9 Jun 2006 17:19

```
Hi,
I am trying to run your implicit diffusion solver on a 2D 500x500 mesh.
However, I would like to repeatedly run this solver to evolve the same
mesh, without losing previous values.  So for example:

mesh = Grid2D(dx = 0.000002, nx=500, ny=500)
var = CellVariable(name="solution variable", mesh=mesh, value=0)

if __name__ == '__main__':
i = 0
while (i < steps):
# <do something to var>
ImplicitDiffusionTerm(coeff = 1).solve(var, dt=2)
# <do something else to var>
i = i + 1

However, I can't currently do this because whenever I call the solve()
method, it resets 'var' to all zeros.  Is there anyway I can stop this
from happening?  Appreciate it!

Best,
Trevor

--

--
-------------------------------------------------------
Live every moment, leave nothing to chance.
Swim in the sea, drink of the deep
Embrace the mystery of all you can be.
```

9 Jun 2006 19:44

### Re: Question about Implicit Diffusion

```
On Jun 9, 2006, at 11:19 AM, Trevor M Cickovski wrote:

>
> Hi,
> I am trying to run your implicit diffusion solver on a 2D 500x500
> mesh.  However, I would like to repeatedly run this solver to
> evolve the same mesh, without losing previous values.  So for example:
>
> mesh = Grid2D(dx = 0.000002, nx=500, ny=500)
> var = CellVariable(name="solution variable", mesh=mesh, value=0)
>
> if __name__ == '__main__':
>   i = 0
>   while (i < steps):
>      # <do something to var>
>      ImplicitDiffusionTerm(coeff = 1).solve(var, dt=2)
>      # <do something else to var>
>      i = i + 1
>
> However, I can't currently do this because whenever I call the solve
> () method, it resets 'var' to all zeros.  Is there anyway I can
> stop this from happening?  Appreciate it!

We probably need to know a bit more about what's involved in <do
something to var> and <do something else to var>, but I think I can
guess what's happening to you. If I'm right, then we discuss this
situation near the beginning of Example 9.1, phase.simple.  The
source term of the phase equation isn't important here; it's the
behavior of trying to solve a steady-state diffusion term that causes
```