Numerical simulation of unsteady aerodynamic characteristics of parafoil airfoil

The unsteady aerodynamic characteristics of parafoils are a matter of flight stability and flight safety and are worthy of in-depth study. In this paper, the computational fluid dynamics (CFD) method was used to carry out an unsteady numerical simulation of the parafoil airfoil under the dynamic change of the angle of attack, so as to analyze the influence of the average angle of attack, the amplitude of the angle of attack, and the reduced frequency on the unsteady aerodynamic force and flow field pattern of the parafoil airfoil. The results show that an increase in any one of the above three parameters leads to a significant increase in the aerodynamic unsteadiness of the parafoil airfoil. The average angle of attack and the amplitude of the angle of attack amplitude jointly determine the dynamic range of the angle of attack of the airfoil, which significantly affects the dynamic stall characteristics of the parafoil airfoil; the change in reduced frequency affects the lift hysteresis effect of the parafoil airfoil, with the maximum lift coefficient increasing linearly with increasing reduced frequency. Further flow field analysis shows that the unsteady effect of the angle of attack of the parafoil airfoil in the dynamic increase stage delays the occurrence of airfoil flow separation on the one hand, and on the other hand, it flattens the separating vortex against the upper airfoil, which together contributes to a significant increase in the critical angle of attack and maximum lift coefficient of the parafoil airfoil relative to the constant case. The results of this essay will help to enhance the understanding of the unsteady aerodynamic force and flow field patterns of parafoil airfoil, support the prediction of unsteady aerodynamic forces and safety assessment of parafoil in complex wind environments.