Architecture Myths #22: Biomimesis
Learning From Nature introduced aspects of the troubled and confused history of architecture’s relationship with the natural world.
The concept of biomimesis was never going to make it any clearer.
On reading this, I did bristle at contemporary philosophy and wonder what was meant by sustainability in nature but the rest was good. I approved of the bit about not by replicating natural forms, but by understanding the rules governing those forms and the bit about following a set of principles rather than stylistic codes. However, given architecture’s historic appetite for reducing potentially useful ideas to representations of useful ideas, the concept of a biomimetic architecture is just asking for trouble.
ONE. A clear definition of a term is a good thing but mightn’t a term like biolearning been better? Learning isn’t synonymous with mindless copying and repetition. Mimicking is.
TWO. Biomimicry is easily misunderstood as referring to appearance – shape – FORM if you will. Despite the disclaimers, the definition aims to learn from forms and for that learning to inform architectural form. This practically guarantees we will miss everything of value. The most valuable thing we can learn from the biological processes of Nature is that they randomly rearrange matter and any forms that result, result because they are good at doing something. It follows that there is something that can be learned from every form that results from the processes of Nature. How are we to know where to look, and for what? Sometimes it’s easy.
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Birds have wings and tails to help them move through space but there’s nothing especially architectural to be learned from that. There’s a difference between biomimicry and zoomorphism. Axially symmetrical airport buildings as tedious metaphors for flight is zoomorphism.
Buildings, even those at airports, don’t move through space. However, arranging things in space is one thing the processes of Nature and the processes of Architecture do have in common. A study on how birds use air turbulence to their advantage when flying in formation might provide some insights into better ways for air to move around buildings. Perhaps – but so far we haven’t found a problem we can apply this knowledge to. I’m not sure anyone’s looking.
The field of aviation however, has many problems to which it can apply the mechanics of birdflight for both deal with objects powering through air. Aircraft have tails and wings not because they’re mimicking the form of birds but because they’re required to do much the same thing in much the same environment. There are important similarities that have to do with aerodynamics, but there are also crucial differences such as aircraft having fixed wings. Bio-mimicry was the first avenue of exploration but not the best place to start.
Although airships forever seem to be on the verge of making a comeback they never actually return. The fixed aerofoil wing coupled to a means of thrust remains our preferred way of getting something into the air and making it move through it. Developments in commercial aviation have concentrated on factors such as lower weight, improved safety, increased passenger capacity, and more powerful and efficient engines – all of which are directly linked to commercial advantages. One of the features of the Boeing 787 Dreamliner is the use of carbon fibre composites for the fuselage, wings and other major components. Their higher strength-to-weight ratio makes the 787 lighter and more fuel efficient. $$.
It’s a different story for fighter aircraft. The dogfight isn’t so common a form of military engagement these days but development of fighters continues as a matter of national prestige. Some birds hunt and attack. Some aircraft hunt and attack. Range and speed are important but manoeuvrability is now top priority and birds, especially birds of prey, suddenly have a lot to offer. Have a look at this.
242 mph is 390 kmph. The bird was able to decelerate and turn so quickly because of alula. These are the small “winglets” at the front of the wing. Birds of prey tend to have more pronounced ones as they improve manoeuvrability.
Alula function in more than one way. When flying at slow speeds or landing, the bird moves its alula slightly upwards and forward, which creates a small slot on the wing’s leading edge. This functions in the same way as the slats on the wing of an aircraft, allowing the wing to achieve a higher than normal angle of attack – and thus lift – without stalling. The leading edge slats on this Airbus A318 function as alula.
Manoeuvrability is about maintaining laminar airflow by not exceeding the angle of attack (alpha) of the wing. It’s a serious design problem.
Solving this problem of laminar flow is why people go “oooh” at airshows when aircraft do impossible looking turns without falling out of the sky.
Also important for both birds and aircraft but particularly fighter aircraft is a very low wing-loading. This is the loaded weight of the aircraft ÷ area of the wing. Aircraft with low wing loadings produce more lift per unit area of wing, have better agility and higher landing and take-off speeds.
This means bigger wings. With its tiny wings optimised for supersonic flight, the Lockheed F104 Starfighter was the hummingbird of fighter aircraft. It was very stable at high speeds but required high speeds to turn, take off and land. “Banking, with intent to turn” was an in-joke for F-104 pilots.
Hummingbird wings have no alula.
There is no need to compromise between speed and manoeuvrability and this is where a bit of selective biomimicry is a very useful thing. At high speeds, alula function differently. They generate vortexes that suppress flow separation over the wing surface and so provide increased lift and better manoeuvrability when flying at high angles of attack. In this next image you can see vortexes doing just that, being generated by the wing leading edge parts extending forward to beside the cockpit.
These vortexes are created by airflow changes where the circular fuselage meets the leading edge extensions. We see them because of the water vapour that forms when air is suddenly compressed, expands again.
These vortexes are powerful and stable air streams having mass and inertia. They keep air flowing across the part of the wing where it is most useful. They follow the surface of the wing and, even if we can’t see them, remain in the air long after the aircraft has passed.
The canard is the aviation equivalent that best mimics how birds use their alula to improve lift, control or stability.
But canard? Why the French word for “duck”? Here’s why.
Static canards optimise one of these three but operable canards can optimise any of the three as required. This is a SAAB Viggen, the first production canard aircraft.
Canard design continued to evolve with the Sukhoi T-50 to the extent that its operable forward-facing leading edge extensions are now something entirely new, enabling vortex control for better stability or the controlled instability linked to better manoeuvrability.
It’s a sad fact of life that anything that might offer military advantage is enthusiastically researched and applied. Even if we despise the end goals of military research and application, we should admire its focus and rigour. The goal of military aircraft design has never been to create things that look threatening, although the Sukhoi S-37 manages to do that,
as also, for that matter, does the B2 bomber – although now we’re no longer talking about manoeuvrability.
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For both bird and machine however, flight is an energy-intensive activity and saving energy is one crucial area where research into birdflight does offer something to commercial aviation – at least as far as freight transport is concerned. When pelicans fly just above water, they are making use of something known as ground effect.
What happens is this. Vortexes generated at the wingtips of a flying bird or aircraft create something called downwash that acts to push the airflow behind the wing downwards. This isn’t good if the aircraft is trying to take off as it reduces lift and can only be countered by increasing the angle of attack, which increases drag and the likelihood of stalling.
When the bird flies just above the surface of the water, trailing vortexes are blocked to reduce the amount of downwash with the effect of producing more lift. This “ground effect” increases with speed and is why pelicans and other heavy birds such as swans fly close to the surface of the water until they reach take-off velocity. The effect is most pronounced when the bird flies at a height of one tenth its wingspan.
These birds are using ground effect to improve their lift-to-drag ratio and make themselves more efficient. Any bird or aircraft that used ground effect all the time would be more efficient than one at cruising altitude. You can read more about the history of ground effect aircraft here. Rostislav Alexeiev provided proof of concept with this 1966 aircraft. It’s an aircraft because it’s making use of aerodynamic principles to move through air unlike hovercraft that use the brute force of airflow for lift prior to propulsion kicking in.
Here’s a more recent Boeing prototype aimed at low-cost cargo transport. It’s called Pelican.
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Aviation is a good biolearner because it admits to using the same physics, encountering the same constraints and operating in the same medium for much the same ends as birds. So much for air. What about water? Many people including me, here, wanted to believe Speedo’s new range of swimsuit was the intelligent application of biomimicry to facilitate a human body moving through water. It was enthusiastically announced as resulting from an understanding of the skin of sharks functions to facilitate movement through water.
You can read the science here but it turns out the swimsuits didn’t mimic shark skin after all. Whilst it’s true shark skin does have an amazing structure that assists sharks’ movement by reducing drag, the effect only occurs if you have the body of a shark and move as sharks do – literally, not metaphorically. Speedo’s fancy swimsuits still had to be banned because of other competitive advantages they offered, but those advantages had nothing to do with sharks.
This swimsuit example highlights the dangers budding biomimeticists face when they select an inappropriate object for biomimetic study in anticipation of a certain result. Architecture is particularly susceptible this fundamentally flawed approach. The chain of thought goes something like “Shells are good – things live in shells – we live in things – let’s make shells!”
From seeing what gets presented as biomimetic architecture, one might think its endgame is for humans to someday secrete self-hardening goo and become their own 3D printers.
Both approaches are misguided. We really seem be getting good at looking at Nature and making shapes and patterns we struggle to find a use for.
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I was going to finish by saying that Nature doesn’t make random things and then try to find a use for them but, actually, Nature does make random things. Some of them happen to fit some evolutionary niche and so survive and earn a chance to repeat the same trick. The last three examples are like genetic mutations supremely adapted to flourish in academic environments. It’s by no means certain they’ll evolve beyond.