Prediction of advanced propeller noise in the time domain

This paper presents a brief derivation of a formula for prediction of the noise of high-speed propellers in the time domain. This formula is based on the solution of a linear wave equation (Ffowcs Williams-Hawkings equation) assuming that the sources are located on the actual blade surface. An approximation of this formula, using the assumption that the sources are on the mean surface of the blade, is also presented which is considerably simpler than the full surface expression. Both the mean and full surface formulas are suitable for prediction of noise of supersonic sources on the blade. They were derived to overcome some of the practical numerical difficulties associated with other acoustic formulations. A discussion of coding these formulas for numerical work follows. Some comparison of predicted results with experimental data is also included which demonstrates the usefulness of the derived analytic expressions.

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