[aspect-devel] Aspect melt_fraction

Juliane Dannberg dannberg at gfz-potsdam.de
Mon Mar 17 04:09:26 PDT 2014

Dear all,

I agree that it is a great idea to track the melt fraction more easily. 
On the way to implementing active melt migration (i.e. porous flow), my 
postprocessor was only a preliminary way to calculate the melt fraction. 
However, we should think about how we want this to be implemented in the 
end. I imagined that the melt fraction (or porosity) will be handled in 
a way comparable to the temperature or composition (as a solution 
variable), and in the material model only the melting rate/ rate of 
solidification will be calculated. If someone needs the melt fraction 
only as output quantity, the postprocessor will still be there, but if 
active melt transport is switched on, the melt fraction output is 
generated by default, just like for the temperature/pressure/...

I already started implementing something like this in my own Aspect 
branch (Jonathan, if you want to have a look:
--> branches --> j-dannberg). Until now, melt fraction is only handled 
as any other compositional field for purposes of advection, but there is 
the material model 'latent heat', where latent heat of melting is 
already generated and material properties can depend on the melt fraction.

So if the Aspect community thinks we should add such a feature to the 
main branch soon, maybe we should figure out together how we want to 
implement this.


On 03/16/2014 10:39 PM, Louise Kellogg wrote:
> I agree, this seems like a useful addition to the main branch.
> On Mar 14, 2014, at 1:00 PM, Magali Billen <mibillen at ucdavis.edu 
> <mailto:mibillen at ucdavis.edu>> wrote:
>> I think it would be great to have a module for calculating melt 
>> fraction in the main branch.
>> This doesn't come up for every problem, but there's often a problem 
>> that you're working
>> on and then part way through you realize that melt fraction might be 
>> helpful. If we are looking
>> ahead to more realistic theologic models, for example, being able to 
>> have rheology depend
>> on melt fraction would require calculating melt fraction first.
>> Magali
>> On Mar 14, 2014, at 12:04 PM, Jonathan Perry-Houts wrote:
>>> Hash: SHA1
>>> Hi all,
>>> I'm starting work on melt migration in ASPECT, and the first step was
>>> to make melt fraction a more easily tracked quantity.
>>> In December Juliane made a nice postprocessor to visualize the amount
>>> of melt generated in the model based on Katz, 2003 paper. The
>>> algorithm is great but I don't like the fact that it's hard-coded in
>>> to the postprocessor. I think it would be more useful to make melt
>>> fraction a quantity calculated by the material model and have the
>>> postprocessor display it in the same way viscosity and density are
>>> displayed.
>>> This also allows material properties to be easily derived from the
>>> melt fraction without calculating the same thing twice for each
>>> timestep. If anyone has a better suggestion for dealing with melt I'd
>>> be happy to hear it.
>>> I'm not sure that other people would be interested in these changes
>>> enough to put them in the main branch, but I figured I'd share them
>>> with the mailing list in case anyone does find them useful. The
>>> changes are relatively unobtrusive, except for breaking Juliane's
>>> melt_fraction visualization postprocessor, but that functionality can
>>> be easily replicated by including the same algorithm in the material
>>> model.
>>> I can also send out an example material model which calculates melt
>>> based on Juliane's algorithm if people are interested.
>>> The modified files are:
>>> include/aspect/material_model/interface.h
>>> include/aspect/postprocess/visualization/melt_fraction.h
>>> source/material_model/interface.cc <http://interface.cc>
>>> source/postprocess/visualization/melt_fraction.cc
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>>> <interface.h><melt_fraction.h><interface.cc 
>>> <http://interface.cc>><melt_fraction.cc>_______________________________________________
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>> --------------------------------------------------
>> Professor of Geophysics & UCD Chancellor Fellow
>> Chair, Geology Graduate Program
>> Earth & Planetary Sciences Dept., UC Davis
>> Davis, CA 95616
>> 2129 Earth & Physical Sciences Bldg.
>> Office Phone: (530) 752-4169
>> http://mygeologypage.ucdavis.edu/billen/
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> ********************************************
> Louise Kellogg
> Professor, Dept. of Earth & Planetary Sciences
> One Shields Avenue, University of California, Davis, CA 95616
> Phone: (530)752-3690
> ********************************************
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