An approximate 1/10th scale model turbofan exhaust rig, along with additional modern turbofan hardware models, is housed in a 24’x24’x11’ anechoic chamber with a
cutoff frequency below the frequencies of interest in scale model testing, about 350 Hz.
The coaxial stream rig can operate with the core stream heated up to about 350 degrees F,
at up to Mach 1.3, and with the bypass stream at ambient temperature, up to sonic velocity.
For military type engine simulation, the core nozzle can be replaced with a suitable geometry,
and a simple bypass stream hardware change can be made to allow for simulated freestream
An array of far-field microphone holders are permanently mounted in the chamber, employing
up to 12 1/4" B&K microphones, calibrated at 1000 Hz at 1Pa prior to any data acquisition.
A robotic traverse, controlled on three independent axes, capable of any three-dimensional movement,
is used to generated near-field contour maps of SPL with a narrow band frequency resolution of 50 Hz.
The system is currently (January 2006) being upgraded to include data management features,
new TEDS microphone chips, additional microphone channels and DAQ boards to allow beamforming and
near-field acoustic holography applications.
Flow measurements are taken to accompany the acoustic data and determine the influence of both the
mean flow and turbulence characteristics on the radiated noise. PIV and simultaneous near-field acoustics
have been used to reconstruct the large coherent structures using LES. Other flow measurements on the jet
include stereoscopic 3D PIV, hotwire mapping, supersonic pitot measurements, 2-component LDV, and schlieren