Reynolds Number and Shear Effects on NACA 0012 Airfoil

This work investigates the influence of the chord Reynolds number [Formula: see text] and the dimensionless freestream shear rate K on a NACA 0012 airfoil in the ranges of [Formula: see text] and [Formula: see text]. Loads on the airfoil and the streamwise velocity over the suction surface are measured using a load cell and molecular tagging velocimetry. For the range of parameters examined, the dominant effects are attributed to [Formula: see text], whereas shear has a weak influence, except at angles [Formula: see text] near stall. A key finding is the change in behavior from trailing-edge to leading-edge (LE) stall with a small [Formula: see text] increment in the range of [Formula: see text]. The lift coefficient characteristics [Formula: see text] for both uniform and shear flows exhibit a nonlinear behavior where the slope [Formula: see text] initially increases beyond [Formula: see text]. The increase, which occurs abruptly for LE stall cases, is unambiguously connected to closure of the separation bubble on the suction surface. [Formula: see text] at [Formula: see text] is found to generally increase with K but decrease with [Formula: see text]. Shear creates asymmetry by enhancing the magnitude of the maximum lift-to-drag ratio [Formula: see text] for [Formula: see text] and all [Formula: see text] as compared to uniform flow. For [Formula: see text], there is little change except in the narrow range of [Formula: see text], where [Formula: see text] decreases when shear is present.