dolfin team mailing list archive

["Garth N. Wells" <gnw20@xxxxxxxxx>]

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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