[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

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 50.35%. Comparing base (5e52d67) to head (681922d).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4731      +/-   ##
==========================================
- Coverage   50.36%   50.35%   -0.02%     
==========================================
  Files         181      181              
  Lines       30666    30659       -7     
==========================================
- Hits        15444    15437       -7     
  Misses      15222    15222              

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[je-cook]

The code here is not really the main change, the idea needs a modeller to have a look

[ajpearcey]

So we are assuming that if $\rho_{n,ped}$ and $\rho_{t,ped}$ are not equal the peak pressure is at the smaller rho of the two positions? Is a simple argument for this for arbitrary $T$ and $n$ profiles I do not see. I see this is also what we did before, right it just wasn't explicit in the comment.

I see you want to make the calculation simpler to avoid this bug. how was the bug changing the answer before?

Addendum: If we switched the order we call calculate_profile_factors and calculate_parabolic_profile_factors and we not easily compute all of this from the ideal gas law and chain rule?

[chris-ashe]

So we are assuming that if ρ n , p e d and ρ t , p e d are not equal the peak pressure is at the smaller rho of the two positions? Is a simple argument for this for arbitrary T and n profiles I do not see. I see this is also what we did before, right it just wasn't explicit in the comment.

I see you want to make the calculation simpler to avoid this bug. how was the bug changing the answer before?

Addendum: If we switched the order we call calculate_profile_factors and calculate_parabolic_profile_factors and we not easily compute all of this from the ideal gas law and chain rule?

Have made a play around graph for the pressure here:

https://www.desmos.com/calculator/428370dffa

The assumption that the pedestal point will always generally be at the lowest rho value, seems to be true upon inspection