Particle nibbling in XL

This merge request implements particle nibbling in the XL model, in analogy to what is done in COLIBRE.

changed milestone to %Improved black hole model

added EAGLE feature request labels

added 2 commits

• 1153197b - Remove unwanted COLIBRE files
• 4a857158 - Applied code formatting tool

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Ah, thanks. I had thought I had removed these already, but evidently they had sneaked back in...

Any reason we store both spec_angular_momentum_gas and circular_velocity_gas ?

I think at some point there was a request to store the accumulated angular momentum of the BH. It's of course related to circular_velocity_gas, so I think it's not critical, especially if this is not in the current master branch already.

I know I have asked this before but I forgot the answer, in chemistry_transfer_part_to_bpart() is nibble_mass the same as gas mass times nibble_fraction ?

added 1 commit

• 6c42d8e5 - Minor stylistic changes

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And as a last comment: Do we not want the nibbling "on" by default in our XL runs?

Yes, I see no reason not to use it. I have tested it extensively now and it does not give any strange results.

The other changes you made seem fine with me.

added 3 commits

• 4964372f - In the BH swallow, abort early if we are nibbling
• b5828811 - Document the relation between nibble_mass nibble_fraction and gas particle mass.
• 4a8ba8a5 - Remove the variable spec_angular_momentum_gas from the BH particles that was...

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resolved all threads

I have applied the changes.

The only place that needed some care was in the BH feedback preparation. We want angular mometum there so had to undo the multiplication by h that leads to the circular velocity.

added 1 commit

• 9d5fe580 - Switch on the nibbling in all the EAGLE examples and document the change from...

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What is the minimal mass for nibbling you'd recommend we use?

Can I double-check what exactly you mean by the BH feedback preparation wanting angular momentum? Is this in the accretion limiter part, or later where the BH angular momentum tracker is updated?

Minimal nibbling mass should be 0.5 * initial gas particle mass. That number is more or less made up, but it seems a conservative limit, given that we allow particles to grow to 4x the initial mass before splitting. In practice, no particle should get close to this limit.