[CIG-LONG] Fwd: CIG-LONG Digest, Vol 47, Issue 2

[Walter Landry]

<Guillaume.Duclaux at csiro.au> wrote:
> Indeed.
> 
> But, shouldn't it be possible to solve purely thermal problem with
> Gale?  (let's pretend the thermal expansion is null is Nicolas'
> problem).  ie a sill at a temperature of 1000 K has intruded a mass
> of rock at constant temperature (600 K) and I want to simulate the
> thermal evolution of the system as I change the thickness of the
> dyke or the radiogenic heat production of one or the other material.

It is possible to do pure thermal conductivity problems with Gale.
You have to turn off all of the Stokes flow stuff, but it does seem to
work.

> To ensure the solver timestepping is not missing the temperature
> perturbation timescale, how should the time be scaled?
> I guess viscosity doesn't matter if the problem is purely thermal,
> but as soon as the thermal expansion is on, some body forces act too
> creating some 'slow' displacement.

For this particular case, the displacement is so slow that it can be
neglected.  If you still want to solve the Stokes flow, then you can
set the timestep explicitly with 'dt' (see Appendix A.1.4).  Gale
should probably take the thermal diffusivity into account when
deciding upon a timestep, but it does not do that now.

Cheers,
Walter Landry
walter at geodynamics.org