A hybrid wing body transport aircraft model was tested in NASA Langley's 14 by 22Foot Subsonic Tunnel to evaluate proposed "low noise" technology. The experiment was set up to evaluate the community noise impact of the hybrid wing body design, as well as study the noise components of propulsion-airframe noise and shielding. A high fidelity 5.8-percent scale model, including landing gear, cruise and drooped wing leading edges, trailing edge elevons, vertical tail options, and engine noise simulators, was built to test both aerodynamic and acoustic configurations. The aerodynamic test data were used to establish appropriate flight conditions for the acoustic test.To accomplish the acoustic portion of this test, two major upgrades were required of NASA Langley's 14 by 22 Foot Subsonic Tunnel; first, a fuel delivery system to provide realistic gas temperatures to the jet engine simulators; and second, a traversing microphone array and side towers to measure full spectral and directivity noise characteristics.The results of this test provide benchmark hybrid wing body aircraft and noise shielding data to assist in achieving NASA's 2020 noise emission goals. I.

The Low Speed Aeroacoustic Wind Tunnel (LSAWT) at NASA Langley Research Center has recently undergone a configuration change. This change incorporates an inlet nozzle extension meant to serve the dual purposes of achieving lower freestream velocities as well as a larger core flow region. The LSAWT, part of the NASA Langley Jet Noise Laboratory, had historically been utilized to simulate realistic forward flight conditions of commercial and military aircraft engines in an anechoic environment. The facility was modified starting in 2016 in order to expand its capabilities for the aerodynamic and acoustic testing of small propeller and unmanned aircraft system (UAS) rotor configurations. This paper describes the modifications made to the facility, its current aerodynamic and acoustic capabilities, the propeller and UAS rotor-vehicle configurations to be tested, and some preliminary predictions and experimental data for isolated propeller and UAS rotor configurations, respectively. Isolated propeller simulations have been performed spanning a range of advance ratios to identify the theoretical propeller operational limits of the LSAWT. Performance and acoustic measurements of an isolated UAS rotor in hover conditions are found to compare favorably with previously measured data in an anechoic chamber and blade element-based acoustic predictions.

The effect of nozzle trailing edge thickness on broadband acoustic radiation and the production of tones is investigated for coannular nozzles. Experiments were performed for a core nozzle trailing edge thickness between 0.38 mm and 3.17 mm. The on-set of discrete tones was found to be predominantly affected by the velocity ratio, the ratio of the fan velocity to the core velocity, although some dependency on trailing edge thickness was also noted. For a core nozzle trailing edge thickness greater than or equal to 0.89 mm, tones were produced for velocity ratios between 0.91 and 1.61. For a constant nozzle trailing edge thickness, the frequency varied almost linearly with the core velocity. The Strouhal number based on the core velocity changed with nozzle trailing edge thickness and varied between 0.16 and 0.2 for the core nozzles used in the experiments. Increases in broadband noise with increasing trailing edge thickness were observed for tone producing and non-tone producing conditions. A variable thickness trailing edge (crenellated) nozzle resulted in no tonal production and a reduction of the broadband trailing edge noise relative to that of the corresponding constant thickness trailing edge.

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