Nonlinear Attenuation and Quantitative Evaluation of Aerodynamic Performance for Wing Hail Pits Based on Damage Tolerance

This study aims to analyze how hail pit damage on aircraft wing surfaces affects flight safety after hail impact, characterize the aerodynamic performance degradation, and establish a quantitative evaluation method. Computational fluid dynamics (CFD) simulations are performed using a three-dimensional wing model, and the Shear Stress Transport (SST) k-ω turbulence model is adopted for numerical simulation. The effects of hail pits with different numbers (0–50) and diameters (10–20 mm) on the aerodynamic performance of the wing are investigated under various Mach numbers (0.7–2.0) and angles of attack. By analyzing lift, drag and lift-to-drag ratio and introducing a decay rate for quantitative analysis, it is found that the attenuation of aerodynamic performance exhibits distinct nonlinear characteristics. The maximum performance variation rate does not appear under the condition with the largest number of hail pits. Instead, it peaks at ten pits, and the maximum lift–drag ratio variation rate reaches 33.7% at the transonic Mach number of 1.3. As the number of pits continues to increase, the extent of aerodynamic performance variation does not intensify concurrently but enters a slowly growing plateau stage. Simulation results reveal that intense flow separation and consequent drastic variation in aerodynamic performance are observed for airfoils with sparse hail pits under transonic conditions. As the number of pits increases, densely distributed pits restrain severe flow separation and drive aerodynamic performance degradation toward saturation, and the relevant mechanism is tentatively attributed to surface roughening and flow turbulization effects. As a parametric engineering CFD study, the present findings can serve as preliminary engineering references for similar parametric CFD analyses, as well as for aircraft release assessment and pilot operational decision-making when in-flight hail damage occurs.