<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><br></div><div>Hi Charmaine,</div><div><br></div><div><br></div><div>We have a quite mature version of "Underworl-GT" (geothermal) that has been applied to heat flow (and fluid flow in its infancy). We've applied to work at a few surveys, importing in gocad models, etc. O'Neill has been using it too. Dietmar's here next week... we'll have a chat to him about it.</div><div><br></div><div>Thanks</div><div><br></div><div><br></div><div>Steve</div><div><br></div><br><div><div>On 20/10/2010, at 11:00 AM, Charmaine Thomas wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">Hi Walter,<div><br></div><div>I did a series of experiments to get Gale to do pure thermal conductivity problems without having a non-zero velocity boundary applied to the right/left walls, ie velocity=0.</div><div><br></div>
<div>Firstly I tried turning off the Stokes flow and the uzawa condition, and although everything ran very smoothly and quickly, it took ridiculously big timesteps, despite having an explicitly set 'dt' (I assumed later that Stokes flow has to be turned on for this parameter to kick in?). This predictably resulted in very high temperatures. I had to do this experiment because I was dealing with non-newtonian rheologies, and needed to model a time of quiescence in my crust. </div>
<div><br></div><div>Finally I found the best option was to leave the Stokes/uzawa stuff turned on and to apply either a very low strain-rate, or set the right/left velocities as zero, but also have a right and left wall stress boundary condition. This second option runs smoothly even with non-newtonian rheologies, and takes more reasonably sized timesteps - I could also try changing the dtfactor to speed things up. So does this method sound more reasonable? Is there a better way?</div>
<div><br></div><div>Cheers,</div><div><br></div><div>Charmaine Thomas</div><div>School of Geosciences | University of Sydney</div><div><br><br><div class="gmail_quote">On Wed, Oct 20, 2010 at 10:21 AM, Walter Landry <span dir="ltr"><<a href="mailto:walter@geodynamics.org">walter@geodynamics.org</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div class="im"><<a href="mailto:Guillaume.Duclaux@csiro.au">Guillaume.Duclaux@csiro.au</a>> wrote:<br>
</div><div class="im">> Indeed.<br>
><br>
> But, shouldn't it be possible to solve purely thermal problem with<br>
> Gale? (let's pretend the thermal expansion is null is Nicolas'<br>
> problem). ie a sill at a temperature of 1000 K has intruded a mass<br>
> of rock at constant temperature (600 K) and I want to simulate the<br>
> thermal evolution of the system as I change the thickness of the<br>
> dyke or the radiogenic heat production of one or the other material.<br>
<br>
</div>It is possible to do pure thermal conductivity problems with Gale.<br>
You have to turn off all of the Stokes flow stuff, but it does seem to<br>
work.<br>
<div class="im"><br>
> To ensure the solver timestepping is not missing the temperature<br>
> perturbation timescale, how should the time be scaled?<br>
> I guess viscosity doesn't matter if the problem is purely thermal,<br>
> but as soon as the thermal expansion is on, some body forces act too<br>
> creating some 'slow' displacement.<br>
<br>
</div>For this particular case, the displacement is so slow that it can be<br>
neglected. If you still want to solve the Stokes flow, then you can<br>
set the timestep explicitly with 'dt' (see Appendix A.1.4). Gale<br>
should probably take the thermal diffusivity into account when<br>
deciding upon a timestep, but it does not do that now.<br>
<div class="im"><br>
Cheers,<br>
Walter Landry<br>
<a href="mailto:walter@geodynamics.org">walter@geodynamics.org</a><br>
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