The constructal theory of global optimization under local constraints explains in a simple manner the shapes that arise in nature.
This theory replaces the belief that nature is fractal, and allow one to design and analyse systems under constraints in a quest for optimality.
This theory allows the design and understanding of natural systems, thermal dissipators, communication networks, etc...
The constructal theory was invented by Adrian Bejan.
History
The constructal theory was developped by Adrian Bejan, Ph. D. [MIT] (1975) in the late 90's.
Adrian Bejan taught at MIT until 1976 and is now J.A. Jones Professor of Mechanical Engineering at Duke University, Durham, North Carolina.
Bejan's research areas cover: entropy generation minimization, exergy analysis, condensation, convection in porous media, transition to turbulence, etc.
Principles
The constructal theory can be applied to kind of flow system displaying at least two regimes: one highly resistive and a less resisitive one, and it can be applied at any scale: from macroscopic to microscopic systems.
| Application | What flows | Tree channels | Interstitial spaces |
|---|---|---|---|
| Packages of electronics | Heat | High-conductivity inserts (blades, needles) | Low conductivity substrate |
| Urban traffic | People | Low-resistance street car traffic | Street walking in urban structure |
| River basins | Water | Low-resistance rivulet and rivers | Darcy flow through porous media |
| Lungs | Air | Low-resistance airways, bronchial passages | diffusion in alveoli tissues |
| Circulatory system | Blood | Low-resistance blood vessels, capillaries, arteries, veins | diffusion in capillaries tissues |
The main principle of the constructal theory is that every system is destined to remain imperfect.
According to this, the best that can be done is to optimally distribute the imperfections of the system, and this optimal distribution of imperfection will generate the geometry or shape of the studied system.
The constructal way of distributing the system's imperfection is to put the more resistive regime at the smallest scale of the system.
The constructal principle was enonced in the 90's by Adrian Bejan as follows: "For a finite system to persist in time, it must evolve in such way that it provides easier access to the imposed currents that flow through it."
External links
- Author's description of the theory.
- Shape and Structure, from Engineering to Nature , Cambridge University Press, Cambridge, UK, 2000.
- Proceedings of the Symposium "Bejan’s Constructal Theory of Shape and Structure" Edited by Rui N. Rosa, A. Heitor Reis & A. F. Miguel, Centro de Geofísica de Évora, Évora Geophysics Center, Portugal, 2004, ISBN: 972-9039-75-5