dolfin team mailing list archive

["Matthew Knepley" <knepley@xxxxxxxxx>]

On Jan 14, 2008 8:56 PM, Gideon Simpson <grs2103@xxxxxxxxxxxx> wrote:
>  Related question for both incompressible flow and elasticity problems.
> Suppose I have a plane of symmetry that will allow me to reduce my
> computational domain.  If
>
> \sigma_ij
>
> is the relevant stress tensor, then I will have that
>
> t^k_i \sigma_ij n_j = 0
>
> where t^k is the k-th tangential vector of the local geometry.  Physically,
> this is vanishing shear stress.  This is in addition to the condition
>
> u_i n_i = 0
>
> for no normal flow (the slip condition).
>
>
> Any thoughts on implementing the vanishing shear stress condition?

If we discretize with primitive variables and have Newtonian stress, this
just amounts to a Neumann condition on the velocity. At bottom, Neumann
conditions are just extra weak forms, so I think for more complicated
constitutive relations, you just add the relevant weak form for the condition.

   Matt

> -gideon
>
> On Jan 14, 2008, at 2:57 PM, Murtazo Nazarov wrote:
>
>
> Is there an obvious high level way to implement normal flow type
> boundary conditions or symmetry type boundary conditions?
>
> -gideon
>
>
>
> If you mean slip boundary condition which for normal velocity, it is
> already implemented and soon will be available with UNICORN.
>
> The slip with friction is also implemented.
>
> /murtazo
>
>
>
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