Airfoil Optimization and Rotor Aerodynamics Exploration for Mars Helicopter using Direct Numerical Simulation

Abstract

This study presents a Direct Numerical Simulation (DNS) based airfoil design optimization and 3D rotor aerodynamic analysis tailored to the challenging low Reynolds number environment of the Martian atmosphere. To enhance the hover performance of the Mars Airborne Explorer (MAE) during Pit craters exploration, airfoils are optimized at three radial stations of the blade to minimize mean drag across a range of design lift coefficients. The optimization employs Improved Geometric Parameterization (IGP) method with Non-Uniform Rational B-Splines (NURBS) and surrogate-based efficient global optimization to efficiently explore the design space. The optimized airfoils demonstrate 21-28% reductions in mean drag compared to the baseline clf5605 airfoil. This improvement is primarily achieved through Sharp Raised-Lip (SRL) and thin-cambered geometries, which force leading-edge shear layer separation and reduce skin friction drag. The optimized airfoils are integrated into a full 3D rotor and evaluated under hover conditions. Results show a 7% increase in Figure of Merit and a 7.6% reduction in power coefficient at the design thrust condition. The comparison of 2D and 3D behaviors of the optimized airfoils reveals that the midboard region exhibited similar characteristics in both 2D and 3D, while in the outboard tip region, spanwise flow induces unsteadiness, resulting in behavioral differences. Furthermore, an off-design analysis is carried out to investigate the rotor’s performance variations across a broad thrust range.