(PhysOrg.com) -- Nature, in the simple form of a tree canopy, appears to provide keen insights into the best way to design complex systems to move substances from one place to another, an essential ingredient in the development of novel "smart" materials.
Duke University engineers believe that an image of two tree canopies touching top-to-top can guide their efforts to most efficiently control the flow of liquids in new materials, including the next generation of aircraft and rocket "skins" that can self-repair when damaged, or self-cool when overheated.
"Examples of this branching design tendency are everywhere in nature, from the channels making up river deltas to the architecture of the human lung, where cascading pathways of air tubes deliver oxygen to tissues," said Adrian Bejan, J.A. Jones Professor of Mechanical Engineering at Duke's Pratt School of Engineering.
Developing the most efficient and effective manner of controlling flow is becoming increasingly important, as engineers strive to create the next generation of nanodevices and "smart" materials. The goal of this research is to create materials that act like human skin by delivering liquid healing agents through a network much like blood vessels. Materials such as these will need efficient delivery systems, Bejan said.
Working with Sylvie Lorente, professor of civil engineering at the University of Toulouse, France, Bejan found that the laws of constructal theory (http://www.constructal.org/), which he first described in 1996, could guide the creation of these novel "smart" materials.
The constructal theory is based on the principle that flow systems evolve to minimize imperfections, reducing friction or other forms of resistance, so that the least amount of useful energy is lost. The theory applies to virtually everything that moves, Bejan said.
"We examined a flow system that looks more like the canopy-to-canopy model and found it to be more efficient than models in use now that are made up of parallel flow channels," said Bejan, whose analysis was published early online in the Journal of Applied Physics. The research was supported by the Air Force Office of Scientific Research and Lawrence Livermore National Laboratory. "We believe that this strategy will allow for the design of progressively more complex vascular flow systems."
In addition to finding that flow is maximized by these branching larger-to-smaller-to-larger systems, the researchers discovered that to maintain this gain in efficiency, the tree vasculature needs to become more complex as the flow increases. This is an important insight, Bejan said, because as new "smart" components become smaller, the efficiency of the flow systems will need to increase.
"Constructal design concepts serve the vascularization needs of these new 'smart' structures ideally, because trees have evolved a natural architecture for maximally delivering water throughout the tree volume," Bejan said. "If a single stream is to touch a structure at every point, then that stream must serve that structure much like a tree, or much in way the bronchial tree supplies air to the total lung volume."
Earlier, the constructal law was used to explain traffic flows, the cooling of small-scale electronics and river currents. Bejan recently reported that the theory can explain basic characteristics of locomotion for every creature, whether they run, swim or fly. The physics principle also explains many essential features of global circulation and climate, including the boundaries between different climate zones, average wind speed and the average temperature difference between night and day.
Most recently, Bejan demonstrated that the constructal theory also helps explain why annual college rankings tend not to undergo major changes year-to-year.
Provided by Duke University
Related stories:
Trees, forests and the Eiffel tower reveal theory of design in nature
What do a tree and the Eiffel Tower have in common? According to a Duke University engineer, both are optimized for flow. In the case of trees, the flow is of water from the ground throughout the trunk, branches and leaves, and into the air. The Eiffel Tower's flow carries stresses throughout the structure without collapsing under its own weight or being downed by the wind.
Physics Explains Why University Rankings Won't Change
A Duke University researcher says that his physics theory, which has been applied to everything from global climate to traffic patterns, can also explain another trend: why university rankings tend not to change very much from year to year.
Mouse studies suggest daily dose of ginkgo may prevent brain cell damage after a stroke
Working with genetically engineered mice, researchers at Johns Hopkins have shown that daily doses of a standardized extract from the leaves of the ginkgo tree can prevent or reduce brain damage after an induced stroke.
What energy upgrades would you make for $250?
It's a double whammy: Home energy costs are rising just when most of us can least afford it.
Smart Home exhibit mixes cool green design with easy high-tech living
Just inside the first floor of Chicago's Museum of Science and Industry's Smart Home, a 20-year-old re-covered Crate & Barrel sofa flanks a cool-to-the-touch, ethanol-burning fireplace that floats in the middle of the room. The flame can also be seen from any of the six thrift-store dining chairs revived in creamy white faux leather and tucked in around the high-sheen, rough-edged slab of a fallen Michigan ash tree given new life as a sculptural table.
Vine invasion? Ecologist looks at coexistence of trees and lianas
Among the hundreds of species of woody vines that University of Wisconsin–Milwaukee ecologist Stefan Schnitzer has encountered in the tropical forests of Panama, the largest has a stalk nearly 20 inches in circumference.
Scientists remove thousands of aspens to glimpse forest's future
Armed with chainsaws and pry bars, University of Michigan researchers and their colleagues recently hastened the end for nearly 7,000 mature aspen and birch trees in a large-scale, long-term experiment to glimpse the Great Lakes region's future forests. A band of bark was stripped from each tree to kill it without cutting it down.
Researchers synthesize compound to flush HIV out of hiding
Any hunter will tell you that when your quarry goes into hiding, you have to flush it out to get a good shot at it. Such is the case with HIV, the virus that causes AIDS.
