Design of Supercritical Low-Reynolds-Number Airfoils for Fixed-Wing Flight on Mars

Abstract

Aerodynamic shape optimization for the high-subsonic low-Reynolds number flow regime represents an area of on-going research. The interaction between supercritical compressible flow and laminar boundary layer separation is not well understood due to the high challenges associated with setting up relevant experimental work. However, in the design of future fixed wing aircraft for flight in extra-terrestrial atmospheres, such flow conditions might commonly occur. The present study presents a family of single-point and multi-point optimized airfoils designed for high-subsonic flight at a high-lift condition in the Martian atmosphere. A gradient based optimizer is used, with a second-order finite-volume flow solver and a second-order continuous adjoint solver for determining surface sensitivities with respect to the objective function of minimizing drag. Both fully turbulent and transitional flow are considered, to evaluate the impact on the resulting design and to stress the importance of continuing research to develop robust shape optimization including laminar boundary layer and transition prediction. Both on-design and off-design conditions are evaluated, the airfoils obtained when considering transition effects demonstrating good overall performance.