The Real Reason Moist Air Reduces Aerodynamic Lift

Beyond the boundaries of established science an avalanche of exotic ideas compete for our attention. Experts tell us that these ideas should not be permitted to take up the time of working scientists, and for the most part they are surely correct. But what about the gems in the rubble pile? By what ground-rules might we bring extraordinary new possibilities to light?

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The Real Reason Moist Air Reduces Aerodynamic Lift

Unread postby jimmcginn » Wed Mar 15, 2017 12:35 pm

There is a general misconception that the reduction is lift that aircraft experience in moist air is a result of moist air being lower in density than dry air. Supposedly this confirms the notion that the moisture in moist air is monomolecular H2O, the molecular equivalent of steam (gaseous H2O). Actually, this is impossible. As confirmed by hundreds of years of experimental evidence, steam (gaseous H2O) can only exist above the boiling temperature/pressure of H2O. Obviously earth's atmosphere never gets hot enough to support the existence of steam which has a boiling point temperature greater than any temperature found in the atmosphere. So, contrary to what people generally assume, all of the moisture in earth's atmosphere consists of microdroplets/clusters of H2O. And as long as the diameter of these microdroplets stay smaller than the length of a photon they are invisible--just as invisible as steam.

Nevertheless, aircraft do experience reduced lift in moist air. And (due to the fact that moist air contains droplets of H2O that are larger than the N2 and O2 molecules that they replace) moist air is denser (heavier) than dry air. And so, given that it is generally true that denser air provides more lift than less dense air there appears to be a contradiction here. If all of this is true, why does heavier, denser, moist air not increase lift? Why does it reduce lift?

Before we can answer that question there are two other truths about aerodynamics that we need to clarify:
1) The energy that causes lift in an airplane doesn't come from the engine of the airplane. The energy that comes from the engine of the airplane is used to overcome drag. The energy that causes lift comes from air pressure--it comes from the atmosphere itself; And,
2) there is a finite amount of energy per volume of air. And, therefore, there is a finite amount of energy that can be efficiently extracted from a volume of air. Flying faster allows you to use more air and, thereby, extract more energy from it. But flying faster doesn't increase the amount of energy per volume that an airplane gets out of the air.

The reason lift is reduced in moist air is because liquid H2O has a very high heat capacity, which is just a fancy way of saying that it absorbs energy. Specifically, it is harder to extract the finite amount of energy from a volume of air because so much of it is soaked up by the liquid water that is in the air. So, stating that you know moist air is lighter because it reduces lift is, well, nonsense. It is an ignorance based assertion.

This falsehood has been promoted by the meteorological lobby. The truth is that moist air is heavier, not lighter, than dry air. And claiming that reduced drag associated with moist air is evidence that substantiates the notion that moist air is lighter is an invalid argument. Because it fails to account for other factors that may actually be causing the reduction in lift. The fact is, as indicated, water's ability to absorb energy is greater than that of any other liquid. This is the reason why moist air reduces lift. And it is one of the reasons pilots are advised to avoid clouds (another good reason is because clouds tend to hide high energy vortices and wind shear). And if it was true that denser air increases lift that wouldn't be the case, pilots would be advised to go skipping across the atmosphere on clouds, taking advantage of the increased lift provided by their increased density.

The best way to know the weight/volume of moist air is to measure it. Nobody ever has. Meteorologists absolutely refuse to measure it. Being ensconced in a paradigm dominated by group-think stupidity, meteorologists measure the relative humidity and think that that also indicates the weight/volume. And that simply ain't so. (Meteorologist look at things very differently than real scientist. They have their narrative that they hide from the public. They are more concerned about looking scientific than they are being factual.) If you measure you know. If you guess based on indirect evidence you are just guessing. Reality is too complex. People are gullible. People are easily fooled. People miss details and the devil is in the details. People tend to be easily convinced by anecdote and experts. And they don't realize that very often the experts are using the same flawed methods to come to the same flawed conclusion. When meteorologists are talking about "density," you never know when they are talking about 1) the ratio of water to air or 2) the weight of air per volume. These are two very different concepts that they employ interchangeably. Sometimes they use them interchangeably in the same paragraph or the same sentence. And if you try to get them to clarify they throw a hissy fit and stamp off. Meteorology is, in many respects, a belief system and not a real science.

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Re: The Real Reason Moist Air Reduces Aerodynamic Lift

Unread postby comingfrom » Thu Mar 16, 2017 5:06 pm

Hi there Jim.

You've found another reason (or way) to promote your microdroplet theory.
And I'm trying to follow it.

Definitely in clouds the water is clustered into microdroplets, and droplets. When water molecules cluster into droplets they refract sunlight, so we see clouds.
Outside of the clouds there isn't less water in the air, witness a humid day. But we don't see the water outside of the clouds because the water isn't clustered into droplets.

Notice I said droplets. I'm leaving open that you may be right, that the water outside of clouds may still be microdroplets. Maybe, as you say, microdroplets don't refract enough light to become noticeably visible.

But how big are your photons?
Or do you mean the wavelength of a photon?

Visible wavelength photons pass through the droplets to get refracted.
Is that why your microdroplets must be smaller than a photon?

I would attribute the invisibilty of the microdroplets to their small size not refracting enough photons.
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Re: The Real Reason Moist Air Reduces Aerodynamic Lift

Unread postby jimmcginn » Thu Mar 16, 2017 6:41 pm

comingfrom wrote:I would attribute the invisibilty of the microdroplets to their small size not refracting enough photons.
~Paul


You might be right.

I don't claim any direct knowledge on any of this.

I wish I could provide a direct reference. You know how it is. I pick up these tidbits here and there on the internet.

One time I watched a column of genuine steam that remained genuine monomolecular steam (from what I could tell) for about a quarter inch before it cooled into a mist. It was perfectly clear, but it did have a glassy shimmer. So I think even steam has some effect on light. But--possibly--it is only when they get to a certain size that they start to actually scatter the photons.

All of this stuff seems so obvious to me now that I get impatient that other people aren't picking up on it. But when I'm being honest with myself and I think back to about 5 years ago I can remember having struggled with it.

At that time I had no clue about the other realizations that would follow--such as the zeroing of polarity that is the mechanism of H2O's huge heat capacity.

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Re: The Real Reason Moist Air Reduces Aerodynamic Lift

Unread postby willendure » Fri Mar 17, 2017 5:03 am

If a plane is flying in level flight, then no energy is expended in lifting it up. It needs a force of lift equal to its weight in order to remain in level flight, but as the plane is not changing its height, no work is done, no energy is expended, its gravitational potential energy remains the same.

In order to create the force of lift, the air needs to exert an upward force on the wings. This is done partly through a pressure differential and partly through the fact that the wing simply pushes the air down. Either way the air is being accelerated by the wing resulting in drag on it.

So you are right that the engine is working to overcome the drag. But you are wrong that the air is supplying energy to keep the aircraft aloft. The engine is supplying energy to overcome drag, but the drag is a result of a mechanism that works on the air to produce the up-lift. So the force of lift is being created by work done by the engine.

If the air is less dense, there will be less of it for the wing to work on, so there will be less lift. So I think it is true that moist air is less dense.

Still, your micro-droplets assertion is not necessarily defeated by this. I can still believe that air with micro-droplets may be less dense than dry air.

If we cannot see the micro-droplets with visible light as they are too small, we could use shorter wavelengths to see if they really are there. I don't know what size would be needed to check, x-rays perhaps?

=========

I am also curious whether wet air makes the engine more efficient? You can inject very fine water droplets into a diesel engine and it will produce more power, for example. These would definitely be liquid water droplets, and typically sprayed from a fine mechanical nozzle, so significantly larger than your proposed micro-droplets. They turn to steam in the engine, increasing the density and heat capacity of the gas during combustion making it more efficient in much the same way that an inter-cooler does.

I can believe the same effect would be noticed by both jet and piston air engines. Perhaps there are other factors which might offset it.
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Re: The Real Reason Moist Air Reduces Aerodynamic Lift

Unread postby sketch1946 » Fri Mar 17, 2017 7:14 am

Do you people know this guy, I am a bit of a fan of his, he is a great lecturer in my opinion,
Richard Feynman:
"if you think you understand quantum mechanics, then you don’t"

Here's a couple of snippets out of one of his lectures:

"On an ordinary day over flat desert country, or over the sea, as one goes upward from the surface of the ground the electric potential increases by about 100 volts per meter. Thus there is a vertical electric field E of 100 volts/m in the air. The sign of the field corresponds to a negative charge on the earth’s surface. This means that outdoors the potential at the height of your nose is 200 volts higher than the potential at your feet! ..."

"...Having suggested how we can measure the electric field in the atmosphere, we now continue our description of it. Measurements show, first of all, that the field continues to exist, but gets weaker, as one goes up to high altitudes. By about 50 kilometers, the field is very small, so most of the potential change (the integral of E) is at lower altitudes. The total potential difference from the surface of the earth to the top of the atmosphere is about 400,000 volts...."

"As the warm, moist air at the bottom rises, it cools and the water vapor in it condenses. In the figure the little stars indicate snow and the dots indicate rain, but because the updraft currents are great enough and the drops are small enough, the snow and rain do not come down at this stage. This is the beginning stage, and not the real thunderstorm yet—in the sense that we don’t have anything happening at the ground. At the same time that the warm air rises, there is an entrainment of air from the sides—an important point which was neglected for many years. Thus it is not just the air from below which is rising, but also a certain amount of other air from the sides."

"Why does the air rise like this? As you know, when you go up in altitude the air is colder. The ground is heated by the sun, and the re-radiation of heat to the sky comes from water vapor high in the atmosphere; so at high altitudes the air is cold—very cold—whereas lower down it is warm. You may say, “Then it’s very simple. Warm air is lighter than cold; therefore the combination is mechanically unstable and the warm air rises.” Of course, if the temperature is different at different heights, the air is unstable thermodynamically. Left to itself infinitely long, the air would all come to the same temperature. But it is not left to itself; the sun is always shining (during the day). So the problem is indeed not one of thermodynamic equilibrium, but of mechanical equilibrium. Suppose we plot—as in Fig. 9–8—the temperature of the air against height above the ground. In ordinary circumstances we would get a decrease along a curve like the one labeled (a); as the height goes up, the temperature goes down. How can the atmosphere be stable? Why doesn’t the hot air below simply rise up into the cold air? The answer is this: if the air were to go up, its pressure would go down, and if we consider a particular parcel of air going up, it would be expanding adiabatically. (There would be no heat coming in or out because in the large dimensions considered here, there isn’t time for much heat flow.) Thus the parcel of air would cool as it rises. Such an adiabatic process would give a temperature-height relationship like curve (b) in Fig. 9–8. Any air which rose from below would be colder than the environment it goes into. Thus there is no reason for the hot air below to rise; if it were to rise, it would cool to a lower temperature than the air already there, would be heavier than the air there, and would just want to come down again...."
http://www.feynmanlectures.caltech.edu/II_09.html
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Re: The Real Reason Moist Air Reduces Aerodynamic Lift

Unread postby jimmcginn » Fri Mar 17, 2017 1:46 pm

willendure wrote:If a plane is flying in level flight, then no energy is expended in lifting it up. It needs a force of lift equal to its weight in order to remain in level flight, but as the plane is not changing its height, no work is done, no energy is expended, its gravitational potential energy remains the same.

In order to create the force of lift, the air needs to exert an upward force on the wings. This is done partly through a pressure differential and partly through the fact that the wing simply pushes the air down. Either way the air is being accelerated by the wing resulting in drag on it.

So you are right that the engine is working to overcome the drag. But you are wrong that the air is supplying energy to keep the aircraft aloft. The engine is supplying energy to overcome drag, but the drag is a result of a mechanism that works on the air to produce the up-lift. So the force of lift is being created by work done by the engine.

The energy that keeps an airplane from falling out of the sky does not come from the thrust of the airplane's engines, it comes from air pressure. The thrust of the airplane's engines provides the energy that allows the airplane to overcome drag and achieve a velocity that enables laminar flow over the top of the plane's air-foil wings. Accordingly, the energy from the thrust of the airplane's engines is conserved in the velocity of the airplane. It being a consequence of velocity, laminar flow removes the energy of air pressure from the top of the wing. It does not remove it from the bottom of the wing. Consequently, energy literally flows up into the wing FROM THE ATMOSPHERE, producing an acceleration force, lift. And so, aerodynamics involves the rules/principles by which the abundant energy in air (air pressure) can be tapped into or channeled.

All in all, aerodynamics involves an exchange, with air pressure being the source of the energy flow that causes lift (an acceleration force). And so, if we were to model the pathway of the energy that causes the lift on an aircraft it originates in the atmosphere. It does not originate with the airplane's engine. (This is a common misconception.) It is extracted from the atmosphere by the air foil. Nevertheless, the atmosphere does not experience a net loss in energy as a result of the aircraft passing through it but actually experiences a net gain in that the amount of energy associated with thrust/drag more than compensates for the loss of energy associated with lift.

willendure wrote:If the air is less dense, there will be less of it for the wing to work on, so there will be less lift. So I think it is true that moist air is less dense.

It's more dense and heavier, as explained here:
viewtopic.php?f=8&t=16306

willendure wrote:Still, your micro-droplets assertion is not necessarily defeated by this. I can still believe that air with micro-droplets may be less dense than dry air.

As explained in the link above, this is impossible. Moist air is always more dense and heavier. There is no getting around it. (And once you understand that convection is, largely, a non-player in the atmosphere you realize that there is no reason to need to get around it.[/quote]

willendure wrote:If we cannot see the micro-droplets with visible light as they are too small, we could use shorter wavelengths to see if they really are there. I don't know what size would be needed to check, x-rays perhaps?

Interesting idea. You'd think this must already have been done or, at least, that there must be some data somewhere that might have detected it.

willendure wrote:I am also curious whether wet air makes the engine more efficient? You can inject very fine water droplets into a diesel engine and it will produce more power, for example. These would definitely be liquid water droplets, and typically sprayed from a fine mechanical nozzle, so significantly larger than your proposed micro-droplets. They turn to steam in the engine, increasing the density and heat capacity of the gas during combustion making it more efficient in much the same way that an inter-cooler does.

I can believe the same effect would be noticed by both jet and piston air engines. Perhaps there are other factors which might offset it.

I think the biggest complicating factor on this is the fact that the boiling temperature of H2O goes up precipitously with increases in pressure. And so, it might only stay steam for the beginning of the power stroke and then turn back in to energy absorbing liquid water through to the end of the power stroke.

James McGinn / Solving Tornadoes
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Re: The Real Reason Moist Air Reduces Aerodynamic Lift

Unread postby fosborn_ » Fri Mar 17, 2017 4:53 pm

jimmcginn..
And so, if we were to model the pathway of the energy that causes the lift on an aircraft it originates in the atmosphere.

And yet there was no powered flight until the engine could be utilized in an airframe. Equal and oposite reaction to the forced acceleration of an angled wing surface agenst an air mass.
Your so wrong.Humid air is less dense than dry air if we ignore your assertions of what you imagine water vapor is. H2O gas it what reduces the air density. Evaporation does take place in the Form of gas. In artic experments in the 50s they micro filtered and chemical scrubbed the air of ice and micro droplets and still was able to condense 5% water vapor out -40 to -70 deg F air samples.
Your imagination can't model anthing better than the current accepted science.
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Re: The Real Reason Moist Air Reduces Aerodynamic Lift

Unread postby jimmcginn » Fri Mar 17, 2017 5:39 pm

fosborn_ wrote:
jimmcginn..
And so, if we were to model the pathway of the energy that causes the lift on an aircraft it originates in the atmosphere.

And yet there was no powered flight until the engine could be utilized in an airframe.

Drag is a bitch.
fosborn_ wrote:Equal and opposite reaction to the forced acceleration of an angled wing surface against an air mass.

Then why aren't wings flat on top?
fosborn_ wrote:Your so wrong. Humid air is less dense than dry air if we ignore your assertions of what you imagine water vapor is.

Since we have no data either way, whose imagination would you suggest? Meteorologists? And keep in mind, you wouldn't just be ignoring me, you'd also be ignoring the voluminous evidence that indicates the boiling temperature of H2O is higher than anything in our atmosphere.
fosborn_ wrote:H2O gas is what reduces the air density.

Believe what you want to believe.
fosborn_ wrote:Evaporation does take place in the Form of gas. In arctic experiments in the 50s they micro filtered and chemical scrubbed the air of ice and micro droplets and still was able to condense 5% water vapor out -40 to -70 deg F air samples.

Superchilled (liquid) water microdroplets. (This is very real.) I discussed this briefly in my "Breakthrough" paper. Superchilled water (microdroplets) are also involved in sublimation.
fosborn_ wrote:Your imagination can't model anything better than the current accepted science.

Feel free to make an details argument to that effect.

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Re: The Real Reason Moist Air Reduces Aerodynamic Lift

Unread postby jimmcginn » Sat Mar 18, 2017 10:16 am

sketch1946 wrote:Do you people know this guy, I am a bit of a fan of his, he is a great lecturer in my opinion,


Yes, of course. I'm a fan too. Thanks for posting this.

Feynman was highly critical of meteorology. I think he referred to it as a cargo cult science, but I've been unable to confirm that.
sketch1946 wrote:Richard Feynman:
"if you think you understand quantum mechanics, then you don’t"

Here's a couple of snippets out of one of his lectures:

"On an ordinary day over flat desert country, or over the sea, as one goes upward from the surface of the ground the electric potential increases by about 100 volts per meter. Thus there is a vertical electric field E of 100 volts/m in the air. The sign of the field corresponds to a negative charge on the earth’s surface. This means that outdoors the potential at the height of your nose is 200 volts higher than the potential at your feet! ..."

This is amazing. But I have to admit, I don't know how to interpret this.

I wonder, does this give us any reason to assume that microdroplets will levitate? If so that would indicate a real problem for my experiment to measure the weight of moist air.
sketch1946 wrote:
"...Having suggested how we can measure the electric field in the atmosphere, we now continue our description of it. Measurements show, first of all, that the field continues to exist, but gets weaker, as one goes up to high altitudes. By about 50 kilometers, the field is very small, so most of the potential change (the integral of E) is at lower altitudes. The total potential difference from the surface of the earth to the top of the atmosphere is about 400,000 volts...."

"As the warm, moist air at the bottom rises, it cools and the water vapor in it condenses.


It's not clear here whether Feynman is assuming that the rise of the moist air is a consequence of the electric field or convection.
sketch1946 wrote:

In the figure the little stars indicate snow and the dots indicate rain, but because the updraft currents are great enough and the drops are small enough, the snow and rain do not come down at this stage. This is the beginning stage, and not the real thunderstorm yet—in the sense that we don’t have anything happening at the ground. At the same time that the warm air rises, there is an entrainment of air from the sides—an important point which was neglected for many years. Thus it is not just the air from below which is rising, but also a certain amount of other air from the sides."

"Why does the air rise like this? As you know, when you go up in altitude the air is colder. The ground is heated by the sun, and the re-radiation of heat to the sky comes from water vapor high in the atmosphere; so at high altitudes the air is cold—very cold—whereas lower down it is warm. You may say, “Then it’s very simple. Warm air is lighter than cold; therefore the combination is mechanically unstable and the warm air rises.” Of course, if the temperature is different at different heights, the air is unstable thermodynamically. Left to itself infinitely long, the air would all come to the same temperature. But it is not left to itself; the sun is always shining (during the day). So the problem is indeed not one of thermodynamic equilibrium, but of mechanical equilibrium. Suppose we plot—as in Fig. 9–8—the temperature of the air against height above the ground. In ordinary circumstances we would get a decrease along a curve like the one labeled (a); as the height goes up, the temperature goes down. How can the atmosphere be stable? Why doesn’t the hot air below simply rise up into the cold air? The answer is this: if the air were to go up, its pressure would go down, and if we consider a particular parcel of air going up, it would be expanding adiabatically. (There would be no heat coming in or out because in the large dimensions considered here, there isn’t time for much heat flow.) Thus the parcel of air would cool as it rises. Such an adiabatic process would give a temperature-height relationship like curve (b) in Fig. 9–8. Any air which rose from below would be colder than the environment it goes into. Thus there is no reason for the hot air below to rise; if it were to rise, it would cool to a lower temperature than the air already there, would be heavier than the air there, and would just want to come down again...."
http://www.feynmanlectures.caltech.edu/II_09.html


One criticism I have of Feynman is that his understanding of water is rather amateurish. I see no understanding of H2O polarity and he does not appear to be concerned about water's many anomalies.
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Re: The Real Reason Moist Air Reduces Aerodynamic Lift

Unread postby GaryN » Sat Mar 18, 2017 12:14 pm

Theory vs Experiment: What is the Surface Charge of Water?
http://www.waterjournal.org/uploads/vol ... haplin.pdf
In order to change an existing paradigm you do not struggle to try and change the problematic model. You create a new model and make the old one obsolete. -Buckminster Fuller
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Re: The Real Reason Moist Air Reduces Aerodynamic Lift

Unread postby comingfrom » Sat Mar 18, 2017 5:27 pm

fosborn_ wrote:
Equal and opposite reaction to the forced acceleration of an angled wing surface against an air mass.

Then why aren't wings flat on top?
Plenty of them are.

Google images: flat airplane wings

They aren't angled either.
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Re: The Real Reason Moist Air Reduces Aerodynamic Lift

Unread postby fosborn_ » Sat Mar 18, 2017 11:56 pm

willendure wrote:If a plane is flying in level flight, then no energy is expended in lifting it up. It needs a force of lift equal to its weight in order to remain in level flight, but as the plane is not changing its height, no work is done, no energy is expended, its gravitational potential energy remains the same.

In order to create the force of lift, the air needs to exert an upward force on the wings. This is done partly through a pressure differential and partly through the fact that the wing simply pushes the air down. Either way the air is being accelerated by the wing resulting in drag on it.

So you are right that the engine is working to overcome the drag. But you are wrong that the air is supplying energy to keep the aircraft aloft. The engine is supplying energy to overcome drag, but the drag is a result of a mechanism that works on the air to produce the up-lift. So the force of lift is being created by work done by the engine.

If the air is less dense, there will be less of it for the wing to work on, so there will be less lift. So I think it is true that moist air is less dense.

Still, your micro-droplets assertion is not necessarily defeated by this. I can still believe that air with micro-droplets may be less dense than dry air.


Defiantly Mr Newton has the most influence.

http://www.allstar.fiu.edu/aero/airflylvl3.htm
We are going to show you that lift is easier to understand if one starts with Newton rather than Bernoulli. We will also show you that the popular explanation that most of us were taught is misleading at best and that lift is due to the wing diverting air down.


As far a microdropletes its a question of where do the micro droplets come from. Mcginns has a lot of conjecture. Current science presents a great case for condensing of h2o gas if a aerosol is present to provide a nucleus seed. The way I understand it its nearly impossible for droplets to form with out an aerosol. Mcginn can only pontificat his imagination. He has yet to explain anything that anyone else can understand. The overwhelming curvature of surface tension creates internal pressures greater than can be contained by the droplets surface tension. Its self annihilating. So I think is you have to have h2o gas and aerosols to get droplets. The only reason Mcginn strives here is our ignorance of the current models. I don't need weeks of theory that require Mcginns re-education camp and therefor the potential of suspicious cool aid.

I think the whole confusion about less dense humid air is Mcginns enjoying, making us dummer because of his filling our ignorance with something worse.
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Re: The Real Reason Moist Air Reduces Aerodynamic Lift

Unread postby fosborn_ » Sun Mar 19, 2017 12:21 am

fosborn_ wrote:Evaporation does take place in the Form of gas. In arctic experiments in the 50s they micro filtered and chemical scrubbed the air of ice and micro droplets and still was able to condense 5% water vapor out -40 to -70 deg F air samples.

James McGinn...Superchilled (liquid) water microdroplets. (This is very real.)
I discussed this briefly in my "Breakthrough" paper. Superchilled water (microdroplets) are also involved in sublimation.

I've given up reading your word dumps, they are incomprehensible when you make up your own definitions that create utter confusion. vary cult like methodology IMO
fosborn_ wrote:Your imagination can't model anything better than the current accepted science.

James McGinn...Feel free to make an details argument to that effect.


You don't seem to absorb much form actual research. You mention super chilled droplets ? You don't seem able to comprehend the artic research paper I referenced for you.
They used scales and did a vary sophisticated mechanized and chemical effort that leaves only h2o gas and condense it. They were trustworthy investigators. Another example to set your bar to.
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Re: The Real Reason Moist Air Reduces Aerodynamic Lift

Unread postby sketch1946 » Sun Mar 19, 2017 12:50 am

Hi Jimmy,
jimmcginn wrote:One criticism I have of Feynman is that his understanding of water is rather amateurish. I see no understanding of H2O polarity and he does not appear to be concerned about water's many anomalies.

Feynman does make a lot of comments about water and charge in the atmosphere:
He does discuss polarity of water droplets, did you miss it?
I guess it's a long page with a lot of stuff in there....
He mentions water 33 times, and the eighteenth time he says:

" ...it does show the effect of an electric field on water drops. We say that it may be irrelevant because it relates to an experiment one can do in the laboratory with a stream of water to show the rather strong effects of the electric field on drops of water."

"With a weak electric field you will find that the stream breaks up into a smaller number of large-sized drops. But if you apply a stronger field, the stream breaks up into many, many fine drops—smaller than before. With a weak electric field there is a tendency to inhibit the breakup of the stream into drops. With a stronger field, however, there is an increase in the tendency to separate into drops."

"The explanation of these effects is probably the following. If we have the stream of water coming out of the nozzle and we put a small electric field across it one side of the water gets slightly positive and the other side gets slightly negative. Then, when the stream breaks, the drops on one side may be positive, and those on the other side may be negative. They will attract each other and will have a tendency to stick together more than they would have before—the stream doesn’t break up as much. On the other hand, if the field is stronger, the charge in each one of the drops gets much larger, and there is a tendency for the charge itself to help break up the drops through their own repulsion.

Each drop will break into many smaller ones, each carrying a charge, so that they are all repelled, and spread out so rapidly. So as we increase the field, the stream becomes more finely separated. The only point we wish to make is that in certain circumstances electric fields can have considerable influence on the drops."

"Somebody discovered that if you have a drop of water that breaks into two pieces in a windstream, there is positive charge on the water and negative charge in the air. This breaking-drop theory has several disadvantages, among which the most serious is that the sign is wrong."

F wants to show that the top of the thundercloud should be positively charged, so positive charged droplets of water would have the wrong charge and would be propelled downwards...

F says if we could find a mechanism for water droplets to be charged differently at the top and bottom of a single drop, we would have a new theory....
"....if we could imagine some way for the charge to be different at the top and bottom of a drop and if we could also see some reason why drops in a high-speed airstream would break up into unequal pieces—a large one in the front and a smaller one in the back because of the motion through the air or something—we would have a theory. (Different from any known theory!)"

F then introduces a theory which may explain how it works:
"One of the more ingenious theories, which is more satisfactory in many respects than the breaking-drop theory, is due to C. T. R. Wilson. We will describe it, as Wilson did, with reference to water drops, although the same phenomenon would also work with ice.

So this theory works with both water drops and ice:

Suppose we have a water drop that is falling in the electric field of about 100 volts per meter toward the negatively charged earth.

F says Wilson's theory explains how water droplets could be charged differently at the top and bottom of each drop:
"The drop will have an induced dipole moment—with the bottom of the drop positive and the top of the drop negative, as drawn in Fig. 9–13.

The falling differentially charged droplets interact with charged particles on their way down:

"Now there are in the air the “nuclei” that we mentioned earlier—the large slow-moving ions. (The fast ions do not have an important effect here.) Suppose that as a drop comes down, it approaches a large ion. If the ion is positive, it is repelled by the positive bottom of the drop and is pushed away. So it does not become attached to the drop. If the ion were to approach from the top, however, it might attach to the negative, top side. But since the drop is falling through the air, there is an air drift relative to it, going upwards, which carries the ions away if their motion through the air is slow enough. Thus the positive ions cannot attach at the top either. This would apply, you see, only to the large, slow-moving ions. The positive ions of this type will not attach themselves either to the front or the back of a falling drop.

On the other hand, as the large, slow, negative ions are approached by a drop, they will be attracted and will be caught. The drop will acquire negative charge—the sign of the charge having been determined by the original potential difference on the entire earth—and we get the right sign.

Negative charge will be brought down to the bottom part of the cloud by the drops, and the positively charged ions which are left behind will be blown to the top of the cloud by the various updraft currents. The theory looks pretty good, and it at least gives the right sign. Also it doesn’t depend on having liquid drops. We will see, when we learn about polarization in a dielectric, that pieces of ice will do the same thing. They also will develop positive and negative charges on their extremities when they are in an electric field."

In his lecture he first establishes there is a charge field in the air, increasing voltage with altitude at 100V/m:
jimmcginn wrote:It's not clear here whether Feynman is assuming that the rise of the moist air is a consequence of the electric field or convection.

F goes into considerable depth about the mechanisms that influence both rising and falling currents of moist air in a thundercloud 'cell'
F first lays the groundwork describing how the different components involved interact with each other, ions, nuclei, ie dust, salt, water and cosmic rays interact...

He talks about electrical **currents in the atmosphere:
"Another thing that can be measured, in addition to the potential gradient, is the current in the atmosphere. The current density is small—about 10 micromicroamperes crosses each square meter parallel to the earth. The air is evidently not a perfect insulator.."

"...and because of this conductivity, a small current—caused by the electric field we have just been describing—passes from the sky down to the earth.

Feynman establishes the electric currents move between sky and ground, and then the how and why:

"Why does the atmosphere have conductivity? Here and there among the air molecules there is an ion—a molecule of oxygen, say, which has acquired an extra electron, or perhaps lost one."

Here Feynman seems to be agreeing with your proposal that droplets of water are not single molecules:

"These ions do not stay as single molecules; because of their electric field they usually accumulate a few other molecules around them."

"Each ion then becomes a little lump which, along with other lumps, drifts in the [electric gradient] field—moving slowly upward or downward—making the observed current."

"Where do the ions come from? It was first guessed that the ions were produced by the radioactivity of the earth. (It was known that the radiation from radioactive materials would make air conducting by ionizing the air molecules.) Particles like β-rays coming out of the atomic nuclei are moving so fast that they tear electrons from the atoms, leaving ions behind."


Feynman describes how the ions were found to be created by cosmic rays and not earth bound radioactive decay:

"This was a most mysterious result—the most dramatic finding in the entire history of atmospheric electricity. It was so dramatic, in fact, that it required a branching off of an entirely new subject—cosmic rays. Atmospheric electricity itself remained less dramatic. Ionization was evidently being produced by something from outside the earth; the investigation of this source led to the discovery of the cosmic rays. We will not discuss the subject of cosmic rays now, except to say that they maintain the supply of ions. Although the ions are being swept away all the time, new ones are being created by the cosmic-ray particles coming from the outside. "

Feynman is saying there are many tiny things floating in the air, up or down depending on charge and weight:

"To be precise, we must say that besides the ions made of molecules, there are also other kinds of ions. Tiny pieces of dirt, like extremely fine bits of dust, float in the air and become charged. They are sometimes called “nuclei.”

"For example, when a wave breaks in the sea, little bits of spray are thrown into the air. When one of these drops evaporates, it leaves an infinitesimal crystal of NaCl floating in the air. These tiny crystals can then pick up charges and become ions; they are called “large ions.”

So we have large ions and small ions, that have picked up greater or smaller charges,
They move through the air with different speeds:

"The small ions—those formed by cosmic rays—are the most mobile. Because they are so small, they move rapidly through the air—with a speed of about 1 cm/sec in a field of 100 volts/meter, or 1 volt/cm."

The big ions steal charge from the small ions, works just like economics:

The much bigger and heavier ions move much more slowly. It turns out that if there are many “nuclei,” they will pick up the charges from the small ions.

The size of the ions affects conductivity:

"Then, since the “large ions” move so slowly in a field, the total conductivity is reduced. The conductivity of air, therefore, is quite variable, since it is very sensitive to the amount of “dirt” there is in it."

"There is much more of such dirt over land—where the winds can blow up dust or where man throws all kinds of pollution into the air—than there is over water. It is not surprising that from day to day, from moment to moment, from place to place, the conductivity near the earth’s surface varies enormously."

The voltage gradient F talked about is affected by this conductivity,
So the conductivity affects the voltage, they affect each other:

"The voltage gradient observed at any particular place on the earth’s surface also varies greatly because roughly the same current flows down from high altitudes in different places, and the varying conductivity near the earth results in a varying voltage gradient."

F goes on to give the standard explanation of why the moist air rises, later he will qualify further:

"On the other hand, if we think of a parcel of air that contains a lot of water vapor being carried up into the air, its adiabatic cooling curve will be different. As it expands and cools, the water vapor in it will condense, and the condensing water will liberate heat. Moist air, therefore, does not cool nearly as much as dry air does. So if air that is wetter than the average starts to rise, its temperature will follow a curve like (c) in Fig. 9–8. It will cool off somewhat,..."

"....but will still be warmer than the surrounding air at the same level...."

"... If we have a region of warm moist air and something starts it rising, it will always find itself lighter and warmer than the air around it and will continue to rise until it gets to enormous heights..."

"This is the machinery that makes the air in the thunderstorm cell rise."
sketch1946
 
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Re: The Real Reason Moist Air Reduces Aerodynamic Lift

Unread postby jimmcginn » Mon Mar 20, 2017 9:43 am

sketch1946 wrote:Hi Jimmy,
jimmcginn wrote:One criticism I have of Feynman is that his understanding of water is rather amateurish. I see no understanding of H2O polarity and he does not appear to be concerned about water's many anomalies.

Feynman does make a lot of comments about water and charge in the atmosphere:
He does discuss polarity of water droplets, did you miss it?

I can't find it. But I've read this previously and I remember being disappointed that he didn't--as best as I recall--discuss the underlying basis of Polarity. It seems he just assumed the mistaken notion that polarity is a constant--as does everybody else, except me:
viewtopic.php?f=10&t=16582#p117061

sketch1946 wrote:I guess it's a long page with a lot of stuff in there....
He mentions water 33 times, and the eighteenth time he says:

" ...it does show the effect of an electric field on water drops. We say that it may be irrelevant because it relates to an experiment one can do in the laboratory with a stream of water to show the rather strong effects of the electric field on drops of water."

"With a weak electric field you will find that the stream breaks up into a smaller number of large-sized drops. But if you apply a stronger field, the stream breaks up into many, many fine drops—smaller than before. With a weak electric field there is a tendency to inhibit the breakup of the stream into drops. With a stronger field, however, there is an increase in the tendency to separate into drops."

"The explanation of these effects is probably the following. If we have the stream of water coming out of the nozzle and we put a small electric field across it one side of the water gets slightly positive and the other side gets slightly negative. Then, when the stream breaks, the drops on one side may be positive, and those on the other side may be negative. They will attract each other and will have a tendency to stick together more than they would have before—the stream doesn’t break up as much. On the other hand, if the field is stronger, the charge in each one of the drops gets much larger, and there is a tendency for the charge itself to help break up the drops through their own repulsion.

Each drop will break into many smaller ones, each carrying a charge, so that they are all repelled, and spread out so rapidly. So as we increase the field, the stream becomes more finely separated. The only point we wish to make is that in certain circumstances electric fields can have considerable influence on the drops."

This is VERY interesting! But it sure does create problems for measurement. I wonder how pervasive and how persistent is this electric field. Is there any way to eliminate or suspend its effects on microdroplets? If not then it will be impossible to detect these microdroplets by weighing them.
sketch1946 wrote:"Somebody discovered that if you have a drop of water that breaks into two pieces in a windstream, there is positive charge on the water and negative charge in the air. This breaking-drop theory has several disadvantages, among which the most serious is that the sign is wrong."

I don't know what he means here.

Another common misconception I see is that people tend to assume that H2O must be ionic if it is to be effected by an electric field. If H2O can become ionic (which I doubt) I think it is rare. But what people really don't get is that H2O does not have to be ionic to he electromagnetically active. H2O just has to have broken H bonds, which are plentiful along its surface--this being the basis of "surface tension"--to be electromagnetically active.

It does not appear that Feynman comprehended this.

sketch1946 wrote:F wants to show that the top of the thundercloud should be positively charged, so positive charged droplets of water would have the wrong charge and would be propelled downwards...

F says if we could find a mechanism for water droplets to be charged differently at the top and bottom of a single drop, we would have a new theory....
"....if we could imagine some way for the charge to be different at the top and bottom of a drop and if we could also see some reason why drops in a high-speed airstream would break up into unequal pieces—a large one in the front and a smaller one in the back because of the motion through the air or something—we would have a theory. (Different from any known theory!)"

A very provocative statement. I don't know about a difference in charge from top to bottom of a raindrop but I know for a fact that there is a difference in charge between the internal body of a microdroplet and its surface. And, as I've explicated, this certainly does result in a theory that is, to quote Feynman, "Different from any known theory!"

sketch1946 wrote:F then introduces a theory which may explain how it works:
"One of the more ingenious theories, which is more satisfactory in many respects than the breaking-drop theory, is due to C. T. R. Wilson. We will describe it, as Wilson did, with reference to water drops, although the same phenomenon would also work with ice.
So this theory works with both water drops and ice:

Suppose we have a water drop that is falling in the electric field of about 100 volts per meter toward the negatively charged earth.

F says Wilson's theory explains how water droplets could be charged differently at the top and bottom of each drop:
"The drop will have an induced dipole moment—with the bottom of the drop positive and the top of the drop negative, as drawn in Fig. 9–13.

The falling differentially charged droplets interact with charged particles on their way down:

"Now there are in the air the “nuclei” that we mentioned earlier—the large slow-moving ions. (The fast ions do not have an important effect here.) Suppose that as a drop comes down, it approaches a large ion. If the ion is positive, it is repelled by the positive bottom of the drop and is pushed away. So it does not become attached to the drop. If the ion were to approach from the top, however, it might attach to the negative, top side. But since the drop is falling through the air, there is an air drift relative to it, going upwards, which carries the ions away if their motion through the air is slow enough. Thus the positive ions cannot attach at the top either. This would apply, you see, only to the large, slow-moving ions. The positive ions of this type will not attach themselves either to the front or the back of a falling drop.

On the other hand, as the large, slow, negative ions are approached by a drop, they will be attracted and will be caught. The drop will acquire negative charge—the sign of the charge having been determined by the original potential difference on the entire earth—and we get the right sign.

Negative charge will be brought down to the bottom part of the cloud by the drops, and the positively charged ions which are left behind will be blown to the top of the cloud by the various updraft currents. The theory looks pretty good, and it at least gives the right sign. Also it doesn’t depend on having liquid drops. We will see, when we learn about polarization in a dielectric, that pieces of ice will do the same thing. They also will develop positive and negative charges on their extremities when they are in an electric field."

In his lecture he first establishes there is a charge field in the air, increasing voltage with altitude at 100V/m:
jimmcginn wrote:It's not clear here whether Feynman is assuming that the rise of the moist air is a consequence of the electric field or convection.

F goes into considerable depth about the mechanisms that influence both rising and falling currents of moist air in a thundercloud 'cell'
F first lays the groundwork describing how the different components involved interact with each other, ions, nuclei, ie dust, salt, water and cosmic rays interact...

He talks about electrical **currents in the atmosphere:
"Another thing that can be measured, in addition to the potential gradient, is the current in the atmosphere. The current density is small—about 10 micromicroamperes crosses each square meter parallel to the earth. The air is evidently not a perfect insulator.."

"...and because of this conductivity, a small current—caused by the electric field we have just been describing—passes from the sky down to the earth.

Feynman establishes the electric currents move between sky and ground, and then the how and why:

"Why does the atmosphere have conductivity? Here and there among the air molecules there is an ion—a molecule of oxygen, say, which has acquired an extra electron, or perhaps lost one."

Here Feynman seems to be agreeing with your proposal that droplets of water are not single molecules:

"These ions do not stay as single molecules; because of their electric field they usually accumulate a few other molecules around them."

Okay, but his wording suggests that he is assuming that they start out as single molecules (presumably upon evaporation) and my theory says this is impossible.

Whatever the case, thanks for posting this. It's great to see the sharp contrast in approach from how a real theoretical scientist approaches this topic in contrast to the brain-dead, wishy washy, (sweep all contradictions under the rug) that we get from the pretentious meteorological lobby.

I think we all can learn from the fact that Feynman is not concerned about being wrong. He doesn't pretend to have it all figured out. Nor is he the slightest bit embarrassed or defensive about this.

Thanks again for posting this.

James McGinn / Solving Tornadoes
jimmcginn
 
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