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Revision as of 11:28, 12 January 2015

Starting Vortex

I'm intrigued to know why you find Batchelor's description of the starting vortex on a wing (and so presumably,Turner's description of the starting or head vortex on a plume) misleading. The nice thing about vorticity (idda fort) is that it has to be transported from somewhere; and the strength of Batchelor's textbook was that it presented topics like vorticity generation and transport at an undergraduate level. Bob aka Linuxlad 10:16, 5 December 2006 (UTC)

Sorry for the delayed response. I'm new to Misplaced Pages and wasn't thinking to check my own talk, only the article's talk. I find the starting-vortex scenario misleading because it seems to mislead some people into thinking of the starting vortex as some sort of prime mover, i.e. as the cause of the establishment of the circulation on the airfoil and thus of the lift. It seems to imply for some readers that the physical cause-and-effect flows in the same direction as the narrative, from the starting vortex to the circulation to the lift. It's true that you can't have any one of these things without the others, but the physical cause-and-effect isn't a simple one-way street. The cause-and-effect relationship between the circulation and the lift is circular. The starting vortex, on the other hand, is a byproduct of the establishment of the other two, not a cause.

I agree that vorticity provides some great shortcuts to understanding what happens in many flow situations, but it also has a tendency to lull us into wrong ways of thinking. It's just too easy to start thinking of the vorticity at one point in the field as causing what's happening somewhere else, through the Biot-Savart law. Many of the inventors of useless devices for dealing with the wingtip vortex have fallen into this trap. J Doug McLean 23:17, 3 February 2007 (UTC)

Lift

I've been trying to steal myself to write a classical theory of lift article, mainly stolen from Batchelor - it's still languishing in my sandbox, because I can't face the maths editor (and I want to be careful to unpick Batchelor's working carefully, because it's spread as bits over about 200 pages).

But one of the interesting statements I wanted to get down plausibly (which I've drawn to people's attention before) is on p407:

It follows from the calculation immediately preceding (6.4.26) that the side-force exerted by the cylinder appears in the fluid far from the body half as a momentum flux and half in the form of a pressure distribution

This is for a 2-d system of course.

Any comments? Bob aka Linuxlad (talk) 16:54, 15 January 2008 (UTC)

Lift (force)

Doug, many thanks for your kind offer to improve Lift (force), and for your major contribution at Talk:Lift (force) - diff. I have perused it (and your sandbox) quickly but I will get back to it more thoroughly in the next day or two, and let you know my thoughts. Best regards. Dolphin (t) 02:52, 31 January 2013 (UTC)

I have now added some comments at Talk:Lift (force) - see my diff. Dolphin (t) 07:18, 31 January 2013 (UTC)

Doug, we are privileged to have an author of your calibre willing to assist in fine-tuning Lift (force). I have added some more of my thoughts at the Talk page - diff. My words may look like I am adversely criticizing your proposal, or your writings, but they are not intended to be adverse criticism. I have just written down thoughts as they occurred to me as I read through your posts so they won't be well organized. Hopefully, I will get around to some solid and constructive suggestions in the days to come. Best regards. Dolphin (t) 10:53, 1 February 2013 (UTC)

Thanks for the recent invitation to look at the proposal in your sandbox. I have looked at it quickly and made some brief comments on the Talk page. See my comments. Dolphin (t) 06:15, 6 April 2013 (UTC)

Thanks for the comments. See my responses (comments. Dolphin) J Doug McLean (talk) 17:05, 30 April 2013 (UTC)

Hi Doug. You may have missed this comment about the current state of our article on Lift. Dolphin (t) 08:11, 5 September 2014 (UTC)

FYI

There is currently a discussion at Misplaced Pages:Administrators' noticeboard/Incidents regarding an issue with which you may have been involved. Thank you. Burninthruthesky (talk) 16:15, 19 November 2014 (UTC)

Deleted Posts Regarding "The Statement".

Hello Doug. This afternoon I posted some comments on the Talk page ("Extended Discussion" section) of the Lift article. Now, several hours later, I have found that those words were deleted. FYI, here are those words again:

"(Zapletal writes ->) I only have time for a short note, so briefly:

• This issue is most definitely NOT RESOLVED.
• "The Statement" is nonsense.
• Doug McLean is right. (Lanchester also explained this position very well in 1907).
• "Steelpillow" and "Burnin..." are clearly dilettantes in the field of Fluid Dynamics.
• The AAPT is, IMO, criminally negligent in its promotion of "The Statement" (and in suggesting that F->dP/dt is Newton's THIRD!!!).
• NII, paraphrased , is "F CAUSES P-dot". Only Americans are so poorly taught that they think that NII is "F=ma". This is probably due to the AAPT's incompetence.
• "The Statement" should be IN the article, but with Doug's explanation for why it is so MISLEADING. Else future generations will continue on our current downward spiral into IDIOCRACY.
• The "mob rule" (~"consensus") advocated by S and B, together with their repeated attempts to close this discussion, is an excellent example of this current downward spiral...

(Doug, I may write more in few weeks, if I have time. You are NOT ALONE (but here you do seem to be surrounded by dimwits). "Hourglass" thinking is good. NB the "upwash" always present in front of the aerofoil. A single vortex in unbounded fluid is as likely as a magnetic-monopole, because it implies infinite (edit: angular-)momentum and energy, hence difficulty with calculations. So calcs that include ground-plane (= image vortex underground) work better. And there is most definitely a "wavelike" motion in lifting flows that explains most of above (see Lanchester, 1907).) (End Zapletal)101.171.127.236 (talk) 04:21, 27 November 2014 (UTC)"

Regards Erik Zapletal101.171.42.155 (talk) 09:55, 27 November 2014 (UTC)

Hello Doug again. I have now found that the above post and a subsequent one were (repeatedly) deleted because they are considered "personal attacks". I will slightly revise those two posts, removing whatever words seem offensive, and repost them.

However, I remain convinced that "The Statement" should be mentioned somewhere in the article, and (IMPORTANTLY!) it should be explained how WRONG it is. It is this sort of "dumbing down" of things that took the ancient Greeks from believing that the Earth and other Planets revolved around the Sun, to being forced to accept the religous/idealogical belief system that the Earth was stationary and at the centre of the Universe. And then followed a 1000 years of Dark Ages...

More later, and hopefully on the "open" (ie. uncensored?) talk pages.

Regards Erik Zapletal101.171.213.76 (talk) 02:45, 30 November 2014 (UTC)

Thanks. Actually, I saw your first post before it disappeared, and was glad to see that you reposted it in the less confrontational form. I appreciate having at least one other participant who understands the physics correctly.

I see now that Steelpillow has replied, saying that you are "prejudiced against position" and calling your post "rhetoric". I've been around and around with them on this, and it seems nothing can shake their conviction that The Statement is somehow a simple and correct application of NII. I assume they sincerely believe they're applying the physics correctly, but the fact is that the arguments they offer don't square with basic physical principles as they apply to a continuum flow. It seems like a lost cause. At this point Steelpillow is opposed even to my proposed addition of a subsection titled "Momentum balance in lifting flows", where I proposed to explain the findings of the classical control-volume analyses, including the fact that dp/dt = -L is not generally true, but only for the infinitely tall sliver.

Their most recent posts recast their arguments in new forms that cry our to be rebutted, and I'm tempted to give it one more try. And along with that to point out that their consensus can no longer be described as "strong", since the size of the opposing contingent just doubled.

J Doug McLean (talk) 01:49, 3 December 2014 (UTC)

Hello Doug,

I have added a reeeaally long post to the Talk page. I'm all written out right now, but just wanted to offer my support to you. My "robust" :) earlier post was frustration from spending too much time on this particular merry-go-round myself.

Regards, Erik Zapletal 101.171.127.232 (talk) 12:19, 6 December 2014 (UTC)

Time to call it a day

Hi,

You have made many welcome contributions to the article on Lift (force), and I have done my best to thank you for them and to integrate your beneficial material into the article. But you have also been unsuccessfully pushing a point of view about the Newtonian models. Several of us scoured what sources we could find and they did not back you up. This has now been going on for months, perhaps years, and your efforts in this direction are no longer constructive. In particular, many of your expressed views on other issues appear colored by their applicability to your PoV. I know that it can be hard to accept "verifiability not truth" and to read the sources dispassionately rather than in one's own favour, but that's just the way it is. Seeking to bend WP:POLICY to one's own agenda rather than the other way round is also a common failing. Other editors have expressed how tired they are of this endless debate, and I cannot disagree with them. It is time to be realistic and to call a halt to it. I am sure that you have other knowledge still to offer, and I would like to suggest that your time editing Misplaced Pages would be better spent helping out there. If say a topic ban were to be introduced, that work could be hampered, so I am hoping that the matter can be resolved without any need to escalate it. 11:28, 12 January 2015 (UTC)