U. Michel

It is shown that Lighthills acoustic analogy can be used to derive scaling laws for the broadband shock noise of supersonic jets, including the effects of highspeed flight. The solution for the power-spectral density of the sound pressure in the far field of a circular jet is used for the derivation. The mean flow field ea.used by the shock cells within the jet is assumed to modulate the source terms which is shown to cause additional noise termed broadband shock noise. It is discussed, how this noise is influenced by source coherence (large scale vs small scale turbulence) and source interference. It is shown that large scale structures are not required for broadband shock noise, as is sometimes stated. Experimental data from engine tests and from many model tests show that broadband shock noise is characterized by rather broad humps in the frequency spectra. This is shown to be only compatible with a rather small scale turbulence. Only the narrow peaks in the shock noise spectra of low Reynolds number jets indicate a dominance of large seale structures. The scaling laws for the influence of jet speed, flight speed, and emission angle on the frequency of broadband shock noise are derived and found to agree with previous theoretical results.

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.545-554; 1995; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

NA

aeroacoustics

Bibliothek

1995