Jan Peter Apel

The Same at Aircraft and Insect

The basic principle of flying is to accelerate air mass downwards. This is accomplished by both flight modes, the continuous forward motion of a rigid wing in accordance with the principle of the inclined plane and the swinging back and forth of wings by insects according to the principle of the inclined plane too. Thus, there must also be shared images about downward air flow.
Each forward or backward swing of an insect wing is nothing more than a very short flight of a rigid wing. The in "How Insects Fly" shown vortices are not only exist on the wings leading and rear edges, but also, as shown in the following sketch, around the wing tips.

Vortices arise on the borderline of air, which is moving in ambient air. That has the consequence, that there is a vortex also around the wing of a bumblebee. This however does not apply to the contour of the wing, but the contour of the cross section of the downwash, produzed by the wing.
The vortices at leading and trailing edges of the wings from the bumblebee are not visible in this perspective. What one does not see also, is that these vortices were accelerated with its mass by the start-up of the wings down and thereby flow behind the bumblebee down. In these vortices are content only about the half of directly from the wings downward accelerated air. Therefore, the downward velocity of the vortices has also only about the half of that velocity, which has granted the air by the wings in the first moment.

On an airplane, resulting in this perspective, is to see the similar image:

Also here the vortices generated by the wings moving air from under the wing to the top. And also these vortecies flows with about the half of the velocity, which the wings gives the air in the moment of emergence. These vortices are named whith wake turbulence. There pushing down arise also by the down wash, caused by the horizontal moving inclined plates.

In the following sketch is illustrate an airplane wing, which has even only a very short forward movement like a wing of a bumblebee. It caused the same vortices as the wing of the bumblebee in the previous chapter.

Because an airplane but still continues to move forward, the distance between the front and the rear vortex is widening. The front vortex rotates around the airfoil, so that it is no longer visible as a separate vortex like on the bumblebee wing. In a wind tunnel, only the increased speed over the wing can be measured, leading to the misinterpretation of the Bernoulli theory. Only with an exaggerated angle of attack of the wing the air arises a vortex on the leading edge like on the wing of the bumblebee. A plane then do not crash because it has no more lift, but because the lift is no longer sufficient. Overpowered aircrafts can hold above, although the wing is "stalled" like on a bumblebee wing.

Vortices by flying objects arise only by mechanical movements of air masses. The higher pressures under and the lower above wings arise only by accelerete air masses. These vortices are never compensation flows of overpressure below and under pressure above wings, so logically that might be. Such only compensation flows caused by pressure differences would be on place and never fall down. The down fall of air by wings is that, what makes fly!

Lift force is caused by accelerate air mass down 

That is the whole secret of flying!


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