The coil is not free in the air it is surrounded by feromagnetic steel and the results using the Lorentz are comletely incorrect. This is an actual design of a solenoid
valve which I have done analytically and used FEMM for verifications. However, to save time checking many variations manually I tried to use Lua but stumbled with the lineintegral() which worked beautifully when I am doing it manually.
>From: jim271@xxxxxxxxxxx
>Reply-To: femm@xxxxxxxxxxxxxxx
>To: femm@xxxxxxxxxxxxxxx
>Subject: [femm] Re: Lua sample of line integral
>Date: Thu, 16 Aug 2001 14:58:49 -0000
>
>There is a sample script file that's distributed with FEMM 3.1
>showing how to do this very thing using the Lorentz force on the
>coil. I've found this to be much easier than drawing a contour to use
>for the stress tensor. Just highlight the object used for the coil
>and then calculate the Lorentz force. The force on the coil is equal
>and opposite (opposite sign) to the force on the plunger.
>
>I've included a script file that I use, which also shows some
>additional formating I've incorporated. One thing I found helpful is
>to restore the original fem file after running the script. When first
>learning to use lua, I often made edit changes to the "temp" file
>left in the display after running a script. Of course, this doesn't
>work, so I started reloading the original file automatically. You
>have to "save" the file in order to change the file name that appears
>in the upper left corner of the screen.
>
>
>**** Primary script : *********
>
>open_femm_file("coil_1inch.fem")
>save_femm_file("temp.fem")
>
>handle=openfile("lua_data.txt","a");
>
>write(handle,"\n","======= ",date("%c"),"
>=================================================","\n")
>
>closefile(handle)
>
>seteditmode("group")
>for n=0,15 do
> analyse()
> runpost("lua_post.lua")
> if (n<16) then
> selectgroup(1)
> move_translate(0,0.1) -- move plunger upward.
> end
>
>end
>open_femm_file("coil_1inch.fem") -- Restore original fem file
>save_femm_file("coil_1inch.fem")
>
>******* End of primary lua file
>**********************************************
>
>*** lua_post.lua *** Post processing script:
>
>handle=openfile("lua_data.txt","a");
>groupselectblock(2) -- select the coil
>fzr=blockintegral(12) -- Lorentz force
>
>write(handle,format("LForce= %8.2f \n",fzr))
>
>closefile(handle)
>exitpost()
>
>************* End of post processing
>**********************************
>
>
> -- Jim
>
>