EXPERIMENTAL INVESTIGATION OF NOISE REDUCTION IN SUPERSONIC JETS DUE TO JET ROTATION

✍ Scribed by R. Neemeh; S. AlGattus; L. Neemeh

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 1019 KB
• Volume: 221
• Category: Article
• ISSN: 0022-460X
• DOI: 10.1006/jsvi.1998.2029

✦ Synopsis

In the present work a swirl chamber is employed to study the eect of ¯uid rotation on noise reduction in supersonic jets. Fluid rotation is attained by means of a vortex chamber in which four moveable slabs are inserted. Schlieren photography is employed to visualize the ¯ow and shock structure associated with any degree of ¯uid rotation. Static and Pitot pressure measurements are used to obtain the velocity distribution in the swirl chamber. These measurements show that the ¯uid inside the chamber is irrotational and that choking of the nozzle takes place at dierent critical pressure ratios depending on the degree of the ¯uid rotation. The resulting gain in noise reduction was determined using sound pressure measurements. The results show that small ¯ow rotation (M f = 0Á39) weakens the internal shock strength, reduces the cell length and decreases the screech noise generated. Higher ¯uid rotation is found to have no additional eect on noise reduction in supersonic jets. A maximum noise reduction of 12 dB is found to take place in jets with 1Á18 Mj 1Á4.