Aerodynamic performance under windblown sand conditions of a UAV's airfoil at low-Reynolds number and transonic flow under the Martian carbon dioxide atmosphere

In response to the challenges posed by the low-Reynolds-number transonic sandy environment on Mars on the aerodynamic performance of airfoils, this study investigated the flow field characteristics and anti-erosion capabilities of optimized airfoils under dynamic sand disturbance through numerical simulation and theoretical analysis. The γ-Transition SST k-ω turbulence model coupled with a discrete phase model was employed to establish a high-precision computational framework for sandy two-phase flow. The key findings are as follows: Under short-term sand impact lasting 0.02 s (Ma = 0.9, 400 particle count), the average lift-to-drag ratio of the optimized airfoil (Opt) during the stable period reached 3.75, representing a 49.4% improvement compared with the original airfoil (Ori). The fluctuation amplitude decreased to 3.7 ± 0.001, demonstrating Opt's enhanced transient anti-disturbance capability achieved by suppressing shock wave oscillation and boundary layer separation; During long-term sand exposure (0–0.1 s), the initial lift value of Opt was 2.963 N, which was 11.4% higher than that of Ori. After stabilization, the decay rate of Opt was 13.5%, which was significantly lower than that of Ori (21.1%). This improvement was attributed to the secondary vortex shedding effect induced by the λ wave system, which reduced the average sand concentration on the pressure surface by 10.3%. Entropy production analysis revealed that the high dissipation zone at the tail of Opt disappeared, the number of shock waves decreased from two to a single main shock wave, wave drag was reduced, and the uniformity of sand distribution improved, effectively mitigating surface wear and flow separation. This study provides a theoretical foundation and engineering guidance for optimizing airfoil designs for Martian flight vehicles operating under extreme aerodynamic–erosion coupling conditions.