I love this thread its like someone read my mind. Its been my long term plan to desing and construct low material intensity structures inside large out structure, 90% transparent. A dome our some such thing. Tis very efficient overall.
Me I’ve always wanted to live in a bubble, a massive bubble, visible from miles around, I’ve asked loads of house experts where to get one but they all say you can’t, no such bubbles exist, no one’s making 'em.
Guess that’s it then.
Ok, I apologise. The kindest way I can put it is that I’ve found some theories espoused on the Pin to be off the wall.
I’ll admit to not having heard of constructal theory until it was linked above. A quick hour of research left me very unconvinced:
It is a non-reductive theory; that in itself is not bad, just very ambitious
It has no rigorous mathematical basis; that’s generally a bad sign in physical theories
Bejan’s language generally lacks a lot of rigour, for example in “Constructal theory of global circulation and climate”, A. Heitor Reis and A. Bejan, in International Journal of Heat and Mass Transfer 49 (2006), pp.1857–1875;
It doesn’t read like the writing of a scientist writing in his area of expertise; most non-experts – even scientists – claiming to have invented novel theories are crackpots;
The theory claims to govern everything from snowflakes to biological evolution; it is over-reaching in scope, and only widely applicable because it is pretty nebulous;
Bejan comes across as a potential charlatan; his Wikipedia page is a self-serving advertisement; his own descriptions are utterly pretentious, e.g. “constructal from Latin verb construere, to construct” … FFS, how about “constructal from English construct”, the rest of the etymology being glaringly obvious?
he admits his unfamiliarity with relevant scientific work in his response to referees of a 2006 paper; he also accuses them of being envious of his theory and wishing to have invented it themselves – the ad hominems don’t make for a very convincing scientific argument
There are several articles refuting the theory, for example:
“A critical review of constructal theory”, L. Kuddusi and N. Egrican, in Energy Conversion and Management 49 (2008), pp.1283–1294
“Conceptual study on constructal theory”, L. Ghodoossi, in Energy Conversion Management 2004;45(9-10), pp.1379–95.
The two articles above contains 17 examples of flow systems that do not behave according to the constructal law
Last I heard there was no news. But there will be by end of 2012 or, at least, at that point “no news” will be treated as “news” … that the standard model of particle physics needs some tweaking. There are plenty of non-Higgs theories around.
Ya see that’s the kind of post that gives rigor to disdain. I’ll admit I didn’t pick up on the author of Constructal theory or care to as I took it as an interesting facet of areas like biomimicry and peaked something I had observed in the natural world and other designers work.
I apologise again for the disdain. And I hasten to point out that I am no kind of expert. I was quite interested in the link to constructal theory, just not convinced after a quick look into it. (PM’d you back about accessing the articles cited above).
I picked up on it because the general issue of why there are so many more reductive theories about nature, and so few about overall system behaviour is interesting (to me, at any rate… maybe I just don’t understand it well enough ). Constructal theory seems to want to be one of the latter type. But even Bejan’s own solution to the location of the Hadley and Ferrel cells in his paper on the atmospheric circulation involves finding optima in linear differential equations governing heat flow. Well, that way lies madness, because I would’ve thought that the complexity of real-world system behaviour often arises out of non-linear dynamics ( – cleverer people than me have suggested so at any rate). Indeed, very simple models of convective behaviour like Rayleigh-Bénard convection exhibit complex instabilities under certain conditions. Global Circulation Models tend to assume that earth’s climate is subject to similar instabilities, and not simply trying to optimise certain handpicked rates of flow as Bejan assumes. Also, the complexity seems to arise naturally from simple mathematics (if we’re to believe chaos theory) so I’m not certain we even need a theory like Bejan’s. (Usually at this point my brain starts hurting at the notion that trivially simple mathematical rules can lead to complex behaviour, so that the behaviour is simultaneously explicable and completely unpredictable forever ).