Influence of Unsteady and Kinematic Parameters on Aerodynamic Characteristics of a Pitching Airfoil

Abstract

Most unmanned aerial vehicles which fly with moving wings or encounter gusts at low Reynolds number conditions make pitching oscillation motions. The aerodynamic forces and flow field around the wings vary dramatically with the unsteady motion parameters (reduced frequency, mean angle of attack, and amplitude). This study conducts numerical simulations to investigate the influence of such parameters on the aerodynamic characteristics of a pitching NACA 0012 airfoil. The respective cases are researched through computational fluid dynamics (CFD) based on the finite-volume method (FVM). The governing equations are the unsteady, incompressible two-dimensional Navier–Stokes (N-S) equations. The airfoil performs sinusoidal pitching oscillations with respect to the quarter chord at the Reynolds number 2.53×105. A detailed analysis of the force coefficients and how their evolution is affected by the dynamics of flow structures generated during pitch oscillations is presented. The results show that these parameters change the instantaneous force coefficients quantitatively and qualitatively. The effective angle of attack is different at various locations of the airfoil chord during the oscillation motion, which determines the deviations of forces at the same angle of attack during pitch-up and pitch-down periods. It is also observed that the strength, interaction, and convection of the vortex surrounding the airfoil are significantly affected by the variations of these parameters.