Search found 55 matches

by wbeaty
Sun Oct 10, 2010 11:08 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 0803: "Airfoil"
Replies: 243
Views: 101209

Re: 0803: "Airfoil"

And then it gets WORSE: It's impossible to understand airplanes by only employing 2D flow diagrams. These diagrams depict an odd sort of "flatland flight" where no work is performed on the air, and an airfoil could ideally coast along forever. While it's true that most 2D flow diagrams yo...
by wbeaty
Fri Oct 08, 2010 7:59 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 0803: "Airfoil"
Replies: 243
Views: 101209

Kline-Fogleman airfoil, longer path underneath.

Be aware that Kline-Fogleman and supercritical airfoils fly just fine. Their upper pathlength is the short one. Actually, the incorrect equal-distance explanation (or, rather, the incorrect different-distances-but-supposedly-same-time explanation) CAN hold up as the only reason that something flies,...
by wbeaty
Fri Oct 08, 2010 7:36 am UTC
Forum: Individual XKCD Comic Threads
Topic: 0803: "Airfoil"
Replies: 243
Views: 101209

Re: 0803: "Airfoil"

And then it gets WORSE: It's impossible to understand airplanes by only employing 2D flow diagrams. These diagrams depict an odd sort of "flatland flight" where no work is performed on the air, and an airfoil could ideally coast along forever. In the real world, this type of flight is call...
by wbeaty
Fri Oct 08, 2010 7:19 am UTC
Forum: Individual XKCD Comic Threads
Topic: 0803: "Airfoil"
Replies: 243
Views: 101209

Re: 0803: "Airfoil"

The only answer I've ever gotten that I have been satisfied with is that fluid flow is so complex (see Navier-Stokes) that lift isn't fully understood even by those with PhD's in the subject. VERY TRUE! Remember that the lifting force created by flapping insect wings wasn't understood until recent ...
by wbeaty
Fri Oct 08, 2010 7:08 am UTC
Forum: Individual XKCD Comic Threads
Topic: 0803: "Airfoil"
Replies: 243
Views: 101209

Re: 0803: "Airfoil"

I've never understood how the "equal transit time" theory got started. There's really no reason other than a misunderstanding of physics to think that the streamlines would have meet up at the trailing edge of the airfoil. Dr. Klaus Weltner discovered the probable source: Prandtl got it w...
by wbeaty
Fri Oct 08, 2010 6:58 am UTC
Forum: Individual XKCD Comic Threads
Topic: 0803: "Airfoil"
Replies: 243
Views: 101209

Re: 0803: "Airfoil"

It's hard to explain lift without delving into aerodynamics and lots of mathematics. Nah, math is a tool for high rigor and numerical results. To explain things (or even understand them,) you first have to grasp the pure concepts. Example: if you can run a SPICE program, does it mean that you under...
by wbeaty
Tue Apr 27, 2010 1:18 am UTC
Forum: Science
Topic: Assumptions that the Scientific Method makes?
Replies: 45
Views: 5571

Re: Assumptions that the Scientific Method makes?

Hold on thar... You're all assuming that "The Scientific Method" exists. Be careful with that. In the last few years, the NSTA (National Science Teachers Assn) and the grade school textbook publishers have stopped teaching about "THE" Scientific Method. Those chapters have been r...
by wbeaty
Tue Apr 27, 2010 12:43 am UTC
Forum: Science
Topic: Is a High School Science teacher considered a "Scientist"?
Replies: 28
Views: 3928

Re: Is a High School Science teacher considered a "Scientist

But are you an AMATEUR Scientist? :) And grad students tend to draw major ire from colleagues if they start call themselves "scientist" before successful completion of their degree. Most people, when they speak the phrase "The Scientists," are talking about: - Professional scient...
by wbeaty
Tue Apr 27, 2010 12:11 am UTC
Forum: Science
Topic: Favorite home experiments
Replies: 590
Views: 481789

Re: Favorite home experiments

Hey, Rich O. below made a Wilson Cloud Chamber without dry ice:

Double stack of CPU coolers (Peltier thermoelectric module), w/large heat sink below

http://www.youtube.com/watch?v=eKfx4Rjf0BU

http://www.youtube.com/watch?v=iFizFjlIA4A
by wbeaty
Thu Mar 11, 2010 8:53 am UTC
Forum: General
Topic: Lucky Ten Thousand (TIL)
Replies: 13421
Views: 1745993

Re: Today I Learned

Somehow, I don't believe this. Fake perpetual motion machines: judged impossible without evidence? :) The (untested) theory is trivial: two attracting magnets as part of rotor/stator, if slightly demagnetized at closest approach, will experience net velocity gain. It's not hard to demagnetize a pat...
by wbeaty
Thu Mar 11, 2010 2:26 am UTC
Forum: General
Topic: Lucky Ten Thousand (TIL)
Replies: 13421
Views: 1745993

Re: Today I Learned

Today I learned that a permanent-magnet-powered, permanent magnet rotor is quite feasible (the rotor accelerates enough to defeat friction, as the magnets are slowly demagnetized.)

Now I gotta build a fake PM machine and see how many hours I can make it run.
by wbeaty
Thu Mar 11, 2010 2:06 am UTC
Forum: General
Topic: Uh-oh. It's a Youtube party and you're up next. What do you show 'em?
Replies: 2150
Views: 738801

Re: Something on Youtube

Stannous allotropoic transition
http://www.youtube.com/watch?v=sXB83Heh3_c

Thermographic hydrocarbon evaporation
http://www.youtube.com/watch?v=j_NswgZFgzA

Container catastrophic compression!!!
http://www.youtube.com/watch?v=E_hci9vrvfw
by wbeaty
Sun Apr 12, 2009 9:26 am UTC
Forum: Individual XKCD Comic Threads
Topic: 0567: "Urgent Mission"
Replies: 129
Views: 33232

Re: WHY SHOULD ELECTRONS BE POSITIVE?

The only reason, the *only* reason to prefer one or the other is to make it simpler to think about, to teach, to work with. Repeating "only" is a red flag. (Perhaps other reasons do exist?) I'd agree that redefining electric current to mean "electron flow" is very imprecise, and...
by wbeaty
Sun Apr 12, 2009 2:45 am UTC
Forum: Individual XKCD Comic Threads
Topic: 0567: "Urgent Mission"
Replies: 129
Views: 33232

Re: "Urgent Mission" Discussion

The reason my future self hasn't come here and given me a time machine is that he's used it to go to the Restaurant at the End of the Universe. Perhaps that's where yours is, too. I figured that there must be some law against it. That's more fun than assuming that it doesn't exist. So... Travellers...
by wbeaty
Sun Apr 12, 2009 2:31 am UTC
Forum: Individual XKCD Comic Threads
Topic: 0567: "Urgent Mission"
Replies: 129
Views: 33232

WHY SHOULD ELECTRONS BE POSITIVE?

Hold on thar! Nobody's asking the question "why should electrons be made positive?" The typical answer is this, and it's wrong: "Electric current is a flow of electrons." It's a flow of electrons? Says who? Certainly nobody even slightly associated with the physics community says...

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