Reynolds and Mach Number Effects on the Aerodynamics and Design of Airfoils for the Martian Atmosphere

A parametric study is carried out to assess numerically the flow dependence on the Reynolds and Mach numbers in the Martian atmosphere, under the RANS approximation. The Ishii airfoil at Re=23,000 is taken as a reference. The Laminar Separation Bubble (LSB) and large separations are identified as the leading cause for the small lift-to-drag ratio in the low-Reynolds regime. Numerical simulations highlight a strong sensitivity of the aerodynamic coefficients on these non-dimensional parameters, which influence the LSB. The reference Ishii airfoil is optimized for different flight conditions using global and local techniques. The output optimal geometries exhibit a strong dependence on the Reynolds number and a weak dependence on the Mach number. By reducing the Reynolds number, optimal airfoils are thinner, the leading edge radius gets smaller, the camber increases, and the geometry of the suction side exhibits a lower curvature.