ISSN 1002-1027  CN 11-2952/G2

Acta scientiarum naturalium Universitatis Pekinensis

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Coherent Acoustic Sources in the Mixing Layer of A Planar Jet

SUN Zhili, YAN Dachun, NIE Jin   

  1. Department of Mechanics and Engineering Science, Peking University, Beijing, 100871
  • Received:2002-03-29 Online:2003-01-20 Published:2003-01-20

Abstract: Experimental researches on coherent characteristics of sound generated by instability waves in the mixing layer of a planar jet under acoustic excitation are proceeded through the measurement of the coherent time scale. It demonstrates that the coherent time scale keeps a high level in the growing stage of coherent structures under the motivation of instability waves and then turning down abruptly at the breaking point where the large-scale eddies begin to shed downstream. It provides a criterion whether the instability wave or convective eddy becomes dominant in the contour map of the fluctuating velocity amplitude distribution with their particular expression of Lighthill stress.