Change default wave speed for Local Lax-Friedrichs

[DanielDoehring]

See #2273

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Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 96.66%. Comparing base (c3cee00) to head (abc9078). Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2458   +/-   ##
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  Coverage   96.66%   96.66%           
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  Files         507      507           
  Lines       42011    42011           
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  Hits        40609    40609           
  Misses       1402     1402           

Flag	Coverage Δ
unittests	96.66% <100.00%> (ø)

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[DanielDoehring]

@ranocha This is good from my side - but it would be good to get a second pair of eyes looking at test_unit and test_type.

[tristanmontoya]

I'm not arguing against making the change, and this has perhaps been pointed out before, but it's interesting to see that the "conservative" wave speed estimate is not just something from the beginning of Trixi.jl, but actually comes from how the wave speed is computed in FLEXI:

https://github.com/flexi-framework/flexi/blob/9a6bd75fde2f410df93bb996e86cd79d84e2ffdc/src/equations/navierstokes/riemann.f90#L580

[DanielDoehring]

I'm not arguing against making the change, and this has perhaps been pointed out before, but it's interesting to see that the "conservative" wave speed estimate is not just something from the beginning of Trixi.jl, but actually comes from how the wave speed is computed in FLEXI:

https://github.com/flexi-framework/flexi/blob/9a6bd75fde2f410df93bb996e86cd79d84e2ffdc/src/equations/navierstokes/riemann.f90#L580

True - in itself, this estimate is probably a decent approximation for non-convex flux functions. The main reason for this change is that we estimate the wave speeds in the CFL callback differently and thus, by default, different wave speeds are employed in different parts of the code which I would consider bad practice.

[ranocha]

@DanielDoehring Is this ready from your point of view?

[DanielDoehring]

@DanielDoehring Is this ready from your point of view?

Yes, I think I got every place where LLF is used