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Author Topic: Flight  (Read 7456 times)

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Why a butterfly flutters by

by David Catchpoole

Have you ever thought that the butterfly, with its jerky fluttering flight, is a ‘primitive’ and inefficient flyer? After all, its wings don’t look even remotely aerodynamic, compared to the beautifully streamlined ‘aerofoil’ wings of birds and airplanes.


Indeed, just 10 years ago, conventional laws of aerodynamics could not explain how any of the insects could fly at all,1 let alone maneuver so masterfully at low speeds—hovering and flying backwards and sideways, in complete control.

In the last decade, however, researchers have uncovered a variety of ‘unconventional’ ways that these gossamer aeronauts use their wings to stay aloft.2 For example, one particular flapping movement creates a spiraling airflow (vortex) along the edges of the wings, generating some of the lift which ‘conventional steady-state aerodynamics’ could not account for.3

The fluttering of butterflies is not a random, erratic wandering, but results from the mastery of a wide array of aerodynamic mechanisms.


LEVs (Leading edge vortices) are the main lift generating mechanism for insects and is totally different from the steady state aerodynamics design of aircraft

Now, after filming red admiral butterflies flying in a ‘wind tunnel’, researchers have been surprised by a whole range of complicated wing movements which generate more lift than simple flapping would do:

‘wake capture,

two different types of leading-edge vortex,

active and inactive upstrokes,

in addition to the use of rotational mechanisms and

the Weis-Fogh “clap-and-fling”? mechanism’.

What is more, the red admirals often used completely different mechanisms on successive wing strokes!

So, rather than being ‘primitive’, we now understand that butterflies flutter because they choose each wing stroke from a customized armory of twists, flaps, claps and flings. In the words of the researchers, ‘the fluttering of butterflies is not a random, erratic wandering, but results from the mastery of a wide array of aerodynamic mechanisms’.4 No wonder butterflies are so adept at taking off, maneuvering, maintaining steady flight and landing.

Aeronautics engineers even desire to copy these mechanisms, e.g. for robotic spy ‘insects’,5 but there is still a long way to go before they can match the capabilities of insect flyers.6 

For example, the software design in man-made aircraft requires many man-years of work and powerful computer chips for its implementation. In contrast, the flight control center in the brain of a fly has been estimated at about 3,000 neurons, which ‘gives the insect less computational power than a toaster, :o yet insects are more agile than aircraft equipped with superfast digital electronics.’7 So how do insects exercise flight control over such a wide range of aerobatic abilities?8 One commentator observed, ‘If engineers ever understand that, there will be a revolution in aeronautics.’7 

There is one engineer who understands. He is the One who originally put these flying marvels together in the first place—the Lord, the Maker of the heavens and the earth, and the sea, and all that is in them.

Agelbert NOTE: If you watch closely in the video above, you can almost see the butterfly creating the double vortices at the trailing edge of his wings on the down stoke and then being sucked up by them as it goes into the up stroke. There's an energy saving secret here! The vortices actually allow the butterfly to use much less energy to lift its wings for the upstroke! Amazing!

Related Articles
Astonishing acrobatics—dragonflies
Why a fly can fly like a fly
Beautiful black and blue butterflies
Aces of the Air
Butterfly brilliance
Dragonfly design tips
Watch a glasswing passing (without flying colours)
Lessons from locust wings

Further Reading
Pterosaurs flew like modern aeroplanes
Amazing discovery: Bird wing has ‘leading edge’ technology
Good design in miniature
Fancy flying from advanced aeronautics:
Expert engineer eschews “evolutionary design”

References and notes
1. Brookes, M., On a wing and a vortex, New Scientist 156(2103):24–27, 1997. Return to text.
2.Wieland, C., Why a fly can fly like a fly, Journal of Creation 12(3):260–261, 1998. Return to text.
3.Insects defying the laws of aerodynamics? Creation 20(2):31, 1998. Return to text.
4. Srygley, R.B. and Thomas, A.L.R., Unconventional lift-generating mechanisms in free-flying butterflies, Nature 420(6916):660–664, 2002. Return to text.
5. Butterflies point to micro machines, BBC News, news.bbc.co.uk/2/hi/science/nature/2566091.stm, 13 January 2003. Return to text.
6.Sarfati, J., Can it bee? Creation 25(2):44–45, 2003. Return to text.
7. Zbikowski, R., Red admiral agility, Nature 420(6916):615–618, 2002. Return to text.
8. See also: Sarfati, J., Astonishing acrobatics dragonflies, Creation 25(4):56, 2003. Return to text.

« Last Edit: November 28, 2013, 11:06:11 pm by AGelbert »
Rob not the poor, because he is poor: neither oppress the afflicted in the gate:
For the Lord will plead their cause, and spoil the soul of those that spoiled them. Pr. 22:22-23


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