Applying inverse methods to distributed aeroacoustic sources

Holland, K.R. and Nelson, P.A. (2012) Applying inverse methods to distributed aeroacoustic sources. In Collection of Technical Papers - 11th AIAA/CEAS Aeroacoustics Conference. vol. 4, American Institute of Aeronautics and Astronautics. 2533 - 2540 . (doi:10.2514/6.2005-3000).

Abstract

The application of inverse source location and quantification methods to distributed aeroacoustic sources usually requires discretisation of the source region into finite-sized elements. To yield realistic estimates of the source strength distribution, the number of sensors used to sample the radiated sound field must, in general, be equal to, or greater than, the number of elemental source regions. Furthermore, the elemental source regions must be no larger than one-half of an acoustic wavelength at the frequency of interest if spatial aliasing is to be avoided. The combination of these requirements when considering large source regions and / or high frequencies can give rise to the need for very large numbers of sensors. This paper describes a technique that can drastically reduce the required number of sensors in situations where the source distribution is known to possess certain correlation structures. Distributed sources encountered in aeroacoustics problems can often be subdivided into regions of high mutual correlation in which case the model source cross-spectral matrix takes the form of a set of sub-matrices arranged along the diagonal. It is shown that under these circumstances, the minimum required number of sensors is reduced from the dimensions of the full source cross-spectral matrix to that of the sub-matrices. Examples and simulations of the application of this technique to typical aeroacoustic source distributions are presented

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Contributors

Author: K.R. Holland

Author: P.A. Nelson

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