Merged DDWFTTW in a “Real” Wind

[humber]

Humber's lack of a cogent argument is based on two problems, only one of which is his communication skills.

Gratuitous use of "cogent"..."fractal ignorance". Hallmarks of a mountebank.

No, but 20 seconds later I know that it is an open joke. A prank known by a large community to be a prank. How is that relevant?

Manipulation of identity.

Anyone can come on to the internet and imply they have qualifications, eh,
Doctor?


We can use Newton's impact theorem. Not accurate, but good enough.

Each air molecule strikes the prop over impact time, t

f =ma, so
f*t = ma*t (1)

V= at. ( the wind velocity derived from the acceleration)
f = (mV)/t (2)

During the impact time, N molecules will hit the prop, so the force is
Fd = N*f. (3)

To find the force, we need to know N, and the area hit by those molecules.

The prop has the disk area A. Instant deceleration is impossible, so as the molecules decelerate over time 't', the wind moves distance x. That is, deceleration takes place over a small but finite distance x.

Consider an area, A, of the blade.

Distance = velocity*time
x = V*t
Volume = V*t*x

Combining
N = A*V*t (Number/Volume)
Multiply N by the single molecule force, f.

Fd = m*(Number/Volume)*A*V^2

The density of the molecules (number/volume) can be found from p, the air density. The final product is:

So Fd = p*A*V^2.

That is the force that will accelerate the prop (cart) when in a tailwind, but slow it when a headwind, and does not depend upon "how far the prop moves relative to the air", but only on the amount of air over impact time t.

That equation makes many simplifying assumptions, but when refined as Rayleigh and other did, we get the familiar drag equation.

Fd = 1/2*Cd*p*A*V^2

The headwind slows the cart. If you think that rotation helps because the blade can move the the other way, then you are forgetting that the whole blade move forwards too. When at constant speed, the translation of the surface in the direction of the cart is constant, and independent of the angular velocity of the rotor. Carteers confuse perceptual errors and "insight".

 

[windgrins]

A newwwt!

And windgrins is a witch. She turned me into a newt.

He sincerely hopes "you got better"

WG

 

[windgrins]

Carteers Confusion!

Gratuitous use of "cogent"..."fractal ignorance". Hallmarks of a mountebank.



Anyone can come on to the internet and imply they have qualifications, eh,
Doctor?


We can use Newton's impact theorem. Not accurate, but good enough.

Each air molecule strikes the prop over impact time, t

f =ma, so
f*t = ma*t (1)

V= at. ( the wind velocity derived from the acceleration)
f = (mV)/t (2)

During the impact time, N molecules will hit the prop, so the force is
Fd = N*f. (3)

To find the force, we need to know N, and the area hit by those molecules.

The prop has the disk area A. Instant deceleration is impossible, so as the molecules decelerate over time 't', the wind moves distance x. That is, deceleration takes place over a small but finite distance x.

Consider an area, A, of the blade.

Distance = velocity*time
x = V*t
Volume = V*t*x

Combining
N = A*V*t (Number/Volume)
Multiply N by the single molecule force, f.

Fd = m*(Number/Volume)*A*V^2

The density of the molecules (number/volume) can be found from p, the air density. The final product is:

So Fd = p*A*V^2.

That is the force that will accelerate the prop (cart) when in a tailwind, but slow it when a headwind, and does not depend upon "how far the prop moves relative to the air", but only on the amount of air over impact time t.

That equation makes many simplifying assumptions, but when refined as Rayleigh and other did, we get the familiar drag equation.

Fd = 1/2*Cd*p*A*V^2

[qimg]http://www.internationalskeptics.com/forums/attachment.php?attachmentid=22002&stc=1&d=1304094331[/qimg]

The headwind slows the cart. If you think that rotation helps because the blade can move the the other way, then you are forgetting that the whole blade move forwards too. When at constant speed, the translation of the surface in the direction of the cart is constant, and independent of the angular velocity of the rotor. Carteers confuse perceptual errors and "insight".

Humber, I think Carteers are under the impression that aircraft with props can actually generate thrust into a headwind.

WindGrins

 

[Dr. Keith]

Gratuitous use of "cogent"..."fractal ignorance". Hallmarks of a mountebank.

I thought the "fractal ignorance" thing was original to spork. If it's in common usage I'm gonna be pissed.

Anyone can come on to the internet and imply they have qualifications, eh,
Doctor?

Yeah. See my sig.

I'm not a medical doctor and the use of Dr. in my screen name is meant to highlight the fact that appeals to authority are silly.

What matters are logical arguments. Have you seen many of those lately?

We can use Newton's impact theorem. Not accurate, but good enough.

I knew there was a reason I stopped responding to you. Sorry for the lapse.

 

[Dr. Keith]

He sincerely hopes "you got better"

WG

Nobody believes in male witches. That's just stupid.

 

[humber]

I thought the "fractal ignorance" thing was original to spork. If it's in common usage I'm gonna be pissed.

Google it.

I'm not a medical doctor and the use of Dr. in my screen name is meant to highlight the fact that appeals to authority are silly.

Both obviously redundant.

What matters are logical arguments. Have you seen many of those lately?

To expand on the Newton argument.

A plate moves frontally through a gas with velocity +v.
Assume the simplest case, where the air has no viscosity, and the molecules are reflected straight back. In practice, they will be scattered over a 3D space by surface profile, roughness and molecular incident angle.

1) A molecule moving vertically towards the plate with velocity -u in the ground frame has a velocity -u-v in the reference frame of the plate and hence bounces back from the front side with the velocity u+v ( the plate (prop) is more massive than the air molecules), so in the ground frame the velocity of the molecule is now u+2v.
(You can check in a text that is so for any collision of such relative masses)

2) At the backside of the plate, a molecule with velocity u in the ground frame has a velocity u-v in the reference frame of the plate and thus after reflection, a velocity -u+v
In the ground frame the velocity is now -u+2v.

3) This means in the ground frame, the kinetic energy of the molecules being reflected from the front has increased from m/2*u² to m/2*(u+2v)² =m/2*u² +2*m*u*v + 2*m*v²,
A change of +2*m*u*v + 2*m*v².

4) Molecules reflected from the back side, have changed their energy from m/2*u² to m/2*(-u+2v)² = m/2*u² -2*m*u*v + 2*m*v²
A change of -2*m*u*v + 2*m*v².

Adding and averaging (3) and (4) gives the average increase of the kinetic energy of the molecules with mass m hitting the plate with velocity v as ΔK = 2*m*v².

5) If the plate has an area of 1m², and a velocity of 10 m/sec it will collide with 3.10^26 molecules per second, the number of molecules in 10 cubic meters of air.
Assuming an average molecule mass of 4.5.10^-26 kg, ( air is a mixture of gases) amounts to a total mass of M=13 kg per second.

Replacing m ( individual molecular mass) with M (bulk mass) in the above equations, results in the kinetic energy gained by the total air molecules per second, corresponding to the kinetic energy of a plate of about 26 kg
i.e. a plate of with a mass of 26 kg, a cross section of 1m² and a velocity of 10m/sec would lose its energy within about one second. This result accounts for observed drag in air, and obviously suggests that the same holds for the aerodynamic lift.

The cart will lose KE to the air, rotating prop or not. 500m/s is fast, and will not be defeated by silly and boyish notions or cartoon propellers, nor any cart speed.

http://www.internationalskeptics.com/forums/attachment.php?attachmentid=22005&stc=1&d=1304097988

 

[Dr. Keith]

Google it.

I got 20 hits and most of them had commas, so I wouldn't say it is a common phrase. Sporks usage was elegant, so I'll not be too pissed.

A plate moves frontally through a gas with velocity +v.

Brilliant.

A carrot is orange, and has as much relevance.

 

[humber]

I got 20 hits and most of them had commas, so I wouldn't say it is a common phrase. Sporks usage was elegant, so I'll not be too pissed.

And once is enough for it not to be original and do you think all usages are recorded?
"elegant" More flannel

Brilliant.
A carrot is orange, and has as much relevance.

It applies to any surface moving in air. A Galilean Transform will confirm that a plate moving at 20m/s in a 10m/s downwind, is the same as a plate moving at 10m/s in still air.
Air pressure exists because of the 500m/s average velocity.

This is for fun. The TM is already done, and the NALSA data will not stand.

 

[jduffy77]

This is for fun. The TM is already done, and the NALSA data will not stand.

You say the data "will not stand", what do you mean by that? Will they be removing it from their website sometime soon?

 

[humber]

You say the data "will not stand", what do you mean by that? Will they be removing it from their website sometime soon?

Not to stand, to fall over...is that not clear to you?
Math and physics give Carteer headache. A small one, by dint of physical circumstance.

 

[Dr. Keith]

And once is enough for it not to be original and do you think all usages are recorded?

When it comes to this phrase I will grant you some authority. No doubt you are more familiar with it's usage than most of us here.

For the rest, I pass the baton. I've got drinking to do this afternoon.

 

[jduffy77]

Not to stand, to fall over...is that not clear to you?

No, as always with you, it is not clear. How can data fall over? Since I know you are having trouble again I will explain. I know you will not make a wager because you don't really believe what you write but let's say I could find someone who would. Your statement "the data will fall over by Jun 20th" would be rejected by the lawyers of the wager site we chose. It would be ineligible because it cannot be verified by the escrow agent. A statement like "the data will be removed from the NALSA site by Jun 20th" on the other hand would be acceptable.

What do you mean when you say the "data will not stand"?

 

[humber]

No, as always with you, it is not clear. How can data fall over? Since I know you are having trouble again I will explain. I know you will not make a wager because you don't really believe what you write but let's say I could find someone who would. Your statement "the data will fall over by Jun 20th" would be rejected by the lawyers of the wager site we chose. It would be ineligible because it cannot be verified by the escrow agent. A statement like "the data will be removed from the NALSA site by Jun 20th" on the other hand would be acceptable.

What do you mean when you say the "data will not stand"?

It is all out of your hands, so your questions and the braggadocio of the gambler are irrelevant.
Your math has fallen down at TR, so with the passing of the TM, that's 2 strikes. You can guess the 3rd.

 

[spork]

I thought the "fractal ignorance" thing was original to spork. If it's in common usage I'm gonna be pissed.

I think I said he's fractally wrong. Can't remember. In any event, that simply seemed like an accurate description. But just like the downwind cart, it seems I've stolen the concept from every possible person before me.

http://www.urbandictionary.com/define.php?term=fractally wrong

I also suspect the concept can't work and I'm doing it all wrong. Worse yet, there is no textbook support for the concept of fractally wrong - so it will fall over - cannot stand, etc.

 

[zooterkin]

It is all out of your hands, so your questions and the braggadocio of the gambler are irrelevant.
Your math has fallen down at TR, so with the passing of the TM, that's 2 strikes. You can guess the 3rd.

Are you still playing on the internet when you should be doing your homework? Come on, that data's not going to analyse itself.

 

[jduffy77]

It is all out of your hands, so your questions and the braggadocio of the gambler are irrelevant.
Your math has fallen down at TR, so with the passing of the TM, that's 2 strikes. You can guess the 3rd.

Humber, you are embarrassing yourself again. As to it being out of my hands that doesn't make any sense at all. I never thought it was in my hands but either way I bet on the Superbowl and that outcome definitely wasn't in my hands.

Since you won't state anything clearly we are left guessing but when you talk about math having "fallen down" at TR you must be referring to Yev's. He posted some math which purported to show that the cart could not work but instead in proved that it must.

No idea what you mean about the "passing of the TM", are you referring to your not understanding the direction of the wheel rotation?

I cannot guess the third.

 

[Subduction Zone]

humber, your attempt to analyze the force on a propeller was interesting. It seems that you came up with the amazing conclusion that air pushes on at least one side of the propeller. It would be nice if you could do an analysis of both sides, and to do that you need to take into account the relative velocity of the prop through the wind. If you do it correctly, like Hyev, you won't like your results.

 

[windgrins]

Post from the future!

Since few have a sense of humor here except Dr. K and a few others-the following is a Joke:

Post from the Future!

Humber:

It was clear those NALSA people understood nothing about physics and they are simply trying to protect their reputation so they can't retract the record even when I definitively showed them how wrong this record was. The BlackBird is a Joke, the record is a sham. They are now crooks in a conspiracy to keep a falsehood alive to keep from looking completely foolish!

Spork is an internet conman!

WG

 

[jduffy77]

Since few have a sense of humor here except Dr. K and a few others-the following is a Joke:

Post from the Future!

Humber:

It was clear those NALSA people understood nothing about physics and they are simply trying to protect their reputation so they can't retract the record even when I definitively showed them how wrong this record was. The BlackBird is a Joke, the record is a sham. They are now crooks in a conspiracy to keep a falsehood alive to keep from looking completely foolish!

Spork is an internet conman!

WG

Actually he has already posted many times that NALSA understand nothing about physics and that they are now crooks in a conspiracy to keep a falsehood alive. He does this as you surmise to preempt the possibility of being wrong about a concrete prediction like "NALSA will retract the record by Jul 15th". After they laugh at his objections he will say "I told you they were idiots".

He made so many predictions in the first year or two which turned out to be demonstrably and laughably wrong that he has now stopped. In fact he predicted many many times that the NALSA trials would never take place. When they did he predicted the record would never be ratified, etc, etc.

 

[windgrins]

A hopefully amusing Ditty for Spork!

Sung to the tune of "Rambling Wreck"


Spork’s a Ramblin' Wreck from Georgia Tech, and a hell of an engineer--
A helluva, helluva, helluva, helluva, hell of an engineer.
Like all the carting fellows, His BlackBird has no peer.
He’s a Ramblin' Wreck from Georgia Tech and a hell of an engineer.

Oh! If I were the Humber, sir, I'd ,declare “It is a sham”.
It breaks the laws of physics. Not fast as the wind be damn’ed.
And He has a buddy-Harold, I'll tell you what he’ll do--
He will loudly yell, '!' It can’t work-“I say it is a fake too!”

Oh, I wish I had a barrel of rum and a giant drinking glass,
I’d drink it all at once, and forget their silly ass!
I'd drink to all the good fellows who come from far and near.
To see this slow mo train wreck and a hell of an engineer!

WindGrins