This is the accepted version of the paper. This version of the publication may differ from the final published version. Permanent repository link: https://openaccess.city.ac.uk/id/eprint/23398/ Link to published version: http://dx.Abstract The[AU: Please check edited affiliations for accuracy][AU: Please check edited title; 'airfoil' is the US spelling. Is 'Investigation of the' necessary in the title? Often titles omit wording such as that since it's understood.]main focus of this paper is on investigating the noise produced by an aerofoilairfoil at high angles of attack over a range of Reynolds number[AU: Journal style does not use italics/math mode for Re. Please check for consistency.]Re ≈ 2 × 10 5 -4 × 10 5 .[AU: Journalstyle uses multdots only in vector math; they have been changed to multcrosses. Please check for consistency.]The objective is not modellingmodeling this source of noise but rather understanding the mechanisms of generation for surface pressure fluctuations, due to a separated boundary layer, that are then scattered by the trailing edge. To this aim, we use simultaneous noise and surface pressure measurement in addition to velocimetric measurements by means of hot wire anemometry and time-resolved particle image velocimetry. Three possible mechanisms for the so-called "separation-stall noise" have been identified in addition to a clear link between far fieldfar-field noise, surface pressure, and velocity fields in the noise generation. * G.Lacagnina@soton.ac.uk

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This paper employs serrated leading edges to inject streamwise vorticity to the downstream boundary layer and wake to manipulate the flow field and noise sources near the blunt trailing edge of an asymmetric aerofoil. The use of a large serration amplitude is found to be effective to suppress the first noise source—bluntness-induced vortex shedding tonal noise—through the destruction of the coherent eigenmodes in the wake. The second noise source is the instability noise, which is produced by the interaction between the boundary layer instability and separation bubble near the blunt edge. The main criterion needed to suppress this noise source is related to a small serration wavelength because, through the generation of more streamwise vortices, it would facilitate a greater level of destructive interaction with the separation bubble. If the leading edge has both a large serration amplitude and wavelength, the interaction between the counter-rotating vortices themselves would trigger a turbulent shear layer through an inviscid mechanism. The turbulent shear layer will produce strong hydrodynamic pressure fluctuations to the trailing edge, which then scatter into broadband noise and transform into a trailing edge noise mechanism. This would become the third noise source that can be identified in several serrated leading edge configurations. Overall, a leading edge with a large serration amplitude and small serration wavelength appears to be the optimum choice to suppress the first and second noise sources and, at the same time, avoid the generation of the third noise source.