Modélisation analytique du bruit aérodynamique à large bande des machines tournantes : utilisation de calculs moyennés de mécanique des fluides
Noise radiated by low-speed fans or aircraft engine fans is made up of tonal noise and broadband noise, the latter being sometimes dominant. The present study suggests a hybrid method to model broadband noise based on analytical formulations using appropriate post-processings of Reynolds-Averaged Navier-Stokes equations. A bibliographic study on broadband noise radiated by airfoils is first carried out. Amiet’s analytical models are presented for the turbulence-interaction noise and trailing-edge noise mechanisms, and some extensions are also proposed. Sensors are then placed into blades from a low-speed fan to measure the wall-pressure fluctuations in the vicinity of the trailing edge. The trailing-edge noise model is extended to the case of a fan blade and validated by comparing with the acoustic pressure measured in an anechoic chamber. An extension is proposed to apply the free-field aforementioned formulation to the aircraft engine fan acoustic power. In an industrial context, Reynolds-Averaged Navier Stokes simulation of the flow around fan blades provides only mean aerodynamic values. In simple cases, semi-empirical models are able to deduce the wall-pressure spectra from the aforementioned data. Since adverse pressure gradient induces a wall-pressure spectrum level increase, semi-empirical models can not be applied for airfoils or blades. An improved model is then proposed.