Theory
The compressible solver solves an energy equation, so every inlet needs a temperature. It is written as fixedValue in 0/T (OpenFOAM user guide, 2026). The outlets use inletOutlet (zero gradient for outflow, the initial temperature for any backflow); walls are adiabatic unless a heat-loss or fixed-temperature condition is set on them (Thermal condition of a wall).
The value is stored as "follow the material" (empty) when it equals the Material temperature, so a later change on the Material step moves the inlet temperature with it. The inlet temperature also enters:
- the inlet Mach number shown on the card;
- the start of the heat-transfer setup: the first guess of the outer-surface temperature of heat-loss walls uses the first inlet that has its own temperature;
- the viscosity used in a packing's Darcy term (Sutherland's law at the inlet temperature).
The incompressible solver has no energy equation; there the field is not shown, and the gas properties follow from the Material temperature alone.
Equations
| where | meaning | unit |
|---|---|---|
| Inlet static temperature | K | |
| Dynamic viscosity of the gas (Sutherland) | Pa s | |
| Sutherland coefficient (Sutherland coefficient As) | kg/(m s K^{1/2}) | |
| Sutherland temperature (Sutherland temperature Ts) | K |
Default and rule
- Default
- the Material temperature (stored as 'follow the material')
- Rule
The Material temperature, converted to kelvin.
- Source
The boundary condition is as documented for OpenFOAM (OpenFOAM user guide, 2026); the viscosity follows Sutherland's law (Sutherland, 1893).
Valid range > 0 K; compressible cases only
Units
Kelvin here, whereas the Material step and the wall temperatures use degrees Celsius.
Static temperature
The value is the static temperature of the entering gas; at high Mach numbers the total temperature is higher by .