Enhancing the airfoil performance for a fixed-wing Martian aircraft

In this paper, a series of low-Reynolds number airfoils were explored in application to the Long-Endurance Mars Exploration Flying Vehicle (LEMFEV) project. The end goal of the study was twofold:

• to identify the most effective airfoil or airfoil-boundary layer trip combination for the given aircraft in cruise and unveil the underlying physical mechanism for this effectiveness;

• to determine if the operating range of angles of attack for the selected airfoil could be expanded by placing the boundary layer trips in a relatively aft position such that they affected the boundary layer at a higher angle of attack.

The paper presented two sample specifications for the LEMFEV project; discussed the effect of turbulence on the performance of airfoils under the given conditions; justified the selection of an amplification factor for simulations; developed and justified the measure of merit for airfoil selection and optimization; as well as considered boundary layer trips as a means of enhancing the performance of the selected airfoil. For design and analysis, MATLAB and X-FOIL were used. The analysis showed that for the given design conditions, both considered sample mission profiles were performed better by an airplane with the SD7037-092-88 airfoil. Furthermore, for this airfoil and design conditions, boundary layer trips would only increase drag at lift coefficients where they forced transition, and the boundary layer trips didn’t expand the airfoil's operating range of angles of attack. In other words, eliminating the bubble had a detrimental effect on the lift-to-drag ratio of the airfoil. The friction drag increase due to early transition by far outweighed the pressure drag produced by the laminar bubble.