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Vortex generators:
  • A
    take kinetic energy out of the boundary layer to reduce separation.
  • B
    transfer energy from the free airflow into the boundary layer.
  • C
    reduce the spanwise flow on swept wing.
  • D
    change the turbulent boundary layer into a laminar boundary layer.

Refer to figure.
Flow separation occurs because the boundary layer loses kinetic energy as it flows against the adverse pressure gradient.

Increasing the kinetic energy of the boundary layer will reduce flow separation. Simple devices called vortex generators are used to re-energize the boundary layer.

Vortex generators are small plates, vanes, blades or wedges mounted in spanwise rows along the wing surface.

Each vortex generator produces a vortex at its tip which will induce high energy air from the free stream flow to mix with the boundary layer, thus increasing its kinetic energy and with retarding separation.

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