Averaged inflow velocity

[LasNikas]

The animation below shows a pulse wave propagation scenario (with reference_pressure_in = 5000 and reference_pressure_out = 0). In the upper part, the simulation is performed without averaging the extrapolated inflow velocity. In the lower part, the same simulation is shown, but with the inflow velocity averaged, leading to a more stable simulation.

When no velocity is prescribed at the inflow, the velocity is extrapolated from the fluid domain.
Thus, turbulent flows near the inflow can lead to non-uniform buffer-particles distribution, resulting in a potential numerical instability. Averaging mitigates these effects.

# Without averaged inflow velocity
trixi_include(@__MODULE__, joinpath(examples_dir(), "fluid", "pipe_flow_2d.jl");
              open_boundary_layers=14, domain_size=(2.0, 0.4), tspan=(0.0, 2.0),
              open_boundary_model=BoundaryModelTafuni(),
              pressure=0.0, wcsph=true, particle_spacing=0.02,
              saving_callback=SolutionSavingCallback(dt=5e-3, prefix=""),
              particle_shifting=ParticleShiftingCallback(),
              average_inflow_velocity=false,
              reference_velocity_in=nothing, reference_density_in=nothing,
              reference_velocity_out=nothing, reference_density_out=nothing,
              reference_pressure_in=5000, reference_pressure_out=0)

# With averaged inflow velocity
trixi_include(@__MODULE__, joinpath(examples_dir(), "fluid", "pipe_flow_2d.jl");
              open_boundary_layers=14, domain_size=(2.0, 0.4), tspan=(0.0, 2.0),
              open_boundary_model=BoundaryModelTafuni(),
              pressure=0.0, wcsph=true, particle_spacing=0.02,
              saving_callback=SolutionSavingCallback(dt=5e-3, prefix="averaged"),
              particle_shifting=ParticleShiftingCallback(),
              average_inflow_velocity=true,
              reference_velocity_in=nothing, reference_density_in=nothing,
              reference_velocity_out=nothing, reference_density_out=nothing,
              reference_pressure_in=5000, reference_pressure_out=0)

averaged_velocity_.mp4

Snapshot after 1.5 sec: highlighting more stable simulation even with no-slip BC
(the simulation without averaged inflow velocity fails at 0.11 sec).

[codecov]

Codecov Report

Attention: Patch coverage is 88.88889% with 2 lines in your changes missing coverage. Please review.

Project coverage is 70.49%. Comparing base (785ade6) to head (5eaa528).

Files with missing lines	Patch %	Lines
src/schemes/boundary/open_boundary/mirroring.jl	86.66%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #833      +/-   ##
==========================================
+ Coverage   70.43%   70.49%   +0.05%     
==========================================
  Files         106      106              
  Lines        6867     6884      +17     
==========================================
+ Hits         4837     4853      +16     
- Misses       2030     2031       +1     

Flag	Coverage Δ
unit	70.49% <88.88%> (+0.05%)	⬆️

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.

[LasNikas]

/run-gpu-tests