why I speak of humid air, because the amount of humidity in the air creates a different mass in an equal volume, as a result, if at point A there is 50% humidity and at point B there is 55% humidity there is an imbalance, so naturally an equilibrium will be created by creating a displacement of air whatever the altitude.
I know the relationship between relative humidity, temperature and dewpoint. I still donât get the comparison with wind? You mean the stronger the pressure difference the stronger the geostrophic wind speed?
If we are trying to help people understand this subject, we need to be careful about the information we offer up.
In the top quote it would seem that a dry airmass is required to displace a humid one to get wind. Not sure if that is what you meant to say , but that is the way it reads.
You are correct when you say that wind does not move air. Wind is the measurement of, or perceived result of, an airmass moving across the earthâs surface. There are many things that will cause that airmass to move, but again you are correct that high pressure airmass will always move into a low pressure space.
The 2nd law of thermodynamics in its simplest form dictates that nature is always trying to find a balance. Water will always find level, high pressure will always fill up low pressure until the pressure balances. Temperature, humidity, density, if left in a closed system will eventually all even out. It is this entropy of fluids trying to achieve balance that contributes to airmasses moving around the globe.
Of course the globe is not a closed system, and as such there are many influencers on our atmosphere that keep it in motion. Not the least of which is drag. Drag is on of the most influential effects on airmasses that the pilot needs to deal with. I am not talking about drag on the airplane, but if you understand that concept, then imagine the drag between the atmosphere and the planet. This is what controls the difference between our surface winds and winds at altitude. It is one of the great contributors to unstable, turbulent flow of the airmasses.
If I had to pick one âmodelâ that we need to have fixed to be able to feel flight âas real as it getsâ, it would be that atmospheric model that governs the medium that we fly in.
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All nice and fun but this is not the main force causing wind.
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I donât think you understand everything about physics.
Anyway, it doesnât matter, you are a pilot, I am not. I may be wrong, but when I write it, in a language that is not mine, it is too complicated for me to try to explain it to you, it is a very interesting debate that is the basis of aviation, of why the plane flies. Finally you have your knowledge, I have mine, too bad we canât talk about it in person, Iâm sure you would teach me a lot, I like to say stupid things and to be corrected to learn more.
Iâm sorry but your explanation about how lift is created is completely wrong, with a basic understanding of physics thats clear as day.
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Not much else to sayâŠbut your statement âyou have your knowledge, I have mineâ doesnât fit.
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Building RC models and designing experimental airfoils for them, I found a really easy way to calculate lift. It involves a pickup truck, a long straight piece of quiet highway, an airfoil and two fish scales.
@willisxdc
@PZL104
@anon50268670
Not serious friends, as I said you are pilots, you know how to fly a plane, something I donât know how to do, Iâm not and unfortunately never will be, and as you are a pilot, you know, what is normal, why your plane flies, as well as the mechanics of the air, so Iâll bow and be done with it for this topic 'but not for the topic 
This has nothing to do with being a pilot.
You would be surprised how little some pilots know about aerodynamics.
Iâm pretty sure that there are even real pilots who would support your theory.
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Indeed, you are right, I speak about pilot because it seems to me that you are all three pilot, BUT it is true that, to be pilot does not necessarily mean, to understand something to the physics or to know how his plane or thought to know how and this mistake what does not make a bad pilot.
you may be three against me, but I know Iâm right, or maybe Iâm being misunderstood by the wrong translation and we all agree, hard to say. 
Nobody is against anybody but the equal time theory for explaining lift is plain wrong. You could even look up wind tunnel footage on Youtube and see for yourself.
Around 30 seconds into the video you can observe the air on top of the wing moving way faster, therefore not meeting up with the airflow from below the airfoil. Disproving the equal transit time theory.
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Itâs neither a translation problem, nor is it a misunderstanding.
You are simply supporting one of the common false theories.
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I think we are losing a bit of your explanations through translation, and, as I have been guilty of here before, It is not good to try to generalize or over simplify an explanation as it will likely by misinterpreted.
I followed some of your lift explanation and some of it (high pressure vs low pressure) are in effect correct but much of what generates those pressure differences is not well defined in your explanation.
This is also reflected in your âwindâ explanation. It is possible to have two areas of different pressure that have the same amount of moisture content. Based on your description, or our interpretation of it, this condition would result in calm air between the cells, and this is incorrect.
It is not three against one. It is more four people trying to demonstrate entropy and all end up at the same place with the same understanding.
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I understand better your explanations and contradiction now after seeing this video
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I invite you to watch these videos, I do not know if you understand French, but in your opinion by what phenomenon and why the air accelerates above the wing?
explanation for children, I think that if you donât speak French you should understand
your second video totally demonstrates my theory, lol.
There are two competing theories:
One is a combination of the continuity law and Bernoulli principle, the other is Newtons 3rd law.
According the first theory A x V = C (continuity law), so if the cross section (area) is halved the speed doubles and vice versa. This explains why speed of the airflow changes when flowing through a Venturi tube.
Bernoulli then explains the relationship between speed and pressure for a subsonic airflow: Ps + Pd = C. If dynamic pressure (speed) increases, static pressure decreases.
Due to the shape and angle of the wing, top of the wing is basically causing a Venturi while the lower side of the wing leaves the airflow below the wing more or less unaffected. The continuity law explains why speed increases, Bernoulli explains why that results in a lower pressure on top of the wing.
The second theory simply states that the air on top of the wing is deflected downwards (downwash), this would create an equal and opposite reaction which we know as lift.
No it doesnât, you can clearly see the air on top of the wing is moving way faster and doesnât meet up with the airflow below the wing. The equal transit time theory has been busted over and over. The theory might be used to explain little children how airplanes fly but its not correct. See below:
your shot is not good i did mine, look carefully at what the air does in direct contact with the wing! the image rate is too low and lacks a reference point to verify my theory. I think weâll disagree on the why and how. I donât know what your real level of understanding of mechanics, physics, or just a factual reading follow-up is, but, even if you are a fan of everything, there are so many divergent theories, that everyone agrees with their own.
