Design and analysis of a supersonic jet noise reduction concept

The design and analysis of a simple jet noise reduction concept is discussed. The concept is intended for use on the type of supersonic exhaust nozzles typically employed on tactical aircraft. The concept addresses both broadband shock-associated noise and turbulent mixing noise. Broadband shock-associated noise is addressed through a reduction in the effective exhaust area, which reduces the strength of the shock cell structure in the jet. Turbulent mixing noise is reduced by enhancement of mixing in the jet shear layer, which creates a shorter region of strongly turbulent flow and breaks up the large-scale turbulent structures. This paper describes an active control device that deflects a fraction of the adjustable seals in the divergent section of the engine exhaust nozzle. After takeoff, the deflected seals are returned to their undeflected position. Very favorable jet noise reductions are demonstrated at multiple observer angles for nominal takeoff conditions.