Jan Peter Apel

Mystery of Circulation

Almost no pilot can understand what the so-called circulation is. It is the basis invented by Kutta-Joukowski to enable calculations and make with it Bernoulli theory to scientific. It is intended to answer the question of why the air flows faster on the upper side of the wing. That the air does this is only an observation from the wind tunnel, and thus in the coordinate system of the moving airplane. There is no explanation for this, only the assumption that because the air does so, there must be a fictitious circulation flow of air circling around the wing profile. The cause would be the so-called start-up vortex, which would create this counter-vortex according to the thesis that a vortex always needs a counter-vortex.

How is the truth found?
The correct cause of the ability to fly can be represented with a normal, horizontally arranged plate. It is the ideal structure to show the basis of flying. It has the least possible drag to horizontal movement in the air, but a maximum to vertical movement in the air.

The picture shows how the air moves when the plate is moved vertically downwards. It presses air down with its underside, but air also escapes upwards on the sides. Of course, the top of the plate also sucks in air from above, which also sucks in the amount of air flowing around the edges of the plate from below. Air flows like a vortex around the side edges of the plate upwards.
Basicly arised an overpressure on the underside of the plate and a negative pressure on the top of the plate. Both pressures arise by the accelerations of air mass and together lead to an buoyancy in the vertical direction. Due to this buoyancy, a plate falls down more slowly.

Please note during this process: the plate moves, the air is passive. The plate must provide the energy to move air so that buoyancy is created. The energy that the plate has here is its potential energy. It is the same one that a glider flies with.
It should also be noted that everything a body does in the air with the air happens in the coordinate system of the air. The air, that is still untouched by these local processes around the plate (airplane), is the absolute reference point for flying.

In Figure 2, the plate not only performs a vertical downward movement, but also a faster horizontal movement. The lateral flow around the plate edges caused by the vertical movement of the plate also occurs here.

In the direction of movement to the front, this flow occurs at the front edge, as is known, but it then extends into the upper plate surface. This is a condition that arises in an airplane wing when the airplane flies too slowly and threatens to crash.

If an airplane flies fast enough, 3rd image, the front vortex extends from the air that swells up to the rear edge of the plate (wing), where its air volume is accelerated downwards together with that air, that is accelerated down by the inclined plane of the plate (wing) by its angle of attack in relation to the moving direction.

The vortex from the upswelling air from the rear edge of the plate can be seen at the right at the start of the movement. It is the so-called start-up vortex that would supposedly start the circulation. But the circulation is a myth that does not exist.

There are two movements above the plate (wing) from the viewpoint of the plate (wing, wind tunnel): the fiktiv airstream out of the moving plate and the air movement from the vortex from the front edge. Only the sum of the two is detectable. The airstream out of the moving plate is not a flow of air, it represent only the speed of the plate (wing). Only the increase in air velocity in the coordinate system of the plate (wing, wind chanel), arised out of the vortex around the plate's leading edge, is a real flow. This vortex is shown in the following animation using the upper air particle. The absolut movement of the air particle of the flow vortex from front to back (shown in red) only takes place during the time in which the plate (wing) moves through the air in this location.

There are basic physical laws for movements. Only movements that are invariant are effective, so that they are true or real. Invariant motion quantities are only those, that are contained in all possible views, i.e. all possible coordinate systems. When flying, two views are used: the view from the aircraft, i.e. the coordinate system of the aircraft, which is also the wind tunnel view, and the view from the ground, the coordinate system of the ground. The right view, the right coordinate system, is the air in and with which a flying object interacts. When there is no wind, the view from the ground is identical to that from the air. In wind, the entire process of flying moves unchanged with the entire air mass above the earth's surface. There are two possible views for flying: the coordinate system of the aircraft and that of the surrounding air mass, regardless of whether it is moving as a wind or not.

Wind on the moving plate (wing) is an air movement in the coordinate system of the airplane. But it does not exist in the coordinate system of the air. So head wind is not an invariable, but a variable movement, therefore relative and ineffective.
The supposedly fictitious movement of the circulation, in reality the true air flow that swells up in front of the wing, is an invariant and therefore effective air flow. It is directly present in the coordinate system of the air, in the coordinate system of the airplane it only leads to an increase in the head wind.

According to the physical rules, which are neglected in teaching, it is forbidden to add invariant and variant movement quantities from two coordinate systems, which differ in their movements!

The apparent increase in the speed of the air from the head wind and  the real flow of the air of the vortex from the front edge in the coordinate system of the airplane must not be regarded as a common air movement.
The faster "airflow" over a wing, which can be felt in the wind tunnel and from the relative point in the view of a pilot or occupant, is not a real airflow in the physical sense, but only a relative observation from the airplane's moving coordinate system, but which is the wrong. The plane is the actor, it provides the energy, i.e. the action force, only the air accelerated downwards by the plane generates the buoyancy force as a reaction force.

The real air flow from the vortex from the front edge is only a tenth of the head wind. In there can according to the physical laws (pressure profiles in flow paths) arise a Bernoulli effect. And this even happens and increases the negative pressure around the wing nose as a narrowing of the cross-section, but until the end at the rear edge there is then a diffuser effect with pressure increase, which compensates the negative pressure on the nose. Thus there is no influence on the level of lift due to the recoil force of the downward accelerated air, so that the resulting buoyancy force moves forward.

According to Newtonian physics, every flying object heavier than air,
from paper planes to jet fighters and fruit flies to bumblebees,
"rides" on reaction forces by down accelerated air mass.