dolfin team mailing list archive

["Johan Hoffman" <jhoffman@xxxxxxxxxx>]

>> 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
>
> Ones you have tangential and normal vectors, you can include this as a
> boundary term to the ffc form?

As I said, in this particular case you can "do nothing".

But if you have a non zero shear stress you must add a weak form (boundary
integral) where you will need to define normals and tangents.

For this case (Neumann conditions: not Dirichlet condition) it may work
fine with normals and tangent defined based on the boundary mesh (or other
representation of the boundary), it should not be neccessary to define
normals and tangents separately for each dof.

/Johan

>>
>> 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?
>>
>> -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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