| Acoustic Measurements of Rectangular Nozzles with Bevel Contributor(s): Bridges, James E. (Author), Nasa Technical Reports Server (Ntrs) (Created by) |
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ISBN: 1289156530 ISBN-13: 9781289156534 Publisher: Bibliogov OUR PRICE: $14.18 Product Type: Paperback Published: July 2013 |
| Additional Information |
| BISAC Categories: - Political Science |
| Physical Information: 0.06" H x 7.44" W x 9.69" (0.16 lbs) 30 pages |
| Descriptions, Reviews, Etc. |
| Publisher Description: A series of convergent rectangular nozzles of aspect ratios 2:1, 4:1, and 8:1 were constructed with uniform exit velocity profiles. Additional nozzles were constructed that extended the wide lip on one side of these nozzles to form beveled nozzles. Far-field acoustic measurements were made and analyzed, and the results presented. The impact of aspect ratio on jet noise was similar to that of enhanced mixing devices: reduction in aft, peak frequency noise with an increase in broadside, high frequency noise. Azimuthally, it was found that rectangular jets produced more noise directed away from their wide sides than from their narrow sides. The azimuthal dependence decreased at aft angles where noise decreased. The effect of temperature, keeping acoustic Mach number constant, was minimal. Since most installations would have the observer on the wide size of the nozzle, the increased high frequency noise has a deleterious impact on the observer. Extending one wide side of the rectangular nozzle, evocative of an aft deck in an installed propulsion system, increased the noise of the jet with increasing length. The impact of both aspect ratio and bevel length were relatively well behaved, allowing a simple bilinear model to be constructed relative to a simple round jet. |