High Velocity Jet Noise Source Location and Reduction. Task 3. Experimental Investigation of Suppression Principles. Volume IV. Laser Velocimeter Time Dependent Cross Correlation Measurements

摘要

Experimental investigations were conducted of suppression principles; 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. In-jet/in-jet and in-jet/far-field exhaust noise diagnostic measurements were conducted using a Laser Velocimeter (LV). Measurements were performed on a conical nozzle and a coannular plug nozzle. Two-point, space/time measurements using a two-LV system were completed for the conical nozzle. Measurements of mean velocity, turbulent velocity, eddy convection speed, and turbulent length scale were made for a subsonic ambient jet and for a sonic heated jet. For the coannular plug nozzle, a similar series of two-point, laser-correlation measurements were performed. In addition, cross correlations between the laser axial component of turbulence and a far-field acoustic microphone were performed. This volume is part of the four volume set that constitutes the Task 3 final report. The other volumes are: Volume I-Verification of Suppression Principles and Development of Suppression Prediction Methods, Volume II-Parametric Testing and Source Measurements, Volume III-Suppressor Concepts Optimization. (Author)