Turbulence-airfoil interaction noise reduction using wavy leading edge: an experimental and numerical study

International audiencePassive treatments aiming at reducing turbofan broadband noise have been recently studied in the framework of European Project FLOCON. A concept based on a sinusoidal variation of the leading edge of a single airfoil expected to decrease interaction noise has been investigated by ONERA. Turbulence-airfoil interaction mechanism is achieved using a turbulence grid located upstream of a NACA airfoil tested in ISVR anechoic open wind tunnel. High noise reductions are obtained (3-4 dB) for all studied flow speeds. Experimental work is supplemented by numerical simulations using RANS/LES and CAA Euler-based approaches to predict the acoustic response of the wing. Isentropic turbulence is synthetically injected by means of a suited inflow boundary condition. Unsteady simulations are restricted to the baseline case (without treatment) and the present paper focuses on direct Euler methodology which provides reliable power spectrum density comparing to experiment. Effect of leading edge serrations on aerodynamics and noise is emphasized using Amiet thin airfoil theory, RANS solutions and available measurements