Fix computation of max_abs_speeds for the SWE

[patrickersing]

The wave speed in max_abs_speeds for the SWE computes the wave celerity as c = equations.gravity * sqrt(h) instead of c = sqrt(equations.gravity * h). This PR fixes the computation and adjusts the test values accordingly.
In some elixirs the cfl had to be set back to cfl = 1.0, because they became unstable when using the new wave speed.

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.30%. Comparing base (0f60ebc) to head (1a89afe).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1898   +/-   ##
=======================================
  Coverage   96.30%   96.30%           
=======================================
  Files         448      448           
  Lines       36006    36006           
=======================================
  Hits        34672    34672           
  Misses       1334     1334           

Flag	Coverage Δ
unittests	96.30% <100.00%> (ø)

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[patrickersing]

The modified wave speed affects the downstream tests for Trixi2Vtk.jl using elixir_shallowwater_ec.jl on UnstructuredMesh2D. I think we just need to update the respective reference files in Trixi2Vtk_reference_files.

[andrewwinters5000]

The modified wave speed affects the downstream tests for Trixi2Vtk.jl using elixir_shallowwater_ec.jl on UnstructuredMesh2D. I think we just need to update the respective reference files in Trixi2Vtk_reference_files.

Yes, that is indeed the case. We will need a new reference file.

[DanielDoehring]

Good spot!

I am a bit embarrassed that I did not spot this when adding more refined wave speed estimates, as it is for the 1D case only 10 lines below :O

https://github.com/trixi-framework/Trixi.jl/blame/main/src/equations/shallow_water_1d.jl

[andrewwinters5000]

I am even more embarrassed because I introduced this bug in my initial implementation of the 2D shallow water equations. I have no idea how/why I wrote the function this way. The 1D bug just propagated my initial mistake.

[andrewwinters5000]

LGTM!

[ranocha]

The modified wave speed affects the downstream tests for Trixi2Vtk.jl using elixir_shallowwater_ec.jl on UnstructuredMesh2D. I think we just need to update the respective reference files in Trixi2Vtk_reference_files.

Yes, that is indeed the case. We will need a new reference file.

Could you please prepare a PR for that? I would like to see green CI before merging this PR.

[patrickersing]

Do we also need to create new releases for the changes to take effect across packages?

[ranocha]

Yes. I just started the registration process for Trixi2Vtk.jl. It should be released in half an hour or so. Please update this PR later so that the new version is used in CI. Afterwards, we can merge this PR and release a new version of Trixi.jl so that CI for Trixi2Vtk.jl works again.

[andrewwinters5000]

Yes. I just started the registration process for Trixi2Vtk.jl.

The new version merged, so I merged main into this PR to trigger the CI again.

[ranocha]

Thanks