[aspect-devel] Question on layered and temperature-dependent viscosities

[FELIPE ORELLANA ROVIROSA]

 Hi Wolfgang,

   I think I understand you..

   So, for the setting I showed you, does it means that if a hot anomaly
was ~10 times less viscous than its surroundings on layer 1 (with an
initial ambient log visc = 22), then if that hot mass goes through the
interface, its viscosity will down-jump two orders of magnitude following
the new environment (where initially log visc = 20 ) , and it will continue
being something like ~10 times less viscous than the environment (if
thermal diffusion didn't occur), so it will be approximately log visc=18 ?

considering

  visc(T) = viscref.exp(-(T-To)/To)

   this seems to require that the reference viscosity changes according to
the position, what layer the mass is in at that time. Maybe this is built
as

     viscref=viscref(z) independent of what the flow is on the system.

   whereas the variable T responds to the flow, via the energy equation.

 I hope to be interpreting this correctly.
cheers,
thank you,
Felipe



On Tue, May 15, 2018 at 8:12 PM, Wolfgang Bangerth <bangerth at colostate.edu>
wrote:

> On 05/16/2018 09:59 AM, FELIPE ORELLANA ROVIROSA wrote:
>
>>
>>     It is based on position:
>>
>>     subsection Depth dependent model
>>
>>      set Base model = simple
>>      set Depth dependence method = List # Function
>>      set Depth list = 1e6, 2.9e6
>>      set Viscosity list = 1e20, 1e22
>>
>
> Then the viscosity is determined exclusively based on the position ("which
> layer are you in") and the temperature a material happens to have at a
> particular location. Where that material came from originally is not
> relevant for the determination of the viscosity -- the material model does
> not know this, nor does it care.
>
> There are ways to tell a material model where material came from, and to
> base the viscosity also on this information. You would do this with
> compositional fields.
>
>
> Best
>  W.
>
> --
> ------------------------------------------------------------------------
> Wolfgang Bangerth          email:                 bangerth at colostate.edu
>                            www: http://www.math.colostate.edu/~bangerth/
>
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