Influence of Wake Interference and Freestream Turbulence on Airfoil Performance in the Cylinder-Airfoil Configuration

摘要

Time-averaged lift and drag of a NACA 0012 in the wake of a circular cylinder of diameter D were obtained via wind tunnel experiments. Reynolds number based on airfoil chord c was 1 × 10~5 while the gap distance G between the cylinder and airfoil varied from 2.0D to 9.6D. Lift and drag decreased in the cylinder wake, with drag being negative for angles of attack less than 10°. Two distinct force trends were observed depending on the gap distance. For G/D < 3.8, the cylinder and airfoil were aerodynamically coupled as vortex shedding in the cylinder wake was suppressed. The two bodies were decoupled for G/D ≥ 3.8. Vortex shedding reappeared, forming vortices at the airfoil leading edge. The influence of freestream turbulence was investigated using a turbulence grid with an average streamwise turbuluence intensity of 10 % and was found to cause an increase in lift and drag. The coupled region between the cylinder and airfoil was reduced to G/D < 2.0. With or without the turbulence grid, the airfoil stall was delayed to 18° compared to 10° for the isolated NACA 0012.