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Theoretical study of refraction effects on noise produced by turbulent jets
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Graham, E. W. Graham, B. B. |
| Copyright Year | 1975 |
| Description | The transmission of acoustic disturbances from the interior of a jet into the ambient air is studied. The jet is assumed infinitely long with mean velocity profile independent of streamwise location. The noise generator is a sequence of transient sources drifting with the local fluid and confined to a short length of the jet. In Part 1, supersonic jets are considered. Numerical results for mean-square pressure versus angle in the far-field show unexpected peaks which are very sharp. Analysis of simplified models indicates that these are complex quasi-resonant effects which appear to the stationary observer in a high frequency range. The peaks are real for the idealized model, but would be smoothed by mathematical integration over source position, velocity, and frequency. Subsonic jets were considered in part 2, and a preliminary study of the near-field was attempted. Mean-square radial displacements (or mean radial energy flow or space-time correlations of radial pressure gradient) are first found for very simple cases. The most difficult case studied is a sequence of transient sources at the center of a uniform-velocity circular cylindrical jet. Here a numerical triple integration is required and seems feasible although only preliminary results for mean square radial displacement are now available. These preliminary results show disturbances decreasing with increasing radial distance, and with increasing distance upstream and downstream from the source. A trend towards greater downstream disturbances appears even in the near field. |
| File Size | 2763718 |
| Page Count | 94 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_19760006795 |
| Archival Resource Key | ark:/13960/t1kh5c703 |
| Language | English |
| Publisher Date | 1975-12-01 |
| Access Restriction | Open |
| Subject Keyword | Acoustics Supersonic Flow Numerical Integration Jet Aircraft Noise Sound Transmission Subsonic Flow Refraction Atmospheric Attenuation Turbulent Jets 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 |
