Aerodynamic Performance Degradation Due to Canopy Bulging in Semi-Rigid Parafoils

This study investigates the aerodynamic performance degradation of semi-rigid parafoils caused by canopy bulging during inflation. Wind tunnel tests and numerical simulations, including Computational Fluid Dynamics (CFD) for rigid parafoil model and Fluid-Structure Interaction (FSI) for semi-rigid parafoil model, were conducted to analyze the aerodynamic effects of flexible canopy deformation. Experimental and numerical results consistently show that canopy bulging in semi-rigid parafoils leads to a reduction in the lift-curve slope, decreasing from K1 = 0.044 to K2 = 0.032. This degradation is primarily attributed to two mechanisms: (1) increased curvature near the leading edge of the upper surface slows the upper-surface flow and elevates static pressure; and (2) localized flow separation on the lower surface reduces static pressure beneath the canopy. These effects jointly diminish the pressure differential between the upper and lower surfaces of the parafoil, thereby reducing lift. Moreover, the semi-rigid parafoil shows greater susceptibility to large-scale flow separation at high angles of attack. These findings provide critical insights into the design and optimization of parafoil-based recovery systems in aerospace applications.