Wingtip vortices

Wingtip vortices are regions of high vorticity which develop at the tip of a wing as it flies through the air (or potentially another fluid). Wingtip vortices are a form of induced drag, an essentially unavoidable side-effect of the wing generating lift. Designing a wing with a vortex of preferable shape is critically important in aerospace engineering. Wingtip vortices also form the major component of wake turbulence.

As a wing flies through the air, it generates aerodynamic lift by creating a region of higher air pressure beneath the wing than above it, among other factors like air deflection for instance. It must be kept in mind that lift is a sum of forces not a single force. Fluids are forced to flow from high to low pressure and the relatively high pressure air below the wing tends to escape to the top of the wing. The air does not escape around the leading or trailing edge of the wing due to airspeed, but it can flow around the tip. Consequently, air flows from below the wing and out around the tip to the top of the wing in a circular fashion. This leakage will raise the pressure on top of the wing and lower the overall lift that the wing can produce. It also produces an emergent flow pattern with low pressure in the center surrounded by fast moving air with curved streamlines.

Wingtip vortices only affect the portion of the wing closest to the end. Thus, the longer a wing is, the smaller the affected fraction of it will be. As well, the shorter the chord of the wing, the less opportunity air will have to form vortices. This means that for an aircraft to be most efficient, it should have a very high aspect ratio. This is evident in the design of long-range airliners and gliders, where fuel efficiency is of critical importance. However, increasing the wingspan reduces the maneuverability of the aircraft, which is why combat and aerobatic planes usually feature short, stubby wings despite the efficiency losses.

Another method of reducing fuel consumption is use of winglets, as seen on a number of modern airliners such as the Airbus A340.