ufl team mailing list archive

["Garth N. Wells" <gnw20@xxxxxxxxx>]

On Apr 25 2009, Anders Logg wrote:

> On Sat, Apr 25, 2009 at 11:40:35AM +0200, Martin Sandve Alnæs wrote:
> > I've verified the curl vs wikipedia and defined rot as the z-component
> > of the curl of the 2D vector operand embedded in 3D. Is that right?

rot is just a synonym for curl. For simplicity, I would remove rot.

> > ez = (0, 0, 1)
> > u = (u0, u1)
> > rot(u) =  ez . (nabla x (u0, u1, 0))
> >
> >     def curl(self, o, a):
> >         # o = curl a = "cross(nabla, a)"
> >         def c(i, j):
> >             return a[j].dx(i) - a[i].dx(j)
> >         return as_vector((c(1,2), c(2,0), c(0,1)))
> >
> >     def rot(self, o, a):
> >         # o = rot a = "cross(nabla, (a0, a1, 0))[2]"
> >         def c(i, j):
> >             return a[j].dx(i) - a[i].dx(j)
> >         return c(0,1)

What about

    def curl(self, o, a):
        # o = curl a = "cross(nabla, a)"
        def c(i, j):
            return a[j].dx(i) - a[i].dx(j)
        if a.d == 2:   # whatever the function is for the dimension
            return c(0,1)
        else if a.s == 3; 
            return as_vector((c(1,2), c(2,0), c(0,1)))
        else:
            erorr . . . . 

Garth


> > Martin
>
> It looks correct, but shouldn't there be some dimension check?
>
> Maybe rot can be implemented directly as
>
>     def rot(self, o, a):
>         return curl(as_vector([a[0], a[1], 0]))[2]
>
> ?