S. Kaji, N. Nishijima

Supersonic jet screech experienced by the rectangular nozzle with one pair of side walls added is studied both experimentally and numerically. A detailed observation on the screech phenomenon made here advances considerably the understanding on the mechanism of sound generation. The numerical simulation proves that the computational aeroacoustics is effective for strongly coupled flow-acousto problems such as screech. The flow visualization by the Acoustically Triggered Pulse Laser Schlieren System clearly shows the dynamic motion of the third shock cell in the flapping mode. A traveling shock is found to exist in the third shock cell and the sound is generated at the moment when the traveling shock coalesces into the end shock of the third shock cell. The instantaneous pressure distribution on the side wall shows that the pressure wave convecti vely propagates along the jet in the near field of the jet, while it propagates acoustically in the vertical direction away from the jet. Numerical simulation gives various similar aspects of screech to those obtained by the experiment; the screech frequency, the flow field, the fluctuating pressure distribution, etc. The calculated acoustic intensity shows that the acoustic energy is radiated at the end of the compression portion of each shock cell. The source of the first shock cell seems to supply the acoustic energy to its own shear layer to sustain the oscillation. It is also shown that the dimple spots observed in the pressure amplitude contour are due to the interaction between discrete sources located at the end of each shock cell.

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.131-140; 1995; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

NA

aeroacoustics, noise measurement

Bibliothek

1995