Reading densities directly from and ASCII file

ASPECT
1

Hi!

I’m trying to solve the instantaneous mantle flow in a portion of the Earth within a 3D box. Outside ASPECT, I use a tomographic model of the area to derive densities and temperatures. I would like to read such densities from an ASCII file and use them directly in ASPECT, i.e. not deriving densities from temperatures. However, at the same time I would like to have the temperature field (also read from a file) so that I can compute the dependent viscosities. I’ve been through quite a lot of cookbooks, but I can’t figure out how to achieve it. Do you know if it is possible to do that with the existing tools? or should I write a plugin that does that?

I tried to fake temperatures so that when using “rho=rho0 alpha (T-T0)”, it gives the density I want. The problem is that then I will not have a useful temperature field to compute the viscosity. I also thought about using a compositional field “c0” as density (read from a file) and use “rho=rho0 alpha (T-T0) + deltaRho c0” to obtain the density I want (maybe setting rho0=0 or alpha=0 and deltaRho=1). But I’m not sure whether this may break something inside or complicate things too much.

I’m afraid I’m missing something and there is a much simpler and straighforward way to achieve this.

Thank you very much in advance

Olga

2

Hi Olga,

I think your idea of using a compositional field and setting the thermal expansivity to zero makes sense. I think this should work, and I think that’s the simplest way to achieve this.

The closest cookbook to what you want is this, I think:

But density and viscosity are still not completely independent, this only allows for different depth-dependent scalings for the two. So I think your idea is the way to go!

Cheers,
Juliane

3

Hi Juliane!

Thank you very much for your fast reply.

I checked the cookbook you suggested and yes, it is very similar to what I wanted to do, but the implementation and dependences differ a bit. I will continue with the compositional field approach then!

Thank you very much!
Cheers!
Olga