Forward flight effects on mixer nozzle design and noise considerations for STOL externally blown flap systems

Abstract

Experimental data of the peak axial-velocity decay in a moving airstream are presented for several types of nozzles. The nozzles include a six-tube mixer nozzle of a type considered for reduction of jet-flap interaction noise for externally-blown-flap STOL aircraft. The effect of secondary flow on the core flow velocity decay of a bypass nozzle is also discussed. Tentative correlation equations are suggested for the configurations evaluated. Recommendations for minimizing forward velocity effects on velocity decay and jet-flap interaction noise are made.

Velocity decay and acoustic characteristics of various nozzle geometries with forward velocity

“…Thus the peak axial velocity decay curve is effec- With forward velocity, the peak axial velocity at a given axial station is greater with forward velocity than for the static condition (ref. 3). An example.of this effect, taken from reference 3, is shown by the data for a circular nozzle in figure 10 in which the ratio'of peak velocity to the jet exhaust velocity, U/U-, is plotted as a function of the distance…”

“…5), a bypass nozzle, a 6-tube mixer nozzle (ref. 3), and, finally, a 6-tube mixer nozzle with ejector.…”

Aerodynamic and acoustic performance of ejectors for engine-under-the-wing concepts

“…much like the U /U term for a bypass nozzle (ref. 8). Such aneAppioach, however, is geyond the scope of the present work.…”