A site on Aerodynamics

Translated by BabelFish

La couche limite
Dispositifs pour augmenter la portance

Bearing pressure

In level flight, it is necessary to apply a force opposed to the force of gravity, perpendicular at the speed of the apparatus to balance the weight. To this end, one uses profiles of wings (adapted).

Bearing pressure

Why the plane flies: The airflows passing near the suction face have a distance to traverse higher than that which they had in atmosphere nondisturbed by the wing. As there cannot be accumulation of energy along the profile, the airflows on the suction face accelerate what involve a dépression.(Effet Venturi)

Trainée of a profile

It is the resistance induced by the bearing pressure. Friction along the wall of the profile involves a deceleration of the fluid close to the wall. Conversely, the profile undergoes a force which tends to involve the profile in direction of the flow: it is the trail.

The flow around 1 wing is carried out according to the diagram:


If the length of the wings is increased: resistance is decreased. The air in the swirl of corner dun large airliner can still turn a few minutes after the passage of the plane. These swirls absorb by their rotational movement of energy and create the induced trail. Thus the total trail of a plane is:

Fxtotale = Fxforme + Fxfrottement + Fxinduite


Lengthening, noted L, is worth L = (B²)/S.


The lengthening and especially the shape of the wing make it possible to decrease the induced trail. Thus certain manufacturers adapted ~Winglets~ (devices of tip of wing)


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