ufl team mailing list archive

[Martin Sandve Alnæs <martinal@xxxxxxxxx>]

On Tue, Apr 7, 2009 at 5:17 PM, Anders Logg <logg@xxxxxxxxx> wrote:
> On Tue, Apr 07, 2009 at 02:48:44PM +0200, UFL wrote:
>> One or more new changesets pushed to the primary ufl repository.
>> A short summary of the last three changesets is included below.
>>
>> changeset:   811:b96d2bbe8284a7255ca510c2fbb35b1445f85a11
>> tag:         tip
>> user:        "Martin Sandve Alnæs <martinal@xxxxxxxxx>"
>> date:        Tue Apr 07 14:50:30 2009 +0200
>> files:       doc/manual/chapters/formlanguage.tex ufl/operators.py
>> description:
>> Added support for this syntax:
>>
>> x = cell.x
>> Df = diff(f, x)
>>
>> Note that
>>   diff(f, x) == grad(f).T
>> because of the way diff is defined.
>> Thus diff(f,x) is the same as the FFC grad.
>> If we want to change this, it touches a lot
>> of places in AD code, so that won't happen now.
>
> How should the Navier-Stokes convective term be expressed in UFL?
>
> I guess one needs to write
>
>  grad(u).T*u
>
> ?

Like you write it on paper:

w . grad u = dot(w, grad(u))

And:

w . grad u . v = dot(dot(w, grad(u)), v)

Martin