Numerical study of dynamic stall effects on VR-12 airfoil with pitch oscillation and accelerated inflow

This study investigates the effects of positive horizontal acceleration of the freestream velocity on a pitch-oscillating VR-12 airfoil using computational fluid dynamics. The shear stress transport k–ω model, coupled with a low-Reynolds number correction, was employed for Re <10⁵ during dynamic stall. The flow equations were solved in two-dimensional, incompressible form using the finite volume method. The study examined various parameters, including positive acceleration values of the inflow and the angle of attack of the airfoil, to determine their impact on lift and drag coefficients, as well as the ratio. Additionally, the maximum lift coefficient was analyzed under different inflow and airfoil motion conditions. The results indicate that aerodynamic force coefficients and the ratio are influenced by both the attack angle and the acceleration of the inflow. Furthermore, inflow acceleration affects the onset of dynamic stall conditions. Generally, inflow acceleration modifies the lift coefficient of the airfoil during the upstroke, while having minimal effect on the drag coefficient, except near dynamic stall points. The findings also suggest that, for a specific airfoil, the sequence of factors with the greatest influence on lift force generation before static stall occurs is as follows: asymmetric airfoil oscillation, symmetrical airfoil oscillation, accelerated inflow, constant velocity inflow, and static airfoil.