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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) distribute...

The noise levels caused by high-performance aircraft are relatively high in the close proximity experienced by crew on board aircraft carriers, which can interfere with communications and may pose a risk for hearing loss. This paper reports on preliminary results of noise measurements of the operations of F-35B aircraft performing short-takeoff and vertical-landing (STOVL) operations on the flight deck of an LHA aircraft carrier. This noise measurement campaign was performed in late 2016, by scientists from the Air Force Research Laboratory (AFRL) in collaboration with the Naval Air Systems Command (NAVAIR) and the F-35 Integrated Task Force (ITF). The measurements were taken using hand-held noise recorder systems, and the recording engineers shadowed actual locations of crew. These data will be used to validate STOVL models of crew noise exposures on deck. [Work supported by F-35 JPO.]

The noise levels generated by tactical fighter aircraft can result in Noise Induced Hearing Loss for Navy personnel, particularly those involved in carrier deck operations. Reductions in noise source levels are clearly necessary, but these must be achieved without a loss in aircraft performance. This paper describes an innovative noise reduction technique that has been shown in laboratory scale measurements to provide significant reductions in both mixing as well as broadband shock-associated noise. The device uses the injection of relatively low pressure and low mass flow rate air into the diverging section of the military-style nozzle. This injection generates “fluidic inserts” that change the effective nozzle area ratio and generate streamwise vorticity that breaks up the large scale turbulent structures in the jet exhaust that are responsible for the dominant mixing noise. The paper describes noise measurements with and without forward flight that demonstrate the noise reduction effectiveness of the inserts. The experiments are supported by computations that help to understand the flow field generated by the inserts as well as help to optimize the distribution and strength of the flow injection.

Experimental research has shown how the addition of properly designed chevrons to model scale supersonic nozzles reduces the noise of the high speed jets issuing from such nozzles. It has also been shown that, to reasonable accuracy, this noise benefit scales between small‐ and moderate‐scale nozzle geometries. The new advanced acoustic model (AAM) developed by Wyle Laboratories has the capability to use noise source data to produce dynamic acoustic footprints showing noise exposure in the vicinity of airfields: especially for landing and take‐off operations. AAM uses information on aircraft engine jet exhaust noise sources for specific aircraft engine operating parameters and given flight conditions. This presentation describes the measurement and modeling of jet noise reduction using chevrons in both small and moderate scale nozzles. Then the AAM is used to demonstrate the expected change in acoustic footprint size for a full‐scale jet aircraft, where it equipped with chevrons. The effects of the chevrons are described as a decibel correction to the noise source spheres used by the model. The AAM is run for a simulated trajectory of a typical operation for a jet aircraft with and without chevrons to show the effects on the acoustic footprint.