The constructal law of organization in nature: tree-shaped flows and body size.

Journal Article (Review;Journal Article)

The constructal law is the statement that for a flow system to persist in time it must evolve in such a way that it provides easier access to its currents. This is the law of configuration generation, or the law of design. The theoretical developments reviewed in this article show that this law accounts for (i) architectures that maximize flow access (e.g. trees), (ii) features that impede flow (e.g. impermeable walls, insulation) and (iii) static organs that support flow structures. The proportionality between body heat loss and body size raised to the power 3/4 is deduced from the discovery that the counterflow of two trees is the optimal configuration for achieving (i) and (ii) simultaneously: maximum fluid-flow access and minimum heat leak. Other allometric examples deduced from the constructal law are the flying speeds of insects, birds and aeroplanes, the porosity and hair strand diameter of the fur coats of animals, and the existence of optimal organ sizes. Body size and configuration are intrinsic parts of the deduced configuration. They are results, not assumptions. The constructal law extends physics (thermodynamics) to cover the configuration, performance, global size and global internal flow volume of flow systems. The time evolution of such configurations can be described as survival by increasing performance, compactness and territory.

Full Text

Duke Authors

Cited Authors

  • Bejan, A

Published Date

  • May 2005

Published In

Volume / Issue

  • 208 / Pt 9

Start / End Page

  • 1677 - 1686

PubMed ID

  • 15855399

Electronic International Standard Serial Number (EISSN)

  • 1477-9145

International Standard Serial Number (ISSN)

  • 0022-0949

Digital Object Identifier (DOI)

  • 10.1242/jeb.01487


  • eng