Lift-induced drag

This drag force occurs in airplanes due to wings or a lifting body redirecting air to cause lift and also in cars with airfoil wings that redirect air to cause a downforce.

For a constant amount of lift, induced drag can be reduced by increasing airspeed.

The total aerodynamic force acting on a body is usually thought of as having two components, lift and drag.

[7][4]: Section 5.3  At practical angles of attack the lift greatly exceeds the drag.

[6]: 4.6 [6]: 4.7 [9]: 8.1.4, 8.3, 8.4.1 The vortices reduce the wing's ability to generate lift, so that it requires a higher angle of attack for the same lift, which tilts the total aerodynamic force rearwards and increases the drag component of that force.

However, there is an increase in the drag equal to the product of the lift force and the angle through which it is deflected.

Deviation from the non-planar wing with elliptical lift distribution are taken into account by dividing the induced drag by the span efficiency factor

[citation needed] Similar methods can also be used to compute the minimum induced drag for non-planar wings or for arbitrary lift distributions.

[citation needed] According to the equations above, for wings generating the same lift, the induced drag is inversely proportional to the square of the wingspan.

[11] The drag characteristics of a wing with infinite span can be simulated using an airfoil segment the width of a wind tunnel.

[12] An increase in wingspan or a solution with a similar effect is one way to reduce induced drag.

[citation needed] Typically, the elliptical spanwise distribution of lift produces the minimum induced drag[15] for a planar wing of a given span.

A small number of aircraft have a planform approaching the elliptical — the most famous examples being the World War II Spitfire[13] and Thunderbolt.

This is also the speed for greatest range (although VMD will decrease as the plane consumes fuel and becomes lighter).

Flying higher where the air is thinner will raise the speed at which minimum drag occurs, and so permits a faster voyage for the same amount of fuel.

Induced drag is related to the angle of the induced downwash in the vicinity of the wing. The grey vertical line labeled "L" is the force required to counteract the weight of the aircraft. The red vector labeled "L eff " is the actual lift on the wing; it is perpendicular to the effective relative airflow in the vicinity of the wing. The lift generated by the wing has been tilted rearwards through an angle equal to the downwash angle in three-dimensional flow. The component of "L eff " parallel to the free stream is the induced drag on the wing. [ 3 ] [ 4 ] : Fig 5.24. [ 5 ] [ 6 ] : 4.4
Total drag is parasitic drag plus induced drag