Aerodynamics and Design for Ultra-Low Reynolds Number Flight

Chapter 1
Introduction
1.1 Looking to Nature
Mankind has dreamed of flight for as long as he has dreamed. Flight in nature, in all its
shapes and sizes, has been the seed of these dreams. Mankind has flown for barely over
one hundred years, since the days of Lilienthal, then Chanute and the Wrights, but there
has been flight in nature since before history. We have progressed, our technology has
progressed, and our aircraft have progressed. Faster, and bigger, and bigger still, but
rarely smaller and slower. Using the Reynolds number as a measuring stick, we have
conquered flight first in the tens of thousands with models, progressed to the hundreds of
thousands with gliders, and now operate in the millions and beyond, but nature still flies
alone in realm of the hundreds and thousands: the ultra-low Reynolds number regime.
We have done well, but man-made flight at the tiny scales that nature takes for granted
has eluded us, but that is now changing.
The flight of small birds and insects has always held a fascination for mankind and entire
lifetimes and careers have been devoted to the study of single species. We have studied
their shapes and motions, theorized and modeled their mechanisms of flight, but we have
been unable to emulate their success. A concise overview of both the challenges and
possibilities for micro-air-vehicles has been provided by Spedding and Lissaman [1].
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