[firedrake] function at a point

[David Ham]

Hi Onno,

I'm afraid I don't think we understand what you are asking for. Can you
show us the maths please?

Regards,

David

On Thu, 23 Feb 2017 at 08:07 Onno Bokhove <O.Bokhove at leeds.ac.uk> wrote:

> Dear Firedrake(rs),
>
>
> I am considering a "standard" FEM problem with the following variables
> h(chi,tau) and phi(chi,tau) as function of transformed coordinate chi and
> time tau in chi=[0,L].
>
>
> In the weak formulation, the point value h(Lp,tau), so the function value at
> 0<chi=Lp<L
>
> as well as, of course, the function h(chi,tau) appear in the space
> integral of the weak form.
>
> In essence, due to a transformed moving boundary this point evaluation
> arises.
>
>
> I can formulate the detailed (nonlinear) matrix-vector FEM and its time
> discretisation
>
> because after the expansion of h(chi,tau) the coefficients h_j(tau) appear
>
> and h(Lp,tau) = h_Np(tau) for j =Np, say, such that the distinction
> between function
>
> and point values disappears.
>
>
> I am struggling to see how I can do this on the weak form level in
> firedrake.
>
> It would work in integral form by using a delta function after
> introducing h(Lp,tau)
>
> as an auxiliary scalar variable but I assume that is not available?
>
>
> What is the FD-tactic here which one can employ?
>
>
> Thank you and best wishes,
>
>
> Onno
>
>
>
>
> --
Dr David Ham
Department of Mathematics
Imperial College London
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