Aerodynamics of Nature

Aerodynamics of Nature


A man who knows nature underneath of his heart, can fly naturally...

Vortex rings in Nature

Bats

Birds

Insects

Fish & aquatic animals

Flying Seeds

Trees

Crops

Atmosphere

Wind Flow pattern

Ocean flow pattern

Tornadoes

Blood flow

Respiratory flow

"Once       upon        a time some      scientists and engineers    or college professors (different versions     have        different names and specialties) were at a dinner party.     The subject      of bee flight     came up and the aerodynamic engineer that just happened to be present decided to do a quick calculation on   bee aerodynamics. He       used a conventional stiff airfoil-shaped      wing,       with steady      state, or partially steady state, air flow analysis techniques, and lo and behold, the calculations did not work for the bee. Someone     jokingly said,    "I guess that      proves bees      can't fly", and they all had a good laugh. But, of course, they all knew        it just       proved that       bee flight is      too complicated to analyze        with conventional     airplane aerodynamic methods."

Here is the basis of the problem:

Conventional aerodynamic calculations are relatively simple, being based on large fixed wings and steady state or  quasi-steady state flow.

Insect wings are small, flat, rough surfaced, and flexible. During flight they flex and twist in all kinds of horribly complicated ways. Also they are so small that important  dimensional fluid analysis numbers like the Reynold's Number are very different, resulting in significantly different fluid characteristics when compared to the bigger wings of birds and airplanes (even a sparrow wing is huge compared to most insect wings). In addition, the small size and high speed of most insect wings makes it very difficult to study insect flight (imagine trying to attach a pressure sensor to an insect wing). Finally, the pressures and flow characteristics of the air around the wings are very unsteady, constantly changing as the wind flaps, bends, and twists, unlike aircraft wings which are stiff with relatively simple constant flow patterns and pressures.

Conventional aerodynamic analysis methods simply don't apply to insect wings.

Typical Applications

A STEALTH AIRCRAFT DESIGNED BY NATURE

A Case Study

The  insect  thorax  is  shielded  by  cuticles  of  thin walled   chitinous   shells,   joined   with   an   elastic material, resilin. The wings and the thorax shell form a distributed vibration system.

The sequence of insect flight: Cruising Mode (Sir J. Lighthill)

Recent Attempts (UC, Berkeley)

Flapping Wings using a fourbar mechanism: piezo- electric actuators driving a mechanical amplifying thorax structure

In some insects the wing movements are produced by wing muscles directly inserted into the base of the wing.

In others, these are produced by muscles that pull on the thorax shell, while the shell movement moves the wings.

A bit of Aerodynamics:

Weis-Fogh Mechanism

[Clap and fling (peel)]

Srygley & Thomas (Nature: 2002)