Aerodynamic performance of a characteristic airfoil at low-Reynolds number and transonic flow under Mars sand-containing environment

The propeller tip of an unmanned aerial vehicle on Mars operates at a low-Reynolds number (Re = 1–5 × 10⁴) and transonic velocity range (Ma = 0.7–1.2). Generally, this implies flow separation and shock waves in the flow field. Furthermore, the impact of Martian atmospheric sand particles significantly affects the aerodynamic performance, and numerical simulations of this issue have received increasing attention recently. Aimed at a characteristic airfoil, the study of a low-Reynolds number transonic flow and the influence of sand-containing flow on airfoil aerodynamic performance were analyzed in this study. The discrete phase model was adopted to simulate the two-phase flow considering Re = 8100–56 800 and Ma = 0.2–1.4. The results indicate that, compared with the atmospheric environment on Earth, the low-pressure atmosphere on Mars can delay the generation of the surface shock wave of the airfoil as well as alter the shock wave structure, significantly increasing the lift-to-drag ratio at high subsonic velocities (Ma = 0.6–0.8). Moreover, due to the weak compressive wave generated at the separation position, the low-pressure atmosphere weakens the strength of the trailing-edge oblique shock wave and reduces the drag when Ma = 0.9–1.4. Compared with a sand-free environment, sand-containing flow can affect the separation and transition positions of laminar separation bubbles, in addition to alter the shock wave structure. At different Mach numbers, the lift and drag of the airfoil first increased and then decreased as the sand particles flowed in the horizontal direction during the entire process of particles entering and exiting the airfoil flow field.