Add variable smoothing length

[LasNikas]

Preparation for #735 and #652

[codecov]

Codecov Report

Attention: Patch coverage is 49.03846% with 53 lines in your changes missing coverage. Please review.

Project coverage is 69.95%. Comparing base (f8ea678) to head (4278290).

Files with missing lines	Patch %	Lines
src/schemes/fluid/fluid.jl	50.00%	10 Missing ⚠️
src/schemes/boundary/system.jl	0.00%	7 Missing ⚠️
src/general/corrections.jl	14.28%	6 Missing ⚠️
src/schemes/fluid/surface_tension.jl	0.00%	6 Missing ⚠️
src/schemes/fluid/viscosity.jl	50.00%	5 Missing ⚠️
...fluid/weakly_compressible_sph/density_diffusion.jl	0.00%	4 Missing ⚠️
test/systems/solid_system.jl	0.00%	4 Missing ⚠️
src/preprocessing/particle_packing/system.jl	0.00%	3 Missing ⚠️
src/schemes/boundary/open_boundary/system.jl	0.00%	2 Missing ⚠️
src/preprocessing/particle_packing/rhs.jl	0.00%	1 Missing ⚠️
... and 5 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #736      +/-   ##
==========================================
- Coverage   69.98%   69.95%   -0.04%     
==========================================
  Files          96       96              
  Lines        6170     6203      +33     
==========================================
+ Hits         4318     4339      +21     
- Misses       1852     1864      +12     

Flag	Coverage Δ
unit	69.95% <49.03%> (-0.04%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[svchb]

In its current form it breaks:

• corrections

pressure_acceleration needs to be adjusted.

[svchb]

wcsph/rhs.jl: grad_kernel = smoothing_kernel_grad(particle_system, pos_diff, distance, particle)
wcsph/density_diffusion.jl: grad_kernel = smoothing_kernel_grad(system, pos_diff, distance, particle)
pressure_acceleration.jl: W_b = smoothing_kernel_grad(neighbor_system, -pos_diff, distance, neighbor)

[LasNikas]

The dam_break_2d_corrections.jl tests fail (instability detected). I have no idea why @svchb and @efaulhaber

Test Summary:                                 | Pass  Fail  Total     Time
dam_break_2d.jl with corrections              |   33     3     36  1m31.7s
  continuity_reinit                           |    3            3     7.7s
  gradient_continuity_correction              |    3            3     7.0s
  gradient_summation_correction               |    3            3     7.6s
  no_correction                               |    3            3     5.3s
  shepard_kernel_correction                   |    3            3     6.8s
  blended_gradient_continuity_correction      |    3            3     7.0s
  mixed_kernel_gradient_summation_correction  |    2     1      3    12.2s
  akinci_free_surf_correction                 |    3            3     5.5s
  kernel_correction_summation_correction      |    2     1      3     7.7s
  mixed_kernel_gradient_continuity_correction |    2     1      3     9.5s
  kernel_correction_continuity_correction     |    3            3     7.4s
  blended_gradient_summation_correction       |    3            3     7.7s

[LasNikas]

/run-gpu-tests

[LasNikas]

/run-gpu-tests

[LasNikas]

/run-gpu-tests