I have no idea why your video series doesn't have more comments. It is a brilliant and easy-to-understand way of explaining the many interacting aspects of lift. I enjoyed it and learned some things and I know other people will too. Please keep making videos. Thank you.
I think it would be most helpful to start the series at 1:27, because it is the most simple and fundamental view of things. Then maybe wing design. And then finally dive into the advanced topics of Bernoulli and Coanda to explain why the different designs behave differently.
If we take a highly cambered very thin wing, the curve on the upper surface is exactly the same as the lower surface and it still lifts. Bernoulli needs to be questioned in this case. A fluid has both Newtonian and Viscous effects and the mass of air particles is forced to basically ACCELERATE vertically up and down when a moving wing displaces the initially stationary fluid particles, laterally. A wing lifts because it has four principal zones which process the air mass fluid particles accordingly, and these are better viewed on a highly cambered very thin airfoil 1. A compression zone just ahead and above the wedge-shaped, moving leading edge of the wing, which reacts on a stationary fluid particle to accelerate it, in a basically upwards direction, just like a wedge-shaped moving golf club hits a stationary golf ball, to give it a high vertically up momentum, eventually. 2. A suction zone midway all the way to the trailing edge on the upper surface. This is brought about by action 1, causing the upwards moving fluid particle to leave a suction zone behind it, which will slow it down and in return, the suction zone will accelerate up, or lift the upper surface of the wing. Any fluid particles above the upper surface, coming later on, will fly into a suction zone ahead and so the fluid particle will not only move up and down but will be displaced towards the trailing edge to be dumped behind the trailing edge. 3. A suction zone under the leading edge that will suck up the fluid particles towards the leading edge. 4. A compression zone all the way further back under the leading edge, will accelerate fluid particles basically vertically down which will react in pushing the wing vertically up. The compression zone moving under with the fast wing will displace the stationary fluid particles under the wing, towards the leading edge. These four zones are diminished or accentuated in different airfoils to fit the purpose of the wing and its speed all the way to supersonic airfoils. They all have in common the four zones mentioned. Note, to simplify the procedure, we only considered the up and down acceleration of the fluid mass particles which will produce lift. Also with the stationary fluid particles and a moving wing combination, the displacement towards the trailing edge of the upper surface particles and the displacement of the underwing fluid particles towards the leading edge was described. This displacement effect in a wind tunnel, where the air moves and the wing is stationary, this relativity, will be seen as the velocity of air above the wing being higher than the velocity of fluid under the wing, and particles starting at the same time will never finish at the trailing edge together in synchronism. So much for Bernoulli!! In real life, the initially stationary particles, ahead of a moving wing, later, have a slight horizontal acceleration and this is what gives the effect of drag on a wing. When dealing with a real moving wing, we must stop talking about the fluid air mass particles moving with such high velocity on the upper and lower surface of the wing, as we do in a wind tunnel. It is the summation "acceleration effect" of the inertia of the rest and motion of the horizontally adjacent, different lumps of heavy fluid particles that are momentarily accelerated/decelerated upwards and downwards, and then dumped vertically down. This helps a wing get its lift. Since the processing of fluid air around the wing, using the four primary zones as described above, does result in the acceleration vectors having a high downward component and a slight horizontal component, then we have to accept a compromise between lift and drag. In good gliders, this can be as high as 70 :1 Note the importance of the fluid having a "viscous" sealing effect between the mass particles as they are processed or operated upon, in suction or compression zones around the wing, for, if instead, we are dealing with, individual, unconnected dry grains of sand or individual and unconnected pebbles, having masses but no, connecting sealing/ sticky/sliding/shearing effect between them, the fluid will not form an instantaneous impervious heavy flexible membrane with inertia properties, and so, with individual, unconnected, dry, sand particles, as the working fluid, a wing will not lift. I did submit another varied comment on this subject of lift, seen in, Part 1 Lift and Bernoulli's principle.
Part #3: I am very pleased to see that you correctly identified the difference in Bernoulli Constant that makes the very common analysis wrong, both Bernoulli-wise and mathematically. However, you do not address why it is a reasonable assumption. Bernoulli deals with accelerations along a flow of fluid not differences in speed between unrelated flows... ... The Wright's wings used the very same funtamental principles in physics as *_ALL_* other wings. It is the path of the airflow that is important and the true focus, not simply the wing shape. This is why the "longer Path" of the wing upper surface argument is still a false focus. It is a known fact that the upper camber is something that has a large part in *reducing* drag. ALL wings produce quite similar pressure differences and, therefore, similar lift forces *_AND_* air flows (accelerations). ALL OF THEM DO. The same pressure gradients you show in Part 2 are correct for all wings producing lift; flat, inverted, symmetric, curved --- even boat sails and boat keels. The true fundamentsl science is the same for all of them. There are only differences in magnitudes in various places for the different wing types. ... Finally, It is easily shown that the true science is that the air that passes over a wing is *_not faster_* than the lower air and, therfore, claiming that it has a lower pressure due to its higher speed per Bernlulli is just plain *false science*. That view is because you are traveling along with the wing. The wing is actually traveling in still air. *_Actual data_* shows that the air above a wing is moved forward only a little by the passing wing (it is josseled around a bit to get up and over the top, but it winds up moving mostly downward behind the wing) and the air under the wing is moved along by the wing much, much more, as the wing moves by (also winding up moving mostly downward). If the lower air is moved a longer distance in the same time, it *_IS_* faster. Yes, Standing and watching an actual wing go by shows us that it is the lower air that is faster, by a large margin. Bernoulli is about accelerations, not absolute speeds. The accelerations are not dependent on the frame of reference, but speeds are, so "speed" can not be used as a criteria. The only correct conclusion being that Bernoulli CANNOT be used to compare the upper and lower air because the "speeds" are not as described! ... If you send me a direct message, I can provide a link to the information showing air *_measured_* motions as a wing passes by. It is from a real wing in real air. -- Regards, ScienceAdvisorSteve www.challengerillinois.org
The above wing reduction gives folks the most trouble. For a better understanding of the detailed cause of the reduced pressure above a wing, try this very short video that I had my 11 yo granddaughter do the editing for: th-cam.com/video/3MSqbnbKDmM/w-d-xo.html Regards.
Because outside the boundary layer where there are no viscous effects, and gravity's effect on the fluid is being ignored (no pgh term), then these streamlines both started in the same freestream conditions where those C's are equal, hence they will still be valid throughout the flow.
@@aerospacedoctorI wanted to see if the owner could answer the question with more complete justification. This is something I discussed with Charles Eastlake because of his paper addressing this. as well as how the lift can be calculated based on it or by the momentum change around a wing. People throw videos up then ignore them. . .
@@Observ45erSteve (if I remember correctly) sorry, reflex reply. How are you? Sadly even Prandtl in the report translated by NASA in 1921 showed you can't calculate the lift as an exclusive momentum transfer, and as a result you also can't do an experiment and measure it. This was explained by Doug McLean and I think he included it in the Wikipedia article on lift towards the end. It is sad when videos are left unattended. Where did we get to in our emails? I will have a look.
@@aerospacedoctor Prandtl ... 1921. . . . Talk with Charles Eastlake in the present, as I did, about his paper and calculations he has done {we have computers these days} and the work he did in the field. . Also, you can talk with McLean about why he says he is not pleased with his explanation. . . Even NASA has astronauts claiming that air out of a blower has pressure lower than ambient and demonstrating it in a classically flawed video demo on the ISS. . NASA also aparently contracted with some outsiders to publish faulty physics in their Museum-in-a-Box series. . . .I hope you and yours are well. . Right now our biggest problem is getting the end started on a fresh toilet paper roll. This is a busy time of year for us and a quite troubling time in general. - - Cheers.
They are not. The above wing reduction gives folks the most trouble. For a better understanding of the detailed cause of the reduced pressure above a wing, try this very short video that I had my 11 yo granddaughter do the editing for: th-cam.com/video/3MSqbnbKDmM/w-d-xo.html Regards.
I have no idea why your video series doesn't have more comments. It is a brilliant and easy-to-understand way of explaining the many interacting aspects of lift. I enjoyed it and learned some things and I know other people will too. Please keep making videos. Thank you.
I think it would be most helpful to start the series at 1:27, because it is the most simple and fundamental view of things. Then maybe wing design. And then finally dive into the advanced topics of Bernoulli and Coanda to explain why the different designs behave differently.
If we take a highly cambered very thin wing, the curve on the upper surface is exactly the same as the lower surface and it still lifts. Bernoulli needs to be questioned in this case. A fluid has both Newtonian and Viscous effects and the mass of air particles is forced to basically ACCELERATE vertically up and down when a moving wing displaces the initially stationary fluid particles, laterally.
A wing lifts because it has four principal zones which process the air mass fluid particles accordingly, and these are better viewed on a highly cambered very thin airfoil
1. A compression zone just ahead and above the wedge-shaped, moving leading edge of the wing, which reacts on a stationary fluid particle to accelerate it, in a basically upwards direction, just like a wedge-shaped moving golf club hits a stationary golf ball, to give it a high vertically up momentum, eventually.
2. A suction zone midway all the way to the trailing edge on the upper surface. This is brought about by action 1, causing the upwards moving fluid particle to leave a suction zone behind it, which will slow it down and in return, the suction zone will accelerate up, or lift the upper surface of the wing. Any fluid particles above the upper surface, coming later on, will fly into a suction zone ahead and so the fluid particle will not only move up and down but will be displaced towards the trailing edge to be dumped behind the trailing edge.
3. A suction zone under the leading edge that will suck up the fluid particles towards the leading edge.
4. A compression zone all the way further back under the leading edge, will accelerate fluid particles basically vertically down which will react in pushing the wing vertically up. The compression zone moving under with the fast wing will displace the stationary fluid particles under the wing, towards the leading edge.
These four zones are diminished or accentuated in different airfoils to fit the purpose of the wing and its speed all the way to supersonic airfoils. They all have in common the four zones mentioned.
Note, to simplify the procedure, we only considered the up and down acceleration of the fluid mass particles which will produce lift.
Also with the stationary fluid particles and a moving wing combination, the displacement towards the trailing edge of the upper surface particles and the displacement of the underwing fluid particles towards the leading edge was described. This displacement effect in a wind tunnel, where the air moves and the wing is stationary, this relativity, will be seen as the velocity of air above the wing being higher than the velocity of fluid under the wing, and particles starting at the same time will never finish at the trailing edge together in synchronism. So much for Bernoulli!!
In real life, the initially stationary particles, ahead of a moving wing, later, have a slight horizontal acceleration and this is what gives the effect of drag on a wing.
When dealing with a real moving wing, we must stop talking about the fluid air mass particles moving with such high velocity on the upper and lower surface of the wing, as we do in a wind tunnel. It is the summation "acceleration effect" of the inertia of the rest and motion of the horizontally adjacent, different lumps of heavy fluid particles that are momentarily accelerated/decelerated upwards and downwards, and then dumped vertically down. This helps a wing get its lift. Since the processing of fluid air around the wing, using the four primary zones as described above, does result in the acceleration vectors having a high downward component and a slight horizontal component, then we have to accept a compromise between lift and drag. In good gliders, this can be as high as 70 :1 Note the importance of the fluid having a "viscous" sealing effect between the mass particles as they are processed or operated upon, in suction or compression zones around the wing, for, if instead, we are dealing with, individual, unconnected dry grains of sand or individual and unconnected pebbles, having masses but no, connecting sealing/ sticky/sliding/shearing effect between them, the fluid will not form an instantaneous impervious heavy flexible membrane with inertia properties, and so, with individual, unconnected, dry, sand particles, as the working fluid, a wing will not lift.
I did submit another varied comment on this subject of lift, seen in, Part 1 Lift and Bernoulli's principle.
Enjoyed your video series on this subject!
OOPS! Forgot to mention... The Wright Brother's wings WERE CURVED. They looked more like a sail boat sail.
Bravo!
Part #3:
I am very pleased to see that you correctly identified the difference in Bernoulli Constant that makes the very common analysis wrong, both Bernoulli-wise and mathematically.
However, you do not address why it is a reasonable assumption. Bernoulli deals with accelerations along a flow of fluid not differences in speed between unrelated flows...
...
The Wright's wings used the very same funtamental principles in physics as *_ALL_* other wings. It is the path of the airflow that is important and the true focus, not simply the wing shape. This is why the "longer Path" of the wing upper surface argument is still a false focus.
It is a known fact that the upper camber is something that has a large part in *reducing* drag. ALL wings produce quite similar pressure differences and, therefore, similar lift forces *_AND_* air flows (accelerations). ALL OF THEM DO.
The same pressure gradients you show in Part 2 are correct for all wings producing lift; flat, inverted, symmetric, curved --- even boat sails and boat keels. The true fundamentsl science is the same for all of them. There are only differences in magnitudes in various places for the different wing types.
...
Finally, It is easily shown that the true science is that the air that passes over a wing is *_not faster_* than the lower air and, therfore, claiming that it has a lower pressure due to its higher speed per Bernlulli is just plain *false science*. That view is because you are traveling along with the wing. The wing is actually traveling in still air.
*_Actual data_* shows that the air above a wing is moved forward only a little by the passing wing (it is josseled around a bit to get up and over the top, but it winds up moving mostly downward behind the wing) and the air under the wing is moved along by the wing much, much more, as the wing moves by (also winding up moving mostly downward).
If the lower air is moved a longer distance in the same time, it *_IS_* faster. Yes, Standing and watching an actual wing go by shows us that it is the lower air that is faster, by a large margin.
Bernoulli is about accelerations, not absolute speeds. The accelerations are not dependent on the frame of reference, but speeds are, so "speed" can not be used as a criteria.
The only correct conclusion being that Bernoulli CANNOT be used to compare the upper and lower air because the "speeds" are not as described!
...
If you send me a direct message, I can provide a link to the information showing air *_measured_* motions as a wing passes by. It is from a real wing in real air.
--
Regards, ScienceAdvisorSteve
www.challengerillinois.org
Doesn’t Bernoulli apply to molecules along the same stream…? The streams in your diagram are not related.
Excellent video thanks a lot!
very nice
But y the pr above the wing is less than below it?
The above wing reduction gives folks the most trouble. For a better understanding of the detailed cause of the reduced pressure above a wing, try this very short video that I had my 11 yo granddaughter do the editing for:
th-cam.com/video/3MSqbnbKDmM/w-d-xo.html
Regards.
@ 1:20, but WHY it is a fair assumption? Can you justify that?
Because outside the boundary layer where there are no viscous effects, and gravity's effect on the fluid is being ignored (no pgh term), then these streamlines both started in the same freestream conditions where those C's are equal, hence they will still be valid throughout the flow.
@@aerospacedoctorI wanted to see if the owner could answer the question with more complete justification. This is something I discussed with Charles Eastlake because of his paper addressing this. as well as how the lift can be calculated based on it or by the momentum change around a wing.
People throw videos up then ignore them. . .
@@Observ45erSteve (if I remember correctly) sorry, reflex reply. How are you?
Sadly even Prandtl in the report translated by NASA in 1921 showed you can't calculate the lift as an exclusive momentum transfer, and as a result you also can't do an experiment and measure it. This was explained by Doug McLean and I think he included it in the Wikipedia article on lift towards the end.
It is sad when videos are left unattended.
Where did we get to in our emails? I will have a look.
@@aerospacedoctor
Prandtl ... 1921. . .
.
Talk with Charles Eastlake in the present, as I did, about his paper and calculations he has done {we have computers these days} and the work he did in the field.
.
Also, you can talk with McLean about why he says he is not pleased with his explanation.
. .
Even NASA has astronauts claiming that air out of a blower has pressure lower than ambient and demonstrating it in a classically flawed video demo on the ISS.
.
NASA also aparently contracted with some outsiders to publish faulty physics in their Museum-in-a-Box series. .
.
.I hope you and yours are well.
.
Right now our biggest problem is getting the end started on a fresh toilet paper roll.
This is a busy time of year for us and a quite troubling time in general.
- -
Cheers.
I thought the Bernoulli principal and Newton's law explain the same thing just in different ways
They are not.
The above wing reduction gives folks the most trouble. For a better understanding of the detailed cause of the reduced pressure above a wing, try this very short video that I had my 11 yo granddaughter do the editing for:
th-cam.com/video/3MSqbnbKDmM/w-d-xo.html
Regards.
.coanda effect on curve