Numerical Assessment of Turbulence-Cascade Noise Reduction and Aerodynamic Penalties from Serrations

Abstract

This work is related to the investigation of innovative stator designs aiming to reduce the dominant interaction noise in aeroengines. The study of turbulent structures definition is crucial for the accurate prediction of broadband noise radiation from passive treatments, as leading-edge serrations studied here. A modified Fourier modes-based methodology is proposed to obtain a fully three-dimensional incompressible turbulence field, while taking into account periodic and wall-boundary conditions. A low-noise geometry is examined along with the reference profile on a rectilinear seven-vane cascade rig using a hybrid computational fluid dynamics/computational aeroacoustics method. Numerically assessed noise reductions from the serrated airfoils are favorably compared with an analytical solution and a semi-empirical law. An overall sound power-level reduction around 4 to 6 dB is obtained at three acoustic certification points. Finally, the aerodynamic performances are also evaluated through Reynolds-averaged Navier–Stokes computations, and an improved variant of the initial treatment is proposed, allowing for acceptable penalties at the aerodynamic design point.