[FLASH-USERS] Boundary conditions of the Multigrid Solver/Gravity

[Josef Stöckl]

Hello,

I'm having a small problem with the Multigrid solver or the Gravity 
Multigrid unit respectively. According to the manual, the supported 
boundary conditions for the Multigrid gravity unit are "periodic, 
Dirichlet, given-value, and isolated". However, when I try to use any 
value other than periodic or isolated for the "grav_boundary_type", I 
get the following error message:

Gravity_init: unrecognized or unsupported gravity boundary type

Looking at Gravity_init.F90 one can see that the routine only allows 
isolated or periodic at the moment. So I'm wondering if the other 
boundary conditions are still to be implemented or if there is any 
version with those enabled available?

I also wonder, if it is possible to have independent boundary conditions 
for the Hydro, Gravity and Particles units? So far I have found that the 
[xyz][lr]_boundary_type controls the overall boundary conditions for the 
Hydro, but the gravity part of the Hydro is controlled by 
grav_boundary_type (which makes a lot of sense). In gr_hgMapBcType.F90 
of the Multigrid solver however only very few of the possible 
combinations of these two settings are handled. So I'm wondering, if it 
would be possible to extend this to handle those settings more 
independently/generally or if there were some problems arising when 
adapting this routine to accept more cases?

Would it require a great change in the MG solver to e.g. combine a Hydro 
"outflow" (or inflow) condition, so that material with low density and 
temperature can come in and out of the computational domain, with a 
gravity "periodic" condition?

Thanks in advance and best regards,

Josef
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