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[Garth Wells <question109900@xxxxxxxxxxxxxxxxxxxxx>]

Question #109900 on DOLFIN changed:
https://answers.launchpad.net/dolfin/+question/109900

Garth Wells proposed the following answer:

On 06/05/10 14:29, Marie Rognes wrote:
> Garth N. Wells wrote:
>>
>>
>> On 06/05/10 14:22, Marie Rognes wrote:
>>> Garth Wells wrote:
>>>> Question #109900 on DOLFIN changed:
>>>> https://answers.launchpad.net/dolfin/+question/109900
>>>>
>>>> Garth Wells proposed the following answer:
>>>>
>>>> On 06/05/10 13:52, Marie Rognes wrote:
>>>>> Achim Schroll wrote:
>>>>>> New question #109900 on DOLFIN:
>>>>>> https://answers.launchpad.net/dolfin/+question/109900
>>>>>>
>>>>>> for a plain Poisson eqn with pure Neumann b.c., how to specify the
>>>>>> scaling condition u*dx = 0 ?
>>>>>
>>>>> If you have a recent dolfin, you can introduce a constant c acting
>>>>> as a
>>>>> Lagrange multiplier corresponding to the constraint. See example
>>>>> below.
>>>>>
>>>>
>>>> Nice. What does 'R' stand for in the definition of the space Q?
>>>>
>>>
>>> "Real" (Space of real numbers)
>>>
>>
>> OK.
>>
>> It would good to add this example as a demo to DOLFIN.
>>
>
> Maybe someone with pushing rights to DOLFIN could do so.... ;)
>

But who would then write the documentation page,

   http://www.fenics.org/newdoc/demos/python/index.html

? :)

Garth

> --
> Marie
>
>> Garth
>>
>>>
>>> --
>>> Marie
>>>
>>>> Garth
>>>>
>>>>> from dolfin import *
>>>>>
>>>>> mesh = UnitSquare(32, 32)
>>>>> V = FunctionSpace(mesh, "CG", 1)
>>>>> Q = FunctionSpace(mesh, "R", 0)
>>>>> M = V * Q
>>>>>
>>>>> (u, c) = TrialFunctions(M)
>>>>> (v, d) = TestFunctions(M)
>>>>>
>>>>> f = Expression("x[0]*x[1]*sin(pi*x[0])")
>>>>>
>>>>> a = dot(grad(v), grad(u))*dx + d*u*dx + c*v*dx
>>>>> L = v*f*dx
>>>>>
>>>>> pde = VariationalProblem(a, L)
>>>>> u_h = pde.solve()
>>>>>
>>>>> plot(u_h[0])
>>>>> interactive()
>>>>>
>>>>>
>>>>> --
>>>>> Marie
>>>>>
>>>>>
>>>>> _______________________________________________
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>>>>
>>>
>>>
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