A microphone array system for studying the near field hydrodynamic region adjacent to the supersonic exhaust plume of a tactical aircraft engine in a ground test fixture at approximately 20 feet above the ground. It will consist of approximately 160 microphones aimed radially inward at the edge of the shear layer and extending to 20 diameters downstream of the nozzle exit. A mobile scissors jack will aid positioning. Data will be processed and analyzed using techniques derived from prior work to elucidate the large scale structure and estimate the noise radiated to the far field.
Benefit: The objective of this program is to implement a system for measuring the near field hydrodynamic pressure field surrounding the plume of a full scale engine under ground test. This will allow a better understanding of the underlying physics of noise generation mechanisms within the engine exhaust plume, in particular ranking the multiple noise sources as the first step towards developing and demonstrating more advanced noise control strategies.
Keywords: microphone array, microphone array, unsteady pressure, shear layer instability, turbine engine, Jet noise, phased array, hydrodynamic near field, wave packet
