Acoustics of a moving source in a moving medium with application to propeller noise

In this paper the development of a convective acoustic analogy equation for the case of a moving source in a moving medium is described and the resulting form is compared to that of Blokhintsev and that of Ffowcs Williams and Hawkings. Computational results for a modern propeller with supersonic tips illustrate that both the “moving observer” and “moving medium” interpretations of the acoustic analogy lead to the same results, but that computational efficiency may dictate the use of the moving-medium approach. Using similar programming techniques, the moving-medium calculations show a sixfold decrease in CPU time over those obtained using the moving-observer formulation. The computed waveforms from both methods show improvements over previously published results.