From: David Wilkinson Newsgroups: sci.math,sci.physics.computational.fluid-dynamics,sci.mech.fluids Subject: Re: Bumblebees flying (Was: Uncertainty Invalidates Modus Ponens) Date: Fri, 1 May 1998 09:17:15 +0100 In article <893995974.930525@bats.mcs.vuw.ac.nz>, John Harper writes >In article <35482C6C.7C80@stanford.edu>, >Brooks Moses wrote: >> >>But, then, as I said, I come from a world where the equations used to >>describe flight are perfectly good math, and yet they claim that the >>bumblebee can't fly. > >I have been doing fluid mechanics for a long time and I have often heard >this, but have never seen the alleged proof that bumblebees can't fly. >Can someone please give this proof or say where it can be found? > >John Harper, School of Mathematical and Computing Sciences, >Victoria University, Wellington, New Zealand >e-mail john.harper@vuw.ac.nz phone (+64)(4)471 5341 fax (+64)(4)495 5045 > I have never seen this mythical proof either. Someone must have produced some sort of story many years ago, long before anyone could understand insect flight, based on aircraft wing theory. The aerodynamics of 4 flapping wings is very complex. Lighthill did some work on insect aerodynamics 30 or 40 years ago that showed it was quite different to conventional aircraft aerodynamics. He showed that, by bringing two wings flat against each other and then moving them apart, very strong vortices were produced which could generate unexpectedly large lift. I think this was enough to explain Bumblebee flight. I expect others have added to this since then but I am not up with the field. The earlier "disproof" was based on an inadequate model but the story has an instant and lasting attraction to the non-technical mind. -- David Wilkinson ============================================================================== From: "John" Newsgroups: sci.math,sci.physics.computational.fluid-dynamics,sci.mech.fluids Subject: Re: Bumblebees flying (Was: Uncertainty Invalidates Modus Ponens) Date: Fri, 1 May 1998 20:58:00 +0100 There are only rumours of how the story came about. I quote the following from an article by Ken Zetie published in the IOP's Physics World magazine (Oct 1996 vol9 (10)) entitled 'The strange case of the bumble-bee that flew.' 'J McMasters states that the story was prevalent in the German technical universities in the 1930's, starting with students of the aerodynamicist, Ludwig Prandtl at Gottingen. The story goes that a noted Swiss aerodynamicist, whom McMasters does not name, was talking to a biologist at dinner. The biologist asked about the flight of bumble bees and the Swiss gentleman did a "back-of-the-napkin" calculation of the kind I described earlier, assuming a rigid smooth wing an so on. Of course he found that there was insufficient lift and went off to find out the correct answer. In the meantime, the biologist put the work around that bees could not fly, presumably to show that nature was greater than engineering, and the media picked up the story. The truth, then as now, wasn't newsworthy, so a correction was never publicized' John. ============================================================================== From: Steven Vogel Newsgroups: sci.math,sci.physics.computational.fluid-dynamics,sci.mech.fluids Subject: Re: Bumblebees flying (Was: Uncertainty Invalidates Modus Ponens) Date: Tue, 05 May 1998 09:03:54 -0600 The story somehow refuses to die. John H. McMasters (Boeing) gave an account of the back-of-the-envelope calculation in an article in American Scientist a few years ago. Having done a decent survey of the literature on insect flight, I find the account entirely credible. But insect flight aerodynamics are fraught with complexities - continuously changing angles of attack, interactions of opposite wings at the top of the stroke, issues of how many chord lengths of travel are needed for full lift to be developed, vortex shedding and reformation (with opposite sign) at the bottom of the stroke, spanwise flow, etc., etc. All of which makes back-of-envelope calculations next to hopeless. A little over a year ago, Charles Ellington (Cambridge, UK) pretty well tidied up the bumblebee issue, in my opinion. Tricky business, getting sufficiently high lift coefficient, in fact. See paper in Nature, December ?, 1996. Also see two longer papers on bumblebee flight in J. Experimental Biology (1990) by Robert Dudley & Ellington. Dudley (U. Texas, Austin) is now writing a very extensive review of the entire business of insect flight. But the book is probably almost a year away from publication. So you'll have to make do with my "Life in Moving Fluids." Steven Vogel ============================================================================== From: "McMasters, John H" To: "'rusin@math.niu.edu'" Subject: FW: Bumblebee Flight Date: Wed, 13 Oct 1999 12:47:46 -0700 It's your web site so you get a helping of the below as well. [message below is a cc: of email to several people mentioned above -- djr] > From: McMasters, John H > Sent: Wednesday, October 13, 1999 12:28 PM > Subject: Bumblebee Flight I was stumbling around on the web a couple of days ago and came across a site http://www.math.niu.edu/-rusin/known-math/98/bees that has a string of exchanges from the addressee of this note. Well this is kind of old by now, but I was surprised to find my name mentioned by one of the correspondents, and since there was no clear resolution of the issue, i thought I'd "finish the job" in case anyone still cares. A long time ago [1989] I wrote an article for the journal American Scientist entitled: "The Flight of the Bumblebee and Related Myths of Entomological Engineering" (Am. Sci., Vol. 77, pp. 164-8). In this I gave what still appears to be a correct account of the "Didn't the aerodynamicist prove that the bumblebee can't fly ? [sarcastic ha ha]" story. I too had tried to find the name of "The aerodynamicist" who did this to us. After a long search I was told by a very reputable source that he thought that individual (who was badly misrepresented subsequently by the "press") was the Swiss gas dynamicist Jacob Ackeret - a famous name in supersonic aerodynamics. It was about the right vintage, so I wrote that in my article without naming Ackeret explicitly. Follwoing publication, however, I got mail. Boy did I get mail - including half a dozen xerox copies of portions of the text of the book Le Vol Des Insects (Hermann and Cle, Paris, 1934) by the famous entomologist August Magnan. On page 8 of the introduction, one finds: "Tout d'abord pouss'e par ce qui fait en aviation, j'ai applique' aux insectes les lois de la resistance del'air, et je suis arrive' avec M. SAINTE-LAGUE a cette conclusion que leur vol es impossible." Thus the culprit is finally named: Sainte-Lague, Magnan's lab assistant who was apparently some sort of engineer. Steve Vogel has correctly added some of the rest of the story and there is more to come thanks to the miracles of high-speed photography and advances in computational physics. As an aside, anyone who hasn't read Steve's wonderful books should. They are classics - all of them. Share and enjoy. John McMasters Technical fellow The Boeing company Seattle, Washington