[CIG-LONG] [ExternalEmail] Re: CIG-LONG Digest, Vol 45, Issue 12

[Walter Landry]

Patrice Rey <patrice.rey at me.com> wrote:
> Hi Gilly
> 
> In the power law - linking the strain rate to differential stress, activation
> energy and temperature - the pre-differential stress constant is commonly
> given in MPa^-n . s^-1.
> 
> In the Gale-1.5.0 manuel, the power law shown in the appendix section A.5.2.3
> (page 96) - and its conversion into viscosity - make sense only if one assumes
> that A_Gale = (A_PowerLaw)^1/n.  I have checked the code (NonNewtonian.c) and
> it seems that this is the case. 
> 
> If this is correct it should be commented in the Gale Manual and Underworld
> as pre-stress exponents given in the literature must be risen to the power 1/
> n.  This modifies the scaling factor of A: (StressScalingFactor^-1) /
> TimeScalingFactor^1/n
> 
> Perhaps to keep things simpler the source code could be modified so A-Gale is
> A-Power Law?

Everything in the manual is correct, as far as I can tell.  However,
it is different from the form usually seen in the literature.  I
remember having a definite reason for why I set it up this way, but I
have since forgotten.  I am happy enough to change it to the form used
in the literature.  It would also make it simpler to scale.

Cheers,
Walter Landry
walter at geodynamics.org