[CIG-LONG] cig-long email list

Thu Apr 30 14:52:46 PDT 2009

Hi, Garrett

First of all, thanks for responding to my comments and suggesting an 
interesting  benchmark.

SNAC cannot currently handle Drucker-Prager plasticity, so I'll use 
Mohr-Coulomb model.

A more fundamental issue is that SNAC is hardwired to be 3D, which means 
it can solve a 2D problem using a thin 3D model with plane strain 
conditions.
A pseudo-2D model like this will obviously raise the numerical cost 
compared to a true 2D one, rendering the benchmark unfair.

So, could you please set up a one-element thick 3D model from your 2D model?
Let me know if it's too much work on your side.

I also need to know how long in terms of model time you ran this model, 
if it was run on a single processor, and how many time steps were taken.

Finally, here is a non-technical (I guess) question.
According to the Gale's manual, the Frank Kamenetskii viscosity is 
defined as temperature-dependent only.
Then, why do we see the viscosity field varying consistently with the 
strain rate field?
Such a correspondence is expected when viscosity is also stress-dependent.
Am I misunderstanding something?

Best,
Eunseo

Garrett Ito wrote:
>
> Hi Eunseo,
>
>   Aha! my little comment did catch your eye--good.  Your suggestion of 
> comparing Gale and SNAC is a great one and I'd like to try.  Here's 
> one we could look at.  Its a simple case rifting in which extension is 
> driven by the two side boundaries apart, each at ~12.6 km/Myr (so full 
> spreading rate is 25.2 km/Myr).  Free inflow at the base and top free 
> to move up and down.  Frank Kamenetskii temperature-dependent 
> viscosity with Drucker Prager yielding.  The temperature structure has 
> T=273K at the surface and 1473K at the base with a linear profile in 
> between.  A box of postfailure strain is imposed at t=0 to control 
> where the faults initiate.  The attached pdf shows Gale's solution in 
> 2D with 150x45 elements.  I also attached Gale's input file so you can 
> see the rheology parameters.  How does this sound? 
>
> Garrett
>
> ----- Original Message -----
> From: Eunseo Choi <echoi at ldeo.columbia.edu>
> Date: Wednesday, April 29, 2009 5:34 pm
> Subject: Re: [CIG-LONG] cig-long email list
> To: cig-long at geodynamics.org
>
> > Hi, Garrett
> >
> > SNAC is a 3D code like Gale so it is supposed to be
> > computationally
> > expensive compared to any 2D codes.
> > I believe this is not what you meant.
> >
> > As far as I know, the performance of SNAC and Gale has never
> > been
> > compared quantitatively yet. Please let me know if it's done
> > even
> > qualitatively.
> > So, I wonder why you have the impression that SNAC is too
> > expensive for
> > 3D models.
> >
> > By the way, SNAC can do Mohr-Coulomb plasticity in 3D and
> > doesn't have
> > the restriction that plastic flow should always be incompressible.
> >
> > Eunseo
> >
> >
> > Garrett Ito wrote:
> > >
> > > Hi Mark,
> > >
> > >   Good-- I'm glad to see 3D is starting to get a
> > footing in the
> > > community.  This is my main reason for using Gale as I
> > already do
> > > faulting in 2D with FLAC (and it is my understanding that SNAC
> > is too
> > > computationally expensive in 3D ?).  Correction... Mohr-
> > Coulomb has
> > > been removed from Gale because it was unstable in 3D and is
> > identical
> > > to Drucker-Prager in 2D.
> > >
> > > Garrett
> > >
> > > ----- Original Message -----
> > > From: Mark Fleharty <mark.fleharty at gmail.com>
> > > Date: Wednesday, April 29, 2009 12:46 pm
> > > Subject: Re: [CIG-LONG] cig-long email list
> > > To: Garrett Ito <gito at hawaii.edu>
> > > Cc: cig-long at geodynamics.org
> > >
> > > > Garrett,
> > > >
> > > > It is good to hear from someone else who is doing 3D
> > simulations in
> > > > Gale.  I am also doing 3D simulations with Gale.
> > > > Welcome aboard.
> > > >
> > > > I thought that Mohr-Coulomb doesn't work in Gale in 3D.
> > > > Was that
> > > > something that got fixed?
> > > >
> > > > Mark
> > > >
> > > > On Wed, Apr 29, 2009 at 4:27 PM, Garrett Ito
> > > > <gito at hawaii.edu> wrote:
> > > > >
> > > > > Dear colleagues,
> > > > >
> > > > >   I would like to introduce myself as a new to
> > the cig-long
> > > > list and new
> > > > > GALE user.  I would like to encourage us all to use
> > the cig-
> > > > long list more
> > > > > often to help spread the knowledge of the CIG codes. 
> > I think
> > > > it would be
> > > > > helpful, for example, we made it a practice of sending
> > > > individual questions
> > > > > to cig-long along with questions you send to Walter/Eun-seo
> > > > about the
> > > > > various coding issues.
> > > > >
> > > > > Just to start a conversation...I have started using GALE--
> > > > really in
> > > > > collaboration with Walter Landry--over the last half year with
> > > > interests in
> > > > > applications of studying faulting and magmatism at mid-ocean
> > > > ridges in 3D.
> > > > > A lot of my work to date has been to experimenting with the
> > > > Mohr-Coulomb,
> > > > > Drucker-Prager, and StrainWeakening (e.g., damage laws and
> > > > healing) and
> > > > > understanding the faulting behavior predicted by Gale.
> > > > Recently, we have
> > > > > started running jobs in 3D, which I have found to be
> > > > surprisingly cpu
> > > > > intensive.  I view improving the performance of Gale
> > for 3D faulting
> > > > > problems as an important goal and on which I will be working
> > > > closely with
> > > > > Walter and the Underworld group over the next year.
> > > > >
> > > > > I look forward to hearing more from you.
> > > > >
> > > > > Garrett
> > > > > --
> > > > >
> > > > > =====================================
> > > > >
> > > > > Prof. Garrett Ito
> > > > >
> > > > > SOEST, Geology & Geophysics
> > > > >
> > > > > 1680 East-West Rd., POST 810
> > > > >
> > > > > Univ. of Hawaii
> > > > >
> > > > > Honolulu, HI 96822 USA
> > > > >
> > > > >
> > > > >
> > > > > 808-956-9717
> > > > >
> > > > > gito at hawaii.edu
> > > > >
> > > > > www.soest.hawaii.edu/GG/FACULTY/ITO
> > > > >
> > > > > ======================================
> > > > >
> > > > > _______________________________________________
> > > > > CIG-LONG mailing list
> > > > > CIG-LONG at geodynamics.org
> > > > > http://geodynamics.org/cgi-bin/mailman/listinfo/cig-long
> > > > >
> > > > >
> > > >
> > > >
> > > >
> > > > --
> > > > Mark Fleharty
> > > > +1 505 217-2089
> > > ---------------------------------------------------------------
> > ---------
> > >
> > > _______________________________________________
> > > CIG-LONG mailing list
> > > CIG-LONG at geodynamics.org
> > > http://geodynamics.org/cgi-bin/mailman/listinfo/cig-long
> > >  
> >
> >
> > --
> > =====================================
> > Eunseo Choi
> > Post-Doctoral Research Scientist
> >
> > Lamont-Doherty Earth Observatory
> > 303f 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
> > =====================================
> >
> > _______________________________________________
> > CIG-LONG mailing list
> > CIG-LONG at geodynamics.org
> > http://geodynamics.org/cgi-bin/mailman/listinfo/cig-long 

-- 
=====================================
Eunseo Choi
Post-Doctoral Research Scientist

Lamont-Doherty Earth Observatory
303f 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
=====================================