[FLASH-USERS] split solver, timestepping/refinement and the time accuracy order
Klaus Weide
klaus at flash.uchicago.edu
Tue Apr 23 17:43:32 EDT 2013
On Tue, 23 Apr 2013, Andrea Gatto wrote:
> for stability reasons I find myself forced to reduce the timestep after
> the first call (in the first half of the Strang splitting loop) of the
> source terms when using a split solver in Driver_evolveFlash.F90 .
> This means that the second call of the solver (in the second half of the
> loop) is performed on a different (smaller) timestep.
Hello Andrea,
I am wondering why you want to use the split solver? It seems that
your questions would not even arise if you used the Unsplit variant of
Driver_evolveFlash.F90 .
> Could this cause the Strang splitting scheme accuracy order to be reduced
> from 2 to 1?
Yes, I think so.
> Are there any other problems with this timestep change?
> Could this problem happen also when I force a refinement in a certain
> region during the first call of the source terms?
I think changing the Grid in the middle of one "split timestep" (which
should just be two steps of the same time interval) is asking for trouble;
again, why not go with the simpler Unsplit scheme?
Klaus
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