K.W. Kinzie, D.K. McLaughlin

The aerodynamic and acoustic properties of supersonic elliptic, rectangular, and circular jets are experimentally investigated. All three jets are perfectly expanded with an exit Mach number of approximately 1.5 and are operated in the Reynolds number range of 25,000 to 50,000. The reduced Reynolds number facilitates the use of conventional hot-wire anemometry and a glow discharge excitation technique which preferentially excites the varicose or flapping modes in the jets. In order to simulate the high velocity and low density effects of heated jets, helium is mixed with the air jets. This allows the large-scale structures in the jet shear layer to achieve high enough convective velocity to radiate noise through the Mach wave emission process. Experiments in the present work focus on comparisons between the cold and simulated heated jet conditions and on the beneficial aeroacoustic properties of non-circular jets. Comparisons are also made between the elliptic and rectangular jets. When helium is added to the jets, the instability wave phase velocity is found to approach or exceed the ambient sound speed. The radiated noise is also louder and directed at a higher angle from the jet axis. In addition, near field hot-wire spectra are found to match the farfield acoustic spectra only for the helium/air mixture case. These results demonstrate that there are significant differences between unheated and heated asymmetric jets in the Mach 1.5 speed range, many of which have been found previously for axisymmetric jets. The asymmetric jets were also found to radiate less noise than the round jet at comparable operating conditions. Strong similarities were also found between the aerodynamic and acoustic properties of the elliptic and rectangular jets.

First Joint CEAS/AIAA Aeroacoustics Conference, München, 1995

Conference Paper

englisch

21,0 x 29,7 cm, 10 Seiten

DGLR-Bericht, 1995, 1995-01, First Joint CEAS/AIAA Aeroacoustics Conference - Proceedings; S.81-90; 1995; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

NA

aeroacoustics, noise measurement

Bibliothek

1995