Theory

When OpenFOAM's janaf thermodynamics evaluates the polynomial at a temperature outside $[T_\mathrm{low}, T_\mathrm{high}]$ , it holds the temperature at the nearest end of the range and reports this (OpenFOAM user guide, 2026). The program uses the same polynomial for both halves of the range, with the common temperature at the middle, equation (1), so the heat capacity is continuous there. The Material step shows a warning when its gas temperature lies outside the range.

Equations

T_\mathrm{common} = \tfrac{1}{2}\left(T_\mathrm{low} + T_\mathrm{high}\right)

(1)

where	meaning	unit
$T_\mathrm{low}$	Lowest temperature of the polynomial (Valid from)	K
$T_\mathrm{high}$	Highest temperature of the polynomial (Valid up to)	K
$T_\mathrm{common}$	Temperature where the solver switches coefficient sets (both are the same)	K

Default and rule

Default: 200 K to 1500 K
Rule: 200 K to 1500 K in a new material.
Source: The range definition follows the janaf thermodynamics of OpenFOAM (OpenFOAM user guide, 2026); the choice of the common temperature at the middle is the program's.

Valid range 0 < T_low < T_high

Order

Valid from must be below Valid up to.

Cover the run

Choose a range that covers every temperature of the run: inlet, walls and ambient air.

References 1

OpenCFD Ltd. (2026). OpenFOAM user guide. openfoam.com. Web page

Theory

Equations

Default and rule

Valid range 0 < T_low < T_high

Related 2

References 1