Fill the six equation phasic energies in the primitive variables

[aliencaocao]

Fixes #2047.

Change

s_convert_conservative_to_primitive_variables in src/common/m_variables_conversion.fpp copies the phasic internal energies into their primitive slots for model_eqns = 3:

if (model_eqns == model_eqns_6eq) then
    $:GPU_LOOP(parallelism='[seq]')
    do i = eqn_idx%int_en%beg, eqn_idx%int_en%end
        qK_prim_vf(i)%sf(j, k, l) = qK_cons_vf(i)%sf(j, k, l)
    end do
end if

This is the same treatment the routine already gives the volume fractions, the magnetic field, and the color function. Their primitive and conservative forms coincide.

Why this is correct

In the six-equation model equations.md, Section 2.2), the extra variables are the phasic internal energies αₖρₖeₖ. MFC's serial output definition lists them in both the conservative and the primitive output. post_process also writes the same quantity as alpha_rho_e.

Before and after

The figure shows the shock and helium bubble from the issue, in the six-equation model. It shows the phasic energy of helium from t = 0.2 ms to 1.0 ms.

• Before: prim.8 and prim.9 are 0 in every cell.
• After: both equal the stored cons.8 and cons.9 exactly.
• All 1,584 conservative output files are byte-identical with and without the change.

Tests and goldens

No golden changes as this does not concern the final solution that the golden files checks for.

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---

Acknowledgement

• I confirm this PR meets the above expectations and reflects my own understanding and real-world context.

---

PR template credit: junegunn

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[github-actions]

Claude Code Review

Head SHA: 193c9e0

Files changed:

• 1
• src/common/m_variables_conversion.fpp

Findings:
No issues found. Checked in step 4: src/common/m_variables_conversion.fpp (the new 6-equation int_en copy loop is consistent with the existing adv/MHD copy loops in the same kernel and with the 6eq convention in s_convert_primitive_to_conservative_variables).

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 61.90%. Comparing base (47568a0) to head (193c9e0).

Files with missing lines	Patch %	Lines
src/common/m_variables_conversion.fpp	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2055   +/-   ##
=======================================
  Coverage   61.90%   61.90%           
=======================================
  Files          86       86           
  Lines       22885    22888    +3     
  Branches     3369     3370    +1     
=======================================
+ Hits        14166    14168    +2     
  Misses       6220     6220           
- Partials     2499     2500    +1     

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[github-actions]

Lines of Code

File	Lines	Diff
src/common/m_variables_conversion.fpp	966	+6

Directory	Lines	Diff
common	10532	+6
total	47591	+6

[wilfonba]

This variable is never used in simulation, but this fix means that anyone plotting results from serial I/O primitive outputs will now get meaningful results. I considered putting species pressures in this slot, but since species pressures are equal after relaxation, it doesn't make much sense to copy the same pressure repeatedly in the primitive output text files. This PR is good to go once it passes everything, which it should.