Noise reduction with fluidic inserts in supersonic jets exhausting over a simulated aircraft carrier deck

A developing noise reduction method for supersonic exhaust jets was studied in a model scale aircraft carrier environment. Acoustic experiments of model exhaust jets with (and without) distributed blowing, producing “fluidic inserts”, were performed. The model carrier environment consisted of a ground plane of adjustable distance below the jet, and a simulated jet blast deflector similar to those found in practice. Measurements were performed with far-field microphones, near-field microphones, and unsteady pressure sensors. The constructive and destructive interference that results from the interaction of the direct and reflected sound waves was observed and compared with results from free jets. The noise reduction of fluidic inserts in a realistic carrier deck environment with steering of the “quiet planes” was examined. The overall sound pressure level in heat-simulated jets was reduced by 3-5 dB depending on the specific angle and ground plane height. Jets impinging upon a modeled jet blast deflector were tested in addition to jets solely in the presence of the carrier deck. Observed modifications to the acoustic field from the presence of the jet blast deflector included downstream acoustic shielding and low frequency augmentation. The region of maximum noise radiation for heat-simulated jets from nozzles with fluidic inserts impinging on the jet blast deflector was reduced in overall sound pressure level by 4-7 dB. This region includes areas where aircraft carrier personnel are located.