Subject: Re: [FEniCS-users] Raviart-Thomas with stokes equations

From: Douglas N Arnold <[email-masked]>
Date: Sun, 15 Nov 2009 10:30:19 -0600

Do you mean with the usual velocity-pressure formulation for Stokes? 
Since RT1 is not contained in H^1 it is inconsistent for this problem.  Or 
are you doing some kind of DG penalization of the jumps in tangential 
derivatives across element boundaries?

  -- Doug Arnold

Andy Ray Terrel wrote:
> I was under the impression that using RT1 + DG0 for Stokes was stable,
> but when I switch out these elements in the stokes example in DOLFIN I
> get a completely wrong answer.  Does anyone know if I'm wrong here or
> is there some magic with RT that I'm not doing correctly.

---

From: Andy Ray Terrel <[email-masked]>
Date: Sun, 15 Nov 2009 22:10:08 -0600

Okay I see.  It was the stress-velocity form that was used, not the
velocity-pressure.

-- Andy

On Sun, Nov 15, 2009 at 10:30 AM, Douglas N Arnold <[email-masked]> wrote:
> Do you mean with the usual velocity-pressure formulation for Stokes? Since
> RT1 is not contained in H^1 it is inconsistent for this problem.  Or are you
> doing some kind of DG penalization of the jumps in tangential derivatives
> across element boundaries?
>
>  -- Doug Arnold
>
> Andy Ray Terrel wrote:
>>