Theory
The compressible solver works with absolute pressure. Its initial pressure field and the outlet pressure are written as the reference pressure plus the outlet's gauge value, equation (1); every reported pressure is shown relative to it, so an outlet at 0 Pa gauge reads 0 Pa and not 101 325 Pa. The density, computed by the solver from the ideal-gas law, uses the absolute value.
To change it, change the altitude or the atmospheric pressure (Ambient pressure: mode). Older case files that set a separate operating pressure are converted on loading: a value different from 101 325 Pa becomes the ambient pressure.
Equations
| where | meaning | unit |
|---|---|---|
| Absolute pressure the compressible solver uses | Pa | |
| Reference (ambient) pressure shown in this box | Pa | |
| Gauge pressure of the case (e.g. the outlet pressure) | Pa |
Default and rule
- Default
- the resolved ambient pressure (read-only)
- Rule
The resolved ambient pressure (101 325 Pa at sea level).
- Source
The program builds the compressible initial pressure field (
0/p) on the resolved ambient pressure and reports every pressure relative to it.
Valid range 40 000 to 110 000 Pa (follows the ambient pressure)
Read-only
Set in the Ambient pressure panel.