Jet Aeroacoustic Testing: Issues and Implications

Issues that are important for jet aeroacoustic tests and the critical role of good data in the development of jet noise technology are reviewed and discussed. A major effort for improving the quality of aeroacoustic data acquired at the Boeing Low Speed Aeroacoustic Facility has been carried out. This extensive undertaking targeted all aspects of model-scale testing and acquisition of good quality data and covered issues of flow quality, nozzle performance, and acoustics. Significant improvements have been made in all of the named categories. Simultaneous measurement of nozzle aerodynamic performance and noise is important, especially for the development of noise suppression devices. The capabilities of a jet rig incorporated with a six-component force balance are described. It is clearly demonstrated that the measured thrust with the current rig is in excellent agreement with that obtained using a dedicated force balance over a wide range of nozzle pressure ratios. Results of the efforts at rig refurbishment, carried out over the last few years, are presented. The high quality of noise measurements is established through good spectral agreement with data obtained with a blowdown jet, for a wide range of nozzle conditions. An extensive study of available jet noise data from various jet noise facilities has been completed. Implications of contaminated data from most tests and the obligations of the experimental community for the advancement of jet noise technology are discussed.