[aspect-devel] density for depth-dependent viscosity model

[Juliane Dannberg]

Dear Eleonora,

the density in your model is controlled by which material model you use.
So to figure out why the density has a different value from what you 
would expect, you would have to check what equation the material model 
you use in your computation uses to compute the density. Usually, there 
is a reference density, which is used as a starting value, and a 
dependence on the temperature (as given by the thermal expansivity), 
and, optionally, the pressure and composition.

But if your model is, for example, incompressible (so that the density 
does not depend on pressure) and does not have a composition-dependence 
of the density, then your density is only controlled by the reference 
value an the temperature. So if the temperature in the lithosphere is 
lower than in the mantle below, you would expect that the density in the 
lithosphere is higher.

In reality, of course, the lithosphere has a different composition than 
the asthenosphere, which influences its density. So if you want to have 
that effect in your model, you need to use a material model that allows 
density changes due to compositional fields.

I hope that helps!
Juliane


On 07/05/2018 02:14 AM, Eleonora Ficini wrote:
> Dear all,
> using a depth-dependent viscosity model I got some unrealistic 
> densities in the mantle (like 3300 kg/m^3 for the lithosphere, 
> compared with 3200 kg/m^3 for the mantle). Could this be related with 
> some visualization problem with paraview or am I doing something wrong?
> Some parameters I used that might be helpful to know:
> - Adiabatic Initial Temperature Model
> - Spherical Constant Boundary Temperature Model (Outer temperature = 
> 273; Inner temperature = 3273)
>
> Thank you in advance for your time and help,
> Eleonora
>
> -- 
> Eleonora Ficini, PhD student
> Department of Earth Sciences
> Sapienza University of Rome
> P.le A. Moro, 5 - 00185, Rome, Italy
>
>
>
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