sfepy/sfepy — Issue #63: time derivatives in terms
Author: rc
Created: 2012-01-30 10:25:12+00:00
State: open

The topic is discussed for Stokes-like terms, the same holds, however, for
Biot-like terms, piezo-coupling, and other terms too.

As dw_grad, dw_div, d_div are now all treated by dw_stokes, what to do with
dw_grad_dt? It is still the same term, just the pressure variable is
differentiated w.r.t. time. There are several possibilities:
1. dw_stokes_dpdt, dw_stokes_dudt terms
2. enrich the equation parse to allow:
dw_stokes( v, dp/dt ), dw_stokes( du/dt, q ), possibly with one more
argument saying what kind of numerical derivative is used (backward
(default) or forward difference).
3. ?

Note that variables already support history, so option 2. is feasible.

Opinions?

Migrated from http://code.google.com/p/sfepy/issues/detail?id=59

earlier comments

ondrej.certik said, at 2008-10-14T14:57:00.000Z:

Do what you think is the best. I don't have an opinion here, as I don't use those terms.

robert.cimrman said, at 2008-10-15T14:58:52.000Z:

Option 2. is in, see http://hg.sympy.org/sfepy/rev/186603f3c0aa

Test it, if you can, please, by running '$ ./simple.py input/time_poisson.py'