Experimental Facilities

The NASA Glenn Research Center boasts an array of experimental facilities designed to study aircraft engine aerodynamics and acoustics. One such facility is the 9- by 15-Foot Low-Speed Wind Tunnel (9 x 15 LSWT), which provides a controlled environment to investigate engine performance and noise at takeoff and landing conditions. Recent upgrades have enhanced its flow and reduced background noise, enabling more accurate measurements.

The Aero-Acoustic Propulsion Laboratory (AAPL) is another crucial facility, featuring a 65-foot radius geodesic dome designed to minimize community noise while conducting aeroacoustic tests on aircraft engines and components. The dome's walls and floor are lined with 17,000 custom-made fiberglass wedges, which absorb sound and prevent reflections. AAPL houses several rigs, including the Nozzle Acoustic Test Rig (NATR), the Small Hot Jet Acoustic Rig (SHJAR), and the DGEN 380 Aeropropulsion Research Turbofan (DART).

The Small Hot Jet Acoustic Rig (SHJAR) is a key component of the AAPL, capable of testing single stream nozzles up to 5 cm in diameter, Mach 2.0, and 800 K. Researchers have employed various advanced techniques, such as Rayleigh Scattering, Raman Scattering, digital Schleiren, and real-time Particle Image Velocimetry, to analyze nozzle geometry, jet flow, and noise.

These methods have led to significant breakthroughs in understanding jet noise, including time-resolved measurements of turbulent temperature and space-time correlations of turbulent velocities. The data obtained from SHJAR is instrumental in validating computer codes aimed at calculating jet noise, ultimately helping engineers design quieter propulsion systems.