A theoretical basis for ornithopter research

There is a lot of seductive technology in the Dune novels. While you might like the stillsuit, I have found that my imagination was most captured by the ornithopters (perhaps the idea of recycling my urine, feces, and sweat into drinking water doesn’t capture my imagination).

It’s pretty obvious to me that the engineers in the Dune universe would not discuss the design of the ubiquitous ornithopters using metrics designed for fixed wing aircraft like we, apparently, do now. Phillip Burgers and David Alexander have taken a stab at creating a new measure of lift1 that is readily applicable to fixed wing aircraft, lift generating rotating cylinders, and things with flapping wings (i.e., ornithopters and bats):

For a century, researchers have used the standard lift coefficient CLto evaluate the lift, L, generated by fixed wings over an area against dynamic pressure, ½ρv2, where v is the effective velocity of the wing. Because the lift coefficient was developed initially for fixed wings in steady flow, its application to other lifting systems requires either simplifying assumptions or complex adjustments as is the case for flapping wings and rotating cylinders.

This paper interprets the standard lift coefficient of a fixed wing slightly differently, as the work exerted by the wing on the surrounding flow field (L/ρ·S), compared against the total kinetic energy required for generating said lift, ½v2. This reinterpreted coefficient, the normalized lift, is. . .the same as the standard lift coefficient for fixed wings, but differs for wings with more complex motions. . .We suggest that the normalized lift can be used to evaluate propellers, rotors, flapping wings of animals and micro air vehicles, and underwater thrust-generating fins in the same way the lift coefficient is currently used to evaluate fixed wings.

Not that the authors actually mention ornithopters in the text, but I think it is pretty obvious where this is all headed.

It should be noted that ornithopter research is actually as old as manned flight research.

NOTES

  1. Burgers P, Alexander DE (2012) Normalized Lift: An Energy Interpretation of the Lift Coefficient Simplifies Comparisons of the Lifting Ability of Rotating and Flapping Surfaces. PLoS ONE 7(5): e36732. doi:10.1371/journal.pone.0036732

Author: Josh Witten

http://www.thefinchandpea.com

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