[aspect-devel] Problem: Iterative advection solver does not converge

[FELIPE ORELLANA ROVIROSA]

 Hi,

     Thanks a lot for your replies.

     Thanks Wolfgang, I would have had a hard time understanding the
magnitude of the residuals, which are proportional to the cell size (here
in m3).

     My system is a brick box, conceptually not too different from the 3D
example. Just different initial boundary conditions for T, and it has
inhomogeneous Dirichlet boundary conditions on top, plus free slip
everywhere else.

     I have already 'mastered' this system on Aspect, using unitary
dimensions for all the quantities. Now I want to make it 'real'. Of course
I have kept an eye on the Ra number.

     The parameters are so many, that I wanted to avoid going one-by-one
changing them from the 3D box example. Now I am paying the price..

     The velocities at the end of my computation start to increase
unphysically, up to several m/s, for I expect them to remain below 1 m/s.

I will try to lower this down..

thanks,

Felipe

On Mon, Jun 6, 2016 at 11:25 AM, Wolfgang Bangerth <bangerth at tamu.edu>
wrote:

> On 06/06/2016 12:50 PM, John Naliboff wrote:
>
>>
>> Ouch - The residual in the last step was 1.99733e+21.  Something is
>> definitely
>> amiss ;)
>>
>
> John already asks all of the right questions, but I did wanted to comment
> on this: the residual is like a right hand side vector, which is an
> integral over cells. The mesh size here is around 1e5 meters, so the
> integral already has a factor of 1e15 just by the volume of each cell.
> Depending on what the average values of the integrand are, 1.997e21 may or
> may not actually be a large residual.
>
> Ultimately, what matters is how it compares to the starting residual.
>
> Best
>  Wolfgang
>
>
> --
> ------------------------------------------------------------------------
> Wolfgang Bangerth               email:            bangerth at math.tamu.edu
>                                 www: http://www.math.tamu.edu/~bangerth/
>
>
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