On defining the jet noise source quadrupole structure on the basis of multi-array acoustic data and correlation theory

摘要

Quadrupole structure of jet noise sources is analyzed on the basis of the jet noise data obtained by the azimuthal decomposition technique (ADT). ADT method is used to decompose far-field jet noise into azimuthal harmonics. At the previous stages of the study new correlation model of quadrupole noise sources was developed and validated against ADT jet noise data obtained by 6-microphone array. In the current paper, additional ADT data obtained by means of two microphone arrays are used to specify noise source distribution. It is found that azimuthal modes auto-spectrum is not sensitive to the source axial distribution. On the contrary, the azimuthal modes cross-correlation is sensitive to the source location and distribution over the jet axis. Thus, the cross-correlation data obtained by two microphone arrays provide important additional information which can be used to gain insight into the noise source structure.