Aerodynamic characteristics of airfoils with Gurney flaps in the Martian atmospheric environment

Rotorcraft in the thin and cold Martian atmospheric environment usually operate under low Reynolds number but high Mach number conditions, yielding aerodynamic performance inferior to that on Earth. In the present paper, the aerodynamic characteristics of the low-Reynolds-number airfoil CLF5605 in the Martian atmospheric environment were studied by solving the three-dimensional unsteady incompressible Reynolds-averaged Navier-Stokes equations, employing the k-ω SST turbulence model. It was found that unsteady laminar separation occurs at the trailing edge of the airfoil, resulting in the continuous formation and shedding of separation vortices, low-frequency oscillation of lift and drag coefficients, and deterioration of aerodynamic characteristics. To mitigate the reduction in lift, we propose the installation of Gurney flaps on the trailing edge. We systematically studied the aerodynamic characteristics of airfoils equipped with 2% Gurney flaps across various Reynolds numbers, Mach numbers, and angles of attack. The results show that Gurney flaps can effectively suppress unsteady laminar separation thereby enhancing lift. However, they do not increase the lift-to-drag ratio, and the lift enhancement is only effective within the range of Reynolds numbers Re = 5000 to 30000, angles of attack α = 0 to 3°, and Mach numbers below 0.65. Furthermore, we propose three design schemes for rotors incorporating Gurney flaps, which exhibit superior thrust, torque, and hovering efficiency compared to clean rotors. This study provides a valuable reference for subsequent design optimization of rotors for Mars unmanned aerial vehicles (UAVs).