[aspect-devel] Morency-Dorin with free surface

Payman Janbakhsh payman.janbakhsh at mail.utoronto.ca
Wed Oct 26 08:37:50 PDT 2016 

Thanks John

Payman



Sent from my Samsung Galaxy smartphone.


-------- Original message --------
From: John Naliboff <jbnaliboff at ucdavis.edu>
Date: 2016-10-25 7:18 PM (GMT-05:00)
To: aspect-devel at geodynamics.org
Subject: Re: [aspect-devel] Morency-Dorin with free surface

Hi Payman,

Sounds good and please do keep us updated … many issues you run into are likely of broader interest the community.

Cheers,
John

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


On Oct 25, 2016, at 11:29 AM, Payman Janbakhsh <payman.janbakhsh at mail.utoronto.ca<mailto:payman.janbakhsh at mail.utoronto.ca>> wrote:

Hi John
I just installed the new dealii and updated aspect. Now I can run visco-plastic  model.
With Morency i had used max nonlinear iterations set to 200 before. With these new updates I will try both models and see if any improvements to Morency model with free surface.
Cheers
Payman



Sent from my Samsung Galaxy smartphone.


-------- Original message --------
From: John Naliboff <jbnaliboff at ucdavis.edu<mailto:jbnaliboff at ucdavis.edu>>
Date: 2016-10-24 12:20 PM (GMT-05:00)
To: aspect-devel at geodynamics.org<mailto:aspect-devel at geodynamics.org>
Subject: Re: [aspect-devel] Morency-Dorin with free surface

Hi Payman,

Intrinsically, any highly non-linear rheology can easily produce solver issues and unexpectedly large velocities.  However, maybe there is something about Morency-Doin that is particularly unstable?

Perhaps give the visco-plastic model a shot and if the issues still persist then a closer look at the initial conditions is warranted. As a guide, the continental extension cookbook I sent around via email uses the visco-plastic material model.

Also, for the iterated Stokes solver, what is your convergence limit and how many non-linear iterations does it take to reach this value?

Cheers,
John


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


On 10/23/2016 11:06 AM, Mohamed Gouiza wrote:
Hi Payman

The visco plastic material model is no the same as the Druker model.  The visco plastic material model does allow for multiple compositional fields.
You should look it up in the ASPECT manual.

Cheers
Mohamed

---- Payman Janbakhsh wrote ----

If you are referring to druker-prager material model, yes. But I would need multiple compositions. My understanding is druker model only takes one composition.

payman

-----Original Message-----
From: Aspect-devel [mailto:aspect-devel-bounces at geodynamics.org] On Behalf Of Jonathan Perry-Houts
Sent: October 22, 2016 10:31 PM
To: aspect-devel at geodynamics.org<mailto:aspect-devel at geodynamics.org>
Subject: Re: [aspect-devel] Morency-Dorin with free surface

Have you looked at the "visco plastic" material model?

-JPH

On 10/22/2016 6:27 AM, Payman Janbakhsh wrote:
> Thanks Jonathan,
> I have tried no-slip as well as tangential side boundary velocities but not much difference. I always keep surface vertical projection set to vertical when choosing top free surface. I even increased temperature polynomial degree to 3 to increase the accuracy.
> Then I set thermal expansivity to zero to simplify the problem a bit. so it kept going for few time steps then froze again trying to solve Stokes systems.
> I have noticed this happens when RMS velocities starts going up drastically . I have to figure out why velocities become so unphysical.
> The whole purpose of using this material model was to incorporate a visco-plastic rheology to 3D problems. So need to find my way around to get there.
> Any help is much appreciated from anyone.
>
> Cheers
>
> Payman
>
> -----Original Message-----
> From: Aspect-devel [mailto:aspect-devel-bounces at geodynamics.org] On
> Behalf Of Jonathan Perry-Houts
> Sent: October 21, 2016 8:33 PM
> To: aspect-devel at geodynamics.org<mailto:aspect-devel at geodynamics.org>
> Subject: Re: [aspect-devel] Morency-Dorin with free surface
>
> Hi Payman,
>
> I haven't tried the Morency-Doin with a free surface, but it's caused me trouble in the past in relatively simple models with similar setups to the original Morency & Doin paper on which it's based. -- Point being that the material model is finnicky, and I'm not surprised it's having trouble.
>
> A few thoughts:
>
> Maybe no-slip on the sides is not a good choice, since the top is unconstrained? This shouldn't be a problem, but who knows. Maybe worth playing with?
>
> Using:
>>  subsection Free surface
>>    set Surface velocity projection = vertical  end
> sometimes helps stabilize free surfaces. Failure on the first time step makes this an unlikely cause for your problem, but maybe worth a try.
>
> You mentioned that your model is 2D, so this isn't a problem for now,
> but keep in mind that the Morency-Doin model shouldn't be applied to
> 3D models. The formation of the second invariant of the strain rate
> tensor in the paper has never made sense to me, and so it's not
> generalized to three dimensions in the code (which reminds me, I
> should add an assertion that makes sure this is the case. Not sure how
> I missed that
> before!) -- Any insight from someone else to what the authors meant by
> equation (4) in the paper (Morency and Doin, “Numerical Simulations of
> the Mantle Lithosphere Delamination.”) would be helpful! (e.g. is it a
> weird index notation I'm not familiar with?)
>
> I think that equation, as implemented in the code, is almost certainly wrong. I included it for consistency with the paper after discussions with Timo and Wolfgang like two years ago. Perhaps try replacing it with the actual second invariant and try again?
> (
> https://github.com/geodynamics/aspect/blob/master/source/material_mode
> l/morency_doin.cc#L104
> )
>
> Beyond that I don't know what to tell you. Your parameters sound reasonable from what you described. Keep us updated on what works! I'd love to get that material model working for more than just a cookbook!
>
> Cheers,
> JPH
>
> On 10/21/2016 01:48 PM, Payman Janbakhsh wrote:
>> Hi John
>>
>> 2D , delamination, geometry aspect ration of 2x1 , free top surface,
>> other boundaries zero velocity.
>>
>> Linear temperature profile within the upper 100km and lower 100km and
>> a constant T in between.
>>
>> 25km upper crust, 30km lower crust, a weak zone within the lower
>> crust( with a lower activation energy compare to the enclosing lower
>> crust, so can set off the delamination).
>>
>> Have tried different reasonable densities and activation energies for
>> every layer except mantle.
>>
>> Also have put Boundary composition model as : Initial composition  .
>> not sure if this is correct.
>>
>> Running with IMPES or iterated Stokes made no difference
>>
>> Also velocity polynomial set to 2 and other polynomials set to 1
>>
>> also have turned off Local conservative discretization
>>
>>
>>
>> cheers,
>>
>>
>>
>> payman
>>
>>
>>
>> *From:*Aspect-devel [mailto:aspect-devel-bounces at geodynamics.org] *On
>> Behalf Of *John Naliboff
>> *Sent:* October 21, 2016 3:36 PM
>> *To:* aspect-devel at geodynamics.org<mailto:aspect-devel at geodynamics.org>
>> *Subject:* Re: [aspect-devel] Morency-Dorin with free surface
>>
>>
>>
>> Hi Payman,
>>
>> The Morency-Dorin material model should not have intrinsic problem
>> with handling a free surface.  The issue is likely related to some
>> other aspect of your model design.  What type of processes are you modeling?
>>
>> Cheers,
>> John
>>
>>
>> *************************************************
>>
>> John Naliboff
>>
>> Assistant Project Scientist, CIG
>>
>> Earth & Planetary Sciences Dept., UC Davis
>>
>> On 10/21/2016 12:17 PM, Payman Janbakhsh wrote:
>>
>>     Hi
>>
>>     Does Morency-Dorin material model have difficulty with free surface?
>>
>>     My models get stuck at solving Stokes system even at step zero when
>>     I switch top boundary to free surface.
>>
>>     I have set CFL to 0.1 and theta to 0.7 even chanh3d max time step to
>>     1000 but still same issue. I have all other boundaries set to no
>>     slip boundaries
>>
>>
>>
>>     Thanks
>>
>>     Payman
>>
>>
>>
>>
>>
>>
>>
>>     Sent from my Samsung Galaxy smartphone.
>>
>>
>>
>>
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>>
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