Wingtip vortices are circular patterns of rotating air left behind a wing as it generates lift. The name is a misnomer because the cores of the vortices are slightly inboard of the wing tips. Wingtip vortices are sometimes named trailing or lift-induced vortices because they also occur at points other than at the wing tips. Indeed, vorticity is trailed at any point on the wing where the lift varies span-wise ; it eventually rolls up into large vortices near the wingtip, at the edge of flap devices, or at other abrupt changes in wing planform.
Modern airliners often feature slender wings and wingtip devices
Vortices shed at the tips and from the leading-edge extensions of an F/A-18
Canada geese in V formation
A NASA study on wingtip vortices, illustrating the size of the vortices produced.
When a fluid flows around an object, the fluid exerts a force on the object. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the force parallel to the flow direction. Lift conventionally acts in an upward direction in order to counter the force of gravity, but it is defined to act perpendicular to the flow and therefore can act in any direction.
The 1902 Wright Glider shows its lift by pulling up
A cross-section of a wing defines an airfoil shape.
Angle of attack of an airfoil
An airfoil with camber compared to a symmetrical airfoil