2D URANS simulation of aerodynamic loads on a pitching airfoil: Impact of computational parameters

A numerical study of aerodynamic loads on pitching airfoils using Computational Fluid Dynamics (CFD) is challenging due complicated airfoil-vortex interactions and the possible occurrence of dynamic stall. In the latter case the combination of boundary layer transitions and airfoil oscillations result in the generation, passage and shedding of vortex-like disturbances over the suction side of the airfoil. The challenges in the numerical investigation of aerodynamic loads on a pitching airfoil are twofold: different kinematic parameters can play an important role in flow unsteadiness and dynamic stall behavior, and the CFD results can be very susceptible to the model parameters adopted. Thus, a systematic quantification of how these parameters affect the flow is of great importance to identify crucial computational parameters and to understand the physical effect of kinematic parameters. This paper presents the aerodynamic load coefficients of a NACA 0012 pitching airfoil in the deep dynamic stall regime, and the results obtained are compared with measurements from a reference wind tunnel experiment. The impact of various important computational parameters on the numerical results is investigated, which are the blockage ratio, time step size, freestream turbulence intensity and the specific turbulence model used