[petsc-users] Seeking an example for TS

Matthew Knepley knepley at gmail.com
Wed Oct 30 15:52:11 CDT 2013

On Wed, Oct 30, 2013 at 3:47 PM, Gautam Bisht <gbisht at lbl.gov> wrote:

> Hi,
> I'm wondering if there is a TS example for a similar system:
> d/dt [f(x)] = g(x)
> For example, in PFLOTRAN, we have the following governing equation for
> subsurface flow:
> d/dt [ sat(P)*den(P)*por] = - g(P)
> where,
> sat = saturation,
> den = density,
> por = porosity,
> P = Pressure
> PFLOTRAN uses SNES to solve the nonlinear system of equations that arises
> from a backward Euler time discretization. I'm trying to seek guidance on
> how one would go about reformulating PFLOTRAN's equations to use TS.

All the TS examples (I think) have the form

  F(u, \dot u, x, t) = G(u, x, t)

where the unknowns are u, the coordinates are x, and the time is t. I would
look at the examples
(maybe ex25), and then try coding it up.


> Thanks,
> -Gautam

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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