Some Irregular Aerodynamic Principles in Nature

[jeff88]

I went to the Monterey Bay Aquarium a while back and we happened to watch a short presentation while we there. I was debating if I wanted to watch it or not, but the subject was right up my alley and I decided since we were there we should just watch it. I'm glad I did. It was essentially about biomimicry. The two major things that stood out to me were, surprise surprise, aerodynamic principles certain animals exhibit that go against our thinking, but have been proven to provide less drag, more lift, etc.

The first one was the 'tubercules' on a Humpback whale's fins. 'Human thinking' dictates that the fin or wing (say an airplane) should be a fine leading edge, to reduce drag as much as possible. But the tubercules of a Humpback whale actually reduce drag by as much as 1/3. My question is in layman's terms why this happens and how this could help a car (maybe an air dam with tubercules on them)?

Here is what I am talking about:


Here is my idea for a car (in an extreme situation - an F1 car):

Please excuse the terrible Photoshop (well, Paint), but you get the idea.

Some info: Humpback Whale Case Study

[jeff88]

The other ‘oddity’ was the box fish. The box fish is almost a cube with a pointy front end. You would think in terms of drag, this fish would be like a brick swimming through the water, but it is actually incredibly mobile around the reefs.



Mercedes took this idea and created the Mercedes Bionic; a boxy, yet sleek car with an awesome Cd of .19.





I wonder what this type of design would do here in the U.S. with our love affair for SUVs. We feel like we need SUVs just to go to the grocery store, so instead of changing our culture, this would meet the demands of the public, while meeting the demands of the environment.

[Jack-MTL]

I like the tubercules idea, maybe applied on a splitter or on a spoiler. I don't think it could be applied to most parts on the car front due to obvious pedestrian injury risks but it should work on a splitter or air dam.

I would love to see manufacturer come up with ideas other than "huge box with wheels and moooore pooooweeer!!"

[mcrews]

love Monterey!!!!!

[fidalgoman]

Aerodynamics can be quite complex. Don't forget that water is over 800 times as dense as normal air pressure. Also Reynolds number is very important. Look it up if you don't know how it affects lift and drag.

Also sometimes attached flow can create more drag than a shearing action. See Kammback for examples. Many principles are fairly universal but there's the details that makes it all work for a given scale and form factor.

[euromodder]

It's all about disturbing the medium you go through, as little as possible.

Wings have spanwise flow - air flowing out to the tips - which reduces their performance. In addition, it creates strong vortices at the wing tips that move a huge amount of air. Doing so, obviously costs energy.

These tubercules cause smaller vortices over the wings, and keep the water flowing aft, instead of towards the tips.
In principle, a "dogtooth" on an aircraft's wing works the same .


Adding a little bit of drag to avoid the big drag ...

[kach22i]

Originally Posted by jeff88

The first one was the 'tubercules' on a Humpback whale's fins.

Some information may be buried in these old threads which I was part of.

Old 2007 thread:
A Whale of an Idea - Boat Design Forums

An earlier in 2007 thread.............
New propulsion sytems for ships - Page 19 - Boat Design Forums

And a later 2008 thread:
Whale of an idea for marine applications? - Boat Design Forums

[Occasionally6]

There are a couple of articles in Autospeed on vortex generators (sort of tubercules) that might be of interest.

[jeff88]

@kach22i: Thanks for those links. I perused them a little bit, but I will have to wait for more time and less laziness to read them more thoroughly.

@Occasionally6: I've seen those Autospeed articles around the same time I joined this forum. Oddly enough, at that time, I had thought about using vortex generators on the front undertray upside down. I guess in a way, I was thinking about using them as tubercules without realizing that I was mimicking a whale.

[euromodder]

Way back in time - though not before mid-2010 - we've had a thread about the whale fins.
They were being mimicked in ceiling vent blades etc.

On the EF-18G Growler, Boeing changed the dogtooth on the outer / folding wing from a straight cut, to this :


and added a wing fence .