Re: [Getfem-users] How to impose the normal derivative to zero on a model ?

[Yves Renard]

Dear Sebastien,

No of course. For an order two isotropic pde, a homogeneous Neumann condition 
reads as
dU/dN = 0
This condition does not add any term to the weak formulation. So you do not 
have to add anything to the model.

Yves.

On mercredi 7 avril 2010, sébastien janas wrote:
> Dear Yves,
>
> When we prescribe a zero neumann condition, we impose that the product
> between the unknown and the normal vector is equal to zero, is it equal
> to assume that the product bewteen the GRADIENT of the unknown and the
> normal vector is equal to zero ?
>
> In other words, you advise me to do
>
> n x U = 0
>
> and I want to do
>
> dU/dn = 0
>
> is it equal ?
>
> Best regards,
>
> Sébastien
>
> Le mercredi 07 avril 2010 à 21:12 +0200, Renard Yves a écrit :
> > Dear Sebastien,
> >
> > If you have to prescribe a zero Neumann condition to your unknown
> > (assuming that it is an order two isotropic pde), you
> > do not have to add anything to your model. This is somehow a default
> > boundary condition as it add nothing to the weak formulation.
> >
> > Yves.
> >
> > sébastien janas <address@hidden> a écrit :
> > > hi,
> > >
> > > I am using the python interface of getfem. I want to impose the normal
> > > derivative of my unknow to zero at the boundary, but it seems that the
> > > model method "add.normal_derivative_source_term" don't exist, is it
> > > correct ? If yes, what's the best way to impose such a condition on a
> > > model ?
> > >
> > > Thanks a lot for your help,
> > >
> > > Sébastien
> > >
> > >
> > > _______________________________________________
> > > Getfem-users mailing list
> > > address@hidden
> > > https://mail.gna.org/listinfo/getfem-users



-- 

  Yves Renard (address@hidden)       tel : (33) 04.72.43.87.08
  Pole de Mathematiques, INSA-Lyon             fax : (33) 04.72.43.85.29
  20, rue Albert Einstein
  69621 Villeurbanne Cedex, FRANCE
  http://math.univ-lyon1.fr/~renard

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