Sound radiation from single and annular stream nozzles, with modal decomposition of in-duct acoustic power†
Abstract
An experimental program was carried out to study the acoustic characteristics of single and annular stream duct-nozzle systems at various flow conditions by using a refined acoustic impulse technique developed recently by Salikuddin et al. [1-3] at Lockheed-Georgia Company. In this technique signal synthesis [4] and signal averaging processes are incorporated to generate a desired impulsive signal from acoustic driver(s) and to eliminate background noise (flow noise) from in-duct and far field signals, respectively. The contribution of higher order modes to incident reflected and transmitted acoustic powers is accounted for by using a modal decomposition process described in references [1, 5]. The single stream nozzles include a 12-lobe, 24-tube suppressor nozzle with an equivalent exit diameter of 6.2 cm and a reference round convergent nozzle of equal area. These nozzles were connected to a 10 cm diameter supply duct and were tested statically as well as with simulated flight. The annular stream nozzles include two outer nozzle configurations, a 10 cm diameter duct and a 6·2 cm diameter conical nozzle, both connected to a 10 cm diameter supply duct. A 3·34 cm diameter straight duct, blocked at the upstream end, was used as the inner stream nozzle for both the configurations. These annular stream terminations were tested statically at various annular stream flow velocities with no inner stream flow. The results derived from the experiments include in-duct acoustic powers, termination reflection coefficients, transmission coefficients, far field power, and acoustic dissipation.
- Publication:
-
Journal of Sound Vibration
- Pub Date:
- March 1987
- DOI:
- 10.1016/S0022-460X(87)80133-5
- Bibcode:
- 1987JSV...113..473S
- Keywords:
-
- Acoustic Ducts;
- Annular Nozzles;
- Data Flow Analysis;
- Nozzle Flow;
- Random Noise;
- Sound Waves;
- Far Fields;
- Mach Number;
- Nozzle Geometry;
- Power Spectra;
- Supersonic Flow;
- Transfer Functions;
- Acoustics