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

An innovative noise reduction method for supersonic exhaust jets was studied in a model-scale aircraft carrier environment. Acoustic measurements 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. The noise reduction of fluidic insert jets, above a ground plane, with steering of the “quiet planes” was examined with heat-simulated jets using near- and far-field pressure measurements. For jets exhausting over a ground plane, the fluidic inserts reduced the overall sound pressure level by 3–5 dB in the direction of maximum noise radiation. Upstream and sideline angles showed very little or no increase in sound level. Jets impinging on a modeled jet blast deflector were tested in addition to jets solely in the presence of a ground plane. The deflector resulted in downstream acoustic shielding and an increase in low-frequency noise. The region of maximum noise radiation for heat-simulated jets from nozzles with fluidic inserts impinging on the jet blast deflector was reduced in level by 4–7 dB. This region includes areas where carrier personnel are located.