Split Thread The validity of classical physics (split from: DWFTTW)

[humber]

err, fred...

I'm a Boeing 777 instructor pilot,

That is deeply disturbing, Captain. I may never fly again.

...former Australian champion Aerobatic pilot, Silver C glider pilot and former Parachuting instructor. Can I be on your list?

only silver?

I even know how a kite flys!!

Apparently not. Also, being the end-user does not require such knowledge.

I sometimes race motorcycles at an amateur level. That does not make me think I am Biaggi, or Rossi.
However, I can answer questions regarding the operation of motorcycles. Perhaps you would like to explain the difference between a simulator and the real thing. The general principles, I mean.

 

[humber]

Sorry guys, I'm out. We are trying to explain Aerodynamics to someone who doesn't understand (and won't learn!!) how a kite flys!

Entertainment value has given way to frustration and incredulity.

See you on other threads.

Humber, enjoy your ignorance- You fought hard to preserve it, so you deserve it!

"Enjoy your flight"

 

[fredriks]

However, I can answer questions regarding the operation of motorcycles.

Writing random words is not really an answer humber.

 

[humber]

So you HAVE never flown a kite.

Well, Captain. You demonstrated your lack of knowledge regarding kites with your report from Hamburg. I was not the only one to remark upon your errors,and they are repeated here.

If they are at windspeed, they have no relative airflow, so what are they using to produce lift?

Then you would have to accept that the kite cannot fly when held by a string, either on the belt or in real wind. This is contrary to observation.

Kites do not necessarily need 'lift,' Captain, they may be simply blown by the force of the wind. They can be thought of as a simple sail.

I used to own a glider, humber. Are you suggesting on a windy day I could just climb in it and fly away? You see, we used to attach them to a "String" (a winch) and tow them up.

No, I am stating and demonstrating that a kite, a simple device, does not behave in the wind as on the treadmill. It is said that these two systems are equivalent, but that is obviously not the case.

It clearly shows the dependency of wind power upon friction to the belt. This example is one limiting case, the other being attached to the belt. If one is to be accepted, I see reason why the other should be exempted.

No matter what the horizontal movement of the air, unless there was some vertical somewhere (Thermal, ridge, wave) you couldn;t stay up.

No, it may be aloft by the sheer force of the wind.

And neither can a kite unless something anchors it in order to stop it moving ay windspeed, and thus with no relative airflow.
Amazing that you claim such in depth knowledge, and don't even know how a kite works!!

I have been involved in the design of cockpit equipment, Captain. One design obstacle ( apart from the knee-jerk reaction to automation) is a making sure that pilots do not press the wrong buttons, while satisfying their penchant for them.

 

[humber]

Writing random words is not really an answer humber.

Explicit questions, Fredriks, get explicit answers.

 

[humber]

They fly because they have RELATIVE AIRFLOW. It makes no difference to the aircraft whether IT'S moving through the AIR or THE AIR is moving past IT!

I was talking about this to my bother only a few days ago. A member of his cricket club, an aeronautical engineer, believes that planes cannot take off unless there is wind.

I did a flight to Dehli and back last night. The winds at altitude were 100+ knots directley on route. Tailwind there, headwind back, so a 200Kt difference in groundspeed onthe two flights.
Do you know what difference being in a 100kt head or tailwind makes to the way the aircraft flies? Climb performance? Turn rate? Stall speed? None.

Did you stall the plane? If you slow down, you will go backwards, and don't sit in the jumpseat, or you will never arrive.

An aircraft flies because of the flow of air over it. It has no connection with the ground and it's speed over it makes no difference to the way it flies.

Actually, they get lift because of differential pressure produced by the aerofoils ( though the momentum model is also valid).

Quite right, though. They have engines that power the craft. On the treadmill, the belt powers the wind.
I suppose at takeoff , Captain Voice-Over, the runway powers the plane?

 

[fredriks]

Explicit questions, Fredriks, get explicit answers.

Where? By whom?

Just to prove my point.

Room with still air.
Treadmill moving with speed 10 m/s.
Bunny sitting on the belt.
Bunny have a anemometer and put it 0.0001 m above the belt. What are the anemometer going to show?

Bunny put the anemometer 1 m above the belt. What are the anemometer going to show?

Two questions that can be answered with an accuracy of less than 1 m/s.

Here is another one. Is it possibly to fly a kite an a day without any wind relative to the ground? If so how? Is it possibly to use something that makes it easier to fly the kite on that day? Can a car or long treadmill be used?

So there where a couple of explicit questions. Please answer them (random words with no connection to the questions is not answering them).

 

[humber]

Are you suggesting that it is impossibly to fly a kite indoors (in zero wind)?

No, but that the treadmill-wind, is not equivalent to real wind.

Lord Anubis clearly needs a larger home and a longer treadmill. A home and treadmill was not included in the package from Walmart.

Lord Anubis has a substantial residence. It was his intention to purchase a larger treadmill, according the results of this test. He is angry and disappointed.

 

[fredriks]

Humber, nobody (except you) believes that the kite is going to fly in the boundary layer generated by the treadmill. The kite is going to fly because of the velocity difference between the belt and the air particles "far" above the belt.

Why didn't he purchase a larger treadmill?

 

[Subduction Zone]

I was talking about this to my bother only a few days ago. A member of his cricket club, an aeronautical engineer, believes that planes cannot take off unless there is wind.

Typical humberism, third person hearsay. I am willing to be that the aeronautical engineer did not say that, it is more likely that humber's brother got it wrong, and much more likely that humber himself got it wrong.

And in humber world we see that a kite will stay up on its own without a string to anchor it, as long as it is being blown by a real wind. So when we let go of the string and the kite crashes down that must not be a real wind. So that implies that we must be on a giant treadmill. Okay, I've got it now. To tell whether or not we are in a "real" wind according to humber all we need is a kite. If it flies without its string the wind is real if it crashes someone has transported us to a giant treadmill when we did not have our GPS and accelerometer handy.

 

[humber]

Where? By whom?
Just to prove my point.

Room with still air.
Treadmill moving with speed 10 m/s.
Bunny sitting on the belt.
Bunny have a anemometer and put it 0.0001 m above the belt. What are the anemometer going to show?

That is a contrived question, Fredriks, but OK.
The air immediately next to the belt, i.e. adhered to the belt, travels at belt speed, but this is not a physically realizable situation. There will be turbulence at that point.
(If you look at video #7, you will see the tissue paper flutter. Why? Turbulence, and the instability of the tissue in that flow. A simple anemometer will not give an accurate reading under those conditions. There are rules and limits to the use of anemometers.)
The paddle is simple indicator, that is accurate enough to detect a difference between real and belt flows.

Bunny put the anemometer 1 m above the belt. What are the anemometer going to show?

It may show that the velocity at that point is slower then the belt, but moving in the direction of the belt, but again, the real boundary layer is complicated, and not subject to simplification in that manner.
It is easier and more reliable to think of it as a bulk flow, with an average velocity in the direction of the belt. It is easy to demonstrate that is the case. Smoke, bubbles etc.

Two questions that can be answered with an accuracy of less than 1 m/s.

Absolute accuracy does not matter. No matter what the method, there should be no significant difference between real and treadmill wind, but there is quite a difference that will survive all measurement.

Here is another one. Is it possibly to fly a kite an a day without any wind relative to the ground? If so how? Is it possibly to use something that makes it easier to fly the kite on that day? Can a car or long treadmill be used?

You are suggesting towing? Yes. Moving with the belt is like being towed in still air. The model is for a cart being driven by moving air. That is not the same thing, as Lord Anubis has discovered.

What you are doing here, Fredriks, is saying "being on the treadmill is like being in the real wind", but on the other hand saying, "being on the belt is the same as being towed in the wind."

So there where a couple of explicit questions. Please answer them (random words with no connection to the questions is not answering them).

"Random words" is what Spork says of me. He says little else, either way.

 

[Subduction Zone]

humber almost has it:

You are suggesting towing? Yes. Moving with the belt is like being towed in still air. The model is for a cart being driven by moving air

He can see that sitting on the moving treadmill is the same as being in the wind. But for some odd reason he cannot take that tiny step to see that moving at treadmill speed is the same as moving outside at the speed of the wind. Well at least he is halfway there which is further than I thought he would ever make it.

 

[fredriks]

That is a contrived question, Fredriks, but OK.
The air immediately next to the belt, i.e. adhered to the belt, travels at belt speed,

Hurray, humber finally gets it.

but this is not a physically realizable situation.

???? but the incoherent nonsense start again.

There will be turbulence at that point.

And so what?

(If you look at video #7, you will see the tissue paper flutter. Why? Turbulence, and the instability of the tissue in that flow. A simple anemometer will not give an accurate reading under those conditions. There are rules and limits to the use of anemometers.)

Incoherent nonsense not relevant to the question.

The paddle is simple indicator, that is accurate enough to detect a difference between real and belt flows.

Incoherent nonsense not relevant to the question.

Remember that you have already given the correct answer.

Absolute accuracy does not matter. No matter what the method, there should be no significant difference between real and treadmill wind, but there is quite a difference that will survive all measurement.

Incoherent nonsense and we are finally back to humbers only argument. Humber says it is a different so it must be a difference.

You are suggesting towing? Yes. Moving with the belt is like being towed in still air.

Incoherent nonsense.

The model is for a cart being driven by moving air.
That is not the same thing, as Lord Anubis has discovered.

Who mentioned a cart? Did the Lord mention a cart? The answer is no.

The problem with the great lord is that the world don't work in the same way as your drawing.

What you are doing here, Fredriks, is saying "being on the treadmill is like being in the real wind", but on the other hand saying, "being on the belt is the same as being towed in the wind."

Incoherent nonsense.

Did you answer any questions?

"Room with still air.
Treadmill moving with speed 10 m/s.
Bunny sitting on the belt.
Bunny have a anemometer and put it 0.0001 m above the belt. What are the anemometer going to show?"

You answered this first correctly but later wrote a lot of nonsense.

"Bunny put the anemometer 1 m above the belt. What are the anemometer going to show?"

No answer.

"Here is another one. Is it possibly to fly a kite an a day without any wind relative to the ground?"

No real answer but a lot of nonsense.

" If so how? Is it possibly to use something that makes it easier to fly the kite on that day? Can a car or long treadmill be used?"

No real answer but a lot of nonsense.

Almost one answer and that was also kind of correct. Much much better than expected.

 

[humber]

Typical humberism, third person hearsay. I am willing to be that the aeronautical engineer did not say that, it is more likely that humber's brother got it wrong, and much more likely that humber himself got it wrong.

But you can? I think your brother is invisible. What do you say to that?
(Actually, my brother also, it was a phone call)

And in humber world we see that a kite will stay up on its own without a string to anchor it, as long as it is being blown by a real wind.

Yes.

So when we let go of the string and the kite crashes down that must not be a real wind.

No, the kite may crash or simply get blown with the wind, or a mixture of both. This is because the wind is an independent power source.
That is the condition for a real cart in real wind.

On the treadmill, they always crash and slow with a predictable behavior, which in the simplifying case, is the result of the kite's mass and area. There is no "wind" to consider in that calculation.

This is because the treadmill wind, is dependent upon coupling (friction) to the belt.

So that implies that we must be on a giant treadmill. Okay, I've got it now. To tell whether or not we are in a "real" wind according to humber all we need is a kite. If it flies without its string the wind is real if it crashes someone has transported us to a giant treadmill when we did not have our GPS and accelerometer handy.

No, it means what I said above.
That's the beauty of this demonstration. It circumvents the need for an infinite belt, because it is independent of belt length.
Additionally, a kite can be made to further exploit the difference, so as to make the outcome even more obviously different.

 

[Michael C]

Dear Walmart,
Thank you for your response. However, Lord Anubis remains angry. It was his intention to fly kites indoors, so that he could remain close to his concubines. It transpires that the product is unsuitable for this purpose, and indeed many others. However, it does seem to be useful as an exercise machine, and that may be the more appropriate way to market this product.

Regards,
Imhotep

Dear Imhotep, Lord Anubis's problem with flying a kite indoors is not caused by our patented inertial reference frame (which, as formerly stated, is in perfect working order), but by his treadmill. For kite flying, we suggest that he purchase our longest treadmill model, the "Cheops": with a length of 440 royal cubits, it will guarantee Lord Anubis at least one minute of uninterrupted kite-flying pleasure before he is obliged to step off the end (please remind him to be careful when stepping off). In ever-respectful devotion, Customer service, Walmart Stores Inc.

 

[humber]

???? but the incoherent nonsense start again.

"Not physically realizable". Means that the situation you proposed, is not found in reality.

<snip>

"Room with still air.
Treadmill moving with speed 10 m/s.
Bunny sitting on the belt.
Bunny have a anemometer and put it 0.0001 m above the belt. What are the anemometer going to show?"
You answered this first correctly but later wrote a lot of nonsense.

Done.
One answer pleased you, the other not, that is why you say one is 'nonsense'
Nothing more than that, as your single-word responses amply demonstrate.

"Bunny put the anemometer 1 m above the belt. What are the anemometer going to show?"

Done.
The simplified answer, the one that you seek has already been given. You cannot contradict it, because you cannot do that measurement, or claim to know it. The difference between treadmill and wind is there, no matter how measured.

"Here is another one. Is it possibly to fly a kite an a day without any wind relative to the ground?"

Answered; Towing, running, cycling, skiing, riding a roller coaster. That is the banality of your claim. It happens everywhere, but only you try to make it special.

" If so how? Is it possibly to use something that makes it easier to fly the kite on that day? Can a car or long treadmill be used?"

So? Yes. Put a treadmill on the back of truck and fly the kite from there. Go bigger. Put the treadmill, on top of another treadmill, and put that on the back of a truck. Put that truck on a treadmill...

If there is no wind, the kite will behave much like it does on the treadmill. Guess what? That implies there is no wind on the treadmill.

Almost one answer and that was also kind of correct. Much much better than expected.

Really.

 

[humber]

Dear Imhotep, Lord Anubis's problem with flying a kite indoors is not caused by our patented inertial reference frame (which, as formerly stated, is in perfect working order), but by his treadmill. For kite flying, we suggest that he purchase our longest treadmill model, the "Cheops": with a length of 440 royal cubits, it will guarantee Lord Anubis at least one minute of uninterrupted kite-flying pleasure before he is obliged to step off the end (please remind him to be careful when stepping off). In ever-respectful devotion, Customer service, Walmart Stores Inc.

Dear Walmart,
Thank you again for your response, but I must ask that you accept the return of this product. I have also seen (Lord Anubis does not undertake such chores in person) the even bigger "Mile of Nile" model of your competitor, but that too is unsatisfactory.
His Lord Anubis is a man of means with an extensive property. His Lordship was planning the construction of a circular treadmill of such radius, that it would appear linear to the naked eye.
The test of your otherwise worthy product, showed that in principle, the device would not be of use in truly emulating the nature of the wind, something of absolute necessity to His Lordships' purposes.

Yours,
Imhotep.

 

[fredriks]

"Not physically realizable". Means that the situation you proposed, is not found in reality.

So what is the bunny going to measure? The reality exist.

I didn't propose any situation that cant happen. Bunny on a treadmill with an anemometer.

If there is no wind, the kite will behave much like it does on the treadmill. Guess what? That implies there is no wind on the treadmill.

I have no idea what you are trying to say. Absolutely no idea.

 

[GregLondon]

I'm a Boeing 777 instructor pilot, former Australian champion Aerobatic pilot, Silver C glider pilot and former Parachuting instructor.

Cool, I worked on the fly-by-wire project for the 777 way back when.

 

[GregLondon]

Does humber really understand physics more than is apparent in this thread?

no.

I'm not a gambling man, but I'd wager a sandwich that Humber doesn't know physics more than he has revealed in the thread.