[aspect-devel] boundary pb

Timo Heister heister at clemson.edu
Tue Sep 16 08:50:08 PDT 2014


Hey Cedric,

what is you boundary condition for the temperature on that boundary (and
does it also contain the perturbation term?)? (it should)

On Tue, Sep 16, 2014 at 11:09 AM, Cedric Thieulot <geogarfield at gmail.com>
wrote:

> Hi all,
>
> Anne, Menno and myself have been trying to run a model very similar to the
> convection-box.prm setup (based after the Blankenbach 1989 paper) albeit
> with a more
> complex rheology. Indeed, the setup involves a nonlinear visco-plastic
> rheology and it kept yielding all afternoon abnormal results in the right
> corner of the box.
> Visually abnormal, but also quantitatively abnormal when compared to the
> same setup ran with my ELEFANT code.
> In order to fix ideas, we decided to start all over again, and ran a few
> timesteps of the convection-box.prm setup … and witnessed the same
> abnormal behaviour for three versions of ASPECT (one from two weeks ago,
> i.e. the virtual box made for the GFZ workshop, one from a few weeks back,
> and one from last december).
> As you know, the convection-box is a buoyancy-driven experiment where the
> temperature field is initially prescribed to be
>  T(x,z)=(1-z)-0.01*cos(pi*x)*sin(pi*x)
> so that one expects the velocity field to be symmetric at t=0  (in
> magnitude, not direction). However attached are some screen captures of
> what we obtain.
> Please keep in mind that we get the convection-box.prm from git (or svn
> for the older version), that we do not modify it at all and that the file
> prescribes free slip on all sides.
> So why does the velocity field display a kink on the right boundary ?
> Also by changing the temperature field to T(x,z)=(1-z)*+*0.01*cos(pi*x)*sin(pi*x)
> , the kink is reversed, as if there was a velocity prescribed on the
> boundary no matter what…
> Do you have any idea where this could come from ? Can someone replicate
> this probem with their version by running 1 timestep of the convection-box
> experiment ?
>
> Kind regards,
>
> Cedric, Anne & Menno
>
>
>
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>



-- 
Timo Heister
http://www.math.clemson.edu/~heister/
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