Peter,
Thanks for this interesting response. It would seem to be the last word on this subject, for a time. But we’ll see. I wonder if there is any chance you would make an electronic copy of your article available to the list? No reason for us all to continue to live in darkness. Nick From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Saturday, May 07, 2011 1:22 PM To: [email protected] Subject: [FRIAM] VORTICAL FLOWS and LIFT The videos are wonderful, and I thank Nick, and agree with his opinion. As for the Theory of Tornadoes, it seems that to date it's literally a case of "God only knows"! But mebbe Friam, too. I have 1/2 century background teaching grad fluid mechanics at Caltech, Stanford, and USC and have done a lot of meteorological field work, but really wouldn't try to discuss the subject. I jus' dunno. One should remember that what one sees is a LOT less than what one gets, because that's where the tracer happens to be. This I expressed vividly to my students in auto design, when we took pix of airflow near bluff vehicles on test tracks in the Mohave Desert. A'course there is a huge billowing plume that presages before, and persists long after the vehicle is over the horizon. I remind them that it was not the "dust" doing this, but the air, and an identical disturbance occurs invisibly whenever a body passes through air. To paraphrase, "its bite is just as keen, although it is not seen"! Makes one take car streamlining seriously. I actually hold patents on one of those drag shield things that goes on the cab of a tractor-trailer rig, that was developed on NSF funding at our test base near El Mirage in the Mohave. Does good things for fuel consumption. It would seem likely that the sense of the vorticity in a tornado is related to the shear and Coriolis Effect ( Gaspard-G, 1835), although which way, I know not. I was manager of a big DOE program called the Coriolis Project for three years, so dealt a little with that. Lotta spin on the ball, there, literally! For smaller scale vortical flow Coriolis does not apply. Some interesting anecdotes: In East Africa, delightful Kikuyu tricksters, stand right on the equatorial line and for a few shillings will show you the exit vortex from plastic bucket, then move it north over the line a few feet into t'other hemisphere and "prove" that it rotates in the opposite direction. We seen this! Well, it really does, but not because of Gaspard-Gustave. In the Libyan deserts Holy Men will "attack" a dust devil, with much imprecation and flailing of a broad sword - and "kill" it. It just drops to the ground! You can see this. With your own eyes. Allah is indeed great! According to Bagnold, a great Brit desertologist and fluid mechanicer, whom I have used for some of his results, the secret is to determine in advance what the sense of the vortex is, and then to enter it on the upwind side, at just the right distance from the core, and flail around . It works, too. Ralph Bagnold, soldier, explorer and scientist, whose monumental work I'm lucky to have and reference, was portrayed in The English Patient. Pity when one is better known for a movie than an important book! The subject of how wings work is a much vexed topic. I was interested in what Nick said, but for my part, I don't think it is like that , and I reckon the air doesn't think so either. Authors, profs, and pilots (and I have been all three) are usually wrong on this topic. I respect only real airfoil designers on this issue, and have a few honest-ta-God airfoils named after me, that can be seen on the internet and in books. They all worked much better than we expected. In fact they have carried, safely, many men and women to record heights. There's an article in the Smithsonian about the first airfoil I designed, in 1955, that me delightfool, but authoritarian, Teutonic boss-fuhrer, Herr Doktor Oberst Gustave Von ---, refused to name after me. Well, it flew nobly for the RAF, carried nuclear payloads in the good old, bad old days and kept the Ruzskies at bay. Mebbe!. I have given up noting the incorrect theories on lift. Life too short for that, although if one restricts one's discussion to things one knows conversation gets pretty limited. I am content to simply observe what the air does, and weakly agree with it, much as my intellect may reject that pusillanimous attitude. As an expert witness, I have frequently quoted: "Theory crumbles before the Facts". Juries like it. But some years ago, while on the USC aero faculty, I decided to quit pointing out mistakes and publish my idea of the Truth. The paper (1996) is The Meaning of Lift, published as AIAA 34 th Aerospace Sciences Meeting, paper 96-1191. Funny thing is that, as a joke, I started calling it The Meaning of Life, and that has made it difficult to find by computer, but not by real people! Well, wot the Hell, for me and most of my fellow spirits up in the Big Blue, Lift IS Life! Peter Lissaman, Da Vinci Ventures Expertise is not knowing everything, but knowing what to look for. 1454 Miracerros Loop South, Santa Fe, New Mexico 87505,USA tel:(505)983-7728
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