| Air Density | |
The air density is defined as the mass of a quantity of air divided by its volume. By default, Windographer calculates air density using the following equation:
where: | ||
| r | is the air density considering humidity [kg/m3] | |
| T | is the air temperature [K] | |
| p | is the air pressure [kPa] | |
| f | is the relative humidity [unitless] | |
| psat | is the saturation vapor pressure [kPa] | |
| Rd | specific gas constant of dry air (0.287 kJ·kg-1·K-1) | |
| Rv | specific gas constant of water vapor (0.461 kJ·kg-1·K-1) |
To calculate the saturation vapor pressure, Windographer uses the equation specified by IEC standard 61400-12-1:
where: | ||
| psat | is the saturation vapor pressure [kPa] | |
| T | is the air temperature [K] |
Windographer automatically creates a calculated data column containing the air density in every time step. You can see that data column and edit its properties in the Configure Dataset window. It uses the primary temperature, pressure, and relative humidity data columns, if they exist, to determine temperature, pressure, and RH in each time step. Further details appear in the article on calculating air density.
See also