[aspect-devel] strain rate corner values and velocity boundary conditions

[Thomas Geenen]

he Timo,

for the lithostatic boundary conditions you will have to integrate the
density (Temperature) to get a proper pressure profile.
depending on your scenario this can be done one time (for instance when you
also prescribe the temperature at the boundary) or should be recomputed.
this type of boundary condition only works when the flow is more or less 1D
close to the boundary and the temperature profile as well.

its (not surprisingly) important to make the integration consistent with
the way the buoyancy is computed

@Anne in your scenario i suppose you also want to have a plate with
constant thickness(age) at the boundary?


cheers
Thomas


On Sun, Nov 3, 2013 at 12:44 AM, Timo Heister <heister at clemson.edu> wrote:

> Dear Anne,
>
> (and back to the list)
>
> > Thanks so much for the patch! I've tried it (only 1 run yet, so not
> thoroughly) and now I get what we want (top figure instead of bottom
> figure).
>
> excellent. If nobody else complains about the format, I will check this in
> soon.
>
> > I've also attached the output file (the model is a bit different from
> the one I sent you). The inputfile was set to a maximum of 200 nonlinear
> iterations, but this is an educated guess of the needed number of
> iterations, usually I use a criterion based on the difference in solution
> for stopping the nonlinear iterations.
>
> Oh, this made me realize that the "iterated Stokes" solver has no
> automatic stopping criterion. I just implemented this. See the new
> "Nonlinear solver tolerance" variable.
>
> > Also, while we're on the subject of boundary conditions (I hope you
> don't mind me asking), it would be very nice to have open boundary
> conditions (imposing a lithostatic pressure condition for the normal
> stress). This would be very useful in mantle models as free slip boundaries
> have been shown to affect mantle flow. I have attached a paper discussing
> this (Chertova et al. 2012).
>
> Thomas Geenen is one of the authors.
>
> @Thomas: if I understand this correctly, you 1. set the tangential
> component of the velocity to zero (Anne, you can do that already) and
> 2. set the stress on the boundary to the lithostatic pressure. Is that
> correct? Are those pressure values set by the user or updated from the
> computation?
>
> > Or do you want me to post this on the mailing list?
>
> Yes (and I just did). :-)
>
> --
> Timo Heister
>
> https://urldefense.proofpoint.com/v1/url?u=http://www.math.clemson.edu/~heister/&k=dsHy%2FVymniCD0osh6tze%2Fw%3D%3D%0A&r=vnv0lsnwGqqpauack1JMxQ%3D%3D%0A&m=z9hze3U4YXlzafuMmng1UpLKmJ%2FmLDkgp2xumawYvjM%3D%0A&s=7c15a77be3a7ef1cec363a10b3aebeea8753102556e3407ce8e5f494ef6c8618
>
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