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Experimental investigation of shock-cell noise reduction for dual-stream nozzles in simulated flight
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Yamamoto, K. Majjigi, R. K. Janardan, B. A. Brausch, J. F. |
| Copyright Year | 1984 |
| Description | Six scale-model nozzles were tested in an anechoic facility to evauate the effectiveness of convergent-divergent (C-D) terminations in reducing shock-cell noise of unsuppressed and mechanically suppressed coannular plug nozzles. One hundred fifty-three acoustic test points with inverted velocity profiles were conducted under static and simulated flight conditions. Diagnostic flow visualization with a shadowgraph and velocity measurements with a laser velocimeter were performed on selected plumes. Shock-cells were identified on the plug and downstream of the plug of the unsuppressed convergent coannular nozzle with truncated plug. Broadband peak frequencies predicted with the two shock-cell structures were correlated with the observed spectra using the measured shock-cell spacings. Relative to a convergent circular nozzle, the perceived noise level (PNL) data at an observer angle of 60 deg relative to inlet, indicated a reduction of (1) 6.5 dB and 9.2 dB with unsuppressed C-D coannular nozzle with truncated plug and (2) 7.7 dB and 8.3 dB with suppressed C-D coannular nozzle under static and simulated flight conditions, espectively. The unsuppressed C-D coannular nozzle with truncated plug, operating at the C-D design condition, had shock-cells downstream of the plug with no shock-cells on the plug. The downstream shock-cells were eliminated by replacing the truncated plug with a smooth extension to obtain an additional 2.4 dB and 3 dB front quadrant PNL reduction, under static and simulated flight conditions, respectively. Other results are discussed. |
| File Size | 43663759 |
| Page Count | 191 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_19850005240 |
| Archival Resource Key | ark:/13960/t88h3g22f |
| Language | English |
| Publisher Date | 1984-11-01 |
| Access Restriction | Open |
| Subject Keyword | Acoustics Plug Nozzles Laser Doppler Velocimeters Jet Aircraft Noise Engine Noise Noise Reduction Convergent-divergent Nozzles Noise Measurement Suppressors Noise Spectra Plumes Convergent Nozzles Shock Waves Jet Mixing Flow Noise Prediction Aircraft Flow Visualization Flow Velocity Shadowgraph Photography Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Technical Report |
