[aspect-devel] [CIG-ALL] ASPECT 1.0 released

[Wolfgang Bangerth]

Hi Carolina,
let me take this to the mailing list since we have more people there with the 
relevant expertise.


> I am a geodynamicist and have been involved in developing a self-consistent
> thermodynamic framework for mantle composition and phases.
> In the past myself and Lars Stixrude (the main author of HeFESTo, the
> self-consistent thermodynamic code we use to predict phase assemblages
> and physical properties of the mantle) we have talked ot CIG about
> incorporating the thermodynamics and even releasing the code and lookup tables
> through CIG. Mostly, time, moving to the UK and slowlgy replacing many
> numerical recipes subroutine have not allowed us to fulfill that commitment.
> In any case, given the way CitcomS was formulated it would not have been very
> useful.
>
> However, this release of Aspect is very exciting and it seems to me could be
> ready to explore the effects of thermodynamics on the flow. The mantle
> has MANY phase transitions especially in the upper 800 km they are essentially
> continuous. Across them there can be latent heat release or absorption but
> also many changes in physical properties, both static and transport (thermal
> conductivity and viscosity say, not something we can compute yet).
> Some of are very sharp (VERY, i.e. hard for typical grids) happening across
> less than 5 kms and some much more gradual. The effects on plate dynamics
> can be quite important, including possibly intermittent layering, and also
> strongly affect surface observables like dynamic topography.
>
> I’ve read the Aspect manual, admittedly quickly, and I wanted to ask you if
> you think the release of Aspect is ready to interface with a thermodynamic lookup
> table for given compositions. These tables include P, T, rho, Entropy, Cp,
> Enthalpy, etc. Plus of course the shear and bulk moduli. It wasn’t clear to me
> from
> the manual whether it was yet possible for Aspect to include the
> self-consistent thermodynamics or not.

I think this should be possible, at the very least as far as the material 
parameters are concerned. We parameterize material models in the following way:
- at every quadrature point, the core simulator evaluates pressure, 
temperature and compositional fields
- it then asks the material model in use for the corresponding coefficients 
such as density, viscosity, thermal conductivity, etc
- we have a few simply material models that compute these coefficients as 
functions of p and T
- but material models can also get the coefficients from lookup tables and 
there is a model that Thomas Geenen has used that does exactly this (I don't 
think we include it in the release because it's his data, but you may ask him 
for the data or at least for the code -- it's not very complicated).

In other words, if all you want is to have a material model based on a lookup 
table, then that's definitely possible and has been for a long time. How 
complicated the lookup table is of course doesn't matter.


Now, on to the second question: thermodynamics. My own understanding of 
thermodynamics is very limited, so I may ask if Juliane could possible chime 
in. Juliane implemented a model in which there is release of latent heat, and 
you can see a simple benchmark on page 141 of the manual that illustrates 
this. I believe this video of hers
   https://www.youtube.com/watch?v=dG-ULmcBr1E
also uses this feature. In other words, I *think* what you need should work, 
but I don't know enough about what parameterization you want to use and how 
that fits into what is currently implemented. In any case, however, we would 
certainly be very interested in seeing this made to work, and we'd be happy to 
provide feedback and support if you or a student wants to work on this!

Best
  Wolfgang

where we simply ask the model to return to the core simulator

-- 
------------------------------------------------------------------------
Wolfgang Bangerth               email:            bangerth at math.tamu.edu
                                 www: http://www.math.tamu.edu/~bangerth/