[petsc-dev] what's q in snes ex62

[Matthew Knepley]

On Fri, Nov 15, 2013 at 5:31 PM, Geoffrey Irving <irving at naml.us> wrote:

> On Fri, Nov 15, 2013 at 3:21 PM, Matthew Knepley <knepley at gmail.com>
> wrote:
> > On Fri, Nov 15, 2013 at 5:09 PM, Geoffrey Irving <irving at naml.us> wrote:
> >>
> >> Is the second equation the weak form of incompressibility?  If so, why
> >> isn't q u?  It's used as q several places throughout the code, so it
> >> seems more likely to be my misunderstanding than a typo.
> >>
> >>   < \nabla v, \nabla u + {\nabla u}^T > - < \nabla\cdot v, p > + < v, f
> > = 0
> >>   < q, \nabla\cdot v >
>     = 0
> >
> > u, v \in V and p, q \in P, and hopefully \div V = P for stability.
>
> Are you using the same variables as
>
>
> http://fenicsproject.org/documentation/dolfin/dev/python/demo/pde/stokes-iterative/python/documentation.html
>
> If so, maybe that line should be
>
>     < q, \nabla\cdot u >
>
> I.e., "u" instead of "v"?


Damn, you are right.

  Matt


>
> Geoffrey
>



-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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