How Do Bees Fly?
Bee and Insect Aerodynamics
from FT Exploring.



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Dr Galapagos in his fabulous single-tortoise copter Can Bees fly? It sure looks like flying to most of us. Then why do some folks say they shouldn't be able to fly? Dr. Galapagos, who can only fly in cartoon land, discusses the mysteries of bee aerodynamics in the answer below

Take me to the Bee Aerodynamics Question and Answer

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Brilliant Question:
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Dear Dr. Galapagos,
I have heard people say that it is aerodynamically impossible for bees to fly.
They say that bees are violating the laws of aerodynamics when they fly.
Apparently the bees get away with this because they have never studied law.

Is this true, or is somebody trying to pull the shell over my head?
I must know the truth.
Hoping to learn,
Puzzled in Peoria

Answer to Question:
Dear Puzzled,
There seems to be two questions in that question.
First, is it aerodynamically impossible for bees to fly;
and secondly, do bees study law?

Let's discuss law first.
It is my learned and not humble opinion (I know more than almost anybody), that bees do not study much of anything in the way of law or physics.  This is because they come into this world already knowing all there is to know about being a bee (this "automatic" type of knowledge is often called instinct by big word using scientists).
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Being somewhat snobby, unimaginative, and totally lacking in curiosity (quite unlike turtles), they think they don't need to know anything else.

However, as lawyers and judges tell us, ignorance of the law is no excuse. That's why it won't do you any good to tell the judge you didn't know you were breaking the speed limit when you were going 55 miles per hour in a 35 mile per hour zone. You were ignorant of the law (or really not paying attention) but you still gotta pay.
Ignorance of the law is even less of an excuse when it comes to the laws of physics. Whether or not you understand the law of gravity, or know it exists, or even believe in it, you will obey it. If you step off the roof of a house, the force of gravitational attraction, exerted between your body and the earth's body, will pull you toward the ground at an increasing speed which is clearly and precisely predicted by a formula easily found in any physics text book. (Of course, on planets with an atmosphere, like earth, air resistance will affect this acceleration process and slow you down somewhat, but alas, not quite enough.)

So, whether or not the bees have studied law, they still have to always obey the laws of physics, which include whatever so-called "laws of aerodynamics" they have not studied.

cross section of bird wing showing airfoil shape But let's be fair to the humans who say such slightly foolish things. It is true that the aerodynamic mechanisms that insects use to dart about in the air are different in some significant ways than the mechanisms that birds and airplanes use to flit (in the case of sparrows and finches), or lumber (in the case of big cargo planes and human powered gossamer albatrosses), or soar (hawks and buzzards), or dart (humming birds), through the air. It is also true that scientists and engineers have only in recent years begun to understand the very complicated mechanisms of insect aerodynamics. The basics are better understood now, and more is being learned, but it is still not fully understood. However, not understanding all the details of how something works doesn't mean the explanation must be magic. Let me say that again. Not fully understanding how something works does not mean the explanation must then be magic (nor does it mean the only possible explanation is aliens from another planet). A violation of the normal laws of physics would be magic or a miracle.

Actually, what you normally hear about this issue is not that bees are violating the laws of aerodynamics, but rather that scientists can't explain how bees fly, or that engineers have proven, according to the laws of aerodynamics, that bees can't fly.
airplane wing cross section
is the basis of the problem:

Conventional aerodynamic calculations are relatively simple, being based on large fixed wings and steady state or quasi-steady state flow.

Insect wings are small, flat, rough surfaced, and flexible. During flight they flex and twist in all kinds of horribly complicated ways. Also they are so small that important dimensional fluid analysis numbers like the Reynold's Number are very different, resulting in significantly different fluid characteristics when compared to the bigger wings of birds and airplanes (even a sparrow wing is huge compared to most insect wings). In addition, the small size and high speed of most insect wings makes it very difficult to study insect flight (imagine trying to attach a pressure sensor to an insect wing). Finally, the pressures and flow characteristics of the air around the wings are very unsteady, constantly changing as the wind flaps, bends, and twists, unlike aircraft wings which are stiff with relatively simple constant flow patterns and pressures.

Conventional aerodymic analysis methods simply don't apply to insect wings.
Big deal! It doesn't mean bees can't fly, or that engineers say they can't fly. It just means that insect flight is very complicated and, even with computers, our fluid dynamic modeling techniques aren't yet able to quite handle such a complicated problem. Then there's the problem of verification. If you can't measure the pressures and velocities around a wing, how can you verify your calculations?

I can tell you from my days of developing diesel engine turbochargers there are lots of fluid dynamics problems where computer modeling is not yet able to accurately analyse or predict the flow. Yet, people don't go around saying, "Gee willickers, engineers have proven turbochargers can't work".
Diesel engine combustion is another area that is presently too complicated to model except with greatly oversimplified models based largely on experimental data. Does that mean engineers have proven fuel can't burn in diesel engines? Hec no. It just means we don't fully understand it yet.

Tornadoes aren't fully understood. If incorrect analysis methods fail to accurately predict tornadoes, does that mean science has proven they don't exist?

We have hardly scratched the surface on understanding the incredibly complex human body. But do you hear people going around saying scientists don't know everything about the human body, therefore, it must be impossible for the human body to function?

Mysteries don't prove science is bunk. They are the reason for science. If there were no mysteries there would be no need for science. There are many mysteries in science a lot more difficult than the flight of insects. I am quite certain we will understand insect flight much sooner than we will understand the human body.

Now for a brief digression. The story of how some scientist or aerodymic engineer proved bees or insects can't fly is, I think, an urban myth. An urban myth is a story that is repeated over and over by all kinds of references and is assumed by everyone to be true because they heard it someplace else, sometimes even in books, magazines, news reports, etc. But, in fact, it is not true. I have researched this urban myth a little through the years and found many different versions of how it came about. None of them were verifiable, but at least one was supposedly based on the testimony of some reputable individuals who were there at the birth of one of these stories. Since it is typical, I will tell it here.

One typical urban myth explanation of the "Bees Can't Fly" story:
"Once upon a time some scientists and engineers or college professors (different versions have different names and specialties) were at a dinner party. The subject of bee flight came up and the aerodynamic engineer that just happened to be present decided to do a quick calculation on bee aerodymics. He used a conventional stiff airfoil-shaped wing, with steady state, or partially steady state, air flow analysis techniques, and lo and behold, the calculations did not work for the bee. Someone jokingly said, "I guess that proves bees can't fly", and they all had a good laugh. But, of course, they all knew it just proved that bee flight is too complicated to analyse with conventional airplane aerodynamic methods."
Unfortunately the story spread in its many inaccurate forms and, to borrow from Jonathan Swift, it appealed to peoples' "nut notes". It caught on - bad luck for science, good luck for inspirational speakers and science nay-sayers.
Well, I doubt if that story is true. It may be that something like that really happened, or has happened in various forms more than once.  
Dragonfly Posters

However, I do not believe that any knowledgeable scientist or aerodynamics engineer ever seriously and straight faced claimed they have proven insects can't fly, or that insects violate the laws of physics. It's just plain silly.
Dragonflies fly fantastically well with flat rough wings, but these wings wouldn't work very well for bigger animals and man-made planes.
Next, Dr. Galapagos discusses deep diving sperm whales:
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quasi-steady state - In the real world, air flow characteristics around airplane wings are not always steady state. Steady state means that the flow characteristics and measurements (like the air pressure over a certain area of the wing) remain steady and constant over time. This is sort of true when a plane is just cruising, but when a plane is turning or yawing or pitching or taking off or landing or going through any other changes, the air flow characteristics are changing also. This makes the aerodynamics much more complicated and difficult to analyse. Engineers compensate for this by using what they call quasi-steady state techniques. They break the complicated changing system into little "pieces" that can be approximated as steady state and analysed with steady state analysis. It works pretty good for relatively simple things, especially if you have a lot of experimental data that can be sort of "fudged" in to fill in the gaps. One of the problems with insect wing analysis is that besides being much more complicated than airplane wings, it is so darn hard to get that experimental data.
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Dimensional Analysis - When a fluid like air or water is moving around objects like ship hulls, or airplane and insect wings, it is being moved by forces acting on it. Often there are opposing forces coming from different places and directions. It also exerts forces on the objects - hence wing lift. These forces are what determine what the fluid does and what the objects do. To help understand and analyse these forces engineers have devised a bunch of ratios they call nondimensional or dimensionless ratios. One of the most famous and useful of these dimensionless ratios is called the Reynolds Number. It is very useful for designing airplanes. It can be thought of as the ratio of fluid inertia force over viscous force. Clear? Probably not, but that's all you get here. To describe it much further would be beyond the scope of this page (and my ability).
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