Adrian Bejan

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January 17 - A Promissory Note | Main | The Taxation Paradox

Nature: Fractal or Constructal?

I love fractals. I love Benoit Mandelbrot. And this is a fantastic piece. But I know

someone who might question this love affair with fractals in nature. Why? Because thisdetractor has taken things a step further. As I have suggested on here before, Adrian

Bejan's constructal law is the as yet most important and underappreciated discovery in

the field of physics, evolutionary biology, economics and, well, you name it...

Bejan points out that fractals are mathematical descriptions with fuzzy edges. But if we

look out in the world, the so-called fractals are not fuzzy. It's nice that we've found

geometric analogs to natural phenomena. And fractals are fruitful. But what if we could

go further -- finding a natural/organizational law that had technical application across

fields?

Here it is: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.

So it is not merely that we get recursion in nature. There are functional reasons for such

recursion. And function has to do with flow -- that is how systems accommodate the

currents that impinge upon a system. Bejan calls this "vascularization." Heart, aorta,

vein, capillary. Trunk, limb, branch, leaf-vein. River basin, tributary, brook, creek,

stream. Highway, boulevard, street, alley.

Constructal theory also explains things like the relationship between energy

consumption and GDP, the "gap" between rich and poor, and countless otherphenomena from swimming fish to the excellence of black sprinters and white

swimmers. In short, it's not just form that's important. It's function.

3/18/2012 @ 9:39AM |1,025 views

"Freedom Is Good forDesign," How to Use

Constructal Theory toLiberate Any Flow SystemMove up Move down
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There's a New Law in

Physics and It Changes Everything Anthony Wing Kosner Contributor

The Constructal Sessions, Part II: Freedom and Design

My last conversation with Adrian Bejan ended on the notion that if design innature is a universal principle of the material world, then freedom is the key

variable that determines how efficiently designs can evolve over time. Bejan grewup in Communist Romania, so he knows first hand what happens when human

social systems are prevented from flowing by ideology.

Bejans new book, Design in Nature (Doubleday 2012, with J.P. Zane), is anintroduction to a new way of looking at the physics of everythingfrom theformation of river basins, to the locomotion of land animals, to the design ofcomputer chipsthat he has named the Constructal Law.

The growing body of Constructal Theory, which follow from the law, resolve many

of the cultural debates of the 20th cantury. Bejan is showing that one need notresort to randomness (and their corollaries meaninglessness and nihilism) in

order to remove the science of evolution from the aesthetic grip of religion. There
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is a unifying design in nature, asserts Bejanbut that fact requires no deity orother supernatural agent.

By placing design in a central place in our understanding of the world around us,and in defining nature and society as sets of interrelated flow systems, Bejan hascreated (or recognized) a new job description: the flow worker. If we expand ournotion of what designers do to include the iterative improvement of any systemover time, we realize that, on some level, we are all designers, all flow workers.

With that in mind, I decided to probe the issue a bit more with Bejan and begin to

identify the method he uses to address the improvement of flow systems both asan engineer and as an educator.

Interview withAdrian Bejan, J.A. Jones Distinguished Professor of MechanicalEngineering, Duke UniversityConducted via email, March 10 17, 2012

Q: You say Freedom is good for design, can you elaborate on that idea more?

A: Freedom is the most fundamental property of nature. Freedom means the

ability of a flow configuration to change, to morph, to spread and to retreat. It isthe natural property that makes all design possible.

The natural tendency expressed by the Constructal Law (toward easier flow, and

greater access to inputs over time) is visible everywhere because all natural flowsystems possess freedom. Without freedom to change, design and evolution

cannot happen.

With freedom, a natural flow system evolves with progressively greater flow

performance. Freedom is the sine qua non condition for improvements over time.Freedom is good for design.

We are all familiar with how freedom empowers design, but we take this truth forgranted. We do not think about it until freedom vanishes. To make a drawing

look better, we change it, we color it, and we replace it. None of this would bepossible without the freedom to change the drawing.

More freedom means to be able to change more features of the flow design.Engineering and civilization are all about this. We can make a fluid flow moreeasily through a pipe if we have the freedom to enlarge the pipe diameter. Wecan facilitate the flow even more ifin additionwe have the freedom to shorten

the pipe.

Freedom can be measured. The design features that can be changed are calleddegrees of freedom. The pipe diameter and length are 2 degrees of freedom. The

width, length and surface type of a road are 3 degrees of freedom. Power plants,cities, businesses and governments have many more. In this direction toward

more degrees of freedom, our imagination, creativity, ingenuityand affluenceblossom.

Freedom is not appreciated precisely because it is everywhere. Just like gravitywas before Galileis law made it a fundamental notion in physics. Today, theConstructal Law makes freedom and its fruits (design, evolution, performance)

fundamental notions in physics.
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Q: But what about bad design, where does that come from?

A: All design is imperfect. This is a good thing, because it leaves the road wide

open for discovering better flowing designs tomorrow. Imagine a world in whichnothing could change because it is already perfect: no change means no lifea

flow system that is not alive.

Bad design is a thought that emerges in retrospect. This thought is trivial,because of the dynamic (evolutionary) nature of design: yesterdays designappears to be weaker that todays.

A human design extension such as the wheel with wooden spokes may strike usas bad today, because of the modern evolution of wheel technology. Yet, in the

1700s and 1800s, the wheel with wooden spokes was a great facilitator of humanmovement over the landscape in comparison with the solid wooden wheel of

antiquity.

The river basin serves as inanimate metaphor for the bad-design-in-retrospectphenomenon. The river channel with a tree log fallen across it may strike us asbad. Yet, the river water will remove the obstacle and make the river basineven better. What appears as bad today serves as an opportunity for betterdesign and evolution tomorrow. Even when the tree log fell in, the river designhad been perfected relative to what it had been decades earlier.

The animate metaphor for bad-design-in-retrospect is animal movement. Running

animals move animal mass on land more efficiently than swimming animals movein water. Fliers move animal mass more efficiently than runners and swimmers.

These designs of animal mass vehicles occurred in the time sequence predictedby the Constructal Lawswimmers then runners and then fliersnotthe other

way around.

Swimming was a perfected design before the emergence of runners, and runningwas perfected before the emergence of fliers. The old design of locomotion looked

bad in retrospect, from the vantage point of the new. Yet, the new did not

displace the old. The new and the old together move a lot more animal mass thanjust the old alone alone. This is the time arrow of the Constructal Law.

Q: But when it comes to design by humans, dont we have the ability to makebad designs and convince ourselves that they are good? Doesnt our self-

consciousness make us uniquely suited to talking ourselves into bad, unnaturalsolutions that would never, otherwise occur in nature?

A: Manmade designs are natural, because on the whole they happen in thedirection of facilitating and enhancing our movement on the landscape. This is the

birds eye view, broadly speaking, the big history that is captured by theConstructal Law.

Not every individual detail agrees at every moment with the broad viewthink ofthe tree log that falls across the brook and slows it. The effect is local and shortlived. The constructal urge is what happens immediately, which is that the riverbasin marshals all its waters to remove the tree log, or to carve a path around it.

Q: So, manmade designs behave like natural flow systems if you have a longenough timeframe, but the puzzling thing for us as humans is the persistence of


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bad designs, of intractable configurations that limit the freedom to improve flow.What explains, for instance, the persistence of the North Korean regime, when itsneighbor to the south enjoys a standard of living ten times as high?

A: Your example with North versus South Korea is very appropriate. When we fly

at night from Tokyo to Seoul, we see the lights below. Over Korea, an explosionof light (power) in the South is in sharp contrast with the total darkness over theNorth. Why? Because power means movement, and the rigid system(communism) strangles all its flows. We see the same night contrast between thelights of Florida and the darkness of Cuba.

Six decades of strangulation are far too long for the three generations sentenced

to die at the bottom of the rain barrel. Yet, this is just one framea blipin themovie of design evolution of civilization in big history. Like the tree log effect, the

rigid designs of North Korea and Cuba are short lived. Dictators and theirenablers better pay attention to this Constructal Law predictionit is physics, notopinion!

Before 1989, the lights of Western Europe burned in sharp contrast with the darkof Eastern Europe. Today, the sea of lights has invaded the dark swamp and set itin motionvascularizing it with freely morphing designs. This is the future of all

the swamps, and the tree logs that stand in the way will be removed orbypassed.

Q: If any flow system can be improved over time (given freedom), do you have astandard series of steps or procedures you use to analyze the degrees of freedom

that are available in a given design configuration and identify whereimprovements can be made?

A: Yes, and in fact I teach the philosophy of this very topic with Prof. SylvieLorente in the textbookDesign with Constructal Theory(Wiley, 2008) and in thecourse with the same name at Duke University and other leading universities allover the world. The best introduction to the method is in Design in Nature, inparticular, chapters 1-5.

Here is a brief sequence of steps toward Constructal Design:

1. Define Your System: Identify clearly and unambiguously what constitutes

your system, i.e. the region in space, or the amount of mass that is thesubject of your thinking, analysis and design.

2. Identify the Flows: Make sure your system has the freedom to change, and

that you understand what flows within it, i.e. why your system is a flowsystem.

3. Start Simple: Allow only one feature of your system to change at first. This

endows your system with one degree of freedom. Study if and howchanges to this feature increase the flow access of the currents thatinhabit your system. Incorporate the first feature with which you foundthat your system performs best into your design (be alert, this is not theend!)

4. Add a Degree of Freedom: Allow a second feature to change freely. As you

investigate this second degree of freedom, you will find another bestfeature, and adopt it. With this second feature in place, go back to step 3and refine that first feature to work with the second.
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5. And Another: Allow a third feature to vary freely, find the best variant of

this feature, and then go back and repeat steps 3 and 4, i.e refine thepreceding two features.

6. And so on: This is a construction process with no end, except the finite time

of the investigator.

In the evolution of technology, this sequence happens naturally, but slowly, inhaphazard bursts of individual creativity. Usually, one step (one degree offreedom) represents a single invention, such as Traian Vuias air-tube tires on the

first airplanes, one century ago. With the method of Constructal Design, I thinkentire companies and industries can fast forward the design evolution of their

technologies and reduce trial and error.

Nature behaves in the same way, imperceptibly, all the time, and on a muchbroader range of degrees of freedom. This is why with the Constructal Law wehave been able to predict (with eyes closed) the designs of inanimate flowsystems (e.g. river basins, turbulence, snow flakes) and animate flow systems

(e.g. lungs, vegetation, animal locomotion). And we can use this method toinvestigate and innovate social, political and technological systems as well.

We will continue with the theme of the relationship between flow systems in our

next installment.

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Adrian Bejan