[firedrake] function at a point

[David Ham]

Aha. I see the issue. I need to give this some thought (although right now
I need to go and teach).

Regards,

David

On Thu, 23 Feb 2017 at 15:28 Onno Bokhove <O.Bokhove at leeds.ac.uk> wrote:

> Attached, see weak form in equation (20).
>
> xp used in equation (20) is define in equation (19).
>
> Hope that settles the question?
>
> You should be familiar with some of this at it also emerged in your OMAE
> paper!
>
> Regarding a time discretisation: any, but just do first order at the
> moment!
>
>
> ------------------------------
> *From:* firedrake-bounces at imperial.ac.uk <firedrake-bounces at imperial.ac.uk>
> on behalf of David Ham <David.Ham at imperial.ac.uk>
> *Sent:* Thursday, February 23, 2017 2:17 PM
> *To:* firedrake
> *Subject:* Re: [firedrake] function at a point
>
> 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
>
-- 
Dr David Ham
Department of Mathematics
Imperial College London
-------------- next part --------------
HTML attachment scrubbed and removed