[CIG-LONG] thermal diffusivity scaling and specifying correct temperature profile in hydrostatic term

[Guillaume.Duclaux at csiro.au]

Hi Karen,


On 05/08/2010, at 11:45 PM, Karen Paczkowski wrote:

Hi,

I had a few questions about adding a thermal field to my subduction
zone model.

1)  On page 16 in the new manual (18 in the old manual) it says that
the thermal diffusivity needs to be scaled like the velocity and the
viscosity.  So for a thermal diffusivity of 1E-6 m^2/s and a viscosity
of 1E21, this should scale the thermal diffusivity to something like
1E15 when viscosity is rescaled to 1.  The example dike xml file has
the thermal diffusivity rescaled like this, but the example subduction
zone program does not have this rescaling.  I was wondering if the
rescaling should or shouldn't be done?


You're right, thermal diffusivity has to be scaled. I guess the diffusivity in the subduction example has been missed.
If you're using any radiogenic heat production, it also needs to be scaled.


2)  My simulation currently goes from the earth's surface to a depth
of 440km.  I have a thermal field given by TemperatureProfile such
that the temperature goes from 273 K at the top of the simulation to
1623K at a depth of 100km.  The temperature is then constant below
100km depth.  I can specify all of the terms for the temperature
profile (upper density, upper alpha, T_0, height, linearcoefficient,
etc) but there is nowhere to specify at what depth the temperature
becomes a constant.  I think my hydrostatic term thinks that my linear
temperature profile extends down through the whole simulation box.  I
believe that this is causing large errors in my flow field.  I would
expect a downward flow driven by the subduction slab (the only forcing
in the system), but instead I get an upward flow with a magnitude over
2 orders of magnitude larger than the slab velocity.  How can I
correctly tell my hydrostatic term what my temperature profile is?

I have attached an input file to the email.  It is currently written
for Gale 1.4.  I was also wondering where I can find the instructions
on how to upgrade my xml input files to be run with the new version of
Gale?

Thank you,
Karen

<2_ThermalField.xml>




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Dr Guillaume Duclaux

Mineral Down Under Flagship & AuScope Grid
CSIRO Earth Science and Resource Engineering

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