Highly Accurate Rotor Performance Analysis with Airfoil Optimization in Martian Atmospheric Environment

Kurzfassung

Martian rotorcraft operate under low Reynolds number and compressible flow conditions due to low atmospheric density and speed of sound. These conditions render conventional airfoil designs aerodynamically inefficient and necessitate accurate resolution of unsteady flow separation and laminar separation bubble (LSB) dynamics while designing new airfoils. Existing Reynolds-averaged Navier-Stokes-based approaches may have limited predictive capability for these strongly unsteady low Reynolds number flows. To address these limitations, this study presents an implicit large eddy simulation-based optimization of airfoils for a Martian rotor, followed by assessment of their impact on rotor performance. It targets drag minimization across a design lift coefficient range relevant to hover. The optimization yields a sharp raised-lip geometry with reversed leading edge camber, and a separate thin-cambered geometry with positive camber. The former reduces skin friction drag by inducing leading edge shear layer separation and promoting the formation of a stable LSB, whereas the latter minimizes pressure drag by shifting the high pressure region from the leading edge to the pressure side. Verification of the optimized airfoils on a rotor demonstrates reductions in torque and pitching moment under the thrust-trimmed hover condition. Rotor aerodynamic analyses show that optimized airfoils produce consistent performance with two-dimensional (2D) simulations at inboard and midboard regions. Near the tip, however, large-scale vortex shedding not captured in 2D causes notable discrepancies. Overall, these results provide physically interpretable and performance-enhancing guidelines for future Mars helicopter development.