[CIG-LONG] turning off elasticity in SNAC

[Eunseo Choi]

  Dear Michael

I believe Dr. Mark Behn at WHOI and Prof. Garrett Ito at U. Hawaii have 
been making efforts to assess the importance of elasticity in 
lithospheric dynamics. You may want to contact them.
Also, to completely turn off elasticity, I think it is a better idea to 
make a new plugin for purely viscous rheology than to tweak the Maxwell 
rheology.

Localization right at boundaries where vel BCs are applied is a 
diagnostic symptom of a larger time step size than what it should be. If 
dynamic time stepping worked properly, it wouldn't happen.
It s0ounds like a bug that time steps are not constrained by maxwell 
relaxation time.
I'll look into it. It would be very helpful if you could send your input 
file to me.

Cheers,
Eunseo


On 7/23/2010 4:22 PM, Michael Kaplan wrote:
> Hi,
>   Im interested in exploring the effects of elasticity on lithospheric 
> dynamics and consequently am looking for a way to use purely viscous, 
> purely plastic, and visco-plastic rheologies in SNAC.  Also, to 
> compare SNAC and GALE it would be helpful to use the same rheologies.  
> Using SNAC's Maxwell plug-in and setting elastic moduli orders of 
> magnitude larger than the viscosity is problematic because it creates 
> a very short maxwell relaxation time, which SNAC enforces must be 
> greater than the time step.
>   Switching dtType from a constant time step to dynamic time stepping 
> allows the simulation to run, but produces seemingly unreasonable 
> results.  It seems with dynamic time stepping that only the first time 
> step is less than the maxwell relaxation time, with all later time 
> steps unconstrained by the relaxation timescale.  For reasons that I 
> dont understand, this seems to create simulations for which all the 
> deformation is localized to the boundaries which have a non-zero 
> kinematic BC.
>   One solution I plan on testing is to create a new plug-in for a 
> purely viscous rheology, but any other solutions or comments would be 
> greatly appreciated.
> Thanks in advance for the help!
>
> -Michael Kaplan
> USC Geodynamics
>
>
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-- 
=====================================
Eunseo Choi
Post-Doctoral Research Scientist

Lamont-Doherty Earth Observatory
305c Oceanography
P.O. Box 1000
61 Rt. 9W
Palisades, NY 10964-8000

http://www.ldeo.columbia.edu/~echoi
Phone: 845-365-8813 Fax: 845-365-8156
=====================================

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