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[Marie Rognes <question109900@xxxxxxxxxxxxxxxxxxxxx>]

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

Marie Rognes proposed the following answer:
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)


--
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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