High Velocity Jet Noise Source Location and Reduction. Task 4. Development/Evaluation of Techniques for 'Inflight' Investigation.
Abstract
This report presents the results of Task 4 as conducted under the subject program over a period of 30 months. Task 4 was formulated to identify and evaluate several inflight simulation techniques, select the most promising technique for demonstration and validation, and employ that technique in testing under Task 5 of the program. Techniques evaluated include closed-circuit wind tunnels, free jets, rocket sleds, and high speed trains. Pertinent results from the evaluation phase and rationale which led to selection of the free jet simulation technique are discussed, including advantages and disadvantages. The results of a theoretical study aimed at relating the noise signature obtained in a free jet facility for simulation of forward flight effects on jet noise with the noise signature in true flight are presented. Transformation is carried out by extracting 'static directivity' of the noise after correcting for refraction, turbulent scattering, and absorption effects, and then employing a suitable multipole source decomposition to evaluate the proper dynamic effect. A flowchart describing the details of the transformation procedure and a listing of the computer program are included. Acoustic results from the Learjet and NASA-Lewis F-106 Aircraft Flyovers and the French Aerotrain Tests, taken with a baseline, 8-lobe, and 104-tube nozzle were used to formulate a data base for verification of the free jet simulation technique. Detailed directivity and spectra comparisons between aerotrain data and transformed free jet data are presented for three primary jet velocities and two flight velocities for the three nozzle types.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 22, 1977
- Accession Number
- ADA041849
Entities
People
- E. J. Stringas
- W. S. Clapper
Organizations
- General Electric