Unsteady Aerodynamic Characteristics of Impulsively Started NACA0012 Wing at Low Reynolds Numbers

Abstract

The unsteady aerodynamic characteristics of an impulsively started NACA0012 wing were experimentally investigated in a towing tank at a low Reynolds number of 36000. The flow field variation between rest to steady state was discussed based on the measured lift and pitching moment coefficients. The trend of the time-series variation in the aerodynamic coefficients depends on the angle of attack. The nondimensional towing distance required to steady-state also depends on the angles of attack. The distance required to reach the corresponding steady state is more than ten times the chord length at low angles of attack and large angles above the stall. The measured lift and pitching moment coefficients indicate that the boundary layer attaches on the wing surface at the early stage of the translation below the stall angle. The laminar separation occurs during the acceleration process. The flow field variation from the occurrence of the boundary layer separation to its steady state depends on the angle of attack. The dependence causes different unsteady aerodynamic characteristics compared to those of flat plate wings reported in previous studies.