Compressible Flow Through a Nozzle/Diffuser
This Demonstration models compressible flow of air through a reversible nozzle/diffuser. The inlet pressure P1, the exit velocity u2, and the exit temperature T2 are calculated from mass and energy balances and that the entropy change is zero. The air exits as a free jet at atmospheric pressure (P2 = 101.3 kPa). Set the oulet diameter d2 and inlet velocity u1 with the slider/s. When d2 < d1, the device acts as a nozzle, with the inlet pressure higher than the exit pressure (P1 > P2) in order to provide the energy needed to accelerate the air through the nozzle. When d2 > d1, the device operates as a diffuser, and the exit pressure is higher than the inlet pressure (P1 < P2). When "plots" is selected, the outlet velocity or outlet temperature is plotted as a function of outlet diameter for compressible air flow (blue) and incompressible air flow (green). Air is assumed to behave as an ideal gas and all flow is subsonic.

Download the CDF file to view the simulation using the free Wolfram CDF player.