A high-order wavepacket model and inversion method for jet near-field noise sources

Conventional source inversion and sound field reproduction method based on microphone array are only applicable to jet far-field noise. An invertible equivalent source and its inversion method for jet near-field noise are proposed in this study. The inversion results can be utilized to reproduce the jet near-field noise. Firstly, the acoustic source model is constructed based on a tanh-type wavepacket, with the azimuthal order extended from the traditional axisymmetric mode to higher-order helical modes. Next, the dominant modes are identified through measurements using a designed circular array, and accurate helical mode power is calculated using principal component analysis. Then, a method based on the PIV measurements is proposed to determine the radial equivalent radius and axial truncation distance of the wavepacket model. Finally, an inversion method is proposed by minimizing the error between the calculated and measured axial distribution of normalized modal power. Experimental results demonstrate that the proposed wavepacket model accurately computes jet near-field noise, showing close agreement with measured data, with an average error of less than 1 dB. The accuracy of the proposed equivalent source model and the inversion method is thereby validated.