CONSTRUCTAL THEORY OF DESIGN IN ENGINEERING AND NATURE

Abstract

This is a brief introduction to an engineering theory on the origin and generation of geometric form in all flow systems: the animate, the inanimate and the engineered. The theory is named constructal, and is based on the thought that it is natural for currents to construct for themselves in time paths of greater flow access. It is shown that this process of flow path optimization can be reasoned on the basis of principle: the maximization of global performance subject to finite-size constraints. One example is the generation of tree-shaped flow patterns, as paths of least resistance between one point (source, sink) and an infinity of points (area, volume), as in the circulatory, respiratory and nervous systems. An other is the generation of regular spacings in heat generating volumes, such as swarms of honeybees. The optimized tree-flow geometries account for allometric laws, e. g., the relationship between the total tube contact area and the body size, the proportionality between metabolic rate and body size raised to the power 3/4, the proportionality between breathing and heartbeating times and body size raised to the power 1/4, and the proportionality between the cruising speed of flying bodies (insects, birds, airplanes) and body mass raised to the power 1/6. The optimized flow structures constitute robust designs, and robustness improves as the complexity of the system increases. Flow architectures that are more efficient look more natural.

Keywords

Dates

  • Submission Date2004-12-02
  • Revision Date2005-01-19
  • Acceptance Date2005-02-10

References

  1. Bejan, A., Shape and Structure, from Engineering to Nature, Cambridge University Press, Cambridge, UK, 2000.
  2. Poirier, H., One théorie explique l'intelligence de la nature, Science & Vie, 1034 (2003), pp. 44.
  3. Bejan, A., Advanced Engineering Thermodynamics, 2nd Ed., Wiley, New York, 1997.
  4. Kim, S. J. and Lee, S. W., Eds., Air Cooling Technology for Electronic Equipment, CRC Press, Boca Raton, FL, 1996.
  5. Bejan, A., Convection Heat Transfer, 2nd Ed., Wiley, New York, 1995.
  6. Bejan, A., Street network theory of organization in nature, J. Adv. Transportation, 30 (1996), pp. 85.
  7. Bejan, A., Constructal-theory network of conducting paths for cooling a heat generation volume, Int. J. Heat Mass Transfer, 40 (1997), pp. 799.
  8. Avnir, D., Biham, O., Lidar, D. and Malcai, O., Is the geometry of nature fractal? Science, 279 (1998), pp. 39.
  9. Wechsatol, W., Lorente, S. and Bejan, A., Tree-shaped insulated designs for the uniform distribution of hot water over an area, Int. J. Heat Mass Transfer, 44 (2001), pp. 3111.
  10. Pennycuick, C. J., Animal Flight, Edward Arnold, London, UK, 1972.
  11. Tennekes, H., The Simple Science of Flight, MIT Press, Cambridge, MA, 1996.
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