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Re: [femlisp-user] femlisp examples

From: Jason Sidabras
Subject: Re: [femlisp-user] femlisp examples
Date: Sat, 22 Sep 2007 13:04:13 -0500

On 9/22/07, Nicolas Neuss <address@hidden> wrote:
"Jason Sidabras" <address@hidden> writes:

>  Quasi-static Maxwell's equations:
> Curl H =  Js + Je
> Del dot B = 0
> Curl E = - j omega B
> Del dot D = 0
> Je = sigma E
> B = mu H
> D = epsilon E

OK, but this is usually treated in a simpler form, e.g. something like

  -curl( mu^-1 curl E) + omega^2 epsilon E  = -i omega J

This is then treated with special edge elements.

Is this what you are aiming for?  [If yes, I am interested in this myself,
and might be implementing edge elements in the near future.]

I am still learning what I have to solve but I believe that is close. The current plan is to formulate the equation based off of the electric vector potential (A) and scalar magnetic potential (phi).

curl (sigma^-1 curl A) =  -i omega mu (A - div phi)

I am waiting to get:
BOSSAVIT, A,: 'On the numerical analysis of eddy current problems',
Comput. Methods Appl. Mech. & Eng., 1981,27, pp. 303-318

Which, according to the abstract, takes Maxwell's equations and forms the variational formula which I should be able to solve with FEM for eddy current problems.

Do you have any good references on edge elements, their importance and how to create them? I have read a number of references in trying to understand this problem and they do mention the use of edge elements, but no real detail into what is different between the element methods. My current understand is the edge elements are mainly just the elements in creating the boundary.

>  BTW, I installed triangle from downloading it from Shewchuk and put it
> in my path. Is this not the preferred way? Do I have to load
> #p"femlisp:src;mesh;triangle.lisp" to get that functionality?

This file should be loaded automatically.  What does the variable
FL.MESH::*TRIANGLE-PATHNAME* contain?  Does it work, if you set it to the
location of your triangle binary?  (However, this should be found
automatically, if it is in your path, see the lines at the beginning of

 none of the objects exist that are part of the Shewchuk library in


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