Vortex generators function by manipulating which part of the airflow?

Vortex generators are designed to enhance the aerodynamic performance of an aircraft by manipulating the boundary layer airflow. The boundary layer is the thin layer of air that adheres to the surface of the aircraft, where the effects of viscosity are significant and the flow can transition from laminar to turbulent.

By introducing vortices into this boundary layer via vortex generators, the devices help to energize the airflow, which can delay flow separation and improve lift at lower speeds. This interaction allows for a more stable flight, particularly near stall conditions, as it helps maintain better airflow over control surfaces. Vortex generation can effectively improve an aircraft's overall aerodynamic efficiency and performance during critical phases of flight, including takeoff and landing.

Other types of airflow, like free stream, laminar, and turbulent flows, do not receive the primary benefits from vortex generators. While these flows are essential for understanding overall aerodynamics, the specific function of vortex generators is to target and enhance the characteristics of the boundary layer airflow to achieve better control and efficiency.