Abstract
The present work uses large-eddy simulations to analyze the effectiveness of a noise reduction strategy on a military-style nozzle based on the GE F400-series engines. The nozzle has a design Mach number of 1.65 and is operated in supersonic overexpanded jet conditions. The characteristics of unheated and heated jets are presented and compared. The noise reduction strategy developed at the Pennsylvania State University is based on injectors blowing air into the diverging section of the nozzle to emulate the effect of interior corrugation. The injection can be activated during takeoff and turned off during other phases of flight so that performance is not adversely affected. The injectors have the potential to break down the shock cells into smaller and weaker structures, affecting the mechanisms that generate broadband shock-associated noise and to weaken the larger-scale turbulent structures. The overall sound pressure levels are reduced along most of the observer angles on a plane in between two injector lines. A maximum noise reduction of about 3 dB is obtained along the direction of maximum sound propagation.
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