dolfin team mailing list archive

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

Anders Logg wrote:
> On Mon, Sep 15, 2008 at 11:21:59AM +0100, Garth N. Wells wrote:
> > DOLFIN wrote:
> > > One or more new changesets pushed to the primary dolfin repository.
> > > A short summary of the last three changesets is included below.
> > >
> > > changeset:   4754:23602808c60413cb8faffca818e7a8c04527d3ec
> > > tag:         tip
> > > user:        Anders Logg <logg@xxxxxxxxx>
> > > date:        Sun Sep 14 19:46:40 2008 +0200
> > > files:       demo/pde/elasticity/python/demo.py
> > > description:
> > > Use symmetric gradient in variational form in elasticity demo
> > In particular reason for this? It is simpler (and still correct) to use 
> > the gradient.
> >
> > Garth
>
> To make the form and the matrix symmetric. I showed the demo to a
> friend (in computational mechanics) and he insisted that we replace
> grad(v) by epsilon(v).

He's wrong :). When you take the inner product A : B, where B is 
symmetric, the inner product only 'sees' the symmetric part of A. It's a 
classic exercise and you can prove it by writing out the indices.

Garth

> ------------------------------------------------------------------------
>
> _______________________________________________
> DOLFIN-dev mailing list
> DOLFIN-dev@xxxxxxxxxx
> http://www.fenics.org/mailman/listinfo/dolfin-dev