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<title>[CIG-MC] Progress in writing the mantle convection code Aspect</title>
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\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\<br>
Dr. Carl W. Gable<br>
Group Leader, Computational Earth Science, EES-16<br>
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MS T003, Los Alamos National Laboratory, Los Alamos NM 87545<br>
Email:gable@lanl.gov Voice:505-665-3533 Fax:505-665-6459<br>
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Homepage: http://www.ees.lanl.gov/staff/gable<br>
LaGriT Mesh Generation Software: http://lagrit.lanl.gov<br>
Mesh Generation, Geological Apps: http://meshing.lanl.gov<br>
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Focus:Geophysics, Hydrology, Mesh Generation, Computational Geometry<br>
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Schedule B<br>
/\/\/Correspondence/TSPA\/\/\/\/\/\/<br>
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-----Original Message-----<br>
<b>From: </b>Wolfgang Bangerth [<a href="mailto:bangerth@math.tamu.edu">bangerth@math.tamu.edu</a>]<br>
<b>Sent: </b>Monday, September 30, 2013 09:47 PM Mountain Standard Time<br>
<b>To: </b>aspect-devel@geodynamics.org; cig-all@geodynamics.org; cig-mc@geodynamics.org; Scott King; Louise Kellogg<br>
<b>Subject: </b>[CIG-MC] Progress in writing the mantle convection code Aspect<br>
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<p><font size="2">All,<br>
there has been some criticism recently that CIG doesn't sufficiently well<br>
communicate what it is working on. I think I share in this problem, not<br>
communicating well what we do with Aspect. Thus, allow me this slightly<br>
longish email. I hope to do these sorts of things periodically in the future,<br>
and I hope that this sparks a conversation about what people want/need and how<br>
this meshes with what we're doing.<br>
<br>
To start with: Aspect is a mantle convection code whose development is<br>
supported by CIG. It has three main goals:<br>
<br>
- Modern numerical methods for discretizations, solver, and software<br>
design; building on well-tested and widely used software libraries.<br>
- Designed to make extending the code simple. In particular, to change<br>
the rheology, geometry, postprocessing, etc, you need not know<br>
anything about how Aspect discretizes and solves the actual equations.<br>
- Designed to scale to large problems on large parallel machines.<br>
<br>
The code's website is here:<br>
<a href="http://aspect.dealii.org/">http://aspect.dealii.org/</a><br>
The manual (currently 129 pages) is here:<br>
<a href="http://aspect.dealii.org/doc/manual.pdf">http://aspect.dealii.org/doc/manual.pdf</a><br>
The central numerical methods are described in paper #34 here:<br>
<a href="http://www.math.tamu.edu/~bangerth/publications.html#x-reviewed">http://www.math.tamu.edu/~bangerth/publications.html#x-reviewed</a><br>
<br>
<br>
I won't go into more detail on what this code is, but wanted to update you on<br>
what has been happening recently:<br>
<br>
1/ Aspect has modules that allow the advection of what we call "compositional<br>
fields" (originally implemented by Juliane Dannberg) -- essentially, these are<br>
quantities you can initialize at the beginning and then they will simply be<br>
advected along with the flow. The idea is that you can, for example, mark<br>
material from a ULVZ by setting the compositional field there to one and zero<br>
elsewhere, and see where this stuff is transported. All material parameters<br>
can of course depend on these field values as well.<br>
<br>
That said, in geodynamics, the role of compositional fields has traditionally<br>
been filled by tracer particles. Eric Heien had previously implemented tracers<br>
but in their current implementation they lack the ability to carry information<br>
about where they came from without having to modify the code (i.e., by setting<br>
something in the input file). Among the projects we've been working on is to<br>
rewrite this functionality in a way that allows attaching information to<br>
particles.<br>
<br>
<br>
2/ I had Sarah Stamps, a postdoc at MIT, here a couple of weeks ago. Her goal<br>
is to model flow under Africa, and this has provided me with an opportunity to<br>
see how people want to use Aspect. We did have a model with real topography, a<br>
realistic initial temperature field, appropriate boundary conditions and a<br>
temperature-dependent viscosity working by the end of the week, which I took<br>
as a pretty good sign for what can be done with Aspect.<br>
<br>
In addition to choosing appropriate parameters in the input file, this<br>
exercise required writing code to describe the surface topography, material<br>
model, initial temperature, and other bits and pieces. This did require decent<br>
C++ knowledge, but maybe a bit to my surprise, some of it also required a good<br>
working knowledge of deal.II (one of the libraries upon which Aspect builds).<br>
Observing and participating in this exercise made me realize that we need to<br>
document these parts better -- currently, the documentation states that<br>
certain classes have to be implemented (if you know C++, you know what this<br>
means) but there were no concrete examples of actually doing so. My conclusion<br>
is that we will need to provide more extensive and hands-on documentation,<br>
which I hope to put into the manual over the next few months.<br>
<br>
<br>
These are the two big projects currently on my plate. As I stated above, I<br>
hope to send similar updates again in the future. Let me know of any feedback<br>
or questions you may have!<br>
<br>
Best<br>
Wolfgang<br>
<br>
--<br>
------------------------------------------------------------------------<br>
Wolfgang Bangerth email: bangerth@math.tamu.edu<br>
www: <a href="http://www.math.tamu.edu/~bangerth/">
http://www.math.tamu.edu/~bangerth/</a><br>
<br>
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