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Why an Airplane Flies (Bernoulli's Principle vs. Newton's Third Law)


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Posted (edited)

 

It’s not a statement, it’s a fact

 

So assume I don't understand, and explain how the link supports your claims.

 

As a matter of fact John Cuthber (and I) referred to carbon dioxide, which is 'heavier' than air.

You referred to carbon monoxide which is marginally 'lighter'.

Edited by studiot
Posted

 

If the air above compresses, the pressure goes up. The air below is at the same pressure, so you have created a situation where there is a pressure difference at the height of the top of the balloon. That's not a stable condition. How does the system maintain the pressure differential?

The air pressure below is not at the same pressure, it is increased because the head of air has risen; Archimedes again.

 

I'm not seeing this. The example was for a sealed room. How do you get the pressure increase being from gravity? The possible increase in height can be made very small.

Posted

Swansont,

I'm not seeing this. The example was for a sealed room. How do you get the pressure increase being from gravity? I never said that. That’s your misunderstanding or misinterpretation.

 

Posted

 

Swansont,

I'm not seeing this. The example was for a sealed room. How do you get the pressure increase being from gravity? I never said that. That’s your misunderstanding or misinterpretation.

 

So, once again, explain your point.

 

This constant provocative denial of others is beginning to smack of troll.

Posted

All over the world there are compressed air containers that are full of high pressure air.

Someone already took lots of air from the atmosphere and put it into those containers.

Yet balloons still rise

John, if all the compressed air in these containers were discharged back into the atmosphere it would rise and increase it potential energy. Also, It’s not the atmosphere’s height that causes balloons to rise, but the potential energy they contain compared to an equal volume of air around them. This is true for a carbon monoxide balloon; so it can’t rise, whether in the atmosphere or a closed environment.

I haven’t forgotten your question about the generator and will answer it in due course.

 

Never mind what would happen.

At the moment, they are full.

So at the moment, if you were not utterly and ludicrously wrong, balloons wouldn't float.

Yet they do.

And even if you have forgotten this

"Also, you have not explained how a balloon on a string can generate electricity by rising unless that energy is taken from the potential energy of the balloon.

If energy is taken from it as it rises then it must have less potential energy when it's high up."

I haven't.

So answer it.

Posted

Swansont,

I'm not seeing this. The example was for a sealed room. How do you get the pressure increase being from gravity? I never said that. That’s your misunderstanding or misinterpretation.

 

 

Perhaps you could explain your choice of terminology if that's not the case. My experience is that "head" refers to pressure owing to a height difference under the influence of gravity, and you had previously claimed the effect was all due to gravitational potential energy. Something in your explanation is not consistent, so perhaps you could explain more clearly, so as to reduce the probability of misinterpretation.

Posted

Swansont,

My experience is that "head" refers to pressure owing to a height difference under the influence of gravity, and you had previously claimed the effect was all due to gravitational potential energy.

I was not talking about an enclosed environment. You introduced that. And what effect are you thinking of.

 

The Earth has air pressure, why is this? The Moon has no atmospheric pressure because there is no atmosphere, why do you think this is? Mars has a slight atmospheric pressure, again, why do you think this is? Jupiter has a high atmospheric pressure, and again, why do you think this is?

 

Posted

Swansont,

My experience is that "head" refers to pressure owing to a height difference under the influence of gravity, and you had previously claimed the effect was all due to gravitational potential energy.

I was not talking about an enclosed environment. You introduced that. And what effect are you thinking of.

 

The Earth has air pressure, why is this? The Moon has no atmospheric pressure because there is no atmosphere, why do you think this is? Mars has a slight atmospheric pressure, again, why do you think this is? Jupiter has a high atmospheric pressure, and again, why do you think this is?

 

 

Yes, I did introduce that, and you responded. You don't get to change the parameters of the example just because they conflict with your explanation. You are claiming a particular reason a balloon has lift. If it has lift under conditions that preclude that explanation, then the explanation isn't right.

  • 2 weeks later...
Posted (edited)

1. I started in this forum by saying, “Airplanes can and do fly in stationary air”, and this was immediately pounced on by Studiot with “ Have you never heard of relative velocity”.

 

Let me say yes of course, and I also say that relative velocity has no place in the analysis of lift. Relative velocity is a substitute for the reality. When air is stationary there is no flow over the wings except insofar as a downwash of air is developed that descends almost vertically downwards. The relative velocity argument can lead to people actually believing in a supposed airflow that streams off behind an airplane. If it did, large migratory birds such as swans, geese, storks...etc, would be swept backwards when they attempt to fly in vee formation behind the bird in front from the upwash associated with the vortices. Also there is no laminar airflow in the air where these large flocks of migratory birds fly together in their thousands. The air here is extremely turbulent...and the same goes for swarms of bees...etc.

 

Another point is: the vortices do not trail off in a supposed slipstream in what relative velocity usually shows as a helix. They are spirals that spin more or less where they are in space, gradually descending along with the downwash, since they are part and parcel of it. They also move forward slightly as they are dragged along with the airplane.

 

2. Studiot goes on: “We are talking about heavier than air’ craft which unlike a helium balloon do not benefit from positive buoyancy forces”.

 

In the old days, 250,000 Europeans flew to America in gas filled airships. In order for their passengers to disembark the airships had to descend, and they could only do this by becoming heavier than air.

 

3. Studiot continues: “Why is it so difficult for people to accept that no laws are broken and that more than one physical law is in action developing lift force”.

 

4. This is untrue. There is only one physical law and it is this: Lift is an equal and opposite reaction to a downwash of air in accordance with Newton’s 3rd law.

 

Studiot’s other comments are irrelevant.

Edited by Talos
Posted

1. I started in this forum by saying, “Airplanes can and do fly in stationary air”, and this was immediately pounced on by Studiot with “ Have you never heard of relative velocity”.

 

It wasn't that statement that was questioned (as it is obviously true), it was the bizarre conclusion that "this means air cannot flow across the wings" that was derided (quite rightly). From that I have concluded you have nothing sensible to say and have not followed the rest of the discussion.

Posted (edited)

 

This is untrue. There is only one physical law

 

Are you really saying you do not consider any other physical laws apply?

Edited by studiot
Posted

2. Studiot goes on: “We are talking about heavier than air’ craft which unlike a helium balloon do not benefit from positive buoyancy forces”.

 

In the old days, 250,000 Europeans flew to America in gas filled airships. In order for their passengers to disembark the airships had to descend, and they could only do this by becoming heavier than air.

 

"becoming" being the key word here.

 

Your words actually supports what Studiot was saying.

Posted (edited)

Studiot has asked twice now, “Where does the descending air come from”?

If he clicks here he will see for himself.

 

http://talosperdix.com/onewebmedia/downwash%20photos.pdf

 

 

Yes indeed and thrice now you have failed to answer since this is now the third time.

 

Which is highly appropriate since ploy # 3 from the manual of tactics for trolls reads.

"When faced with a question you cannot answer, do not try to answer just change the subject"

Of course my post#112 was such a question.

 

I have never disputed that there is descending air associated with heavier-than-air flight and indeed the combined posts by ccweb and myself explained the need for this fully along with the mechanism.

 

What I do dispute is your interpretation of the laws of physics, cavalierly discarding some and cherry picking others to suit your self. Worse you even misapply them.

 

You have linked to some nice photographs, without any proof or explanation that they show descending air, and still without answering the question

 

"Where did it come from?"

 

A further related question might be; "where is the centre of gravity of this descending air in relation to the plane?"

Edited by studiot
Posted

Studiot. How blind can you be. Buy the book...Understanding Flight.

There's none so blind as those who don't want to see.

Posted

Does the book answer the questions we have asked?

Does it, for example, explain this

"Also, you have not explained how a balloon on a string can generate electricity by rising unless that energy is taken from the potential energy of the balloon.

If energy is taken from it as it rises then it must have less potential energy when it's high up."

Does it explain why your bizarre ideas about why balloons shouldn't float because there are compressed air tanks on Earth tally with reality?

If not, why would I buy it?

Posted

John Cuthber.

Can we agree that a helium balloon rises because of its buoyancy?

Can we agree that no airplane can fly as high as a helium balloon?

Can we agree that a helium balloon can rise to within a few miles of the Kármán line?

Can we agree that a helium balloon has acquired an enormous amount of potential energy when it is within a few miles of the Kármán line?

 

Posted (edited)

John Cuthber.

Can we agree that a helium balloon rises because of its buoyancy?

Can we agree that no airplane can fly as high as a helium balloon?

Can we agree that a helium balloon can rise to within a few miles of the Kármán line?

Can we agree that a helium balloon has acquired an enormous amount of potential energy when it is within a few miles of the Kármán line?

 

 

 

 

You either cannot or will not answer John's question about the electricity generator.

 

To answer John's question you need to understand that he is talking about a different potential energy from the potential energy you keep mentioning.

 

John is talking about total potential energy, which includes gravitational potential energy, but is not limited to that.

A tethered helium ballon has at least one additional source of total potential energy besides gravitational.

 

You are talking about gravitational potential energy alone.

 

 

 

Given the above information can you prepare a cogent argument as to all the relevant energy interchanges that occur when we release the tether and the balloon rises?

Edited by studiot
Posted

Can we agree that a helium balloon rises because of its buoyancy?

 

You previously said:

 

Incidentally, the physics that explain the lift of an airplane are the same as the physics that explain the lift of a helium balloon.

 

So you are saying that airplanes fly because of buoyancy.

 

 

Can we agree that no airplane can fly as high as a helium balloon?

 

Then why can't an airplane fly as high as a balloon if it is the same physics?

Posted

Studiot and Strange.

Let John answer for himself, and stop your claptrap and other nonsense.

 

 

I was only quoting you, so if it was nonsense ...

Posted

 

Posted Today, 02:24 PM

Studiot and Strange.

Let John answer for himself, and stop your claptrap and other nonsense.

 

Talos Offline Today, 02:25 PM

Looking at the times of your last visit here, and looking back at your previous posts I find this is typical,

 

You clearly don't wish to hold a discussion, which is the purpose of a discussion forum.

 

You simply wish to preach prepared sermons rather than offer discussion, proof and reasoned argument.

 

And when they are rumbled you resort to insult.

Posted

John Cuthber.

Can we agree that a helium balloon rises because of its buoyancy?

Can we agree that no airplane can fly as high as a helium balloon?

Can we agree that a helium balloon can rise to within a few miles of the Kármán line?

Can we agree that a helium balloon has acquired an enormous amount of potential energy when it is within a few miles of the Kármán line?

 

Yes, don't care, don't care and No respectively.

Now can you please do hat the site rules require of you, and answer my question about the generator?

Posted

Sorry John,

You'll never know. I've decided that none of you want to learn.

I've never come across such a conceited bunch of amateurs.

Talos. British Airways Electrical and Electronics Engineer and PPL(UK) holder.

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