- A. Bejan and S. Lorente, The constructal law of design and evolution in nature,
Philosophical Transactions of the Royal Society B, Biological Sciences, vol. 365
pp. 1335-1347 .
(last updated on 2011/06/23)
Constructal theory is the view that (i) the generation of images of design (pattern, rhythm) in nature is a phenomenon of physics and (ii) this phenomenon is covered by a principle (the constructal law): ‘for a ﬁnite-size ﬂow system to persist in time (to live) it must evolve such that it provides greater and greater access to the currents that ﬂow through it’. This law is about the necessity of design to occur, and about the time direction of the phenomenon: the tape of the design evolution ‘movie’ runs such that existing conﬁgurations are replaced by globally easier ﬂowing conﬁgurations. The constructal law has two useful sides: the prediction of natural phenomena and the strategic engineering of novel architectures, based on the constructal law, i.e. not by mimicking nature. We show that the emergence of scaling laws in inanimate (geophysical) ﬂow systems is the same phenomenon as the emergence of allometric laws in animate (biological) ﬂow systems. Examples are lung design, animal locomotion, vegetation, river basins, turbulent ﬂow structure, self-lubrication and natural multi-scale porous media. This article outlines the place of the constructal law as a self-standing law in physics, which covers all the ad hoc (and contradictory) statements of optimality such as minimum entropy generation, maximum entropy generation, minimum ﬂow resistance, maximum ﬂow resistance, minimum time, minimum weight, uniform maximum stresses and characteristic organ sizes. Nature is conﬁgured to ﬂow and move as a conglomerate of ‘engine and brake’ designs.