Discussion Forum

Hi,

I am not sure what you exactly mean. In the cross section plots arc length is simply the distance from the start point along the line of your line plot.
It may be confusing to call it an arc length because it is actually a straight line.

Regards
Edgar

hi,

I am trying actually to find the length of the electric field lines. i thought that i can find it like that.

so, the arc length are not the field lines?

best regards

Georgeta,

I am not aware of a method to obtain the length of a stream line in a straightforward way. However this issue had been on the forum before. You might try a search on the forum.

But just for my curiosity: Why are you interested in the length of stream lines? What physical or technical meaning do you attribute to them. So far i knew that the spatial density of streamlines can give an indication of field strength. But much depends on the choice of the start point which is arbitrary.

In my work, much of it is AC/DC with an emphasis on the magnetic component, I sometimes use the streamlines for visualisation. Sometimes to visualise to non-experts, because the streamlines are to some degree familiar to many people. However I never found them very useful for something quantitative.

I hope you can find the time to elaborate on the topic.

Best regards
Edgar

Hi

the "arc length" is the integrated "ds" value along an edge and not the filed line length

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Good luck
Ivar

hi Edgar,

i attach a photo so you can picture. there are 2 metal electrodes in a room with air at low pressure.

i am doing the simulation for various diameter of the electrode point, and i need to see if the distribution of the electric field changes or not.

and if it does, i need to calculate the length of the field line, and the angle between the lines and the symmetry axe. after that i have to compare how it changes the electric field with the angle.

hi, to be more explicit,

at low pressure, the electrons follow the electric field lines where they may encounter on their way other molecules to

make collisions so there can be a discharge between the 2 electrodes in the picture. so the electrical breakdown occurs

along the field line. so i need to know for what length of the field lines the breakdown occurs.

i am just assuming that the field lines don`t change with the pressure.
the electrode point has a electric potential of 3600V and the other electrode and the room are grounded.



and i really hope you can help me because i am a bit out of time.

honest thank you, Georgeta

Georgeta,

probably the field lines indeed do not change with pressure, because this doesn't change the dielectric parameters of your partial vacuum very much.
But as soon as you have an electric breakdown you will create a plasma and things will change dramatically. You will have a cathode sheeth and all those plasma discharge phenomena. So, electrostatics only helps you until breakdown. Afterwards you need to deal with plasma.

Isn't the local field strength the major quantity for electric breakdown? Without a breakdown the electrons travel along field lines. But the breakdown will start where the field is maximum and at a certain distance from the cathode (cathode sheeth). After breakdown field lines have little meaning because of all the plasma around.

I assume if you really want to calculate the length of field lines you will need to modify the application module and introduce the equations for integrating the electron trajectories. This is something I know can be done but I haven't done it so far.

Cheers
Edgar