Unsteady Aerodynamic Characteristics of NACA0012 Airfoil Undergoing Constant-Pitch-Rate Motions at Low Reynolds Numbers

Abstract

We investigated the unsteady aerodynamic characteristics of NACA0012 airfoil undergoing constant-pitch-rate motions at low Reynolds numbers (Re = 2.5 ×10⁴ ∼ 1 ×10⁵). In the wind tunnel testing, the lift, drag, and pitching moment were measured at constant pitch rates. The experimental results show that unsteady aerodynamic characteristics are equivalent to near-steady ones when the nondimensional pitch rate r is smaller than 4.5×10^-4. When Reynolds number equals to 5 ×10⁴ or less, the nonlinearity of C_l near the pitch angle of 0° is a significant feature at low Reynolds numbers, even in unsteady cases. It is also found that, in the low-pitch-angle region, large changes in C_l and C_m occur due to the unsteady effect. These changes occur at r smaller than in the cases of higher Reynolds numbers. The hysteresis in C_l significantly depends on pitch angle and nondimensional pitch rate.