Add new div upper lower vars

[chris-ashe]

Description

Checklist

I confirm that I have completed the following checks:

• My changes follow the PROCESS style guide
• I have justified any large differences in the regression tests caused by this pull request in the comments.
• I have added new tests where appropriate for the changes I have made.
• If I have had to change any existing unit or integration tests, I have justified this change in the pull request comments.
• If I have made documentation changes, I have checked they render correctly.
• I have added documentation for my change, if appropriate.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 56.25000% with 21 lines in your changes missing coverage. Please review.
✅ Project coverage is 42.77%. Comparing base (84002e4) to head (fa2a54a).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
process/physics.py	0.00%	11 Missing ⚠️
process/divertor.py	33.33%	6 Missing ⚠️
process/build.py	0.00%	3 Missing ⚠️
process/init.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4019      +/-   ##
==========================================
- Coverage   45.88%   42.77%   -3.11%     
==========================================
  Files         123      123              
  Lines       29082    31463    +2381     
==========================================
+ Hits        13343    13459     +116     
- Misses      15739    18004    +2265     

☔ 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.