Enhancement of Aerodynamic Performance of Inflatable Airfoil Based on Sobol’ Global Sensitivity Analysis

This paper presents an aerodynamic enhancement method for inflatable airfoils based on Sobol’ global sensitivity analysis. Two airfoils commonly used in inflatable wing applications, the cambered NACA4318 and the symmetric NACA0018, are investigated using computational fluid dynamics under a representative low-Reynolds number operating regime for low-speed inflatable-winged unmanned aerial vehicles. The influence of geometric deviations between an idealized rigid airfoil and the corresponding real inflatable wings is first explored to justify the utilization of rigid surrogate airfoils for aerodynamic investigation. The effects of surface undulations are then examined by applying sensitivity analysis to different undulated regions on both airfoils. First- and total-order Sobol’ indices are employed to quantify the direct and combined contributions of individual surface regions to lift and drag over a range of angles of attack. The results indicate that aerodynamic performance is largely governed by individual surface sections, with minimal interactive effects. In particular, undulations on the upper surface, especially near the leading edge, are shown to have a pronounced adverse effect on both lift and drag. Based on these findings, targeted surface-smoothing strategies are proposed to improve aerodynamic performance relative to fully undulated configurations. The effectiveness of the proposed strategies is validated through wind-tunnel experiments. The results provide practical guidance for the aerodynamic enhancement of inflatable airfoils with similar thickness and camber characteristics operating under low-Reynolds number conditions.