[petsc-users] How to add a source term for PETSCFV ?

[Matthew Knepley]

On Mon, Jul 20, 2020 at 9:36 AM Jed Brown <jed at jedbrown.org> wrote:

> How would you like to discretize the diffusive terms?  The example has a
> type of gradient reconstruction so you can have cellwise gradients, but
> there are many techniques for discretizing diffusive terms in FV.  It's
> simpler if you use an orthogonal grid, but I doubt that you are.
>
> As for terminology, the diffusive part is usually stiff and thus must be
> treated implicitly.  In TS terminology, this would be part of the
> IFunction, not the RHSFunction.
>

At a high level, I would say that this is doable, but complicated. You can
see me trying to do something much easier (advection + visco-elasticity) in
TS ex18,
where I want to discretize the elliptic part with FEM and the advective
part with FVM. I assume that is why Jed wants to know how you want to
handle the
elliptic terms, since this has a large impact on how you would implement.

  Thanks,

     Matt


> Thibault Bridel-Bertomeu <thibault.bridelbertomeu at gmail.com> writes:
>
> > Dear all,
> >
> > I have been studying ex11.c from ts/tutorials to understand how to solve
> an
> > hyperbolic system of equations using PETSCFV. I first worked on the Euler
> > equations for inviscid fluids and based on what ex11.c presents, I was
> able
> > to add the right PETSc instructions in an already existing in-house code
> > with different gas models  to solve the problems in parallel (MPI) and
> with
> > the AMR capabilities offered by P4EST.
> >
> > Now my goal is to move to Navier-Stokes equations. Theoretically the
> system
> > is not completely hyperbolic and can be seen as one with an hyperbolic
> part
> > (identical to the Euler equations) and a parabolic part coming from the
> RHS
> > diffusion terms.
> > I have been looking into the manual and also the sources of PETSc around
> > the DM, DMPlex, DS and FV classes but I could not find anything that
> speaks
> > to me as "adding a RHS to an hyperbolic system of equations" or "adding a
> > source term to an hyperbolic system of equations". What's more, that
> source
> > term depends on the derivatives of the context variables ...
> >
> > I wanted to know if anyone maybe had a suggestion regarding this issue ?
> >
> > Thank you very much in advance,
> >
> > Thibault Bridel-Bertomeu
> > —
> > Eng, MSc, PhD
> > Research Engineer
> > CEA/CESTA
> > 33114 LE BARP
> > Tel.: (+33)557046924
> > Mob.: (+33)611025322
> > Mail: thibault.bridelbertomeu at gmail.com
>


-- 
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

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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