The God of Design
Nature vs. Man
While being one with a lasting passion for design optimization, I'm heavily motivated by nature's creations. Why nature? Because she is the god of design, creating wonders that not only bear clear marks of engineering, but also seem infinitely optimized across scales of geometry, size and function. As the graphic here says, while nature is most often doing optimization and less of engineering, it's the other way around with man.
My famous five!
Nature's optimization abilities seem to live in her genes, visible across nano to mega scales. But we could never ever truly know her. This quote from John Archibald Wheeler seems to make that point..
"We live on an island surrounded by a sea of ignorance. As our island of knowledge grows, so does the shore of our ignorance."
From billions of nature's creations to which of course we humans belong to, here are my famous five...
I. Stay low and you'll live long!
The palm tree here is one striking example of how trunk geometry is optimized to serve multi- disciplinary and conflicting needs of designing for gravity and designing for wind. And how's nature doing optimization here? Because as you might have noticed, the trunk's gradient is more like it wants to hug the beach! This isn't some freak act of nature. Rather, by evolving in a low gradient, nature achieves a high and efficient resistance in the trunk, to the high wind force that's (dominantly) towards shore, from sea.
And why do I call it efficient? Because such resistance dominantly is of an efficient ‘thrust’ rather than an inefficient ‘bending’ character. The latter would've been so, had the trunk’s gradient been more vertical than horizontal. Indeed, for palm trees far away from sea shores, nature lets the trunk evolve closer to the gravity vector.
But wait, nature's story isn't finished! Notice how the frond head, that is the leaves and fruits bunch, turns sharply upwards from the trunk. By doing so, I'm clear at least that gravity now is starting to dominate the design, or to put it directly, the local bending moment is knocked down quite well from what it might have been had the frond not evolved skyward. And of course, nature's well aware why a larger trunk girth is needed closer to the ground than at the frond.
II. High- speed machining is perhaps millions of years old!
From that striking example of an optimized structural form, let's dive into another world of mechanical engineering where an ant is at work, employing everything from high speed machining principles to rigid body dynamics. Meet Alfa Cephalotes, the leaf cutter (image copyright: Alex Wild Photography).
Native to much of the Amazon basin of South America as well as Mexico and part of the USA, a leaf cutter ant's systems have evolved to use high frequency vibration to cut a leaf. Seen above, the left serrated pincer serves as an anchor while the right one, partly into the leaf, is busy machining through high frequency vibration, close to 1 kHz. Honestly, given an opportunity, I'd love to study this little machinist more thoroughly to learn what mode/s of vibration is/ are involved and why, though my guess is it's dominantly shear. I'm also guessing the two long feelers (on either side of the pincers) aren't there for nothing and are likely functioning as sensors that'll by tactile means, update the ant on the machining progress in real time. Of course, I'm guessing again the ant likely knows the optimum placement of its legs for efficient machining: neither too far apart nor too close!
and on the way home...
To complete that machinist's story, above is a cut leaf on its journey home. I'm guessing that on the leaf, the free riding buddy isn't there solely for fun or battle, but likely is continuously maintaining the centroid in a near- optimum location on the journey!
III. Watch out! If you can, that is!
Now for a chilling, deadly example: one of the most venomous snakes on the planet, the rattlesnake (Crotalus Durissus).
The rattlesnake is an ambush predator, evolved to prey on mice and small creatures that are unfortunate to enter its strike zone. Equipped with heat sensing pits on its head, the rattlesnake can solely rely on thermal signatures to locate its prey, perhaps relatively more so in the dark of a night when ambient temperature is lower than in the day. But prey aren't stupid and keep their ears open for any suspicious movement. That's exactly why, I'm guessing the rattlesnake wouldn't move much at all. Rather, it configures its body into that deadly strike pose you see here. And for the strike itself? Finished in a cool 1/250 sec! The haemotoxic venom quickly finishes the unlucky prey in minutes.
The strike pose, I'm guessing, is an optimum one, between static stability and strike range as well as that all important muscular energy for the strike itself. Indeed, I'm guessing the strike pose is also geometry- optimized to maximize the snake's potential energy that would turn into kinetic energy in 1/500 sec (time for ½ cycle)!
IV. Arch with no rival!
A natural arch, like the one pictured below (image under Creative Commons License), is one of nature's longest projects, lasting millions of years. What is fascinating is how nature finds a highly efficient solution to support weight without loss of resistance. While weight here is of course is much of the arch curve, resistance can be quite complex. In the pic, the arch is largely what I'd call planar. If we look a bit closely, we could recognize the 'layered' features making up the arch, layers being formed roughly across the gravity vector going downwards from top. This suggests that sometime in its history, this arch was well under water and that water flow was dominantly in the kind of plane the arch presently is in.
From the structural viewpoint, the arch geometry is an optimum topology solution to maximize resistance to the supported weight, under a continuous process of attrition from the flowing water.
V. Aeroelastic Tailoring
