[aspect-devel] Negative pressure

[Wolfgang Bangerth]

On 03/09/2016 07:51 PM, Lev Karatun wrote:
>
> For the model with a fairly simple setup (2D box, influx from the sides of the
> model, outflux from the bottom, no free surface) I'm getting negative pressure
> values in the middle of the lithosphere. Could you please give me an idea of
> what could be the reason for it?

The Stokes equations only determine the pressure up to a constant. So at the 
end of each time step, we normalize it: we either make sure that its average 
value over the entire domain is zero, or its average value over the top 
surface is zero. It seems like you have chosen the first of these options. 
This may result in a negative pressure in the domain.

Best
  W.

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Wolfgang Bangerth               email:            bangerth at math.tamu.edu
                                 www: http://www.math.tamu.edu/~bangerth/