High Velocity Jet Noise Source Location and Reduction. Task 3 - Experimental Investigation of Suppression Principles. Volume I. Suppressor Concepts Optimization
Final rept. Oct 1974-Oct 1977
FEDERAL AVIATION ADMINISTRATION WASHINGTON DC SYSTEMS RESEARCH AND DEVELOPMENT SERVICE
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Experimental investigations of suppression principles were conducted including developing an experimental data base, developing a better understanding of jet noise suppression principles, and formulating empirical methods for the acoustic design of jet noise suppressors. Acoustic scaling has been experimentally demonstrated, and five optimum nozzles have been selected for subsequent anechoic free-jet testing. This report is organized into four volumes under separate cover Volume I - Verification of Suppression Principles and Development of Suppression Prediction Methods, Volume II - Parametric Testing and Source Measurements, Volume III - Suppressor Concepts Optimization, and Volume IV - Laser Velocimeter Time-Dependent Cross Correlation Measurements. The experimental studies reported in Volume II involved acquisition of detailed far-field, acoustic data and of aerodynamic jet-flow-field data on several baseline and noise-abatement nozzles. These data were used to validate the theoretical jet noise prediction method of Task 2 and to develop and validate the empirical noise-prediction method presented herein. A series of seven suppressor configurations ranging from geometrically simple to complex were tested to establish the relative importance of four jet noise mechanisms fluid shielding, convective amplification, turbulent mixing, and shock noise. In general, mechanical suppressors exhibit a significant reduction in shock noise relative to a baseline conical nozzle, reduce the effectiveness of fluid shielding increase rather than suppress noise, reduce the effectiveness of convective amplification reduce noise, and produce a modest reduction in turbulent mixing noise.
- Fluid Mechanics
- Jet and Gas Turbine Engines