[FLASH-USERS] boundary conditions for a constant gravity case

[Kris Murawski]

Hello everyone,

after few years break I just resumed working with Flash 3.1. My 
intention is
to simulate a magnetized atmosphere which is stratified by a constant 
gravity field.
Ideally, I would like to implement a sort of transparent-like (for 
outgoing waves)
boundary conditions along the action of  gravity. I have found several 
options as

grav_boundary_type = "isolated"
grav_boundary_type = "hydrostatic"
grav_boundary_type = "hydrostatic+nvout"
grav_boundary_type = "hydrostatic+nvdiode"

which I put into flash.par. Unfortunately, none of the above works as I 
would wish so,
and some numerically induced flow results at the boundaries.

An alternate solution may be to implement "user" boundary conditions but
I am not able to find any example of that in Flash. Such conditions 
worked pretty
well for outgoing signals in other codes I used so far.

I wonder whether someone has come across a similar problem with Flash
and would appreciate your hand in solving my problem. Thank you in advance
for that.

Best flashing,

Kris