Garth N. Wells wrote:
>
>
> Marie Rognes wrote:
>> Johan Hoffman wrote:
>>>> On Thu, Feb 07, 2008 at 05:43:13PM +0100, Marie Rognes wrote:
>>>>
>>>>> Anders Logg wrote:
>>>>>
>>>>>> On Thu, Feb 07, 2008 at 05:07:46PM +0100, Marie Rognes wrote:
>>>>>>
>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> I would like to construct a vector-valued finite element space
>>>>>>> where
>>>>>>>
>>>>> the
>>>>>
>>>>>>> components may be related to each other on the boundary.
>>>>>>>
>>>>>>> Example:
>>>>>>>
>>>>>>> Let P1 be piecewise linears on K.
>>>>>>> I want the subspace {(u, v) \in P1 x P1 such that u = v on the
>>>>>>> boundary of K.}
>>>>>>>
>>>>>>> Is this possible in DOLFIN today?
>>>>>>>
>>>>>>>
>>>>>> Not that I know. Generally, we can't handle constraints.
>>>>>>
>>>>>>
>>>>>>
>>>>> Darn. How hard do you think it would be to set-up?
>>>>>
>>>> I don't know. There was some discussion a month back on setting
>>>> no-slip constraints (zero normal component on boundaries) which is
>>>> similar. I think the conclusion was that we didn't find a general
>>>> solution. (But most likely there is one...)
>>>>
>>>> --
>>>> Anders
>>>>
>>> I guess you could set it up as a penalty on (u-v)?
>>>
>>>
>>
>> Pardon my ignorance please, but how does this work?
>>
>
> Take a look at
>
> /src/demo/pde/dg/cpp/Poisson.form
>
> It enforces u = 0 using Nitsche's method. If drop all the *ds terms
> except
>
> gamma/h*v*u*ds
>
> you'll get a penalty method.
>
Ok. Thanks!
--
Marie E. Rognes
Ph.D Fellow,
Centre of Mathematics for Applications,
University of Oslo
http://folk.uio.no/meg
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