First published in German, August. 14. 2002
by J. Peter Apel
Translated into English, May, 8, 2008
The Physics of flying
The physical derivative of the nature of flying
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In the beginning there was nothing
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Then the big bang catapulted from nothing masses apart.
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These masses intend to merge again and accelerate themselves through mutual gravity closer and closer together.
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In order to not being pulled completely by gravity to the earth, a matter has to accelerate itself constantly and with equipollent force in the opposite direction.
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Satellites obtain permanent counter acceleration due to the geometry of the orbit and the centrifugal force forms own mass.
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On earth a matter can only accelerate by backstroke via a second mass.
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A rocket or a human being with „backpacked jets“ accelerate against the acceleration of the earth by pushing off picked up(fuel-)mass and its power of backstroke.
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Even an aircraft heavier than air can keep itself above only via backstroke! Anything else is not possible in this universe.
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The mass to manipulate the generated backstroke has not to be carried by the object that is flying in the air: it is available in form of the mass of air itself. Using a plane (wing) it is possible to „grasp“ the air and accelerate it downwards. Thereby backstroke is generated as downwash.
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A board accelerates air downwards by pushing air directly down in a downward stroke and suck air above. In the air there are no edges like these of an enclosed cylinder at the surface of a piston of a pump. There are spacious evasive movements around the borders of the boards in the free air because the air has a lack of ability to compress.
Despite these surrounding „wash – ups” over pressure is created under and low pressure is created above the board. This is comparable to the situation of a piston in a cylinder with the result of accelerations of the affected masses of air including their surrounding wash ups.The over pressure under and the low pressure above the board generate the force of downwash caused by planes.
This is the physically principle of generating aero - dynamic forces.
The movements of the air as surrounding „wash – ups” create the familiar eddies at the edge of the board. They are flow, pushed away directly under the board for the generated flow of air down as much as they are after-flow for the sucked down air on top of the board.
Overall there is an enclosed eddy in form of a ring at the edges over the complete perimeter of the board.
This example demonstrates exactly the generation of down wash at the wing of the bumblebee.
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The eddy migrates accordingly at the front of the board’s edge (leading edge) as the board is simultaneously moving in a direction down and forward. But the eddy at the back edge (trailing edge) of the board rests at the same spot. The same spot that had a flow of air down at the beginning of the movement!
An eddy is therefore not part of the edge that caused it originally. Its place is the immediate coexistence of different movements of air. The flow of air down from the starting point „gets caught“ with the adjacent stationary air in a circular flow.
During forward movement the board pushes and sucks new air from previous position of rest downwards on every location of the course. The forward borderline of this flow of air down is located directly under and above the board (wing). The „hitch of acceleration“ of air caused by a wing is strikingly visible in a laboratory for air flow. A free flying test model through a “wall of smoke” indicates the resting air in the short moment of flying through: Milliseconds under and above the wing.Behind the board (wing) emerges a „street“ of air flowing downwards.
The flow of air vertically under and above, generated by the board and directed downwards, together with the resting air fronting the direction of flight, has to „distort“ in an eddy at the leading edge of the board. This eddy is permanently regenerated. It is thus not stationary, but locally existent for a short moment when the board (wing) rests in one spot in the air.
The eddy in form of a ring that is generated in the complete flow of air down has a long form due to the forward movement of the board (wing).
This example demonstrates exactly a sinking flight shortly before the total stall.
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The ratio of a wing of a gliding sailplane is demonstrated if a board is moving very fast forwards in relationship to the movement downwards. Then the course is almost horizontal.
The air on the flying course in approximate width of the span under and above the airplane is accelerated downwards by pressure and pull. It is the air in between the „eddy of launch“ and the eddy at the leading edge of the wing. This is decisive: the eddy that is locally generated for a short moment at the leading edge of the board (“nose” of the wing), identified as the “profile” eddy, is including the complete board (wing) in the full depth as far reaching as the trailing edge:
This is flying!
That is to say: The generation of aerodynamic lift by means of vertical, downward acceleration of former stationary air via wings. Locally at every spot flown through from far up till far down.
The existent profile of movement of eddies in relationship to the profile of the airfoil results in extreme lack of drag. The flow of air is first sucked from above, then elegantly switched behind by the stream of eddies to flow downwards behind the trailing edge of the wing. In supersonic flying these eddies does not exist anymore. The stream of air is sucked from above and not pushed behind the profile and concentrates on the rear part of the wing. The rear part of the wing has a slanted surface on top of the wing that generates another slip stream. This phenomenon creates additional drag. Mass of air is moving downwards along the course of flight, displaces surrounding air, and is creating clearance. The stationary eddies are all generated next to the course of flight! Profile “eddies” surrounding the nose of the wing are generated by acceleration of air downwards, create lift on the length of the span and in the full depth of the wing. The effective diameter of the eddies is smaller than the depth of the wing.
While air particles are moving in a „arch-like“ manner above the airfoil: the forward moving wing is slipping through these particles.
The diagram illustrates the effective movements of eddies and downward movements of two particles of air.
For the powered flight the angled plane generates the acceleration of air downwards. In result some air is pushed ahead in direction of the course of flight. The horizontally/vertically aligned coordinate system for the gliding flight “rotates” in a way that the declining flight path of the gliding flight in cruise flight mode is horizontal, the climbing flight becomes a rising flight path.
During the flight, a ring of eddies is generated for the entire edge of the downward moving air (flight path). It consists out of four segments: launch-eddy, profile-eddy and two wing eddies. The wing eddies represent the formidable wake!
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This is the phenomenon of flying!
Flying is like swimming:
Air (water) with wings (hands, feet) struck downwards (kicked)
or
Air (water) with a slanted plane of a wing with an angel of attack (hands) (palms of hands) is accelerated downwards by fast horizontal movements with adequate velocity.