[aspect-devel] Visco-Plastic material model

Wed May 25 02:21:26 PDT 2016

Hi Juliane,

Excellent timing! I was reading through the model this morning and started wondering about this.
Thanks for the clarification.

Cheers,
Moh.

From: Aspect-devel [mailto:aspect-devel-bounces at geodynamics.org] On Behalf Of Juliane Dannberg
Sent: 25 May 2016 10:00
To: aspect-devel at geodynamics.org
Subject: Re: [aspect-devel] Visco-Plastic material model

John, Mohamed,

Hi Mohamed,

That's correct, but in the case of 2 viscous materials (e.g. Lithospheric mantle and sublithospheric mantle) can you choose dislocation creep for one and diffusion creep for the other?

Ah, currently you can’t do that … you choose dislocation, diffusion or composite form of the viscosity law and that is applied to all fields.

But you can already adjust the prefactors for diffusion and dislocation creep separately for each compositional field. So you could choose the composite rheology for all of the fields, and if you want your material to be dominantly in the dislocation creep regime, you just have to set the diffusion creep prefactor to a very high value. Then the dislocation viscosity will be much lower, and will dominate the flow.
This is also quite reasonable from a numerical and physical point of view, because the dislocation viscosity alone goes to infinity for the strain rate going to zero, so for very low strain rates diffusion creep would limit that.

Cheers,
Juliane

On May 24, 2016, at 12:32 PM, Mohamed Gouiza <M.Gouiza at leeds.ac.uk<mailto:M.Gouiza at leeds.ac.uk>> wrote:

Hi John,

"FYI, each composition can already be assigned different material properties."
That's correct, but in the case of 2 viscous materials (e.g. Lithospheric mantle and sublithospheric mantle) can you choose dislocation creep for one and diffusion creep for the other?

I will start trying it next week and let you know if I encounter any issues.

Regards,
Moh.

Sent from a mobile device

---- John Naliboff wrote ----

Hi Mohamed,

I think loading the values in manually is the way to go, to many different flow law options people may want to use.

FYI, each composition can already be assigned different material properties.  Please try out the material model and let us know what works and does not work!  There will be constant issues to work out with any models using non-linear viscosity in combination with plasticity.

Cheers,
John

On 05/24/2016 02:13 AM, Mohamed Gouiza wrote:
Hi John,

Are you thinking that someone could specify “quartzite” for a specific composition and have the values be loaded in?  My preference is to have the user input the values themselves, as this way the can modify specific values for testing purposes.
I was thinking that one can either choose to specify “Quartzite” and have the values loaded in or input the values manually. But having a table with the different flow laws is an excellent idea.

The most important, in my view, is what is already on your to-do list: strain-weakening, elasticity, and the possibility to assign each composition field with a specific creep law (diffusion, dislocation, or composite).

Cheers,
Moh.

From: Aspect-devel [mailto:aspect-devel-bounces at geodynamics.org] On Behalf Of John Naliboff
Sent: 23 May 2016 18:34
To: aspect-devel at geodynamics.org<mailto:aspect-devel at geodynamics.org>
Subject: Re: [aspect-devel] Visco-Plastic material model

Hi Mohamed,

Elasticity is not currently included, but that is on the summer to-do list.

Pre-defined flow laws - I think the defaults are for the Hirth and Kohlstedt (2003) dry olivine flow laws.

I’m not sure how different pre-defined flow laws could be incorporated into the input file in a straightforward manner.

Are you thinking that someone could specify  “quartzite” for a specific composition and have the values be loaded in?  My preference is to have the user input the values themselves, as this way the can modify specific values for testing purposes.

A list of the flows (including scaled values of ‘A’) would be useful to have somewhere, though.  Others have suggested having a table somewhere on the CIG website.  Does this sound like a good idea?

Cheers,
John

*************************************************
Assistant Project Scientist, CIG
Earth & Planetary Sciences Dept., UC Davis

On May 23, 2016, at 1:06 AM, Mohamed Gouiza <M.Gouiza at leeds.ac.uk<mailto:M.Gouiza at leeds.ac.uk>> wrote:

Hi John,

Thanks you for the quick reply.

Strain-weakening would be very useful indeed.

Is flexure/elasticity of the lithosphere incorporated?

It would also be nice to have predefined rheologies (e.g. Quartzite: Gleason & Tullis (1995); Olivine: Karato & Wu 1993) which can be scaled.

Regards,
Moh.

From: Aspect-devel [mailto:aspect-devel-bounces at geodynamics.org] On Behalf Of John Naliboff
Sent: 20 May 2016 13:56
To: aspect-devel at geodynamics.org<mailto:aspect-devel at geodynamics.org>
Subject: Re: [aspect-devel] Visco-Plastic material model

Hi Mohamed,

The visco-plastic material model is not available in the new release, but should be incorporated into the master version any day now.

Do note that strain-weakening is not incorporated yet, but it will hopefully be soon (before or during hackathon).

I plan to continuously add features to this material model, so please let me know if there is something you would like added.  Alternatively, by all means incorporate a feature into your version of the code and do a pull request!

Cheers,
John

*************************************************
Assistant Project Scientist, CIG
Earth & Planetary Sciences Dept., UC Davis

On May 20, 2016, at 2:25 AM, Mohamed Gouiza <M.Gouiza at leeds.ac.uk<mailto:M.Gouiza at leeds.ac.uk>> wrote:

Hi John,

I am trying to build a Viscoelastic-frictional-Plastic materiel model, to model deformation of a layered lithosphere.
I’ve just seen that you’ve made a Visco-Plastic material model and I wanted to know if it is included in the new release (that I haven’t had time to check yet)

Thank you
Regards

-------------------------------------------------
Mohamed Gouiza, Research Fellow
Basin Structure Group, Institute of Applied Geosciences
University of Leeds, School of Earth and Environment
Leeds,  LS2 9JT, UK
M.Gouiza at leeds.ac.uk<mailto:M.Gouiza at leeds.ac.uk>
+44 7985 782073
-------------------------------------------------

_______________________________________________
Aspect-devel mailing list
Aspect-devel at geodynamics.org<mailto:Aspect-devel at geodynamics.org>
http://lists.geodynamics.org/cgi-bin/mailman/listinfo/aspect-devel

_______________________________________________
Aspect-devel mailing list
Aspect-devel at geodynamics.org<mailto:Aspect-devel at geodynamics.org>
http://lists.geodynamics.org/cgi-bin/mailman/listinfo/aspect-devel

_______________________________________________

Aspect-devel mailing list

Aspect-devel at geodynamics.org<mailto:Aspect-devel at geodynamics.org>

http://lists.geodynamics.org/cgi-bin/mailman/listinfo/aspect-devel

_______________________________________________
Aspect-devel mailing list
Aspect-devel at geodynamics.org<mailto:Aspect-devel at geodynamics.org>
http://lists.geodynamics.org/cgi-bin/mailman/listinfo/aspect-devel

_______________________________________________

Aspect-devel mailing list

Aspect-devel at geodynamics.org<mailto:Aspect-devel at geodynamics.org>

http://lists.geodynamics.org/cgi-bin/mailman/listinfo/aspect-devel

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.geodynamics.org/pipermail/aspect-devel/attachments/20160525/f9f07751/attachment-0001.html>