[CIG-LONG] April 2 CIG-LTT Conference Call - summary

Dennis Harry dharry at warnercnr.colostate.edu
Sun Apr 6 10:22:51 PDT 2008


Please see below for my draft summary of our conference call. Please 
add/edit as necessary.  Also, please consider prioritizing the future 
work on GALE that we discussed.  We agreed at the end of the conference 
call to have the tasks prioritized prior to the CIG workshop that will 
be held in Davis, CA in July.

By the way, I have added some things not discussed in the conference 
call but that were delivered via email from those who were unable to 
join in the call.

Minutes from April 2 2008 Meeting of the CIG-LTT Working Group

The meeting was convened as a conference call.  Those attending were:
Thorsten Becker
Noah Fay
Dennis Harry
Ritske Huismans
Walter Landry,
Mousumi Roy
Jolante van Wijke

The discussion centered on improvements to GALE and consideration of 
accuracy and efficiency of GALE.  The working group makes the following 
recommendations (not in order or priority):

1) The reasons for GALE's lack of convergence when running the extension 
benchmark need to be understood.

2) Further work needs to be done to determine how GALE scales as compute 
nodes are added.

3) An interface needs to be built to allow GALE to import pre-meshed 

4) The ability to consider pressure and temperature dependence of 
physical properties needs to be added.  Density and thermal properties 
were specifically mentioned.  Others?

5) Some benchmark testing needs to be done to assess if GALE is properly 
behaving according to the plastic material behavior that is selected. 
Can we identify some benchmark tests?

6) Implementation of boundary conditions that can vary along the sides 
of the model domain is desired.

7) Elasticity should be incorporated.  Is this the solution to getting 
the extension benchmark to work?

8) The Working Group discussed the desire to have different element 
constructs (e.g., triangular elements).  Walter indicated that this 
would require a fundamental re-write since GALE inherits it's element 
constructs from Underworld. Is that correct, Walter? And Noah, does this 
capture your comments re: irregular mesh, or was there more to that?

9) Understanding the cause of and eliminating the pressure oscillations 
that appear in some of the cookbook examples is required.

10) Convergence behavior of the Uzawa solver seems odd compared to other 
codes, and needs to be understood. Fixing this may fix the pressure 
oscillation problem.  Or is it the other way around? We should think 
about this when we prioritize tasks.  Also, there was some further 
discussion of solver issues that went a bit over my head.  Could someone 
try to summarize that discussion if I have not fully captured it here?

Via email, Todd Ehlers also added the following:

11) Coupling with a landform (surface process) evolution model is 
desirable.  Two mature codes in the geomorphology/geodynamics 
communities that are well suited for this task are CASCADE and CHILD.

12) GALE output should include prediction of geobarometer and 
thermochronometer observables at the surface. There are mature and free 
codes available that use time-temperature histories of rocks and predict 
observables (e.g. Cooling ages) that could be used to test models. 
Todd, I think GALE already provides the P-T history as output.  Do we 
just need a post-processing filter to convert this into the proper input 
format for the other codes you refer to?  Also, could the working group 
try to identify specific codes that we need to make GALE get cozy with?

Walter's email announcing the GALE 1.2.2 release identified these future 

   * Cleanup friction boundary conditions
   * Better normal stress boundary conditions
   * Deformed lower boundaries
   * Interface with custom surface process models in parallel

I seem to recall that Patrice had also contributed comments via email, 
but I can't find them.  Patrice, please insert them if they are not 
included in the issues I summarized above.


-- dlh
   Dennis L. Harry
   Edward M. Warner Professor of Geophysics
   Department of Geosciences
   Colorado State University
   Fort Collins, CO 80523-1482
   phone: (970) 491-2714  fax: (970) 491-6307

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