Constructal theory - Wikipedia, the free encyclopedia
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(Redirected from Constructal law) The constructal theory puts forth the idea that the generation of design (configuration, pattern, geometry) in nature is a physics phenomenon that unites all animate and inanimate systems, and that this phenomenon is covered by the Constructal Law stated by Adrian Bejan in 1996: "For a finite-size (flow) system to persist in time (to live), its configuration must evolve such that it provides easier access to the imposed currents that flow through it." Constructal design of a cooling system
1 History 2 Principles 2.1 Constructal law 2.2 Thermodynamical analogy 3 Allometric exponents 4 External links 5 References 5.1 Popular literature
The constructal theory was developed by Adrian Bejan in 1996. "Constructal" is a word coined by Bejan, coming from the Latin verb construere, to construct, in order to designate, in the constructal theory's point of view, the naturally optimized forms such as rivers, trees and branches, lungs and also the engineered forms coming from a constructal evolutionary process of maximization of flow access in time.
For example, in point-area and point-volume flows, constructal theory predicts tree architectures, such flows displaying at least two regimes: one highly resistive and a less resistive one. Constructal theory can be applied at any scale: from macroscopic to microscopic systems. Some domains of application 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
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Constructal theory - Wikipedia, the free encyclopedia
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River basins
Water
Low-resistance rivulet and rivers
Lungs
Air
Circulatory system
Blood
Low-resistance airways, bronchial passages Low-resistance blood vessels, capillaries, arteries, veins
http://en.wikipedia.org/wiki/Constructal_law
Darcy flow through porous media diffusion in alveoli tissues 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 law is the principle that generates the perfect form, which is the least imperfect form possible.
Constructal law The constructal law was stated by Bejan in 1996 as follows: "For a finite-size system to persist in time (to live), it must evolve in such a way that it provides easier access to the imposed currents that flow through it."
Thermodynamical analogy Analogies between thermodynamics and constructal theory Thermodynamics Constructal theory State Flow architecture (geometry, structure) Process Change of structure Properties Global objective and global constraints Equilibrium state Equilibrium flow architecture Fundamental relation Fundamental relation Constrained equilibrium states Nonequilibrium architectures Removal of constraints Increased freedom to morph Energy minimum principle Maximization of flow access
In contrast to fractal models of phenomena, the constructal law is predictive and thus can be tested experimentally. One illustration of this is its application to a variety of allometric laws for which extensive data over several orders of magnitude of the variables exist. For example: Kleiber's law, the relationship between metabolic rate q0 and body size M
the relationship between breathing and heart beating times t and body size M
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Constructal theory - Wikipedia, the free encyclopedia
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http://en.wikipedia.org/wiki/Constructal_law
the relationship between the mass transfer contact area A and body mass M:
Bejan's constructal law also explains why we have a bronchial tree with 23 levels of bifurcation. The constructal theory of the flow architecture of the lung predicts and offers an explanation for: the dimensions of the alveolar sac, the total length of the airways, the total alveolar surface area, the total resistance to oxygen transport in the respiratory tree.
Constructal Theory web portal (http://www.constructal.org/en/theory/presentation.html) : publications, events, links, etc. Unified Physics Theory Explains Animals' Running, Flying And Swimming (http://www.dukenews.duke.edu/2005/12/locomotiontheory.html) : Duke University article.
A. Bejan, Advanced Engineering Thermodynamics, Wiley-Interscience, 2nd edition, 896 p. ISBN 0-471-14880-6 ; 3rd edition, 2006, ISBN 0-471-67763-9. A. Bejan, Shape and Structure, from Engineering to Nature, Cambridge University Press, Cambridge, UK, 2000, 324 p. ISBN 0-521-79388-2 Proceedings of the Symposium "Bejan’s Constructal Theory of Shape and Structure" (http://cge1.uevora.pt/~bejansymposium/) 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 A. Bejan, "Constructal theory of organization in nature: dendritic flows, allometric laws and flight", Design and Nature, CA Brebbia, L Sucharov & P Pascola (Editors). ISBN 1-85312-901-1 A. H. Reis, A. F. Miguel, M. Aydin (May 2004). "Constructal theory of flow architecture of the lungs". Med Phys. 31 (5): 1135–40. PMID 15191302 (http://www.ncbi.nlm.nih.gov/pubmed/15191302) . A. H. Reis, A. Bejan, "Constructal theory of global circulation and climate" (http://www.sciencedirect.com/science?_ob=ArticleURL&_aset=V-WA-A-W-A-MsSWYWWUUA-U-AAVUZBZYVY-AABYWADZVY-ZUDBDCYCD-A-U&_rdoc=1&_fmt=summary& _udi=B6V3H-4J2W0N2-4&_coverDate=01%2F19%2F2006&_cdi=5731&_orig=search&_st=13& _sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10& md5=89441fb0b28e21ddd42397b12bbd20de) , International Journal of Heat and Mass Transfer Volume 49, Issues 11-12, Pages 1857-1875, June 2006. Adrian Bejan, Sylvie Lorente, La loi constructale; traduction [de l'anglais] et avant-propos d'Angèle Kremer-Marietti. - Paris ; Budapest ; Torino : l'Harmattan, DL 2005 (14-Condé-sur-Noireau : Impr. Corlet numérique). - 1 vol. (109 p.) : ill., couv. ill. ; 24 cm. - (Collection Épistémologie et philosophie des sciences). Bejan, Adrian (1948-....) Bibliogr. p. 99-109. - DLE-20050511-22456. - 530.4 (21) . ISBN 2-7475-8417-8 (br.) : 11,50 EUR. Abdelkader Bachta, Jean Dhombres, Angèle Kremer-Marietti, Trois Etudes sur la loi constructale d'Adrian Bejan, Paris, L'Harmattan, 2008.
Popular literature Maggie Wittlin, "A Finger on the Pulse of the World" (http://www.seedmagazine.com/news/2006 /01/a_finger_on_the_pulse_of_the_w.php) , January 13, 2006. Retrieved from "http://en.wikipedia.org/wiki/Constructal_theory"
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Constructal theory - Wikipedia, the free encyclopedia
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http://en.wikipedia.org/wiki/Constructal_law
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