[aspect-devel] Progress in writing the mantle convection code Aspect

[Timo Heister]

> As I remember, the last time we changed the default stabilization parameters
> was a year ago, when we unified the chemical field and temperature field
> handling. At that time I tried to find parameters that where as low as
> possible to prevent unnecessary diffusion in benchmark cases like
> Rayleigh-Taylor and Stokes sphere.

Do you still have the prm files you used for that? I would like my
student to play with this.

> The resulting overshooting in the first time steps (5-10% in the beginning
> for a quite sharp interface sounds like the values I got there) seemed to
> decay over time, so I was fine with that.

Was that because the first time step is not 2nd order and we don't
have an entropy residual? Do you have a prm that does exactly this? We
could try to fix this (smaller first timestep, more viscosity, ...).

>The best
> choice of beta and Cr is always a bit dependent on the model parameters, but
> of course we can discuss, whether we should increase them by default.

I think the defaults are pretty good as is and I am sure that the best
parameters depend on the problem.
It sounded like Eric made an "evil" example where a larger value is
acceptable and that is why I mentioned the option to increase the
parameters. I mean if the only measure is the amount of overshoot, we
can just do an O(1) first order diffusion and smear everything out.
:-)

-- 
Timo Heister
http://www.math.clemson.edu/~heister/