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Re: Questions about BIM

From: J Stasko
Subject: Re: Questions about BIM
Date: Thu, 28 Jul 2011 20:20:18 -0700


Thank you for the help.  I can do the time-discretization if that is as easy as it is.  Thank you!


On Wed, Jul 27, 2011 at 3:15 PM, c. <address@hidden> wrote:

First of all, BIM is a package from Octave-Forge, it is
not part of the core Octave project, so the correct place where
to discuss this matter is the Octave-Forge mailing list, so I am moving this thread there.

On 27 Jul 2011, at 19:42, J Stasko wrote:

> I have been looking at the tutorial with BIM,
> bim-1.0.1/doc/tutorial.html
> It seems that the ADR equation (or DAR equation- are they the same thing?)


> involves a du/dt term, as described in this book preview, equation 1.1:

The title of the book you cite says it all,
"Numerical Solutions of TIME DEPENDENT Advection Diffusion Reaction Equations"
while the tutorial deals with a steady state DAR equation

> I do not see this tutorial progressing through time.  Am I correct?

Yes, the extension, though, is quite trivial.
For example, given the equation

du/dt - d/dx (D du/dx - C u) + R u = f       0 < t < N*T

after time semi-discretization with implicit Euler method and a fixed time-step T becomes

- d/dx (D d u_i /dx - C u_i) + (R + 1/T) u_i = f + u_{i-1} / T,    i = 1 ... N

which is a sequence of steady state DAR problems, so once you are able to solve steady-state
you are able to solve time-dependent as well.

If you'd like an example using more advanced time stepping techniques I have quite a few using DASPK
for fully-implicit adaptive time-stepping, but I never added them to the repository because I do not
have time to write documentation for them.

> Thank you,
> John S.


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