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On the use of modern software for the computation of noise of a large aeroacoustic wind tunnel propeller

Hemon P.

Research Bulletin / Warsaw University of Technology, Institute of Aeronautics and Applied Mechanics

1999

nr 9

15-22

The propeller design for the aeroacoustic wind tunnel project at the Institut Aerotechnique is an important activity which requires prediction tools. The aeroacoustic measurements require that no noise generated by the propeller is radiate through the duct to reach the test chamber. We are dealing here with the sound at the blade passing frequency and at its harmonics. In subsonic conditions, the main noise generated is due to the interaction between the rotor and the stator, or a supporting structure, and the resulting frequencies are a linear combination of number of blades in the rotor and in the stator. A parametric study of the problem has good potential in optimising noise radiation when the effect of duct cut-off is taken into account. The principle used for the calculations is derived from the Ffowcs-Williams-Hawkings equation. The wake of the rotor blades is obtained by means of an empirical formula, assuming a Gaussian shape for the velocity deficit, and the unsteady lift is computed using Sears' theory. This approximation is considered sufficient for the purpose of this study which aims at finding an optimum configuration for the propeller.