Basic properties of the flapping wing and features of the flapping flight
Velko Velkov
The principles of the flapping flight of all flying creatures realized either by birds or by insects are just the same. THE FLAPPING WING HAS AN ELASTICITY BOTH ALONG THE SPAN AND THE CHORD. The elasticity along the span conduces to the smoothness and high effectiveness of the flapping flight. The adaptive elasticity of the wing along the chord make it possible to achieve a maximum traction in a wide range of frequencies and amplitudes of the flaps. THE TRACTION IS CREATED BY THE OUTER PART OF THE WING WHILE THE INNER ONE GENERATES THE MAIN PART OF THE LIFT. When the inner part of the wing is moving upward the outer part lags and bends downward in relation to the inner part because of the air drag and inertial forces. In this way the drag of the wing as a whole diminishes. When the inner part is nearing the up position the elastic forces raising the outer part upward and latter continues to create traction while the reaction aids the inner part and the wing as a whole to pass across the up position and to begin moving downward.THE WING ELASTICITY ALONG THE CHORD IS SUCH THAT THE WING PRACTICALY DO NOT BEND IN GLIDING-EQUILIBRIUM POSITION.
The direction of the wing flapping motions is not perpendicular to the flight direction but with declination backwards which decrease by increasing of the flight velocity. The wing behavior and the aerodynamic forces action during a flapping motion are shown on fig.1.(The lines of the paths at the scheme are projections of the solid lines.)
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FLAPPING WING AERODYNAMIC FORCES V - flight velocity U - flapping motion velocity W - total wing velocity X - drag P - TRACTION( U > V ), LIFT(U < V) R - total aerodynamic force |
It is evident from fig.1 that during both the downward and upward
motion the outer part of the wing is creating the traction, while
the inner part does the lift.In the course of the flapping
motions the wing behavior automatically results from the inherent
elasticity of the wing.The inner part of the wing produce lift
during the upstroke too, because the flapping motion velocity U
is little in comparison with the flight velocity V and the inner
part is twisted downwards in equilibrum position.
THE FORCES ARE DIFFERENT(SIZE AND DIRECTION)IN EACH SECTION OF WING AND IN EVRY MOMENT OF CYCLE OF THE FLAPPING FLIGHT.
THE AIR STREAM OF THE FLAPPING WING IS FAN-SHAPED AND IS IN DEPENDANCE FROM CORRELATION FLIGHT VELOCITY/FLAPPING MOTION VELOCITY FOR THE DIFFERENT SECTIONS.
The above statement clarifies the flapping flight mechanism. It is important to point out that the mass distribution and the mass/elasticity ratio are of great significance for a maximum flapping wing efficiency. THE MASS / ELASTICITY RATIO IS DISTRIBUTED OVER THE WING IN A WAY ALLOWING THE WING - WHEN BENDED AND THAN RELEASET - TO COME BACK TO THE EQILIBRIUM POSITION WITHOUT VIBRATION
As result the wing bend along the chord only under air resistance but not under inertial forces. This property determinate the way of bending of the wing at the flapping movements, that decide the problems of the mechanics and aerodynamics of the flapping flight, pitching and hering.
These conclusions illustrated by the wing behavior at level flight but the described properties and relationships give the opportunity to explain the other types of modes of the flapping flight.
Manned ornithopter with 8m. span
RC model of ornithopter with 2m. span
Variant of invention "Wing of ornithopter", realized by RC model
Variant of invention "Wing of ornithopter"
The future...
AUGUST 2003
NO MORE SECRETS OF THE FLAPPING FLIGHT!
The tests of the RC model of ornithopter, by which are realized two of my inventions and my ideas about the properties of the flapping wing are the grounds for this DECLARATION. By exactly correspondence of the elasticity of the wing to the mass of the ornithopter, it is possible to build ornithopters with every desired mass. By realization of principle of distribution of the mass of the wing and correlation to the elasticity, the wings act effectively by high loading too. By virtue of �Ornithopter� and �Wing of ornithopter� inventions, the wings act maximum effectively by different frequencies of the flapping motions by take off and flight. The control through change of angle of incidence of the wings is very effectively at take off and flight with low velocity.
MANNED ENGINE-POWERED ORNITHOPTER. span - 10 m chord - 1.5 m weight - 85 kg (At the images it is withowt elastic rips and fabric of the wings and withowt outer part of the left wing). The ORNITHOPTER have articulated wings and control of the elasticity of the wings. The up-down control is through change of the angle of incidence-angle of attac. The left-right control is through rear-lower ruder, connected with the control of the fore-wheel. The tail is fixed. By take-off the pilot move the control levers forward (image 3). The angle of attac increase,the flapping frequence (gas) and initial tension of the springs (behind the roller of the control lever) connected with outer parts of the wings increase too. At the left control lever is the handle of the clutch, at the right control lever is the handle of the stopper of the control levers.
ORNITHOID
The ORNITHOID is combination of my project of ornithopter and the project of ornithopter (ornithoid) of The University Of Toronto. Rubberpowered model of ORNITHOID span - 85cm weight - 120g chord - 12cm amplitude - 10cm The wing have upper feathers - its form and size determine the elasticity of the wing along the chord. The resistance of the wing upwards is less than downwards. Variant of mechanics of rubberpowered model of ORNITHOID. Electric - powered model of ORNITHOID. Span - 2m. Weight - 1,5kg. Control of the elasticity of the ORNITHOID wing. HUMAN POWERED ORNITHOID HUMAN POWERED ORNITHOPTER HUMAN POWERED ORNITHOID Span - 9 m Weight - 22 kg Chord - 1.6 m The wing is at midle position. It have two additional supports at rest. ENTOID The wings flapp (rotate) 360 degrees in vertical and in horizontal mode. In horizontal mode the flapping (rotating) wings create trust and lift. Rubber powered model of ENTOID ROTATING ELASTIC WING V - flight velocity U - rotating motion velocity W - total wing velocity X - drag P - traction (U>V), lift (U<V) R - total aerodynamic force
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