Half a billion years of streamlining
 

Hello all. For years,I've used the work of the Lillianthal Bros.,Gustav Eiffel,Paul Jaray,etc.,as examples of aero-pioneers,when doing public exhibits on aerodynamics and fuel economy. I have also used fish,marine mammals,shark,and birds to demonstrate" Nature's" design solutions for fluid-dynamic challenges.

After reading "More With Less", about Dr.Paul MacCready of Aerovironment, and his teams which gave us man-powered flight and Solaraycer, to name just a few of their accomplishments, I was introduced to the term "biomimicry", a term used by team members to describe how they observed, and looked to nature for clues for how to overcome physical challenges to moving within our atmosphere or waters.

Digging in a little, I've come to learn that our birds date to the Jurassic Period, about 150-million years ago, and fish, to the Devonian Period, about 400-million years ago, and "proto-fish", with all the streamlining efficiency of today's modern fish, to perhaps a half-billion years ago.

The HONDA Dream solar champion ,with Cd0.10, and 400-mpg potential, borrows heavily from Aerovironment's Solaraycer, which itself was modelled after a pumpkin seed.

NASA has been able to create the efficiency of the 150-million-year-old blue-fin tuna,the most streamlined shape in existence.

Peregrine falcons stoop at over 230-mph terminal velocity. Needletail swifts bound through the skies in level flight at over 200-mph. Ocean prey do their best to evade the clutches of fast swimming mako shark, bottlenose dolphin,emperor penguin,leopard seal,and the like.

Atomic submarines have come to embrace the tuna in their exemplery hydrodynamic forms. Canoe and kayak owe their amazing abilities to organic forms.

As carmakers look to the challenges of higher fuel economy,cleaner air,and lower CO2 footprints,they need only look to the heavens or under the waves for the solutions which await them along their line of sight.You as members of ecomodder needn't wait though,as no lenders, committies,shareholder proxies ,nor sales directors,limit your access to nature's forms.You have only the nuts and the bolts of it in your way.

So look up,look down.It's all the same in nature.The forms just keep repeating themselves.And if you're ever over-takin on the road by a four-wheeled tuna,its probably just some nut like me,who bothered to look around . Get you a shop,get out there, tear it up good,be safe,have fun,save fuel. I'll be taking my own advice.

I find it interesting that you don't see any examples of the Kammback in nature, just boattails. Makes you wonder how low drag competitive a Kammback is compared to a boattail.

Kamm stated when the Kamm tail shape was put forward it was to be a compromise between the ideal theoretical shape and a practical limit for a road going vehicle.

This point is generally missed by a lot of people in discussions on these topics.

Pete.

Aerohead,
Some interesting thoughts there.
Even the 747 looks like a bottlenosed dolphin at the front from some angles.

Pete.

Dr.Wunibald Kamm/Kamm-backs/boat-tails
 

There IS some confusion over Kamm's contribution to aerodynamics.My reading shows that by discharging engine bay air at the base of the windshield,Kamm was able to prevent air from stalling over the windscreen header,allowing attached flow over the roof that would otherwise separate.It was up to the auto designer to chop the body wherever they chose.Airflow would remain attached up to the chop.Kamm's K-car' roof extended to the rear extremity in a continuously descending arc(ie.the "Kamm-back"),and is what people associate with Kamm,not the front-end work that made the attached flow possible in the first place! In nature,we don't see the cropped posterior,as in the K-Car as Nature seems to demand eeking-out the last ounce of efficiency,only found in the long tapered tails we refer to as "boat-tails".It is claimed that truncating the boat-tail ,will produce a "phantom"boat-tail behind the car and its kinda true.I posted a picture of the K-Car in the Volkswagen wind-tunnel over at maxmpg in the Misc.photos.The smoke trace clearly shows the "phantom",however these truncated boat-tails never actually produce the low drag of the long tail.In the movie,"The World's Fastest Indian" we can see Burt Munro's "Munro Special"at speed at Bonneville.The body on the bike takes advantage of the Blue-fin Tuna form for low drag and record-setting speed,however,as is pointed out in the story,it also demonstrates challenges to directional stability associated with center-of-gravity/center-of-pressure domains.BNI will not allow racers to run the course if crosswind speeds get to around 7-8mph,to protect against "weather-vaneing",which could be catastrophic should the vehicles be pushed into a barrel-roll.The T-100 appears to respond favorably to it's truncated boat-tail.I have planned a full 5.5:1 fineness ratio truck/trailer boat-tail,which will allow the vehicle combination to achieve the theoretical ideal form,a full tail extending twelve feet beyond the rear bumper of the T-100.Formulas show a possible 47-mpg at 70-mph.I believe this to be a reach,however it is enticing,and I won't know until I try.As Peter has pointed out,the Kamm-back is a compromise,and in the workaday world avoids the ridiculous lengths I'm going to explore with the trailer.Lower rooflines are the only thing that will allow shorter length and lowdrag together(active-suspension would help).

Hi All,

Aerohead has it right. The issue is cross-wind stability. The Kamm-back is a drag compromise to achieve cross-wind stability. Now depending on the vehicles the stability issue will or will not be as much an issue. A pickup truck for example has the CG way forward, and the cap boatail is actually mostly in front of the rear wheels - not much of a problem. A hatchback civic is similar, but the boatail is now behind the rear wheels, but the rear wheels are way back on the car. As other cars have body parts much farther back behind the rear wheels, the boat tail is probably OK on this vehicle too.

Why no Kamm-backs in nature? Because animals can do variable shapes, and twist their tails to allign with the direction of flow. They can also do vectored thrust. Besides animals can do active fluid dynamic control. Ocean going fish also do not need to align with the roadway, and can just go into and then crosswise to currents. And currents in the ocean are very slow compared to tuna speeds. So cross-wind or cross-current has also been designed for over evolutionary time, or are just not as big a consideration.

If you find this interesting, then you should also look into techniques used to prevent sonic boom on super sonic flights.

It's all a matter of the drag vortex and how you avoid creating one.

CNN News article

I see no reason this cannot be applied to ground vehicles.

I think the aero lessons of the DC3 would apply to cars more than those of the Concorde and the F16.

Super sonic (air travelling more quickly than the speed of sound) aero has a totally different set of parameters than sub sonic aerodynamics.
This principally due to compression at Mach One and above which simply does not apply to road vehicles.

An interesting article none the less.

Cheers , Pete.

On the subject of nature (very good write up, by the way).... I've yet to find an instance of vertical wing tips in nature :p Some birds have fanning feathers at their wing tips - but that's physically very different...

Very nice post, there is some great insight in there and it was very inspiring.

It always fascinated me how nature evolves over time. I can understand evolution when it does things like, adapt a body to live in a wetter area then it used to or breath a different combination of gases then it is used to. But what always baffled me was aerodynamic adaptations. How does nature know what to do to make itself flow better in the medium in which the creature presides?

I personally can't wait to reconstruct my model wind tunnel that I built in middle school for a science fair project (my dad scrapped it because he needed his leaf blower back) so that I can start testing ideas I have on a scale model of my car and some of my custom ideas I make from scratch, I might actually be able to find a very good way to make a very aerodynamic car for myself someday.

Its easy; imagine two hungry samon that have to swim upstream to breed, one more aero (or hydro) than the other. They both have the same amount of energy stored as fat in them. The efficient fish will use less energy and make it's mate whereas the other fish will die. The surviving fish gets to breed and pass on its steamlininess whereas 3-box fish gets a Darwin award. Unfortunately there is no proverbial river that automakers have to swim up to create a new model... the just do whatever sells best.

vertical wingtips
 

I liked donee's post about animals ability to morph their bodies to achieve direction without the need of the weather vanes we see on aircraft.I know NASA and MIT,and others are working on aircraft which will be shape-changers during flight.I will watch with much interest as this technology advances.No doubt,active aerodynamic appliances will make inroads into the road vehicle arena,as energy prices,and competitive forces spawn reactive engineering counter-punches.Hope so!

You would enjoy reading Dr. Heinrich Hertel's "Structure, Form, Movement" book, which looks to Nature for elegant engineering solutions.

The fastest swimming fishes (i.e., tuna, shark, etc.) have max thickness at 44.22% of length, for optimal streamlining. Otherwise, they don't get breakfast, but are breakfast. They've had, oh, ~65 million years to work on it. We do well to listen to Nature.

Nature never made a Kamm back because the tail is where the propulsion comes from. Besides, a fish tail is no fun while parking or in traffic.

The rule in history as we are finding out is that efficiency wins in the long term. We have morbidly obese people because plentiful food is the exception in history rather than the rule. When we have more humans and less food those naturally fat people are going to come into their own, provided that the less efficient high metabolism people don't have other advantages in their favor provided by that high metabolism.

And look at our brains. That much parallel processing ability and such little energy usage compared to the computation achieved. If that had to be done in silicon, the wattage would be incredible. But natural selection brings efficiency.

Squids, cuttlefish, and octopi are jet propelled and don't have tails. When moving fast, they combine their tentacles into the shape of a boattail rather than a Kammback. But if all else was equal, a Kammbacked tentacle package would be preferable from a predator avoidance standpoint, since it doesn't stick out as far as a boattailed tentacle package and would be harder for a pursuing predator to grab. So a boattail must provide drag reduction and higher speed benefits that counteract its additional length and mass

So far, the boattail on my car hasn't been a detriment in parking or in traffic and I've been driving with it on my car for 2 years.

Hmmm. Interesting about parking/traffic.

Squid go tentacle-forward, gathered into a fairing shape, though octupi have tentacles trailing, also in streamlined configuration. Both are jet propelled, as opposed to wagging their tails like normal fish and dolphins, as I understand it.

BTW, have you tested your car with vs. without the front end mods, but with rear end mods, to see how much the front fairing helps?

Dr. Hertel
 

Thanks Otto! I wrote the title and author info,and will try and run down a copy of the book.He may be the resource used by others when making claims about aero/hydro efficiency in the animal kingdom.Thanks again,Phil.

I don't see nature as providing any aerodynamic benefit beyond inspiration. It took mankind thousands of years to master flight primarily because he tried to emulate nature. Look at DaVinci's flying contraption:

Da Vinci Flying Machine
http://artfiles.art.com/images/-/Leo...C13089415.jpeg

What nature did was inspire man to fly. Without birds, flying bugs, or clouds I doubt man would have ever learned to fly. Today, people try to tie in nature with their designs because it has a romantic element. Aerovironment's Solaraycer was designed after a pumpkin seed, yet a pumpkin seed is not inherently aerodynamic...

Lastly, nature does not think. Everything you see around you is (as far as we know) not a master plan, where evolution is heading in a particular direction. What you see exists solely because it was able to survive. Man is not at the "top of the evolutionary ladder," he is simply a leaf on the evolutionary bush. The most evolutionary successful creatures are single-celled organisms like bacteria, who have remained virtually unchanged for billions of years. As far as we know, nature thinks as much as planets do while orbiting stars trillions of miles away.

- LostCause

The Solaraycer demonstrates a 400-mpg vehicle,if fitted with gasoline internal combustion engine with power to provide contemporary levels of acceleration.With concessions made to ingress/egress,survivability,real wheels/tires,emissions controls,etc.,could represent a 200-mpg commuter vehicle in days of plus-$3.00/gallon fuel and U.S.reliance on the Persian Gulf.That's an inspiration for myself and others,no matter its origin.It's origin was a pumpkin-seed,so given the success of Aerovironment's endeavor,I see no reason to berate forms found in nature,and I will personally continue to borrow heavily from the same architecture that inspires the likes of M.I.T.,NASA,Electric Boat Division,General Dynamics,Corp.,Lockheed/Martin,Airbus,Boeing,Grumman,Zeppelin Werke AG,McDonnel/Douglas,Rockwell International,Scaled Composites,Old Town,Winchester,Remington,Marconi,Cal Tech,Mercury Marine,etc..

Squid can go either tentacles-forward and tentacles-backwards (the advantage to being propelled by a directional nozzle). They go tentacles-forward for short distances when capturing prey (the tentacles will flare outwards to capture the prey at the end of the brief forward sprint. But they spend most of their time going tentacles-backwards (especially when they are in a hurry).

I didn't have a SuperMId when I installed the nosepiece and boattail (the boattail was installed earlier than the nosepiece), so I could just go with the change in coasting ability resulting from installing the mod. The boattail produced a larger improvement in coasting ability than the nosepiece, but the nosepiece produced a greater than anticipated improvement. The nosepiece resulted in about the same amount of coasting improvement as when I installed the smooth underbody.

Ornithopter

http://upload.wikimedia.org/wikipedi...41/Skybird.gif

I have no doubt, that if Da Vinci had the proper materials available - he'd have been successful :D

Or the strandbeest - that's a pretty cool wind powered kinetic sculpture (maybe a bit of a stretch).

http://www.sojamo.de/blog/wp-content...trandbeest.jpg

Ornithopters are pretty amazing, but the end of the following video sums up my feelings...:p

UTIAS Ornithopter
http://www.youtube.com/watch?v=a-qS7oN-3tA

I'll give it to them that they were flying. :)

- LostCause

Aerohead, I don't know if you use images during your presentations, but this is a famous painting I remember coming across that represents nature in design. Matthew Baker was an English shipwright during the turn of the 17th century that attributed the quality and speed of his ships to his keen observation of fish.

Matthew Baker Fish Morphology
http://nautarch.tamu.edu/shiplab/01G.../Bakerfish.jpg

- LostCause

fish morphology
 

LostCause,I used to post images over at maxmpg.I use the computer at a local copy center and the fella who owns the business has helped me do all the hocus-pocus.His computers are slow by today's standards and it takes a lot of time for him to isolate individual images from my camera,or scan and Jpeg everything to email it.I haven't asked him to do it in a long time 'cause it seems to be such an imposition.and he's usually quite busy.I need to do it as its such a great way to communicate.I haven't seen your image of Baker's work before.Its great! I get a lot of catalogues for historical and military stuff,and they recently offered a model of Noah's Ark,which appeared remarkably streamlined.Your stills,tables, and video are the way to go.I hope to get some images transferred ( I collect Stuff all the time),however,with work taking me out of town for many weeks lately,just looking in at ecomodder has been a real luxury.Thanks for all your post,Phil.

I seem to remember the Navy using a paint on the hulls that mimics the texture of shark skin giving a substantial gain in efficiency.

hull paint
 

I've heard rumors about this.So far I haven't snagged anything on it.Doesn't mean it isn't out there.There is a fella that did Dolphin research for the US Navy that came out "Laminflo",a coating applied to torpedoes,which lowered skin friction remarkably.

I believe that olympic swimmers are using full-body suits with a poly shark-skin for better hydrodynamics.

I've seen the suits on GOOGLE.Pretty fun stuff! Does the Olympic Committee allows one contestant to compete with such technology,without requiring all to wear such a suit?

Sorry to dig up an old post, but since I found one that related directly to the subject I thought I would post here.
I found an article on biomimicry, specifically biomimicking sharks. It looks like these people also have a book that will be coming out about the top 100 ways they have found to mimick nature. They have found better ways for many things, from heating and cooling homes to solar power to how we clean our boats (this is where sharks come in). I don't want to say too much, just that you should check out the article and I hope you enjoy.

related
 

wyatt,it's a tasty article,thanks much!