The effect of sinusoidal serrations applied to the leading-edge of the vanes of a realistic fan stage is investigated using high-fidelity numerical simulations. The CFD solver PowerFLOW based on a hybrid lattice-Boltzmann/very-large-eddy-simulation model is used to compute the unsteady flow and radiated noise of the 22-in source diagnostic test fan rig of the NASA Glenn Research Center. A computational model validated for three different geometries of the outlet guide vanes with straight leading edge is used. A subset of validation results is reported to prove the capability of the solver to accurately predict the influence of the stator geometry on the far-field noise. Different sinusoidal leading edge serrations are investigated for a radial and a swept stator and the same rotor and operating conditions. The influence of the serrations on the acoustic far-field and noise power level is reported in relation to the statistical properties of the velocity fluctuations in the wake of the rotor. Some noise reductions are obtained when the undulation amplitude and wavelength are large enough compared to the integral scales of the impinging turbulence fluctuations.

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 Noise radiated by modern fan stages are becoming comparable to jet noise due to engine trends:  Increase in bypass ratio  Transonic tip speeds  More compact, thus reduced fan-OGV distance  3 main fan stage noise sources:  Rotor-stator interaction noise  Rotor self noise: ingested boundary layer  Rotor-locked tones (for transonic tip speed)  Objective: demonstrate of the capability of SIMULIA PowerFLOW to simulate broadband and tonal fan noise for a wide variety of operating conditions and geometry variations

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