[aspect-devel] steady state problem

[cedric thieulot]

Dear all, 

we are currently looking at benchmark-type problems and we are only interested in the steady state of the system. 
Long story short, we would like for instance to run the Blankenbach experiment (i.e. convection-box.prm) and arrive at steady state 
as fast as possible since we are not interested in the time evolution of the model: ideally we would like to arrive after 1 timestep at the 
steady state solution, or in other words we would like to zero the \rho c_p dT/dt term in the heat transport equation. 
We have (naively) tried this approach by zeroing the term   bdf2_factor * scratch.phi_field[i] * scratch.phi_field[j])in advection.cc <http://advection.cc/> .

Unsurprisingly, this did not work and the code aborted. Instead of zeroing the term, we tried placing in front of it a coefficient alpha=0.5
but this lead to a temperature field which on average was twice as large as the initial one. (if alpha=0.25, then it is approx 4times larger).
We suspect that this alpha coefficient of ours probably should come in somewhere else too (preconditioner?) but after many hours of trial
and error we could not figure it out. 
What are we missing here, is there a simple way to achieve what we want? 

Cheers, and good week-end to all, 

Ludovic & Cedric

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