{"id":2399,"date":"2012-08-10T00:02:03","date_gmt":"2012-08-10T04:02:03","guid":{"rendered":"http:\/\/www.alexblock.net\/?p=2399"},"modified":"2012-08-10T00:02:03","modified_gmt":"2012-08-10T04:02:03","slug":"cities-and-the-constructal-law","status":"publish","type":"post","link":"https:\/\/www.alexblock.net\/blog\/2012\/08\/10\/cities-and-the-constructal-law\/","title":{"rendered":"Cities and the constructal law"},"content":{"rendered":"
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CC image from Other Think<\/p><\/div>\n

Several months ago, I picked up a copy of Design in Nature<\/a><\/em> as an impulse buy at the bookstore. I was purchasing a gift and the cover caught my eye. A quick perusal of the jacket and a few pages of the introduction was enough for me to fork over the cash. \u00a0I didn’t get around to reading it until I had several airline flights this summer (with the accompanying missed connections) to dig into the book.<\/p>\n

The basic premise of the book is that the similarities we see in nature (why trees and lightning bolts and river deltas share the same branch-like architecture) isn’t a coincidence, and it certainly isn’t the result of divine inspiration. \u00a0Rather, these similarities are explained via thermodynamics and the ‘constructal<\/a> law<\/a>‘ as coined by the author, Adrian Bejan. \u00a0The law states:\u00a0“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.”<\/p>\n

In short, the flow systems and the laws of physics that govern them influence those similarities in design. From the wiki summary:<\/p>\n

The constructal law represents three steps toward making \u201cdesign in nature\u201d a concept and law-based domain in science:<\/p>\n

    \n
  1. Life is flow: all flow systems are live systems, the animate and the inanimate.<\/li>\n
  2. Design generation and evolution is a phenomenon of physics.<\/li>\n
  3. Designs have the universal tendency to evolve in a certain direction in time.[2]<\/a><\/sup><\/li>\n<\/ol>\n

    The constructal law is a first principle of physics that accounts for all design and evolution in nature. It holds that shape and structure arises to facilitate flow. The designs that arise spontaneously in nature reflect this tendency: they allow entities to flow more easily \u2013 to measurably move more current farther and faster for less unit of useful energy consumed.[3]<\/a><\/sup>\u00a0Rain drops, for example, coalesce and move together, generating rivulets, streams and the mighty river basins of the world because this design allows them to move more easily. The constructal law asks the question: Why does this design arise at all? Why can’t the water just seep through the ground? The constructal law provides this answer: Because the water flows better with design. The constructal law covers the tendency of nature to generate designs to facilitate flow.<\/p><\/blockquote>\n

    Reading the book, I thought back to previous examples of similar observations of cities:<\/p>\n