Dust in AstroBEAR - Update 2020/11/02 & 2020/11/09

Objectives

  • Debugging

Progress:

Gas Drag: Did more benchmarking of intermediate calculation steps and they all look fine so still not sure what's going on. I also ran the simulations discussed last time:

  • no wind, just a clump with initial velocity in x → looked fine, did not see the same effect as in the wind+drag simulations
  • Fixed temperature to check the temperature dependence → that's noticeably different. Made a couple of videos: ​1. Normal temperature dependence, ​2. Fixed high temperature (around 2E8K), ​3. Fixed medium temperature (around 2E6K), ​4. Fixed low temperature (around 2E4K). To summarise: Movement looks fine for large T (though I suspect the drag force is still too strong), the movement looks very strange for small T. For small T is looks like the attraction between charged ions in the wind and charged dust grains is so large, that the grains are sucked towards the wind. Potential error sources here: Faulty gas ionisation degree (have checked this before but will again just in case), maybe T is off, drag force too strong, something else? (made a couple of screenshots for the low T case as well with more output steps: ​1 ​2 ​3 ​4 ​5 ​6 ​7

Grain-Grain Collisions: Made quite a bit of progress here, found a lot of smaller errors and the routine now works (previously it crashed because the collision probabilities exceeded 1) but I'm gaining mass here as well just as with the sputtering routine. → Will check the routine which sorts the grains into bins next, if mass conservation is broken, it's most likely because something goes wrong in there. UPDATE: Might have found the bug here, still needs testing but hoping to show some first simulations next week.

Next steps:

  • Continue debugging

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