The evolution of airplane design, from early propeller-driven aircraft to today's giant jet-powered airliners, has mimicked the evolution of living creatures that fly, a study suggests.
Duke University mechanical engineering Professor Adrian Bejan and colleagues have analyzed aircraft designs going back to the the earliest days of manned flight.
Like flying creatures in nature the evolutionary development in aircraft has been a steady march to bigger and bigger sizes, they reported in the journal Applied Physics..
"We showed that larger airplanes are faster, more efficient as vehicles, and have greater range," Bejan says. "Engine mass is proportional to body mass, a design feature that is the same in animals where the mass of the motive organs -- muscle, heart and lungs -- is proportional to body mass."
That proportionality is also found in aircraft between fuselage length and wing span and between body size and fuel capacity, he says.
"This again is akin to what we see among the flying creatures in nature, showing that airplanes converge the architectural design rules that unite them with their living counterparts," Bejan says.
Bejan bases his findings on a fundamental principle of physics he has formulated and dubbed the Constructal Law, which underlies the evolution of systems as they change in form and design over time.
Applying the law to airplane design, he says, allows us to see Darwinian evolution at work, something considered impossible given the immense time scales evolution works at, much greater than any human lifetime.
Looking at airplanes and how they've changed since the Wright Brother first flew in 1903, "we can witness evolution in our lifetime by documenting the evolution of a flow system that is a little more than a century old: the flying 'human-and-machine species,'" he says.
Some evolutionary paths end in dead ends, both in living creatures and in aircraft, he says, citing the supersonic trans-Atlantic Concorde airplane as an example.
Commercial aircraft designs have evolved to efficiently move more people and goods across the face of the Earth, and the Concorde --very fast but with restricted passenger capacity and poor fuel economy-- strayed too far from the evolutionary path of other successful aircraft, which is why it eventually went the way of the dodo and is now "extinct," he says.
The study suggests the aviation industry has been good at "evolving" efficient designs through it history, Bejan says, and that continued evolution of design parameters should create future aircraft that will be successful.
"This study gives the rough sketch of what airplane designs will put you in the game," he says.
