Theory
There is one source for the operating pressure. With the flow solved, the outlets fix it: their absolute pressure is the pressure the gas leaves at, and the mean of their gauge pressures is used when they differ (a warning appears when they differ by more than 1 % of the absolute pressure). Without flow (acoustics only) there is no outlet pressure, so the value is entered here; either the gauge or the absolute value may be typed, the gauge value is stored.
The operating pressure sets the incompressible density, the density and characteristic impedance of the uniform acoustic medium and of the ports, the properties of perforated and porous walls, the water content of humid air and the starting pressure field of the compressible solver. The ambient pressure stays the reference for the reported relative pressures, the backpressure, the radiation from the outlets and the outside air.
Equations
| where | meaning | unit |
|---|---|---|
| Operating (absolute) static pressure | Pa | |
| Ambient pressure | Pa | |
| Gauge pressure of outlet (Outlet gauge pressure) | Pa | |
| Number of outlets | - | |
| This field | Pa |
Default and rule
- Default
- 0 Pa; with the flow solved: the mean of the outlets' gauge pressure
- Rule
0 Pa: the gas is at the ambient pressure.
- Source
A definition of the program.
Valid range -80 000 Pa to 5 MPa; absolute value at least 20 kPa
Different outlet pressures
When the outlets differ by more than 1 % of the operating pressure, their mean is used for the gas properties; each outlet still gets its own pressure in the flow solution.
Minimum
The absolute value must stay above 20 kPa.