Implicit and Explicit Large Eddy Simulations in Martian Aerodynamics

The recent flight of Ingenuity, the Mars Helicopter designed by JPL, marked the first successful atmospheric flight on another planet. Since then, researchers around the world have been actively exploring Martian flight, proposing a variety of concepts ranging from helicopters to fixed-wing Unmanned Aerial Systems (UAS). Martian aerodynamics is particularly unique, combining ultra-low Reynolds number regimes with relatively high subsonic compressible effects due to the low pressure and temperature of a predominantly carbon dioxide (95%) atmosphere. Given the significant difficulty and cost associated with experimentally replicating Martian atmospheric conditions on Earth, numerical simulations have become the primary tool for developing the innovative aerodynamic designs required in this regime. This paper investigates the use of high-fidelity simulations to analyze flow over airfoils in such Reynolds number regimes, as an alternative to the commonly used Unsteady Reynolds-Averaged Navier–Stokes (URANS) methodology. In this context, URANS simulations require a transition model to capture the laminar-to-turbulent transition occurring along the suction side of the airfoils. However, most transition models are highly empirical and often fail to accurately capture transition effects in the low transitional regime. High-fidelity simulations offer a promising alternative, as the extremely low Reynolds numbers make them computationally feasible even for complex geometries. Specifically, this study applies Large Eddy Simulations (LES) to airfoils operating in the low transitional regime, at Reynolds numbers between 5,000 and 20,000. Both implicit and explicit LES approaches are evaluated, using a finite volume code and a high-order flux reconstruction method.