Statistical-Empirical Modelling of Aerofoil Noise and Performance subjected to Leading Edge Serrations

Sinusoidal leading edge serrations of a cambered NACA65(12)-10 aerofoil were analysed with the aim of reducing leading edged broadband noise emissions due to aerofoil-gust-interaction in a high turbulent flow. A statistical-empirical model was developed to quantify the main effect as well as the interdependencies of flow and design parameters on the noise reduction capability of serrated leading edges. Apart from the main effects, significant interdependencies of turbulence intensity and serration wavelength, as well as serration wavelength and angle of attack were observed, validated and quantified. Aeroacoustic findings are complemented by visualisation of the aerodynamic flow pattern via particle image velocimetry for selected leading edge configurations in order to deepen the understanding of the underlying noise reduction mechanisms. It was observed that a noise reduction is accompanied by a reduction of the turbulence intensity within the serration interstices although it could be shown that aeroacoustic effects such as decorrelation effects of the incoming gusts are partly superposed to the effect of an altering turbulence intensity. Moreover, numerical studies were conducted to enable predictions of the aerodynamic performance in terms of lift and drag of the serrated leading edges with the objective to define a multi-optimum of noise reduction and aerodynamic performance.