High-Lift Computational Strategy for Slotted, Natural-Laminar-Flow Airfoils

This work uses a computational fluid dynamics approach to evaluate the ability of the aft element of a slotted, natural-laminar-flow airfoil, designed for transonic applications, to function as a high-lift device. The analysis is based on the Reynolds-averaged Navier-Stokes equations with a laminar-turbulent transition model for subsonic flow at representative flight conditions and a fully turbulent model for the aft-element optimization. Results obtained at angles of attack near maximum lift contribute to the understanding of stall characteristics and show that maximum aerodynamic efficiency is obtained with a constant slot width between the flap and main element. Results indicate that the microflap can augment the effectiveness of the aft element. Drag calculations when compared with angle of attack and lift show insight on the aerodynamic efficiency of the microflap system in landing as a lift effector, as well as a drag device. Pitching-moment data are also presented for completeness. Results obtained with Fowler flaps are consistent with other studies of extended-flap configurations; more specifically, the aforementioned velocity ratio decreases toward the aft-element trailing edge, indicating that the multi-element high-lift system is operating as intended.