Instability and acoustic emission of supersonic overexpanded jets
Abstract
Conditions under which a supersonic jet flow becomes unstable are modeled theoretically by an analogy between a free surface liquid and a twodimensional gas flow. The hydraulic analogy is drawn by considering a threedimensional, nonstationary liquid flow over a plate where vertical speed is much less than horizontal and transverse velocity components and acceleration is less than that of gravity. Partial differential equations describing this flow are noted to be very similar to an ideal gas flowing under certain conditions of pressure and volume, and equating the two types of flow define a 'hydraulic gas'. Tables are given and experimental apparatus described which relate the gas and liquid models and validate the transfer of observed liquid instability moments to those of supersonic gas jets. The case of two waves of oblique shock produced at the nozzle exit is considered and results indicate that a system is stable or not according to the value of the ambient backpressure.
 Publication:

Deutsche Gesellschaft fuer Luft und Raumfahrt
 Pub Date:
 May 1981
 Bibcode:
 1981aaaf.coll.....B
 Keywords:

 Acoustic Emission;
 Flow Stability;
 Hydraulic Analogies;
 Supersonic Jet Flow;
 Gas Flow;
 Nozzle Flow;
 Oblique Shock Waves;
 Partial Differential Equations;
 Two Dimensional Flow;
 Fluid Mechanics and Heat Transfer