The noise emitted by incoming turbulence interacting with an airfoil has many techno-logical applications, and has accordingly received much attention in the literature. Whilenumerous developments are focused on the determination of the airfoil response to a givenincoming gust, the characterization of the incoming turbulence seems to have received lessattention. An important aspect thereto is the validity of the assumptions made to describethe incoming turbulence as isotropic and homogeneous. In this work, hot wire anemometryand stereoscopic Particle Image Velocimetry are combined to obtain detailed measurementsof the turbulence generated by either a grid or a rod, interacting with a NACA 0012 airfoil.A particular focus is placed on the measurement of the turbulence properties in the veryclose vicinity of the leading edge, in order to quantify turbulence distortion and comparethe test data with Rapid Distortion Theory models. The experimental database permits toidentify significant distortions of the mean velocity field, turbulence intensities, correlationlengths and turbulence spectra in a region with size comparable to the airfoil leading-edgeradius of curvature. It is demonstrated that even in cases where the flow is nearly homoge-neous in the spanwise direction, small variations must be taken into account to improve thesound predictions. But the most significant effect to include in the prediction is the distor-tion of the incoming turbulence spectrum, here modeled using Rapid Distortion Theory, ifa meaningful sound prediction is to be obtained.
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