Dust in AstroBEAR - Update 2020/08/10

Objectives

  • Debug the processing routines
  • Continue with the grain-grain collisions

Progress:

I'm somewhat confident that the gas drag is now working correctly. There were a couple of smaller issues in the routines (e.g. wrong units) and I had accidentally counted the ion impacts twice instead of counting ions impacts and electron impacts once each. With the updates, it now looks like the drag might be ok or at least I can't see anything obviously wrong with it:

A couple of things to note here:

  • no matter how long I ran the simulations or with which initial dust grain size distributions, it seems the bug where the dust number density just explodes at some point is gone, as is the NAN error
  • the RK routines also don't throw any timestep related errors indicating that the equations used so far are not too stiff which is good!
  • there's some ​pile-up happening in the centre cell row towards later timesteps; probably happening because there's not dust pressure as discussed previously…
  • there are some ​numerical issues at the start in regions where the dust and gas have not yet interacted with each other significantly; probably also because of lack of dust pressure so no y-velocity yet in those dust fields…

Up Next:

  • Do the same sort of study with the plasma drag
  • Debug sputtering routines
  • Implement collisions (see theory notes from ​last week)

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