Pritchard's Approximation in Array Modeling
Technical rept. Apr-Sep 1999
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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An investigation into the applicability and accuracy of Pritchards approximation for closely packed transducer arrays is undertaken. A new, modal Pritchard approximation is developed, based upon normal modes of the acoustic medium, and is tested for arrays of acoustically hard spheres to ascertain its accuracy in determining the mutual acoustic radiation impedance between array elements. For ka1, it is found that the modal Pritchard approximation works quite well in approximating the mutual radiation impedance of a two element array, even for relatively close spacing, but for arrays of three or more scatterers in close proximity, the approximation may have relatively large errors. The effect of neglecting inter-element scattering is analyzed for the monopole to monopole scattering of various configurations of a three element array and a sixteen element double line array.