NASA9Coefficients#
- class NASA9Coefficients[source]#
Bases:
Flow360BaseModelNASA 9-coefficient polynomial coefficients for computing temperature-dependent thermodynamic properties.
Attributes
- temperature_ranges: list[NASA9CoefficientSet]#
List of NASA 9-coefficient sets for different temperature ranges. Must be ordered by increasing temperature and be continuous. Maximum 5 ranges supported.
Methods
- validate_temperature_continuity()[source]#
Validate that temperature ranges are continuous and non-overlapping.
- validate_thermo_continuity()[source]#
Validate that adjacent NASA-9 ranges agree on cp, h and s where they meet.
Consecutive ranges are separate fits of one substance, so the polynomials must agree at the boundary they share. Nothing in the fit enforces that: cp comes out continuous on its own, but h and s also depend on the a7 and a8 integration constants, which are set per range and so can disagree. A jump in h drives the solver’s nodal caloric surrogate to a negative heat capacity and aborts the run; a jump in s is quieter but reaches stagnation pressure as exp(ds/R).
The tolerance is set by transcription, not by the fits: the curated library agrees to 5e-7 in cp/R and s/R and to 5e-5 in h/(R T), so 1e-4 passes every entry while catching discontinuities orders of magnitude smaller than the ones that break the solver.