Segment V11.4: Supersonic Nozzle Flow

(Related to Textbook Section 11.4.2 - Converging-Diverging Duct Flow)

For a given converging-diverging nozzle, there is one pressure ratio (exit pressure/stagnation pressure) that produces isentropic choked flow. Otherwise, complex shock and expansion waves occur.

Air is shown exiting into the atmosphere from a nozzle on the right. As the stagnation pressure in the tank is raised, the flow, which begins as a subsonic jet, develops oblique shock waves (overexpanded flow). Isentropic flow (no waves) is produced when the pressure ratio is raised further to that value determined by the nozzle area ratio. Finally, for still higher stagnation pressure, expansion waves and shock waves develop (underexpanded flow). (Schlieren video provided by Professor G. S. Settles, Director, Gas Dynamics Lab, Penn State University.)