[aspect-devel] Continental extension model
John Naliboff
jbnaliboff at ucdavis.edu
Fri Oct 21 10:28:11 PDT 2016
Hi Mohamed,
Thanks for the comments on the pull request, I'll take a look once
github is back online.
There is not currently a postprocessor for visualizing the different
creep mechanisms, but it is already on the list of things to do.
Cheers,
John
*************************************************
John Naliboff
Assistant Project Scientist, CIG
Earth & Planetary Sciences Dept., UC Davis
On 10/21/2016 08:42 AM, Mohamed Gouiza wrote:
>
> Hi John,
>
> I added a couple of suggestions to the commit request of the
> continental_extension_cookbook
>
> Thanks for the DG method. I am running the development versions of
> ASPECT and deal.ii but from a month ago or so.
>
> On a different matter, is there a postprocessor that allows to
> visualize the dominant creep law (dislocation vs diffusion) if I
> choose composite flow in my material model?
>
> Cheers,
>
> *From:*Aspect-devel [mailto:aspect-devel-bounces at geodynamics.org] *On
> Behalf Of *John Naliboff
> *Sent:* 20 October 2016 21:53
> *To:* aspect-devel at geodynamics.org
> *Subject:* Re: [aspect-devel] Continental extension model
>
> Hi Mohamed,
>
> The value is indeed related to the fact that there is inflow at the
> base. Many months ago, I was seeing odd behavior in the compositional
> fields and I suspected not having the mantle layer extend well past
> the model base might be one of the reasons.
>
> However, at the moment I can't recall if this alone fixed the issue.
> In theory, the simulation should work fine as long as the mantle layer
> is defined as extending exactly to the model base.
>
> Aside, one way to improve the accuracy of the compositional field
> advection is by using the DG method option for the compositional
> discretization. In the input file I sent you, add the following lines:
> subsection Discretization
> set Use discontinuous composition discretization = true
> subsection Stabilization parameters
> set Use limiter for discontinuous composition solution =
> true # apply the limiter to the DG solutions
> set Global composition maximum = 1.0, 1.0, 1.0, 1.0
> set Global composition minimum = 0.0, 0.0, 0.0, 0.0
> end
> end
>
> To use this option you will need to work of the development version of
> both ASPECT and deal.ii. Let us know if you have any issues getting
> things installed on this front or with using the DG method. If you
> see anything odd in the models, please do not hesitate to email the list!
>
> Last, I just opened a pull request for a cookbook related to this
> input file. You can check out my forked copy ASPECT (branch
> continental_extension_cookbook) if you want to take a look at it
> before it gets merged. Even better, make some comments on the pull
> request!
>
> Cheers,
> John
>
>
> *************************************************
> John Naliboff
> Assistant Project Scientist, CIG
> Earth & Planetary Sciences Dept., UC Davis
>
> On 10/20/2016 08:02 AM, Mohamed Gouiza wrote:
>
> Hi John,
>
> In the continental extension input file that you sent me, the
> mantle compositional field is defined as 70.e3 && y>*-100.e3*
>
> Is the -100.e3 a typo or is it because of the prescribed inflow at
> the base of the model?
>
> Mohamed
>
> *From:*Aspect-devel [mailto:aspect-devel-bounces at geodynamics.org]
> *On Behalf Of *John Naliboff
> *Sent:* 10 October 2016 17:12
> *To:* aspect-devel at geodynamics.org
> <mailto:aspect-devel at geodynamics.org>
> *Subject:* Re: [aspect-devel] Continental extension model
>
> Hi Mohamed,
>
> An example continental extension input file is attached, which
> will be submitted as a cookbook example in the next few days.
>
> In this example, extension is driven by prescribed outflow on the
> sides and inflow at the base. The rheology is dislocation creep
> with different flow laws for the upper/lower crust and mantle.
> Internal friction angle (20 degrees) (20 MPa) are within the range
> of commonly used values. No strain-weakening, but I have a pull
> request open that implements this.
>
> Most extension problems include the asthenosphere, while this
> model only goes down to 100 km. As such, I would only use this
> type of setup for studying early stage extension. Any problems
> examining extension from start to breakup should extend to at
> least 150 km. In this case, one might alter the simple boundary
> conditions I've prescribed.
>
> Hope this helps and let me know you if you have any questions
> about the input file.
>
> Cheers,
> John
>
>
>
>
>
>
> *************************************************
>
> John Naliboff
>
> Assistant Project Scientist, CIG
>
> Earth & Planetary Sciences Dept., UC Davis
>
> On 10/10/2016 12:59 AM, Mohamed Gouiza wrote:
>
> Hi John,
>
> I looked for the continental extension model that you showed
> in the online workshop last month, but couldn’t find it in
> tests/ folder.
>
> I’ve been running several extension models with the
> visco-plastic material model and I am interested in knowing
> the visco-plastic law parameters that you used and how do you
> prescribe the boundary conditions: is the extension rate
> defined the same way as in the crustal deformation example in
> the cookbook by Cedric?
>
> Thank you
>
> -------------------------------------------------
> 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
> -------------------------------------------------
>
>
>
>
>
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