Preliminary analysis of tone-excited two-stream jet velocity decay

Acoustic research related to jet flows has established that sound, by amplifying the naturally occurring large‐scale structures in turbulent shear layers, can cause a more rapid decay of the jet plume velocity and temperature and jet spread. One possible application of this sound‐flow interaction phenomenon is to future STOL aircraft that may require modified jet plume characteristics in order to reduce the loads and temperatures on the deflected flaps during takeoff and landing operations. A preliminary analysis is made herein of the tone‐excitation effect on the velocity decay of model‐scale, two‐stream jet plumes. Measured data are correlated in terms of parameters that include excitation sound level and outer‐to‐inner steam velocity ratio. The effect of plume tone‐excitation on farfield jet noise is examined briefly and its implication for large‐scale two‐stream jets is discussed.