[FLASH-USERS] Smoothing of Particles over Multiple Blocks

[Chalence Safranek-Shrader]

Hi Community,

I'm running a hydrodynamic simulation with FLASH's built in cosmology 
module, adapted mainly from the pancake test problem. In this problem, 
baryons are represented by a fluid while dark matter is represented by 
discrete particles which only interact gravitationally.

The goal of our simulations is to probe star formation in high redshift 
protogalaxies - this requires extreme resoution (sub parsec) in the 
baryons. The simulation is initialized so that each individual zone has 
one particle in it. However, as the simulation refines, the grid zones 
inevitably far outweigh the number of dark matter particles. This is 
unphysical and causes the particles to act as high gravity accretion 
centers which artificially funnel baryons to them. This is a common 
problem in cosmological simulations and has routinely been solved by 
smoothing the influence of the dark matter particle at some level of 
refinement (or length scale). This is the solution we're searching for 
but are having a difficult time implementing it in FLASH.

Currently there is a particle mapping routine (pt_mapOneParticle, and 
others) which has the capability to smooth a particle over its block, 
but not over multiple blocks. We also considered mapping the particles 
to a lower level of refinement and then prolong that mapping to all its 
child blocks, but there appears to be no routine capable of that either.

Does anyone have any suggestions or solutions to this problem? Any 
thoughts or insight would be extremely helpful.

Thanks very much,

Chalence Safranek