Theory
The ideal-gas law relates pressure, density and temperature through the specific gas constant . A heavier gas is denser at the same pressure and temperature and carries sound more slowly. The molar mass enters the density of every run (incompressible: the constant density; compressible: the solver's molWeight), the ratio of heat capacities and the speed of sound of the acoustics.
Equations
| where | meaning | unit |
|---|---|---|
| Molar mass (this setting) | kg/kmol | |
| Universal gas constant, 8314.47 | J/(kmol K) | |
| Specific gas constant | J/(kg K) | |
| Density | kg/m³ | |
| Absolute pressure | Pa | |
| Temperature | K | |
| Speed of sound | m/s | |
| Ratio of heat capacities | - |
Default and rule
- Default
- 28.9644 kg/kmol (dry air); with the temperature-dependent model, the mixture value of the selected gas
- Rule
28.9644 kg/kmol (dry air). Temperature-dependent model: the mixture value, e.g. 28.965 for dry air, 29.04 for diesel exhaust at , 27.74 for natural-gas exhaust at .
- Source
The dry-air value is that of the standard atmosphere (U.S. Standard Atmosphere, 1976). The relations of equation (1) are the ideal-gas law.
Valid range > 0
Values
Above 0. Used only with the constant heat-capacity model.
One definition of R
The program uses one value of the universal gas constant, 8314.47 J/(kmol K), throughout: solver set-up, results and report.