INTRODUCTION

The ATF has been operational since 2001, and has since has contributed to the fundamental and practical knowledge of aeroacoustics. This has been accomplished in part by producing continually advanced experimental acoustic and flow data on a simulated turbofan exhaust model. Concepts tested for noise reduction include both static geometry, such as various types of chevrons, active technologies, and pseudo-active nozzle concepts for use with shape memory alloys (SMA).

FEATURES AND CAPABILITIES

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 conditions.

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 spark imaging.

Key capabilities of the ATF:
  • Heavily instrumented rig & independent core and bypass air sources, providing excellent flow control, and measurement repeatability
  • Modular hardware allows for lower-cost experimental concepts
  • Long blow-down times with flow rates up to 10 lb/s, and fast recharging
  • Large scale design provides realistic simulation based on shear velocity
  • Simulated free-stream conditions with single jet
Gas Dynamics and Propulsion Laboratory
University of Cincinnati
Dept. of Aerospace Engineering and Engineering Mechanics
300 Rhodes Hall
Cincinnati, OH 45221-0070
© 2005 University of Cincinnati