Was Marchaj having us on?

Sailor Al, I certainly did not mean to imply that NASA , prestigious Universities, or agencies relied on Marchaj's studies. only that some of (not all of) his pronouncements have some validity and have been verified by others.

If you wish to act as a critic of writers who are also sailors, take a shot at Manfred Curry (1899 - 1953) He was a German physician, inventor, researcher, and avid sailor. His station included some very desirable connections with Messerschmitt. Curry was able to play around in their wind tunnel where he believed that he had made some discovery.. He wrote some books one of which is titled: Yacht Racing, The Aerodynamics of Sails. Much later a more modern author and recognized practical authority is Tom Whidden. His book: The Art And Science of Sails also mentions vorticity and such. Neither Curry nor Whidden used the gear wheel analogy but the general idea is pretty much the same.

If there is any usefullness of my comments it is that we might do well to acknowledge the efforts, right or wrong, of our predecessors.

 

Magnus effect discovered in 1852 by Gustav Magnus. The first ship to use the Magnus effect to sail across the Atlantic was in 1926 designed by: Anton Flettner. (Flettner Rotor)


Flettner rotor - Wikipedia https://en.wikipedia.org/wiki/Flettner_rotor#:~:text=A%20Flettner%20rotor%20is%20a,and%20the%20direction%20of%20airflow.

Magnus effect - Wikipedia https://en.wikipedia.org/wiki/Magnus_effect

QVI NON INTELLIGENT, AVT TACEAT, AVT DISGAT.
John Dee

 

"Some of his pronouncements have been borne out by the likes of MIT, Cal Tech, even NASA." sure sounded like it, but I accept your informal withdrawal from my challenge.

Nope, that was never my objective. It was to test my perception that one of the most widely quoted authorities on the subject (his book went to 10 reprints!) was having a piece of us.
So far, the best challenge I have is:

and as even the most one-eyed supporter of Marchaj would have to concede, the Flettner Rotor has bugger all to do with the use of sails to propel a racing yacht upwind! The only circulation in the Flettner Rotor is provided by an engine, which directly contravenes RRS 42.1

 

You may want to look at the circulation-thread Is circulation real? https://www.boatdesign.net/threads/is-circulation-real.46025/page-11

 

Or this albatross...

 

And the starting vortex is there for the sails as well:

 

Sailor AI,
Thanks for the link to Marchaj‘s book Aero-Hydrodynamics of sailing. I have never read any of his books, but hope to do so some day.
Cheers

 

Marchaj's discussion of lift based on flow around a rotating cylinder is far from unique to Marchaj. Rather it is very similar to many derivations and presentations of airfoil aerodynamics pre-1960, particularly the work of the mathematical physicists. Marchaj's notes and references section includes some of the classic works on aerodynamics from the first half of the 20th century.

Whether an individual finds such discussion to be useful depends on the individual.

 

He wasn't the first to do this. A Brit named Lanchester was. Next to general relativity, it is probably the greatest realization of the past couple hundred years. It provided the first means to calculate the forces between fluids and objects based on the geometry of the object. It is a bit hard to wrap your head around. Einstein famously dismissed it. His airplane didn't work, either. Marchaj is following the development of theory that has forever been trying to catch up with experimental results. And experiments across the world were not in any way organized around solving the problem systematically. So yes, any survey of what turned out to be important, and how it was learned, is going to involve a great deal of sifting, with mostly small take-aways from any generation of experimenters. In the case of the mechanical rotor, the analogy is poor because it ignores the far field flow perturbation (which we still call circulation). But the rotor led experimenters down a path where results finally intersected with some known results from potential field theory. And the penny dropped for Lanchester and Prandl.

So he wasn't having you on, he was describing the peculiar route by which we came to where we are. For centuries, you had mathematicians and experimenters separately groping in the dark. In Germany, they improved the odds by stuffing all the people working on aero into one place - and eventually, they found each other. A theory of circulation-induced lift developed by Lanchester in 1906, and known to Prandl, finally encountered experiments and development efforts that could put the theory to the test.

Here's Lanchester's 1907 Arial Flight in PDF format - https://ia800304.us.archive.org/6/items/aerodynamicscons00lanc/aerodynamicscons00lanc.pdf
It goes through a very similar survey of experiments by Froude, Reynolds, Langley, and many others. And it shows what that generation was meaning when they talked about circulation. It included a lot more than the limited sense of superposition far-field circulation that is normally thought of today. You just need to recognize that a lot of the terminology has a history all its own. Unlike engineering, words can survive the test of time even if the experiment and theories first associated with them are bollocks.

The above book provides one of the few instances I've seen where sailboat data is used to pursue airplane theory.

 

I do the opposite some of the time. The 2 fields still behave as though fluid mechanics isn't really a thing. There's boat stuff and airplane stuff. Things that are still controversial in one field were worked out and done 70 years ago in the other.

 

I would have to take issue with that statement when applied, as in this case, to a scientific or technical theory. The scientific method favours theories that stand the test of time. A good theory is one which can be reliably applied to predict experimental results. As long as it continues to do so by multiple experimenters in a range of environments, the theory can be considered to be an accurate representation of a natural phenomenon. It is only a naive or dilletante student who chooses theories that happen to be useful rather than those that have withstood the test of time.
The fact that Marchaj bases his exposition on circulation theory (P 167-200) on the way the wind fails to generate lift on a non-rotating cylinder (the mast) (P173-175) amply demonstrates a delightfully quirky humour.

 

Many thanks for the link - what a fun read that is!
[EDIT]
And in the end, his 400 pages of largely obscure mathematics and experimental data comes down to this closing statement on P392:
"The present publication, in this respect, must therefore be regarded more in the light of an exposition of method than a serious experimental demonstration."

Translated:
"The theory was unable to be demonstrated experimentally"
Let's not quote this guy either.

P.S. How good is the technology that can deliver a PDF document which photographically presents the original book and in parallel, enable text searches!!???

 

I'm not denying the existence of vortices.
My issue is with Marchaj who links circulation with the source of lift. His Fig 2.13, P202 ( the cogwheels) indicates that the vortices are the source of circulation.
Cause and effect: vortices cause circulation, circulation generates lift.
Joke!
P.S. your striking video only shows vortices generated at the mast head, not where the aero force is being generated from the body of the jib. I'm not sure what that means for the "vortex generating force" theory.

 

Sailor Al, I really like the way you are thinking about this. Your digging into the subtext of this book reminds me of some of my libral arts classes where we tried to analyze what the author was really saying, looking for the metaphor.

I think the point about the Alice's Through the Looking Glass reference has a lot to do with all those "impossible" theories that have been put forward, from time to time, that later proved to make the theories they replaced impossible.
It use to be impossible to float a boat made of a material heavier than water, it use to be impossible that the Earth traveled an elliptical orbit around the Sun, it use to be impossible to imagine that a heavy object wouldn't fall faster than a light object, it was considered impossible that each species wasn't created instantaneous unto its own form.

Imagine what impossible things there may exist to think about now that later may become so ordinary and acceptable that people will metaphorically stand there watching the Sun set and laugh at the absurdity that people use to believe that the Sun went around the Earth. But then, remember to ask yourself, what would it have looked like if the Sun really did orbit around the Earth?

 

"A picture tells a thousand words" but only if it's put into context with words.
You present some pretty videos without any context.
I fail to see how they contribute to the current discussion.