Assessment of Slat Extensions and a Cove Filler for Slat Noise Reduction

Abstract

The slat of a high-lift wing can be a significant noise source during approach and landing. This paper describes an experimental study of the effects of two passive devices (namely, slat extensions and a cove filler) on the aerodynamics and acoustic radiation from a 30P30N model. Test conditions include three effective free-air angles of attack of 5.5, 7.5, and 13 deg, as well as three Reynolds numbers of 1.2, 1.5, and . Steady surface pressure measurements are used to assess the aerodynamics near the midspan section. Unsteady surface pressure and far-field acoustic array measurements are performed to evaluate the near- and far-field pressure fluctuations, respectively. Delay-and-sum beamforming is applied to localize the noise sources and to provide integrated spectra. The slat cusp extensions barely affect the mean distribution, whereas the longest extension achieves up to a 5.4 dB reduction in the overall sound pressure level. The slat-cove filler yields an even higher noise reduction that is lower than the baseline by up to 14 dB. Even though the aerodynamic assessment of the cove filler is incomplete due to the covered pressure ports, the mean distribution over the remaining surface of the model indicates a rather small change compared with the baseline measurements.