[aspect-devel] Velocity boundary conditions - lithosphere ext/compression

Wed Jul 5 11:57:03 PDT 2017

Hi Phil,

Great, glad you found the source of the error!

An cookbook discussing lithospheric extension or compression with the 
upper mantle would be helpful for a large group of users. Specifically, 
the issue of how to setup and maintain adiabatic geotherms is quite 
tricky. Some groups have used a high conductivity asthenosphere (myself 
included), but the ideal solution is to use adiabatic and shear heating.

For simplicity, let's reserve that conversation for a separate 
discussion on this mailing list or an issue on the github page.

Cheers,
John

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

On 07/05/2017 05:23 AM, HERON, PHILIP J. wrote:
>
> Hi John,
>
>
> I'm getting some stability now through an error in my implementation 
> of asthenosphere rheology properties. Simple error!
>
>
> I'll have a play around for a while and see what errors pop up - 
> hopefully can work this into a cookbook as it is a simple extension of 
> the continental_extension.prm
>
>
> Thanks for your help, will let you know if I run into any other problems.
>
>
> Phil
>
> ------------------------------------------------------------------------
> *From:* Aspect-devel <aspect-devel-bounces at geodynamics.org> on behalf 
> of HERON, PHILIP J. <philip.j.heron at durham.ac.uk>
> *Sent:* 04 July 2017 23:26:20
> *To:* aspect-devel at geodynamics.org
> *Subject:* Re: [aspect-devel] Velocity boundary conditions - 
> lithosphere ext/compression
>
> Hi John,
>
>
> Thanks for the reply - I will look at implementing some of these 
> suggestions. I've already tried playing around with the velocities, to 
> no success.
>
>
> I will try to use a different seed to localize the deformation. An 
> idea was to simply expand the continental extension model, however, 
> this seems like it may require a bit more tweaking.
>
>
> I am interested in continental collision, intraplate deformation 
> (benchmarking my own work with other codes) and indeed continental 
> extension. I have been using the numerical code SOPALE for a while, so 
> it would be interesting to me to be able to reproduce certain 
> established papers of lithosphere deformation that use such a code 
> (and similar). For instance, to be able to produce Huismans and 
> Beaumont (Nature, 2011) paper, or the work you did with Susanne in 2015.
>
>
> I can dig out what benchmarks for such endeavours would be required.
>
>
> I'll apply those changes and get back to you!
>
>
> Cheers,
>
>
> Phil
>
> ------------------------------------------------------------------------
> *From:* Aspect-devel <aspect-devel-bounces at geodynamics.org> on behalf 
> of John Naliboff <jbnaliboff at ucdavis.edu>
> *Sent:* 04 July 2017 21:03:37
> *To:* aspect-devel at geodynamics.org
> *Subject:* Re: [aspect-devel] Velocity boundary conditions - 
> lithosphere ext/compression
> Hi Philip,
>
> I ran the model and the velocities certainly are showing interesting 
> behavior. Over time the velocity magnitudes increase, but the flow 
> pattern is basically reversing at each visualized output (1 Myr 
> intervals).
>
> While the velocity boundary conditions are constant, this change in 
> flow pattern appears to reflect that different portions of the 
> lithosphere (sides vs interior) are alternating between moving and up 
> and down. These vertical motions are swamping out the signal from the 
> applied velocity boundary conditions along the side walls.
>
> In some ways this kind of behavior looks similar to "drunken seaman" 
> behavior (instability associated with free surface), but I don't think 
> that is the case. Rather, I think the model is having trouble to 
> localize large-scale deformation in the lithosphere and this is part 
> of the response. Significantly, I noticed that in the parameter file 
> the velocities may be a bit lower than intended. The variable "cm" is 
> set to "0.001". With the other specified values this gives a 
> convergence velocity of 0.1 cm/year applied on each side in the upper 
> 120 km. This value is quite low for continental convergence and I 
> think if you increase this value to 1 cm/year it may eliminate some of 
> the anomalous behavior. I would also try decreasing the CFL number to 
> 0.2 or 0.1.
>
> Aside from trying those fixes, may I ask if there is a specific end 
> goal of these models? In other words, is this experiment designed to 
> produce a model of long-term continental shortening? If so, different 
> initial conditions may help.
>
> If the goal is indeed to model some form of long-term convergence 
> (continental collision, subduction, ...), is there a particular prior 
> study (or studies) you have in mind? Always happy to help reproduce 
> prior work, which can then be added as benchmarks cases to the ASPECT 
> repository. A number of us are currently working on subduction 
> problems, so lots of information, ideas, tips and parameter files to 
> share.
>
> A note to all new or potential ASPECT users - the offer to help with 
> reproducing prior studies or discussing ideas for new setups is open 
> to everyone.
>
> Cheers,
> John
>
> *************************************************
> John Naliboff
> Assistant Project Scientist, CIG
> Earth & Planetary Sciences Dept., UC Davis
> On 07/04/2017 07:36 AM, HERON, PHILIP J. wrote:
>>
>> Hi John,
>>
>>
>> thanks for the reply - I've attached the log.txt for the prm file I 
>> sent, along with the error output.
>>
>>
>> I have tried and played around with a great number of parameters to 
>> try and get this to work, but I think it is good to get some outside 
>> perspective.
>>
>>
>> Point 1 - thanks for that, I've applied that change to the models.
>>
>>
>> Point 2 - the vertical sides seems to be immune to the fluctuating 
>> velocity, the interior of the model has the blow up in velocity.
>>
>>
>> Point 3 - I'm just running a fixed mesh model now to see where it 
>> gets to. Will keep you posted.
>>
>>
>>
>> Furthermore, I'm going to run a series of tests on reference 
>> viscosity after noticing this post:
>>
>>
>> https://github.com/geodynamics/aspect/issues/1814
>>
>> Issues with linear solver convergence due to choice of Reference 
>> viscosity · Issue #1814 · geodynamics/aspect 
>> <https://github.com/geodynamics/aspect/issues/1814>
>> github.com
>> I've had some issues with choosing the "right" reference viscosity 
>> (in models with varying viscosity) in order to get convergence of the 
>> linear system and was wondering if there might be some way o...
>>
>>
>>
>>
>>
>>
>> Philip J. Heron
>> Junior Research Fellow
>> Dept. of Earth Sciences
>> Durham University
>> web: http://philheron.com <http://philheron.com/>
>>
>> ------------------------------------------------------------------------
>> *From:* Aspect-devel <aspect-devel-bounces at geodynamics.org> on behalf 
>> of John Naliboff <jbnaliboff at ucdavis.edu>
>> *Sent:* 04 July 2017 01:22:47
>> *To:* aspect-devel at geodynamics.org
>> *Subject:* Re: [aspect-devel] Velocity boundary conditions - 
>> lithosphere ext/compression
>> Hi Philip,
>>
>> Yes, certainly happy to help on this front! A few things to discuss.
>>
>> 1. Unrelated to your issue, I completely forgot that there is a small 
>> bug with the heat production term in this cookbook that Anne Glerum 
>> pointed out to me a week or two ago. This will cause the crust to 
>> cool more rapidly than it should over time, but it is not readily 
>> apparent over 10's of Myr with advection on. This is unrelated to the 
>> anomalous velocities in your model, but I will push a fix for this 
>> this evening or tomorrow morning. Apologies to all who are currently 
>> using the cookbook example. The quick fix is to change the "Initial 
>> concentrations crust" parameter from 1 to 1e6. Alternatively, the 
>> "fix" I'll push tomorrow will allow you to set different constant 
>> heating rates for each compositional layer (see "compositional 
>> heating" method).
>>
>> 2.Onto your issue. I've run a similar extension model (1000 x 600 km) 
>> with similar boundary conditions along the sides (balanced inflow 
>> outflow) and the velocity field was stable over time. Are your 
>> horizontal velocities fluctuating throughout the model or near the 
>> vertical sides?
>>
>> 3. In similar models I used a fixed mesh (no AMR). Have you tried the 
>> model with a fixed mesh? Very likely to be unrelated, but might be 
>> worth using a fixed mesh to see if the error occurs at a similar time 
>> and place in the model.
>>
>> 3. I'm running your parameter file now, but in the meantime can you 
>> send the log.txt file from the output folder?
>>
>> Regardless of the root issue, we can get this worked out quickly. If 
>> the issue is not readily apparent, we can start from a similar 
>> working input file and compare the differences.
>>
>> Thanks for sending in this question to the "devel" email list. Really 
>> helpful for others to see where issues are cropping up!
>>
>> Cheers,
>> John
>> *************************************************
>> John Naliboff
>> Assistant Project Scientist, CIG
>> Earth & Planetary Sciences Dept., UC Davis
>> On 07/03/2017 08:14 AM, HERON, PHILIP J. wrote:
>>>
>>> Hello all,
>>>
>>>
>>> I was just extending the 'continental_extension.prm' cookbook to 
>>> include sub-lithosphere mantle, and have ran into issues of 
>>> convergence. I wonder if anyone on the group could help!
>>>
>>>
>>> I've attached the extended cont extension model, I was wondering if 
>>> anyone could point me in the right directions of how to get it to 
>>> converge. The issue is that after 10-15 timesteps velocities within 
>>> the model start to blow up.
>>>
>>>
>>> I feel that the temperature profile initially is fine. Although 
>>> applying a variable horizontal velocity to the boundary, the initial 
>>> horizontal velocity field is smooth. However, almost immediately the 
>>> horizontal velocity starts to fluctuate.
>>>
>>>
>>> Are there better techniques to be able to get this  model to 
>>> converge? Am I missing something simple? I've played around with a 
>>> few different things but with little luck.
>>>
>>>
>>> Thanks in advance!
>>>
>>>
>>> Phil
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> Philip J. Heron
>>> Junior Research Fellow
>>> Dept. of Earth Sciences
>>> Durham University
>>> web: http://philheron.com <http://philheron.com/>
>>>
>>>
>>>
>>> _______________________________________________
>>> Aspect-devel mailing list
>>> Aspect-devel at geodynamics.org
>>> http://lists.geodynamics.org/cgi-bin/mailman/listinfo/aspect-devel
>>
>>
>>
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>
>
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