Bees, Planes & Weight: Exploring the Physics

[KingNothing]

Planes and Bees

Hey everyone...thanks ahead of time. This is a somehwhat general question.

A person concluded that a bumble bee could not fly, and his basis was that he determined that a plane with the same design and wingspan proportions etc. could not fly.

Now, of course this is wrong, but why is it that this particular method is wrong?

-----
I was thinking it was because of the fact that bees have moving wings, which seems pretty alright.

How does the wingspan of a plane vary with the body's size (mass)?

If you double a bee's mass, would doubling the wing size provide sufficient lift (assume mass varies directly with volume in living things)?

Also, aside from biology, why is it that smaller organisms such as ants can lift weight much more than their own (10 times), while mid sized can lift about 5 times their weight, and humans should lift about twice their weight (parallel squat)? There is some sort of physical relation, right?

 

[cookiemonster]

The wings of a bee are not fixed like the wings of an airplane. As far as I know, we don't fully understand the details behind a bee's flying motion.

cookiemonster

 

[ray b]

the interaction of the pairs of moving wings
create a votex that increases the lift and that allows the bee to fly

 

[KingNothing]

Help refute insect flight

Recently a person claimed this:

We don't have the scientific explanation of how insects fly. By our knowledge of physics and airflow, its not possible. There ARE many theories, the most popular one being that the insect creates a vertical swirl of airflow by flapping its wings, and at the same time it allows that motion to lift itself up.

Now, I don't think it's true. I'm not positive it's wrong but I think it is. Could someone help me refute it if it is wrong?

 

[NateTG]

The aerodynamic effects involved insect flight are poorly understood. To model the action of insect flight requires a much more sophisticated model than the ones that are usable for fixed-wing aircraft or for birds. Insect flight is currently an active field of study, and will probably continue to be one for an extended period of time.

Since different insects probably have a large variety of flight modes - think of the differences between butterflies, wasps, and beetles - there will probably be several different mechanisms involved in it.

The description of the mechanics in the statement are rather vauge, and are probably something that has been oversimplified by a scientist, further generalized by a journalist, and then poorly described for use in discussion.

 

[Stingray]

The dynamics of the airflow is very different at the scale of a bee versus an airplane due to viscosity.

As for ants lifting so much, an object's weight scales as its size cubed: L^3. Its strength is given by the cross sectional area of a muscle, which scales as L^2. So as L gets big L^3>>L^2.

 

[Integral]

we do not need 2 threads debating whether or not bees can fly.

 

[Gara]

i once saw a programe about how they glued a dragonfly or something to a tip of something..or other.

it was still alive of course, and they made it try to fly while under a gas (with dirt particles or something) + high speed camara. if i remember right there was also a strobe light used but i might be thinking of another test with the light.

and they could SEE the airflow the wings was making.

first, the wings go up to meet each other, and kind of, 'peel' away from each other, removing almost all the air above the insect, and putting all that air below it, giving it LOTS of lift.

as for the size of something and its strenth, yes, the bigger something is, the less times its own body weight it can carry.

a 200 pound guy can lift more times his own body weight than a 500 pound guy. and the smaller you get the more times your own body weight you can lift.

but that's proberly what all those L^2 stuff means, but i desided to say something about it for people who don't know what any of that L^2 means. (like me)

 

[KingNothing]

Yes, that's what it means. Which works out somewhat bad for me, being a small football player (135-145) I thought I was genuinely lifting a better ratio than the 200 pounders at my school:P. Oh well, they still don't know the truth!

 

[uberzak]

Actually, in the mid 1990's they analysed insects and described some of the main flight mechanisms. There are three: delayed stall, rotational circulation, and wake capture. Insect wings are oriented such that they have an extremely steep angle of attack (they flap them back and forth and rotate them at the end of every half cycle so that the edge hitting the oncomming air first is higher than the back side). A steep angle of attack generates stall, which creates a short lived vortex which pulls the wing upwards (delayed stall).

Indeed the reason a person concluded a bumblebee could not fly is that they assumed the airflow over the wing is constant with time, which would create a stall. The vortex created by this stall would initially pull the wing up, but it dies out very rapidly under a steady airflow and the experiment would conclude the insect could not fly. Insects flap their wings though, so more than one vortex is created. They are even able to 'ride' the vortex from a previous stroke (wake capture), and the rotation of their wings generate even more lift (rotational circulation).

For further info try and get your hands on these sources:
M.H. Dickinson, "Solving the Mystery of Insect Flight," Scientific American, June 2001.
M.H. Dickinson, F. Lehmann, and S.P. Sane,. "Wing Rotation and the Aerodynamic Basis of Insect Flight," Science, vol. 284, no. 5422, 18 June 1999.

Cheers.