homogeneous nucleation of liquid droplets & expansion chamber example

[claresinger]

Copy/pasting the notes @slayoo added from our conversation with @AgnieszkaZaba this morning.

• [x] the laboratory paper uses a Normal distribution rather than Lognormal - perhaps worth adding to PySDM
• [x] a new ExpansionChamber environment (featuring perfect gas expansion, but not featuring hydrostatics) instead of using Parcel would help in making the code readable
• [x] new adiabatic_exponent formulae
• [x] a SuperParticleSpawningDynamic base-class could be best to derive from two dynamics: Seeding and HomogeneousLiquidNucleation
• [x] rename SeedingMethods to shared SpawningMethods
• [ ] could we construct a simple adaptive substepping logic by comparing the nucleation rate and the timestep?
• [x] test idea: J_homogeneous table from S&P
• [ ] test idea: long vs. short timestep
• [ ] test idea: S_max for short vs. long timestep
• [ ] test idea: conservation of total water
• [ ] test idea: check droplet number matches expectation from multiplicity of nucleated SDs

The expansion chamber example is aimed to mimic the laboratory experiments described here: https://arxiv.org/abs/2501.01467

[claresinger]

@AgnieszkaZaba @slayoo - Any status update on the super class NewParticle and code restructure to inherit Seeding dynamic from there? Probably with that structure in place I can easily extend to make the HomogeneousLiquidNucleation dynamic. Let me know if you want to call to discuss further!

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 88.30409% with 20 lines in your changes missing coverage. Please review.

Project coverage is 85.24%. Comparing base (17cf24a) to head (7150f84).

Files with missing lines	Patch %	Lines
PySDM/environments/expansion_chamber.py	68.18%	14 Missing :warning:
PySDM/environments/impl/moist_lagrangian.py	88.88%	2 Missing :warning:
.../physics/adiabatic_exponent/moist_leading_terms.py	66.66%	2 Missing :warning:
PySDM/dynamics/homogeneous_liquid_nucleation.py	96.42%	1 Missing :warning:
PySDM/physics/adiabatic_exponent/dry.py	83.33%	1 Missing :warning:

Additional details and impacted files

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  Coverage   85.24%   85.24%            
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  Files         379      389    +10     
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+ Hits         7925     8044   +119     
- Misses       1372     1392    +20     

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