Which of the following reduces the spanwise airflow around the wingtip?

Winglets are designed to reduce the spanwise airflow around the wingtip, which is primarily caused by the pressure difference between the upper and lower surfaces of the wing. This pressure difference leads to the formation of vortexes at the wingtips, contributing to induced drag. By adding winglets, which extend vertically from the tips of the wings, the airflow is redirected in a way that reduces the intensity of these vortexes and minimizes the associated drag.

The use of winglets allows the wing to maintain a more efficient aerodynamic shape by improving the lift-to-drag ratio. This ultimately enhances overall aircraft performance, especially during cruise phases of flight. The effectiveness of winglets in combating wingtip vortex formations contributes significantly to fuel efficiency and improves climb performance.

Other options, while they may enhance overall wing performance or capabilities in various ways, do not specifically target the reduction of spanwise airflow at the wingtip. Leading edge devices and flaps, for instance, primarily focus on altering the airflow characteristics around the entire wing for better lift and control at different phases of flight but do not specifically address the wingtip effects. Fuselage design can influence the overall aerodynamic efficiency of the aircraft but is not directly related to managing the spanwise airflow at the wingtips