16.2.2 Specifying the Operating Pressure for the System

The system Operating Pressure is used to calculate density using the ideal gas law. For non-adiabatic simulations, the Compressibility Effects under PDF Options can be enabled to account for cases where substantial pressure changes occur in time and/or space. In such cases it is assumed that the species mass fractions do not change with pressure, and the density is calculated as

where $\rho_{\rm op}$ is the density at the specified Operating Pressure ( $p_{\rm op}$), and $\overline{p}$ is the local mean pressure in an ANSYS FLUENT cell.

When the Compressibility Effects option is enabled, the flow operating pressure (set in the Operating Conditions dialog box) can differ from the Non-Premixed model operating pressure. To distinguish this difference, the Operating Pressure name tag in the Species Model dialog box changes to Equilibrium Operating Pressure when the compressibility effects option is enabled.

See Section  16.10 for details about enabling compressibility effects.