Giovanni Lacagnina

Aeroacoustics and aerodynamics of impinging supersonic jets: Analysis of the screech tones

The interaction between acoustics and aerodynamics of a supersonic jet is an actual fundamental topic which has been a matter of discussion in the last decades. The present paper is devoted to the experimental analysis of free and impinging jets with particular attention on the effect of an impinging surface on screech tones. The acoustics is studied using free-field microphones, while Particle Image Velocimetry is used to investigate the velocity field. The analysis of acquired data allowed to verify and explain the coupling between acoustic discrete tones and mean and fluctuating flow velocities.

Leading edge serrations for the reduction of aerofoil separation self-noise

This paper presents an experimental investigation into the use of LE serrations for the reduction of trailing edge self-noise, at least for the NACA-65 aerofoil family. It is shown that the leading edge serrations are able to reduce the self-noise in a low frequency range at small and negative angles of attack. The exact mechanism of this reduction is still not completely discovered, but the LE serrations are discovered able to modulate the mean velocity field and turbulent velocity spectrum in that range of frequencies, as well as to dampen the effect of the angle of attack on the pressure field and to reduce its coherence. We emphasise that this paper represents work in progress and further investigations are still necessary in order to completely understand the dynamics behind this reduction.

Analysis of the characteristic acoustic tones of an impinging jet

The acoustic emission of a supersonic jet is an interesting and fundamental issue due to the several technological applications and the diverse physical aspects to be still clarified. An experiment ...

Effect of Leading Edge serrations in reducing aerofoil noise near stall conditions

This paper aims at evaluating the possibility of reducing the noise generated by the separated flow over an aerofoil, due to conditions near to or of stall, by the introduction of serrations on its leading edge. First of all the onset of the separation on the aerofoil surface and the associated noise have been investigated. Different serration geometries as regards wavelength and height are considered, in order to identify the configuration which performs the best in terms of noise.