Sc/compressible euler multicomponent 2d fluxes

[SimonCan]

Added fluxes to the compressible multicomponent Euler equations in 2d to make it usable on structured 2d meshes.

The convergence tests for elixir_eulermulti_convergence_ec.jl are:

####################################################################################################
l2
rho_v1              rho_v2              rho_e               rho1                rho2                
error     EOC       error     EOC       error     EOC       error     EOC       error     EOC       
1.23e-04  -         1.23e-04  -         1.89e-04  -         4.85e-05  -         9.71e-05  -         
1.51e-05  3.02      1.51e-05  3.02      2.45e-05  2.94      5.90e-06  3.04      1.18e-05  3.04      
1.88e-06  3.01      1.88e-06  3.01      3.09e-06  2.99      7.33e-07  3.01      1.47e-06  3.01      

mean      3.01      mean      3.01      mean      2.97      mean      3.02      mean      3.02      
----------------------------------------------------------------------------------------------------
linf
rho_v1              rho_v2              rho_e               rho1                rho2                
error     EOC       error     EOC       error     EOC       error     EOC       error     EOC       
6.72e-04  -         6.72e-04  -         1.27e-03  -         2.84e-04  -         5.69e-04  -         
8.39e-05  3.00      8.39e-05  3.00      1.50e-04  3.07      3.50e-05  3.02      7.01e-05  3.02      
1.09e-05  2.94      1.09e-05  2.94      2.00e-05  2.91      4.61e-06  2.93      9.23e-06  2.93      

mean      2.97      mean      2.97      mean      2.99      mean      2.97      mean      2.97      
----------------------------------------------------------------------------------------------------
Dict{Symbol, Any} with 3 entries:
  :variables => ("rho_v1", "rho_v2", "rho_e", "rho1", "rho2")
  :l2        => [3.01456, 3.01456, 2.96502, 3.02451, 3.02451]
  :linf      => [2.97283, 2.97283, 2.99359, 2.973, 2.973]

[github-actions]

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[codecov]

Codecov Report

Attention: 45 lines in your changes are missing coverage. Please review.

Comparison is base (3c1762b) 96.23% compared to head (77a4c4b) 94.05%.

Files	Patch %	Lines
.../equations/compressible_euler_multicomponent_2d.jl	34.78%	45 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1681      +/-   ##
==========================================
- Coverage   96.23%   94.05%   -2.18%     
==========================================
  Files         431      431              
  Lines       34816    34872      +56     
==========================================
- Hits        33503    32798     -705     
- Misses       1313     2074     +761     

Flag	Coverage Δ
unittests	94.05% <40.79%> (-2.18%)	⬇️

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[ranocha]

This is just a brief review of the look at the surface - I didn't check the numerics. Looks good in general 👍

[DanielDoehring]

It is probably also a good idea/habit that we check new numerical fluxes for consistency and rotational invariance

[ranocha]

It is probably also a good idea/habit that we check new numerical fluxes for consistency and rotational invariance

@SimonCan?

[SimonCan]

I've added the consistency and rotational invariance.

[ranocha]

Thanks!

[ranocha]

Thanks