An experimental study of the turbulence quantities in the boundary layer and near-wake of an airfoil placed at upstream of a 90° bend

This paper presents the results of an experimental study of the near-wake of a NACA 0012 airfoil placed upstream of a 90 degrees bend section using hot-wire anemometry. The bend has a cross-section of 0.457 m x 0.457 m with a mean radius-to-height ratio of 1.17, and the airfoil is of chord length 0.15 m. Among the features studied are the effects of changes in the orientation of the airfoil with respect to the oncoming flow and the effects of the freestream velocity, namely, 10 m/s, 15 m/s and 20 m/s corresponding to chord Reynolds numbers of 1, 1.5 and 2 x 10(5), respectively. Emphasis is placed on the boundary layer on the upper surface of the airfoil and the wake up to one chord length downstream. The parameters of interest are the mean and turbulence quantities and their variations in the streamwise, normal and spanwise directions. Results from the investigations indicated the sensitivity of the wake characteristics to the boundary layers on the airfoil. Measurements of mean velocity and streamwise turbulence intensity taken in the spanwise direction within the wake revealed wave-like variations which are linked to the presence of vortical structures in the wake. (C) 2010 Elsevier Inc. All rights reserved.