Peter - Fascinating.
I too vote that you make available to the FRIAM alias your referenced
paper so that we all can get the benefit of you wisdom on this.
Grant
On 5/7/11 1:22 PM, [email protected] wrote:
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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FRIAM Applied Complexity Group listserv
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============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org
