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

Thu Aug 19 04:44:17 PDT 2010

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?

Cheers

Patrice

On 19/08/2010, at 5:55 PM, Guillaume.Duclaux at csiro.au wrote:

> Hi again,
> 
> I think Nicolas is right. It seems there is a mistake in the manual (and in my scaling script too - don't use it! - I'm glad I distributed it without guarantee, though)
> 
> Patrice, the unit for A in Gale is [Pa^(-1) s^(-1/n)],
> 
> also the pre-stress constant as you describe it [Pa^(-n)s^(-1)] has to be converted :
> {Pa^(-n)s^(-1)}^(1/n) in order to be in the same unit than Gale,
> then it needs to be scaled  =>
> Anew=Aold * timeScalingFactor ^(-1/n)
> 
> Correct?
> 
> Cheers
> 
> Gilly
> 
> On 19/08/2010, at 8:14 AM, <Guillaume.Duclaux at csiro.au<mailto:Guillaume.Duclaux at csiro.au>> <Guillaume.Duclaux at csiro.au<mailto:Guillaume.Duclaux at csiro.au>> wrote:
> 
> Hi Nicolas,
> 
> I sent a spreadsheet for scaling the Non Newtonian viscosity couple of months ago. It is available here:
> 
> http://geodynamics.org/pipermail/cig-long/2010-May/000389.html
> (attachment: http://geodynamics.org/pipermail/cig-long/attachments/20100509/8766920b/attachment-0001.xls)
> 
> Cheers
> 
> G
> 
> 
> On 19/08/2010, at 5:30 AM, Patrice Rey wrote:
> 
> Hi Nicolas
> 
> The dimension of A (the pre-stress constant) is MPa^-n . s^-1, or ... 10^(-6*n) . s^-1; a bit messy and a common source of errors.
> 
> Common values I use for the continental crust: (5 10^-6) .10^-(6*n); for the lower crust: 8 .10^-(6*n), and for the mantle: 70000.10^-(6*n)
> 
> The scaling factor of A is : (StressScalingFactor^-n) / TimeScalingFactor.
> 
> Cheers
> 
> Patrice
> 
> 
> 
> On 19/08/2010, at 5:00 AM, cig-long-request at geodynamics.org<mailto:cig-long-request at geodynamics.org> wrote:
> 
> 
> ------------------------------
> 
> Message: 3
> Date: Wed, 18 Aug 2010 17:20:19 +0200
> From: Nicolas RIEL <nicolas.riel at free.fr<mailto:nicolas.riel at free.fr>>
> Subject: [CIG-LONG] Non-Newtonian rheology scaling !
> To: cig-long at geodynamics.org<mailto:cig-long at geodynamics.org>
> Message-ID:
> <AANLkTimF7AA1jjOfbcz+QwFTXTpJp-uunMLPp+Jh2Fjn at mail.gmail.com<mailto:AANLkTimF7AA1jjOfbcz+QwFTXTpJp-uunMLPp+Jh2Fjn at mail.gmail.com>>
> Content-Type: text/plain; charset="iso-8859-1"
> 
> Hi,
> 
> I'm encountering some problems when scaling the "A" (creeping parameter) for
> the non-newtonian rheology.
> In gale user manual (2.2.8.2) it is said that the unit of A parameter is *
> s(-1/n).Pa(-1)
> *For other authors the unit of this parameter is most of the time in *
> Pa(-n).s(-1)* or *Pa.s(1/n).*
> 
> I will take an example in order to understand :
> 
> 
> A = 262800* Pa.s(1/n)*
> n = 4*
> 
> *If I want to translate this value for gale, first I have to change the
> units for *s(-1/n).Pa(-1) *by multplying with ^(-1) ?
> 
> Then A unscaled becomes for gale 262800^(-1) = 3.8051e-6
> 
> Based on that and following gale user manual A scaled for gale is 3.8051e-6
> * (10e25)^(1/n) = 6.7574
> However in the dyke example the scaling of A is around 1e-12.
> 
> I'm wondering if there a mistake for the given scaling equation. Maybe this
> equation should be Anew = Aold(10e25)^(-1/n) ?
> 
> When I use this, I obtain Anew = 2.1368e-12 and this works
> 
> Do you have any suggestions about this ?
> 
> Nicolas Riel
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> End of CIG-LONG Digest, Vol 45, Issue 12
> ****************************************
> 
> Associate Professor Patrice F. Rey
> EarthByte Research Group
> School of Geosciences
> The University of Sydney
> +61 2 9351 2067
> patrice.rey at mac.com<mailto:patrice.rey at mac.com>
> patrice.rey at sydney.edu.au<mailto:patrice.rey at sydney.edu.au>
> 
> 
> 
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> 
> Dr Guillaume Duclaux
> 
> Mineral Down Under Flagship & AuScope Grid
> CSIRO Earth Science and Resource Engineering
> 
> Phone: +61 8 6436 8728  | Fax: +61 8 6436 8559  | Mobile:  +61 422 289 732
> 
> guillaume.duclaux at csiro.au<mailto:guillaume.duclaux at csiro.au> | www.csiro.au<http://www.csiro.au/> |
> Address: Australian Resources Research Centre, 26 Dick Perry Avenue, Kensington WA 6151
> 
> PLEASE NOTE
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> 
> Dr Guillaume Duclaux
> 
> Mineral Down Under Flagship & AuScope Grid
> CSIRO Earth Science and Resource Engineering
> 
> Phone: +61 8 6436 8728  | Fax: +61 8 6436 8559  | Mobile:  +61 422 289 732
> 
> guillaume.duclaux at csiro.au<mailto:guillaume.duclaux at csiro.au> | www.csiro.au<http://www.csiro.au/> |
> Address: Australian Resources Research Centre, 26 Dick Perry Avenue, Kensington WA 6151
> 
> PLEASE NOTE
> The information contained in this email may be confidential or privileged. Any unauthorised use or disclosure is prohibited. If you have received this email in error, please delete it immediately and notify the sender by return email. Thank you. To the extent permitted by law, CSIRO does not represent, warrant and/or guarantee that the integrity of this communication has been maintained or that the communication is free of errors, virus, interception or interference.
> 
> Please consider the environment before printing this email.
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> 
> 

Associate Professor Patrice F. Rey
EarthByte Research Group
School of Geosciences
The University of Sydney
+61 2 9351 2067
patrice.rey at mac.com
patrice.rey at sydney.edu.au

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