surface of the wire at radius = 0.001 meters.

Hi Rich, sorry for the late reply, but the forum does not send me any notifications despite I enabled them.

To the issue number 2:
you get 0.0052, I get 0.052, the tutorial states one should get 0.524, so there is definitely a bug.
You get 0.052 because you set my mistake was that I set So the correct value is yours: 0.0052 and the tutorial manual has to be corrected accordingly.

Hello Uwe,

Now that our results agree, I'll take care of updating the tutorial manual.

The forum doesn't send notifications, and hasn't for several years. One tactic is to create a bookmark in your browser to your own forum post, and every day or so, click on the bookmark to check for answers.

Thanks, Rich.

Rich_B wrote: ↑18 Mar 2023, 17:00 The forum doesn't send notifications, and hasn't for several years.

Can this please be fixed? We use phpBB for FreeCAD and it can send emails.

For example, I could not login, tried to change my password, but since the forum does not send any emails, one cannot change the password once one has it forgotten.