Thanks everyone for your suggestions; I will try adding the hydrostatic term and using Q1P0 elements. Is there a way to set the element to Q1P0 in the code or do I just need to use an earlier version? I'll look forward to using Q2P1 elements too; hopefully things will run better when that is fully implemented.<br>
<br>Regarding documentation, I didn't realize Underworld had it's own documentation until now; I'll look through that as well. Maybe Underworld user manual could be posted on the Gale page (<a href="http://geodynamics.org/cig/software/gale">http://geodynamics.org/cig/software/gale</a>)?<br>
<br>Cheers,<br>Brian<br><br><div class="gmail_quote">On Sat, Sep 24, 2011 at 1:00 PM, <span dir="ltr"><<a href="mailto:cig-long-request@geodynamics.org">cig-long-request@geodynamics.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
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Today's Topics:<br>
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1. Re: Conservation of Mass (Louis Moresi)<br>
<br>
<br>
----------------------------------------------------------------------<br>
<br>
Message: 1<br>
Date: Sat, 24 Sep 2011 21:28:10 +1000<br>
From: Louis Moresi <<a href="mailto:louis.moresi@monash.edu">louis.moresi@monash.edu</a>><br>
Subject: Re: [CIG-LONG] Conservation of Mass<br>
To: laetitia le pourhiet <<a href="mailto:laetitia.le_pourhiet@upmc.fr">laetitia.le_pourhiet@upmc.fr</a>><br>
Cc: <a href="mailto:cig-long@geodynamics.org">cig-long@geodynamics.org</a><br>
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<br>
For your information cig-long readers, Walter, Louise and I had a<br>
conversation around this issue two weeks ago.<br>
<br>
I don't think there are any supporters of Q1Q1 for this particular problem<br>
left any more. Underworld defaults to Q1P0 but provides recovered deviatoric<br>
stress and pressure quantities which mitigate the checkerboard problem. This<br>
can be configured quickly and is at least well-understood and tested.<br>
<br>
Q2P1 would be useful to have next. It is implemented in underworld (and<br>
therefore gale) but there are some shortcomings / bugs left to iron out with<br>
the current integration scheme for PIC and (my guess is that) there are some<br>
outstanding issues with multigrid and some of the processing plugins. I am<br>
not sure about the implementation of the stress / pressure recovery for<br>
these elements although they are likely to be less important.<br>
<br>
Walter was very keen to get this particular element working in gale before<br>
he steps back from active development.<br>
<br>
Louis<br>
<br>
<br>
On Sat, Sep 24, 2011 at 20:16, laetitia le pourhiet <<br>
<a href="mailto:laetitia.le_pourhiet@upmc.fr">laetitia.le_pourhiet@upmc.fr</a>> wrote:<br>
<br>
> Hi Brian and the others,<br>
><br>
> There is not much you can do about that I gave up trying to do such models<br>
> with Gale.<br>
> It is now established Q1Q1 elements are not suited for this kind of<br>
> problems.<br>
> What you can do is to<br>
> 1) Remove the free surface/sky to work with delta rho instead of rho<br>
> 2) Increase the resolution.<br>
><br>
> Basically you should only use these elements for extended thin shit<br>
> problems.<br>
><br>
> The old Q1P0 had other problems, but they could be used to model<br>
> drip/subduction problems.<br>
><br>
> If CIG still wants to spend some time/money on Gale<br>
> It would be usefull to have a switch between elements, like in UW so that<br>
> depending on the model set up we can choose the best suited element.<br>
><br>
> hope this was helpfull<br>
><br>
> Laetitia<br>
><br>
><br>
> On 9/24/11 12:44 AM, Brian Wilson wrote:<br>
><br>
> Hi all,<br>
><br>
> I'm working on a model of lithospheric drip and despite having zero flux on<br>
> the boundaries, I am getting downward velocities with no compensating<br>
> upwelling, which would seem to violate the divergence free condition. Has<br>
> anybody else had a similar problem and/or figured out a solution? I've<br>
> attached a copy of my input file if anyone wants to look at it; everything<br>
> is scaled as follows: distance: km, mass: 10^15 kg, time: m.y.<br>
><br>
> Thanks,<br>
> Brian<br>
><br>
><br>
> _______________________________________________<br>
> CIG-LONG mailing listCIG-LONG@geodynamics.orghttp://<a href="http://geodynamics.org/cgi-bin/mailman/listinfo/cig-long" target="_blank">geodynamics.org/cgi-bin/mailman/listinfo/cig-long</a><br>
><br>
><br>
><br>
> --<br>
> *Dr Laetitia Le Pourhiet*<\n> MCF - Institut des Sciences de la Terre<br>
> Paris - UPMC<\n> tel : <a href="tel:%2B33%201%2044%2027%2058%2083" value="+33144275883">+33 1 44 27 58 83</a><\n> web :<br>
> <a href="http://perso.numericable.com/laetitia.le.pourhiet/index.html" target="_blank">http://perso.numericable.com/laetitia.le.pourhiet/index.html</a><\n><br>
><br>
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--<br>
------------------------------<br>
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</blockquote></div><br>