[FLASH-USERS] Expansion of Target

[Klaus Weide]

On Thu, 25 Apr 2019, Brian Kraus wrote:

>                   I am not sure if these shocks affect any dynamics
> from the laser, but it would be nice to properly model a solid that does
> not support these relaxation shocks.

FLASH currently does not track interfaces between materials explicitly, 
and does not know about things such as surface tension or the properties 
of solids such as pressure and tensile forces.  So an initial condition
with a strong pressure gradient somewhere - especially a jump such as
at a solid-gas boundary - will unavoidably lead to some motion.

A workaround that I have used is to "freeze" the solid material until it 
is significantly heated. I don't mean by lowering the initial temperature 
(although that might help, too), but by initially making the interface of 
the solid material act like a domain boundary as far as hydrodynamics is 
concerned. This can be done by using BDRY_VAR and setting it to +1 in the 
solid. After heating (such as by a laser) has started, cells whose 
temperature exceeds some threshold can be released by setting the BDRY_VAR 
value to -1. This can be done every time step in 
Simulation_adjustEvolution, for example.

Klaus