# [Getdp] Multiple natural boundary conditions

Wed Nov 5 01:02:34 CET 2014

```Thanks a lot

Le mardi 4 novembre 2014 17:12:43 UTC+1, michae... at infineon.com a écrit :
>
>  Hi,
>
>
>
> the point is that in GetDP it’s not allowed to subtract or add anything
> from/to
>
> a Dof in a single Galerkin statement. Therefore you have to split your 2nd
>
> Galerkin into two:
>
>
>
> Then it works J
>
>
>
> Cheers,
>
> Michael
>
>
>
>
>
> *From:* getdp [mailto:getdp-... at ace20.montefiore.ulg.ac.be <javascript:>] *On
> *Sent:* Tuesday, November 04, 2014 1:14 PM
> *To:* getdp-... at googlegroups.com <javascript:>
> *Subject:* [Getdp] Multiple natural boundary conditions
>
>
>
> Hello,
>
>
>
> My problem is common, i'd like to solve the heat equation with, for
> example, 2 natural Robin BC and one adibatique BC : -lambda.dnT = h.(T-Ti)
> on Gamma_i with i={1,2} and lambda.dnT = 0 on Gamma_3.
>
> I write the weak form with u in Form0 of the heat equation leads to the
> classical form :
>
>
>
> Equation{
>         In Omega; Jacobian JVol; Integration I1;}
>
>   Galerkin{ [ h[]* (Dof{u} - T[]), {u}];
>        In Ambiance; Jacobian JSur; Integration I1;}
> }
>
>
>
>
>
> In my problem there is no essential BC so i do not have Constraint block.
>
> The computation give a 0 temperature field, I do not understand what's
> wrong.
>
>
>
> Moreover :
>
> 1 - I wan to store in a file the temperature field respects to the nodes
> but PostOperation block computes over elements.
>
> 2 - How can I compute the integral of the flux over Gamma_i, to do so, I
> need for each boundary edge : the flux and the normal vector
>
>
>
> Best regards.
>
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