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Easy Java Simulations (2001- ) => Collaborative Community of EJS => Topic started by: lookang on September 10, 2012, 08:25:26 am



Title: Ejs Open Source Bar Magnetic Field Lines Model Java Applet
Post by: lookang on September 10, 2012, 08:25:26 am
Ejs Open Source Bar Magnetic Field Lines Model Java Applet

made possible thanks to
Michael Galis http://www.compadre.org/osp/bulletinboard/TDetails.cfm?ViewType=2&TID=2226&CID=51612&#PID51613

and Wolfgang Christian http://www.compadre.org/osp/items/detail.cfm?ID=12361

[ejsapplet]

work in progress.

My own naive idea is to use analyticCurve3D but i haven't seen any example on a family of analyticCurve3D, so each is drawn as a single analyticCurve3D.

the match is close but not very accurate
http://en.wikipedia.org/wiki/Ellipse
An ellipse in general position can be expressed parametrically as the path of a point (X(t),Y(t)), where
Minimum = 0
Maximum = 2*Math.PI
Variable = "theta"
X() = "1.4+1.4*Math.cos(theta)*Math.cos(0)-1.4*Math.sin(theta)*Math.sin(0)"
z()= "0+0.5*Math.sin(theta)*Math.sin(0)-1*Math.sin(theta)*Math.cos(0)"


Title: Re: Ejs Open Source Bar Magnetic Field Lines Model Java Applet
Post by: lookang on December 13, 2012, 02:03:18 pm
still cannot make the sim run without run-time errors.
attached is the new sim with 2 sets of field lines


Title: Re: Ejs Open Source Bar Magnetic Field Lines Model Java Applet
Post by: Fu-Kwun Hwang on December 15, 2012, 09:29:21 pm
You have learned how to draw electric field line from http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=539.0

You can use the same method to draw magnetic field line.

I tried to open ejs model from your jar file. However, I was not able to understand what you were doing in the model (evolution page: lambdax, lambday, lambdaz???)


Title: Re: Ejs Open Source Bar Magnetic Field Lines Model Java Applet
Post by: lookang on December 15, 2012, 09:47:11 pm
You have learned how to draw electric field line from http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=539.0

You can use the same method to draw magnetic field line.

I tried to open ejs model from your jar file. However, I was not able to understand what you were doing in the model (evolution page: lambdax, lambday, lambdaz???)
it is very difficult for me to implement it is 3D as i only have very limited knowledge, the codes you invented http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=539.0 are too advanced for me redesign in 3D.
i can remix :)
 


I tried to open ejs model from your jar file. However, I was not able to understand what you were doing in the model (evolution page: lambdax, lambday, lambdaz???)
according to prof mike gallis http://www.compadre.org/osp/bulletinboard/TDetails.cfm?ViewType=2&TID=2226&CID=51612&#PID51613

For a parameterized path in space λ(t) tangent in space which "follows" a field E(r) the rate of change of the path (the "velocity" of the trajectory) is in the direction of the field. The first try:

dλ(t)/dt = E(λ(t))

this method works in principle, but in numerical approaches, the computed path λ(t) will have large step sizes where the field is strong, which is probably undesireable. I prefer:

dλ(t)/dt = E(λ(t))/|E(λ(t))|

which gives the path a "constant velocity".



For a dipole field (from Jackson):

E(r) = (3n(p⋅n)-p)/|r-r0|3
r = field point
r0 = location of dipole
p = dipole moment
n = normal vector pointing from source to field point = (r-r0)/|r-r0|

For the example coded here, the source is at the origin (r0 = 0) and the dipole is oriented along the z axis. With the coordinates of the field point given as x,y,z (and r= x2+y2+z2)1/2 ) the field components are
Ex=3xzp/r5
Ey=3yzp/r5
Ez=3z2p/r5 -p/r3


Title: Re: Ejs Open Source Bar Magnetic Field Lines Model Java Applet
Post by: Fu-Kwun Hwang on December 17, 2012, 12:49:23 pm
OK. I understand what you are trying to do now. I will try to check out your model and see what I can do to help!
 


Title: Re: Ejs Open Source Bar Magnetic Field Lines Model Java Applet
Post by: Fu-Kwun Hwang on December 18, 2012, 08:53:43 pm
The following is the version modified from your EJS model.


Title: Re: Ejs Open Source Bar Magnetic Field Lines Model Java Applet
Post by: lookang on December 19, 2012, 07:46:12 am
The following is the version modified from your EJS model.
ejsuser/2/ejs_fieldlines3Dwee03a3.jar not found

hi prof!
need to upload again?


Title: Re: Ejs Open Source Bar Magnetic Field Lines Model Java Applet
Post by: Fu-Kwun Hwang on December 20, 2012, 06:55:06 pm
Sorry! I should have checked it. It is OK now.