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This paper presents experimental results on the aeroacoustic performances of a NACA 65(12)-10 aerofoil subjected to serrated leading edges. The serration patterns of these leading edges are formed by cutting into the main body of the aerofoil, instead of extending the leading edges. Therefore these serrated leading edges, when attached to the main body of the aerofoil, will always result in the same overall chord length. The experiment was performed in an aeroacoustic wind tunnel facility. These serrated leading edges were investigated for their effectiveness in suppressing four different types of noise sources: laminar instability tonal noise, leading edge separation bubble noise, turbulence–leading edge interaction noise and trailing edge self-noise. Streamwise vortices produced by an optimised serrated leading edge can suppress the separation bubble at the trailing edge, thereby reducing the instability laminar tonal noise significantly. It is found that the most effective serration configuration is the one with the largest serration amplitude and smallest serration wavelength. Without even relying on the streamwise vortices, the sawtooth geometry of the serration itself can already be sufficient to suppress the leading edge separation bubble. Due to the special geometry of the NACA 65(12)-10, it is very effective in the production of laminar separation bubble noise at the leading edge. The use of serrated leading edge can therefore be an effective passive device to suppress this particular noise source. Similarly, the most effective serration geometry in the reduction of turbulence– leading edge interaction noise is the one with the largest serration amplitude and smallest serration wavelength. However, this configuration is also prone to generating superfluous noise at high frequency. Extensive boundary layer and very near wake measurements were performed to investigate the flow structures on the NACA 65(12)-10 aerofoil with a large serration amplitude leading edge. It can be concluded that the serrated leading edge is very disruptive to the hydrodynamic growth of the turbulent boundary layer at the trailing edge. Evidences on the reduction of boundary layer low-frequency turbulence at the trailing edge could support the hypothesis of a reduction in the low-frequency far field noise. This remains to be confirmed in the future studies.

On the Effect of Leading Edge Serrations on Aerofoil Noise Production