Airfoil Design
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- Опубликовано: 14 июл 2024
- When looking at a typical airfoil, such as a wing, from the side, several design characteristics become obvious. You can see that there is a difference in the curvatures (or camber) of the upper and lower surfaces of the wing. The camber of the upper surface is more pronounced than lower surface, which is usually somewhat flat.
The chord line is a reference line drawn from the center of the leading edge straight through the wing to the trailing edge. The distance from this chord line to the upper and lower surfaces of the wing shows the amount of upper and lower camber at any point. Another reference line, drawn from the leading edge to the trailing edge, is the mean camber line. This mean line is equidistant at all points from the upper and lower surfaces.
Different airfoils have different flight characteristics. The weight, speed, and purpose of each aircraft dictate the shape of its airfoil. The most efficient airfoil for producing the greatest lift is one that has a concave, or “scooped out” lower surface
On the other hand, an airfoil that is perfectly streamlined and offers little wind resistance sometimes does not have enough lifting power to take the airplane off the ground.
If the wing profile were in the shape of a teardrop, the speed and the pressure changes of the air passing over the top and bottom would be the same on both sides. But if the teardrop shaped wing were cut in half lengthwise, a form resembling the familiar wing section would result
The pressure difference between the upper and lower surface of a wing alone, does not account for the total lift force produced.
The downward and backward flow of air from the top surface of a wing creates a downwash. This downwash meets the flow from the bottom of the wing at the trailing edge. Applying Newton’s third law, the reaction of this downward backward flow results in an upward forward force on the wing.
Lift is also generated by pressure conditions underneath the airfoil. Because of the manner in which air flows underneath the airfoil, a positive or high pressure results.
The angle of attack of a wing is the angle between the chord line and the flow of air against the leading edge of the wing
The average of the pressure variation for any given angle of attack is referred to as the center of pressure, noted as CP. All aerodynamic force acts through the Center of Pressure. At high angles of attack, the Center of Pressure moves forward, while at low angles of attack the Center of Pressure moves aft.
This Center of Pressure travel is very important, since an airplane’s aerodynamic balance and controllability are governed by changes in the Center of Pressure.
The production of lift is much more complex than a simple differential pressure between upper and lower wing surfaces. In fact, many airfoils do not have an upper surface longer than the bottom. These are called symmetrical airfoils. Symmetrical airfoils are seen in high-speed aircraft having symmetrical wings, or on symmetrical rotor blades for many helicopters whose upper and lower surfaces are identical. With symmetrical airfoils, the relationship of the airfoil with the oncoming air stream, or angle of attack, is all that is different.
As a wing moves through air, it is inclined upward against the airflow, producing a different flow caused by the wing’s relationship to the oncoming air. Think of a hand being placed outside the car window at a high speed. If the hand is inclined in one direction or another, the hand will move upward or downward. This is caused by deflection, which in turn causes the air to turn about the object within the air stream. As a result of this change, the velocity about the object changes in both magnitude and direction, in turn resulting in a measurable velocity force and direction.
So far we have only focused on the air flow across the upper and lower surfaces of an airfoil. While most of the lift is produced by these two dimensions, a third dimension, the tip of the wing also has an aerodynamic effect. The high-pressure area on the bottom of an airfoil pushes around the tip to the low-pressure area on the top. This action creates a rotating flow called a wing tip vortex. The vortex flows behind the airfoil creating a downwash that extends back to the trailing edge of the airfoil. This downwash results in an overall reduction in lift for the affected portion of the wing.
Airplane manufacturers have developed different methods to counteract this action. Winglets can be added to the tip of an airfoil to reduce this flow. The winglets act as a dam preventing the vortex from forming. Winglets can be on the top or bottom of the airfoil. Another method of countering the flow is to taper the airfoil tip, reducing the pressure differential and smoothing the airflow around the tip.
Adapted from the Pilot's Handbook of Aeronautical Knowledge.
I've been looking all over RUclips and this is the only video I got that explains everything my instructor says in an equally relatable way.. God Bless
@joe jitsu Yep.
This video only repeats very common misconceptions and invents a new one, as follows.
.
3:13 The low pressure above the wing allows higher pressure ahead of the wing to accelerate it to the higher speed. It is Newton. The force of pressure accelerates the mass of air.
The movement of the wing creates pressure gradients and as Euler reported to us in the mid 1700s, Pressure gradients accelerate fluids.
Bernoulli never said speed causes a pressure reduction. He only noted that the (static) pressure and velocity have an inverse relationship with no indication of cause and effect. This is a major, common misunderstanding.
Euler determined that pressure gradients accelerate fluids toward the lower pressure. That is the opposite of the common misconception.
...
3:29 The pressure difference top to bottom accounts for ALL THE LIFT. This 'a little of this and a little of that" is bad science. The same pressures that have the net upward lift force on the wing are the very same pressures that cause all accelerations around the wing including ahead, above, below, behind and around the tips.
The higher pressure under the wing pushes up on the wing AND down on the air below to contribute to the down-wash.
The lower pressure above the wing allows atmospheric pressure to push air above the wing downward, to also contribute to the down-wash.
..
NOTE: the whole upward force on the wing is equal to the force required to accelerate all the air in the down-wash. THAT is what satisfies Newton's Third Law. The upward 'push" (force) on the wing equals the downward 'push' (force) on the air accelerated downward.
The downward moving air does not push up on the wing. That air was pushed down by the pressures around the wing.
The down-wash also does not push the wing forward. You've invented a new a fallacy. The net force fore-aft is rearward and is called drag and is not caused by the down-wash as explained above.
When viewed from the still air frame of reference, the down-wash is moving slightly forward.
....
4:27 Bernoulli's Principle is again misused. The flow is not slowed under the wing which is NOT the cause of the higher pressure. . That view is valid only in the stationary wing, wind tunnel reference frame only.
In fact, REAL data from a REAL wing generating REAL lift flying through otherwise still air shows the lower air being moved forward in the direction of flight. This acceleration from still air is CAUSED BY the higher pressure at the lower surface. The increase in pressure at the surface is because the wing is pushing the air out of its way. This push increases the pressure, not the Bernoulli Principle Fallacy.
....
The pressure increase below the wing in combination with the decrease above the wing provides the ENTIRE lift force.
...
If by this magic, the down-wash did just happen to add to the lift, that "addition" would be exhibited as an increased pressure difference on the win...but it DOES NOT.
Bernoulli's Principle causes nothing in the generation of lift because the "speed-causes-pressures" is a fallacy.
It is all explained by Newton, BUT NOT with this ":reaction force" fallacy.
Newton's Third Law "reaction force" is not an originating force, but is a direct result of the originating force which, in this case, is from the pressures around the wing as described above.
....
At 7:11 Please listen to your words: “The high pressure area on the bottom of an airfoil pushes around the tip to the low pressure area on the top.”. This shows that you understand that pressure causes movement, but you fail to apply it on all the other parts of this and, therefore shows the problems with this explanation. The correct story uses this Pressure accelerated air in ALL aspects around the wing, because that I the real science.
The tip vortex does not ‘create the down wash”. You already explained the down-wash without reference to the tip vortex. This is a flaw in this explanation. The tip vortex is CONSISTENT with the wing generated down-wash moving against the still air outside the wing span. Masses of air sliding along each other create vorticity (vortices) along the boundary of the two masses.
…
At 7:47 Winglets DO NOT and CANNOT prevent the tip vortex from forming. They can only reduce the severity and the negative effect because they act to effectively lengthen the wingspan; longer wings have less severe vortices . See Doug McLean’s You Tube video on misconceptions for a full explanation.
ruclips.net/video/QKCK4lJLQHU/видео.html
…
Though well-meaning, the 'Pilot's Handbook of Aeronautical Knowledge.' has bad information in it as do so many other publications and on-line resources such as RUclips.
You can play with the 2D wind tunnel tool in Designfoil to augment some of the principles in this video. It's a shareware app for PC's.
I discovered that Parasite drag is produced by VERTICAL surfaces and Induced drag is created by HORIZONTAL surfaces, for example when the Flaps are at 0 degrees they produce Max Induced drag and Min Parasite drag, at 90 degrees Min Induced and Max Parasite drag and at 45 degrees in the middle of both.
Please let me know if you think it is a valid observation. Thanks
This was EXTREMELY helpful. Thank you.
The existence of the wingtip vortex is a topological requirement and the only way to prevent it from forming is to reduce the angle of attack to the point where the wing is not generating any lift. Winglets are able to regulate the wingtip vortex, but not to eliminate it.
The vortex system of a wing is a ring vortex which passes through the boundary layers around the wing, along one trailing wingtip vortex, through the starting vortex left behind on the runway, and then back through the other wingtip vortex. Vorticity associated with the wing generates lift by the Magnus effect if you want a short explanation, or by the Kutta-Joukowski circulation theorem if you want more detail.
This video only repeats very common misconceptions and invents a new one, as follows.
.
3:13 The low pressure above the wing allows higher pressure ahead of the wing to accelerate it to the higher speed. It is Newton. The force of pressure accelerates the mass of air.
The movement of the wing creates pressure gradients and as Euler reported to us in the mid 1700s, Pressure gradients accelerate fluids.
Bernoulli never said speed causes a pressure reduction. He only noted that the (static) pressure and velocity have an inverse relationship with no indication of cause and effect. This is a major, common misunderstanding.
Euler determined that pressure gradients accelerate fluids toward the lower pressure. That is the opposite of the common misconception.
...
3:29 The pressure difference top to bottom accounts for ALL THE LIFT. This 'a little of this and a little of that" is bad science. The same pressures that have the net upward lift force on the wing are the very same pressures that cause all accelerations around the wing including ahead, above, below, behind and around the tips.
The higher pressure under the wing pushes up on the wing AND down on the air below to contribute to the down-wash.
The lower pressure above the wing allows atmospheric pressure to push air above the wing downward, to also contribute to the down-wash.
..
NOTE: the whole upward force on the wing is equal to the force required to accelerate all the air in the down-wash. THAT is what satisfies Newton's Third Law. The upward 'push" (force) on the wing equals the downward 'push' (force) on the air accelerated downward.
The downward moving air does not push up on the wing. That air was pushed down by the pressures around the wing.
The down-wash also does not push the wing forward. You've invented a new a fallacy. The net force fore-aft is rearward and is called drag and is not caused by the down-wash as explained above.
When viewed from the still air frame of reference, the down-wash is moving slightly forward.
....
4:27 Bernoulli's Principle is again misused. The flow is not slowed under the wing which is NOT the cause of the higher pressure. . That view is valid only in the stationary wing, wind tunnel reference frame only.
In fact, REAL data from a REAL wing generating REAL lift flying through otherwise still air shows the lower air being moved forward in the direction of flight. This acceleration from still air is CAUSED BY the higher pressure at the lower surface. The increase in pressure at the surface is because the wing is pushing the air out of its way. This push increases the pressure, not the Bernoulli Principle Fallacy.
....
The pressure increase below the wing in combination with the decrease above the wing provides the ENTIRE lift force.
...
If by this magic, the down-wash did just happen to add to the lift, that "addition" would be exhibited as an increased pressure difference on the win...but it DOES NOT.
Bernoulli's Principle causes nothing in the generation of lift because the "speed-causes-pressures" is a fallacy.
It is all explained by Newton, BUT NOT with this ":reaction force" fallacy.
Newton's Third Law "reaction force" is not an originating force, but is a direct result of the originating force which, in this case, is from the pressures around the wing as described above.
....
At 7:11 Please listen to your words: “The high pressure area on the bottom of an airfoil pushes around the tip to the low pressure area on the top.”. This shows that you understand that pressure causes movement, but you fail to apply it on all the other parts of this and, therefore shows the problems with this explanation. The correct story uses this Pressure accelerated air in ALL aspects around the wing, because that I the real science.
The tip vortex does not ‘create the down wash”. You already explained the down-wash without reference to the tip vortex. This is a flaw in this explanation. The tip vortex is CONSISTENT with the wing generated down-wash moving against the still air outside the wing span. Masses of air sliding along each other create vorticity (vortices) along the boundary of the two masses.
…
At 7:47 Winglets DO NOT and CANNOT prevent the tip vortex from forming. They can only reduce the severity and the negative effect because they act to effectively lengthen the wingspan; longer wings have less severe vortices . See Doug McLean’s You Tube video on misconceptions for a full explanation.
ruclips.net/video/QKCK4lJLQHU/видео.html
…
Though well-meaning, the 'Pilot's Handbook of Aeronautical Knowledge.' has bad information in it as do so many other publications and on-line resources such as RUclips.
duh, but u gay
well corrected, what is your references, please?
@@makantahi3731 RUclips doesn't appear to let me paste everything I want to. I read a few of the noted experts and I also contacted some of them and talked with them.
.
Understanding Aerodynamics: Arguing from the Real Physics. Doug McLean. Wiley, 2012.
Doug McLean Boeing Technical Fellow, retired: Common Misconceptions in Aerodynamics. Please note that Doug gets pretty heavy with the vorticity talk later in this video, but the earlier parts are easier to understand
ruclips.net/video/QKCK4lJLQHU/видео.html
Millersville U Experiments:
■Aspirators Don't Suck; They Curl The Atomizer. This shows proof that speed does not lower pressure. A curved air path does. NOTE: IT shows a restriction in the flow due to the insertion of the red tube FAR into the flow path!
www.millersville.edu/physics/experiments/093/index.php
Eastwell shows static pressure probe Fig. 2
files.eric.ed.gov/fulltext/EJ1050910.pdf
.
cont...
@@makantahi3731
…..NSF Series: People understood this many years ago:
Packed Overview Video #6:
ruclips.net/video/LI9Mi1KhFTs/видео.html
The above are in the NSF series: ruclips.net/p/PL0EC6527BE871ABA3
Number 10 is the boundary layer video.
Alternate locations:
NSF Harvard Frederick Abernathy #10 : ruclips.net/video/wMxK2GtFFq0/видео.html
Duplicate: ruclips.net/video/x6v3rK4Ikhc/видео.html
Stephen Kline Flow visualization. Harvard. #5 Hydrogen bubble method: ruclips.net/video/nuQyKGuXJOs/видео.html
.................
I have more, but I believe this is some of the best around.
.
............... END REFERENCES ....................
@@makantahi3731
John D. Anderson Fundamentals of Aerodynamics. fifth edition:
aaun.ir/wp-content/uploads/2015/07/John-D.-Anderson-Jr.-Fundamentals-of-Aerodynamics-McGraw-Hill-Science_Engineering_Math-2010.pdf
Understanding Aerodynamics: Arguing from the Real Physics. Doug McLean. Wiley, 2012.
Doug McLean Boeing Technical Fellow, retired: Common Misconceptions in Aerodynamics. Please note that Doug gets pretty heavy with the vorticity talk later in this video, but the earlier parts are easier to understand
ruclips.net/video/QKCK4lJLQHU/видео.html
.
cont...
Beautifully done!
Nope. Terrible.
This video only repeats very common misconceptions and invents a new one, as follows.
.
3:13 The low pressure above the wing allows higher pressure ahead of the wing to accelerate it to the higher speed. It is Newton. The force of pressure accelerates the mass of air.
The movement of the wing creates pressure gradients and as Euler reported to us in the mid 1700s, Pressure gradients accelerate fluids.
Bernoulli never said speed causes a pressure reduction. He only noted that the (static) pressure and velocity have an inverse relationship with no indication of cause and effect. This is a major, common misunderstanding.
Euler determined that pressure gradients accelerate fluids toward the lower pressure. That is the opposite of the common misconception.
...
3:29 The pressure difference top to bottom accounts for ALL THE LIFT. This 'a little of this and a little of that" is bad science. The same pressures that have the net upward lift force on the wing are the very same pressures that cause all accelerations around the wing including ahead, above, below, behind and around the tips.
The higher pressure under the wing pushes up on the wing AND down on the air below to contribute to the down-wash.
The lower pressure above the wing allows atmospheric pressure to push air above the wing downward, to also contribute to the down-wash.
..
NOTE: the whole upward force on the wing is equal to the force required to accelerate all the air in the down-wash. THAT is what satisfies Newton's Third Law. The upward 'push" (force) on the wing equals the downward 'push' (force) on the air accelerated downward.
The downward moving air does not push up on the wing. That air was pushed down by the pressures around the wing.
The down-wash also does not push the wing forward. You've invented a new a fallacy. The net force fore-aft is rearward and is called drag and is not caused by the down-wash as explained above.
When viewed from the still air frame of reference, the down-wash is moving slightly forward.
....
4:27 Bernoulli's Principle is again misused. The flow is not slowed under the wing which is NOT the cause of the higher pressure. . That view is valid only in the stationary wing, wind tunnel reference frame only.
In fact, REAL data from a REAL wing generating REAL lift flying through otherwise still air shows the lower air being moved forward in the direction of flight. This acceleration from still air is CAUSED BY the higher pressure at the lower surface. The increase in pressure at the surface is because the wing is pushing the air out of its way. This push increases the pressure, not the Bernoulli Principle Fallacy.
....
The pressure increase below the wing in combination with the decrease above the wing provides the ENTIRE lift force.
...
If by this magic, the down-wash did just happen to add to the lift, that "addition" would be exhibited as an increased pressure difference on the win...but it DOES NOT.
Bernoulli's Principle causes nothing in the generation of lift because the "speed-causes-pressures" is a fallacy.
It is all explained by Newton, BUT NOT with this ":reaction force" fallacy.
Newton's Third Law "reaction force" is not an originating force, but is a direct result of the originating force which, in this case, is from the pressures around the wing as described above.
....
At 7:11 Please listen to your words: “The high pressure area on the bottom of an airfoil pushes around the tip to the low pressure area on the top.”. This shows that you understand that pressure causes movement, but you fail to apply it on all the other parts of this and, therefore shows the problems with this explanation. The correct story uses this Pressure accelerated air in ALL aspects around the wing, because that I the real science.
The tip vortex does not ‘create the down wash”. You already explained the down-wash without reference to the tip vortex. This is a flaw in this explanation. The tip vortex is CONSISTENT with the wing generated down-wash moving against the still air outside the wing span. Masses of air sliding along each other create vorticity (vortices) along the boundary of the two masses.
…
At 7:47 Winglets DO NOT and CANNOT prevent the tip vortex from forming. They can only reduce the severity and the negative effect because they act to effectively lengthen the wingspan; longer wings have less severe vortices . See Doug McLean’s You Tube video on misconceptions for a full explanation.
ruclips.net/video/QKCK4lJLQHU/видео.html
…
Though well-meaning, the 'Pilot's Handbook of Aeronautical Knowledge.' has bad information in it as do so many other publications and on-line resources such as RUclips.
THANK YOU THE MOST HELPFUL LESSON EVER
Agreed!
Great job breaking down and organizing all of the components of lift.
Superb job..
Plz show us the previous video how to make flaps or how they work
This is not an "Airfoil Design" video, but rather an "airfoil description" video.
The pressure difference between top and bottom surfaces does account for all the lift generated.
Very clear and straight-forward explanations. Great!
+Jongmin Yun Thank you!
I am investigating airfoils to use for a sailboat Wingsail. Most wing sales use a symetrical foil for the front section of the wing. My question is, if possible, am I better off finding a way to designing a wing foil that matches a standard airplane wing foil? More efficient? the Trick is to be able to adjust the leading edge to adjust for left vs. right side attack. Your thoughts?
You gave the answer yourself. The symmetric airfoil is a result of having the sail fit for both directions of wind. Fortunately the pressure side is much less prone to separation due to non. ideal shape, so designing a symmetrical section that is optimised for the suction side is the way to go. Towards the trailing edge you can then use the properties of flexible spherically cambered surfaces to have a sail that takes "close to" the ideal surface depending on the direction of wind.
There are designs of wings that allow for continuous deformation of the wing section. That might be an approach for a sail. It involves rather hardcore mechanical systems, but these are not really unheard of in high-tech sailing.
Somebody know ,wich is the diference between the winglet curverd down and curved up? i saw the cessnas aircrafts like 182 and the winglet is curved down...
I think you've got it backwards - the high pressure causes the airflow to slow down, not the other way around.
In my humble opinion, I think you've got it backward....
Reaction lift is indeed occurring. If a constant stream of solid particles, (say small plastic air soft pellets, for example) were aimed at the front of the wing, of sufficiently large volume to stream past the top and bottom of the wing, it's obvious that the wing would rise. And this is without the Coanda effect taking place.
So, both reaction lift (most often the majority) resulting from impact with the bottom of the wing by the aggregate mass of the air, combined with the boundary layer mass of air flowing over the top and creating a thin, negative pressure area near the top surface of the wing to which it adheres; serve to maximize lift efficiency.
What occurs on the top wing surface is analagous to the effects of orbiting bodies and the "sling shot" effect used by space probes, only substituting vacuum adhesion for gravity. This is also aptly demonstrated with the "chain fountain" phenomenon. A partial orbit of a mass causing lift in the direction of a vector originating at the arc's center of radius and extending out, bisecting the arc at it's center.
This partial orbit of the air mass over the wing, tugging on the wing surface via suction, added to the upward push from the air mass deflecting off the bottom, share responsibilty for lifting the wing.
Both air and sea creatures make very efficient use of alternating these effects above and below the wing or tail (and to appreciable degree with sea creatures, their bodies.) Rapidly alternating negative and positive pressures enable the Black Marlin for instance, to hit a reported 82mph.
Good Journeys All
P.S. See - "Huge media blackout regarding supermoons" on the net
Excellent
I am trying to determine the surface area and camber of a wing to lift a specific weight
I fear that this video may have fallen for some common misconceptions in the aerodynamic community. For one, the figures depicting the low and high pressure arrows imply a suction on the top of the airfoil. This is not the case, it is simply less pressure on top pushing downwards while the higher pressure have much higher magnitudes and push upwards from the bottom. There is another part in the video where you explain the center of pressure. I believe you define it incorrectly, but correctly explain that topic. I think what you meant to say was coefficient of pressure, C_p at 5:30. Center of pressure varies and is a location. Coefficient of pressure is the average pressure variation.
Some have suggested this is "Not correct at all", the "at all" part is very unlikely. Also, please give video suggestions for a more complete rendering of the subject.
The air atop the wing does not cause lower pressure because it accelerates. It accelerates because it experiences lower pressure. And when we say accelerate, we mean air that hits the leading edge at 200 mph accelerates its speed above 200 mph as it travels across the surface of the wing.
Who else is here to see the nerds battle in the comments
"nerds" fighting prevents planes crashing
LOL.
At the least there's no Amy from Big Bang Theory.
Nah I'm here from my tech class
Great video demonstration thanks
He's just reading the PHAK section on airfoil design, but a good visual all the same.
Hallo
Thank you. Great video.
This video only repeats very common misconceptions and invents a new one, as follows.
.
3:13 The low pressure above the wing allows higher pressure ahead of the wing to accelerate it to the higher speed. It is Newton. The force of pressure accelerates the mass of air.
The movement of the wing creates pressure gradients and as Euler reported to us, Pressure gradients accelerate fluids.
Bernoulli never said speed causes a pressure reduction. He only noted that the (static) pressure and velocity have an inverse relationship with no indication of cause and effect. This is a major, common misunderstanding.
Euler determined that pressure gradients accelerate fluids toward the lower pressure. That is the opposite of the common misconception.
...
3:29 The pressure difference top to bottom accounts for ALL THE LIFT. This 'a little of this and a little of that" is bad science. The same pressures that have the net upward lift force on the wing are the very same pressures that cause all accelerations around the wing including ahead, above, below, behind and around the tips.
The higher pressure under the wing pushes up on the wing AND down on the air below to contribute to the down-wash.
The lower pressure above the wing allows atmospheric pressure to push air above the wing downward, to also contribute to the down-wash.
..
NOTE: the whole upward force on the wing is equal to the force required to accelerate all the air in the down-wash. THAT is what satisfies Newton's Third Law. The upward 'push" (force) on the wing equals the downward 'push' (force) on the air accelerated downward.
The downward moving air does not push up on the wing. That air was pushed down by the pressures around the wing.
The down-wash also does not push the wing forward. You've invented a new a fallacy. The net force fore-aft is rearward and is called drag and is not caused by the down-wash as explained above.
When viewed from the still air frame of reference, the down-wash is moving slightly forward.
....
4:27 Bernoulli's Principle is again misused. The flow is not slowed under the wing which is NOT the cause of the higher pressure. . That view is valid only in the stationary wing, wind tunnel reference frame only.
In fact, REAL data from a REAL wing generating REAL lift flying through otherwise still air shows the lower air being moved forward in the direction of flight. This acceleration from still air is CAUSED BY the higher pressure at the lower surface. The increase in pressure at the surface is because the wing is pushing the air out of its way. This push increases the pressure, not the Bernoulli Principle Fallacy.
....
The pressure increase below the wing in combination with the decrease above the wing provides the ENTIRE lift force.
...
If by this magic, the down-wash did just happen to add to the lift, that "addition" would be exhibited as an increased pressure difference on the win...but it DOES NOT.
Bernoulli's Principle causes nothing in the generation of lift because the "speed-causes-pressures" is a fallacy.
It is all explained by Newton, BUT NOT with this ":reaction force" fallacy.
Newton's Third Law "reaction force" is not an originating force, but is a direct result of the originating force which, in this case, is from the pressures around the wing as described aboave.
....
At 7:11 Please listen to your words: “The high pressure area on the bottom of an airfoil pushes around the tip to the low pressure area on the top.”. This shows that you understand that pressure causes movement, but you fail to apply it on all the other parts of this and, therefore shows the problems with this explanation. The correct story uses this Pressure accelerated air in ALL aspects around the wing, because that I the real science.
The tip vortex does not ‘create the down wash”. You already explained the down-wash without reference to the tip vortex. This is a flaw in this explanation. The tip vortex is CONSISTENT with the wing generated down-wash moving against the still air outside the wing span. Masses of air sliding along each other create vorticity (vortices) along the boundary of the two masses.
…
At 7:47 Winglets DO NOT and CANNOT prevent the tip vortex from forming. They can only reduce the severity and the negative effect because they act to effectively lengthen the wingspan; longer wings have less severe vortices . See Doug McLean’s You Tube video on misconceptions for a full explanation.
ruclips.net/video/QKCK4lJLQHU/видео.html
…
Though well-meaning, the 'Pilot's Handbook of Aeronautical Knowledge.' has bad information in it as do so many other publications and on-line resources such as RUclips.
How to decide number of nodes on surface of blade ?
Great video. Please make one explaining about the noise due to aerofoil
Nope... it is mostly rubbish bro... be careful who u believe
What is your modelling method here Yaroslav?
Too many mistakes for me to like
Bro rly he problem took like 8 thousand years to type all that! He deserves a like!
1.) Bernoulli is flow inside a pipe: doesn’t apply to wings
2.) down wash increases lift not what u said.
@@5ty717I’m only responding to your comment to let all of the new aviators know that you are wrong. Bernoulli’s principle, Newtons 3rd law, the law of conservation of energy, the Venturi effect and the coanda effect all combine in the lift process. There are so many sources that you can refer to so I do not need to explain it here but please do your research unlike this gentleman
Why is it always shown with a blunt, rounded leading edge? Wouldn’t a sharp one reduce the frontal drag?
this is a direct read out of the FAA Pilot's handbook
Wrong explanation: Bernoulli laws are not that way. The difference in air flows is an wrong one.
I discovered that Parasite drag is produced by VERTICAL surfaces and Induced drag is created by HORIZONTAL surfaces, for example when the Flaps are at 0 degrees they produce Max Induced drag and Min Parasite drag, at 90 degrees Min Induced and Max Parasite drag and at 45 degrees in the middle of both.
Please let me know if you think it is a valid observation. Thanks
The chord and mean camber line should converge at the leading edge. The image shown is incorrect there.
I was enjoying this lecture until the point the video ended. Is there a part 2 to continue this truncated lecture?
His tenure committee shut it down.
I am not an Engineer but I am interested in this : shapes, designs, forces, lift, stalling, pull push, resistance, friction, angle of deviation.......
Stick to the Bernoulli theorem and forget the Newtons bit, then this is an adequate explanation of ift
4:12 watch wind tunnel videos, upper and lower flows do not meet at trailing edge, they are out of sync.
Thanks for the video, it was very informative and explaned very critical meanings. I would like to know about the image with the types of airfoils, is it from a book? it would save me some time if i could find something with these types rathen than search about them one by one.
Ok I got a question. Where does a glider get its thrust?
Giant catapult
So why does the air on top of the wing move faster?
it has farther to travel !!!to arrive at the same point at the back of the wing
Not another incorrect video on this topic.Will Liebhaber - Please do some research before posting. And no, I'm not gonna write an essay here explaining it to you, do your own study. Please remove this video.
The explanation at 3:12 indicating that speed affects pressure is incorrect. See ruclips.net/video/w78JT6azrZU/видео.html for the correct explanation.
Thanks!
The Lesics video is pretty good.
SIMPLY STATED: Wings create lift because: A The angle of attack creates positive high pressure under the wing, thus pushing upward, this fact being responsible for almost the entirety of the lift generated; and B This same angle of attack generates a partial low pressure above the wing, sucking it upward. This principle ( A ) applies likewise to a water skier who stays above the surface of the water as long as the boat is pulling him forward fast enough. A plane with a FLAT wing (above and below) will fly without a doubt.
INCORRECT. The pressure DECREASE (-delta p) above the wing contributes MORE to the pressure difference. The pressure increase (+delta p) below the wing is *less* than the decrease (-delta p) above the wing. The top-to-bottom pressure *difference* is the lift.
...
The upper pressure drop contributes MORE. This is real data, real science.
..
The top does not suck because there is no such a thing as suction The lower air pushes up more than the upper air pushes down:
ruclips.net/video/Ycef5XXiozc/видео.html
...
A water skier has no water above the skis, so that analogy is very poor.
..
If the water skier had a hydrofoil below the water, it would generate much more lift. As described above.
..
Fact: A flat wing produces the same kind of pressures above and below as does a cambered )curved) wing does. It is the air flow pattern that determines lift, not simply the wing shape and a flat wing has a flow pattern very similar to any cambered wing.
..
@@Observ45er Made a rubber powered model that crashed and broke its properly air-foiled wing. Replaced the wing with another that was just a tissue-covered flat frame. Had some good flights, but have to say that the final glide was not as good. Still puzzled by both the phenomenon of lift and even more so the explanations
Lift is a combination of the Bernoulli effect and the downward deflection from the angle of attack. The Bernoulli effect is when the air has to pass through a narrowed space a more negative pressure is created, usually above the wing.
@@Observ45er I stand by my statement, notwithstanding the lack of fancy terms and jargon in my explanation. A fully symmetrical wing is also subject to the basic lift principles that I stated initially. Many a myth passes as fact for many, many years, in this and others fields as well.
@@d.haroldangel241 I think he likes to hear himself talk and use big words.....I'd like to kno wat qualifies him to challenge bernoulli and newton??..or what he thinks are his qualifications?
@ 5:34 Why does all aerodynamic forces act through the center of pressure?
I'd like to know the answer for this too. Wouldn't the weight be acting at the centre of gravity and the lift at the centre of pressure?
He should of said the *resultant* aerodynamic force acts through the center of pressure. In reality, every point on the surface of a wing is generating an aerodynamic force. If you were to sum (i.e. add) all those infinite force vectors together you would end up with a *resultant* force vector. The center of pressure is simply the point at which the sum of all the aerodynamic forces acting on a wing (i.e. the resultant aerodynamic force vector) causes no moment (i.e. no torque action) on the wing.
It's a similar concept to the center of mass. For simplicity, we say and calculate that the force of gravity acts on a body of mass through its center of mass (or sometimes referred to as its center of gravity). The reality though is that gravity individually acts on each and every atom that makes up the object with mass. But provided all the unique parts of matter that make up the object with mass stay in roughly the same place, we can just say and assume the total mass of the object is concentrated in one location, called the center of mass.
DrR1pper Interesting, thanks.
Matthew Lui You're welcome.
Oh i get it not, thanks!
How do you know all of this? I'm really interested in aerospace engineering. Do you know what's a good place to find online resources to learn more in depth knowledge in this field? Or are there any other youtube channels that you would recommend?
I have an issue with your illustration at 4:34. Looking at the small blue arrows, you purpetuate the myth that the air being split at the leading edge matches up again at the trailing edge. This is false. The air on the top of the wing goes faster and beats the air under the wing at the trailing edge.
so how did you know
Im still confused on center of pressure?
Theoretical point were all lift is considered to act, like being lifted by a piece of string.
Incorrect, it's because of newton's 3rd law, not Bernoulli's. The molecules on the upper surface and on the lower surface don't travel at the same speed
Hien Nguyen Lift is exclusively generated by pressure distribution. I guess technically skin friction could be a tiny bit in the direction of lift... but I’ve never heard of that being considered in any actual analysis.
Your explanation of the Kutta condition is completely incorrect. The Kutta condition is an artificial boundary condition in potential flow theory which states velocity must leave the trailing edge smoothly. It’s not something that can happen or not.
Appable thanks, my understanding of Kutta condition is pretty messed up. Thanks for the redirection. I shall delete my comment.
For Newton’s 3rd law being a factor of lift. I can’t help but see that air molecules striking the bottom surface of an airfoil at a positive AoA would have components of force pushing the airfoil in the lift direction. Can you please explain your thoughts?
@@HienNguyen-cq7qf We're really saying the same thing. For airfoils continuum mechanics is typically used, where flow is modeled as continuous, deformable parcels of air and a pressure field can be defined everywhere. Your interpretation of the pressure field at the surface is more like statistical mechanics, which considers the statistical behavior of a large collection of particles. That's fine and they should agree for dense fluids like air (well, dense relative to air at 70km up or so).
I'm not sure if I'd agree Newton's 3rd law is a "factor of lift" - it's more like one way to predict lift. In particular, you could draw a box around an airfoil and watch how much momentum comes into the box and out of the box. That momentum flow rate will be the same as the resultant aerodynamic force (so lift + drag vector). But you could also find the pressure at every point within that box, sum up all the pressure vectors on the surfaces (normal to the surface), and get the exact same number.
Appable hm so what you’re saying is Newton’s 3rd law and conservation of momentum completely define lift by themselves?
@@HienNguyen-cq7qf Yes, and pressure also completely defines lift. It's different ways of looking at the same problem - you know how in physics you can solve problems by looking at energy conservation or using forces? Sometimes one or the other is more useful, but ultimately they will give the same results because the underlying physics is the same.
Really interesting
I need to replace aerospace with another class, i just wanted to build cool robots, but i gotta deal with this class now!
Can i see air acting on a wing?
yes u can, type "wind tunnel" on the search bar and u'll have a lot of examples of airfoils with smoke flows around them to model the air behaviour
new ider
I have another bone to pick. Air does not "suck". There is no such thing as "negative pressure". There is only less pressure than ambient, but it is still positive pressure. Your blue arrows suggest that the air is magically pulling on the upper surface and that is incorrect. Air pressure can ONLY push. There is no "pulling" of air. The illision is done by reducing the pressure on one side, Therfore allowing the opposing higher pressure to do all of the pushing. That includes the positive air pressure on the inside of the wing pushing on the inside of the upper wing skin.
Back before computers, they simplified as best they could based on their limited experimental data. We don't need to do that these days. Here's a great example: forums.autodesk.com/t5/fusion-360-api-and-scripts/add-in-announcement-hydrofoil-and-airfoil-tools-seeking-your/td-p/9453985 - years of CPU time doing CFD are now free to give you the right shape for what you need, and the math to work out what you need from what you know is now just mouse-clicks away :-)
jihun wong, you are wrong. the airfoil simply redirects the streamlines on the top and bottom, newtons third law applies, and bam; you got lift. Explain to me ground effect, oh wise one...
Lift is due to the top to bottom pressure difference, only.
..
It is the pressure changes caused by the airfoil that *both* produce the lift force AND accelerate the air down.
..
This video only repeats very common misconceptions and invents a new one, as follows.
.
3:13 The low pressure above the wing allows higher pressure ahead of the wing to accelerate it to the higher speed. It is Newton. The force of pressure accelerates the mass of air.
The movement of the wing creates pressure gradients and as Euler reported to us, Pressure gradients accelerate fluids.
Bernoulli never said speed causes a pressure reduction. He only noted that the (static) pressure and velocity have an inverse relationship with no indication of cause and effect. This is a major, common misunderstanding.
Euler determined that pressure gradients accelerate fluids toward the lower pressure. That is the opposite of the common misconception.
...
3:29 The pressure difference top to bottom accounts for ALL THE LIFT. This 'a little of this and a little of that" is bad science. The same pressures that have the net upward lift force on the wing are the very same pressures that cause all accelerations around the wing including ahead, above, below, behind and around the tips.
The higher pressure under the wing pushes up on the wing AND down on the air below to contribute to the down-wash.
The lower pressure above the wing allows atmospheric pressure to push air above the wing downward, to also contribute to the down-wash.
..
NOTE: the whole upward force on the wing is equal to the force required to accelerate all the air in the down-wash. THAT is what satisfies Newton's Third Law. The upward 'push" (force) on the wing equals the downward 'push' (force) on the air accelerated downward.
The downward moving air does not push up on the wing. That air was pushed down by the pressures around the wing.
The down-wash also does not push the wing forward. You've invented a new a fallacy. The net force fore-aft is rearward and is called drag and is not caused by the down-wash as explained above.
When viewed from the still air frame of reference, the down-wash is moving slightly forward.
....
4:27 Bernoulli's Principle is again misused. The flow is not slowed under the wing which is NOT the cause of the higher pressure. . That view is valid only in the stationary wing, wind tunnel reference frame only.
In fact, REAL data from a REAL wing generating REAL lift flying through otherwise still air shows the lower air being moved forward in the direction of flight. This acceleration from still air is CAUSED BY the higher pressure at the lower surface. The increase in pressure at the surface is because the wing is pushing the air out of its way. This push increases the pressure, not the Bernoulli Principle Fallacy.
....
The pressure increase below the wing in combination with the decrease above the wing provides the ENTIRE lift force.
...
If by this magic, the down-wash did just happen to add to the lift, that "addition" would be exhibited as an increased pressure difference on the win...but it DOES NOT.
Bernoulli's Principle causes nothing in the generation of lift because the "speed-causes-pressures" is a fallacy.
It is all explained by Newton, BUT NOT with this ":reaction force" fallacy.
Newton's Third Law "reaction force" is not an originating force, but is a direct result of the originating force which, in this case, is from the pressures around the wing as described aboave.
....
At 7:11 Please listen to your words: “The high pressure area on the bottom of an airfoil pushes around the tip to the low pressure area on the top.”. This shows that you understand that pressure causes movement, but you fail to apply it on all the other parts of this and, therefore shows the problems with this explanation. The correct story uses this Pressure accelerated air in ALL aspects around the wing, because that I the real science.
The tip vortex does not ‘create the down wash”. You already explained the down-wash without reference to the tip vortex. This is a flaw in this explanation. The tip vortex is CONSISTENT with the wing generated down-wash moving against the still air outside the wing span. Masses of air sliding along each other create vorticity (vortices) along the boundary of the two masses.
…
At 7:47 Winglets DO NOT and CANNOT prevent the tip vortex from forming. They can only reduce the severity and the negative effect because they act to effectively lengthen the wingspan; longer wings have less severe vortices . See Doug McLean’s You Tube video on misconceptions for a full explanation.
ruclips.net/video/QKCK4lJLQHU/видео.html
…
Though well-meaning, the 'Pilot's Handbook of Aeronautical Knowledge.' has bad information in it as do so many other publications and on-line resources such as RUclips.
LOL.... try explaining how a plane can fly upside down using the above.
there's more to all this than meets the eye, but its up to us to keep pushing until we comprehend it all. I see no harm in offering above at least a partial explanation, although I concur that it makes like more frustrating...
3:00
Why?
I dont know
Why people always post simply wrong things about lift?? Its just all wrong what you said in the video.
You can see in the comments, even the drolls know that your Video states wrong things. Please remove this video.
I want to build a P51 Mustang Replica for display, I have some sponsors here who help me with free materials and services. I want to use the drawings of mr. Marcel Jurca to do the parts and assembly, but the drawings are in PDF, and I want an assumed, responsible, serious volunteer (free of charge!!!) CAD engineer to help me redraw the drawings from the PDF and put them into DXF files, so it can be easily cut on CNC from plywood, aluminium, steel etc... I have some progress on the frames and formers (pictures attached). The Mustang will be displayed for a new aviation museum project I am currently developing. The CAD engineer will be mentioned on the sponsor's list on the project website.
Definitely not Bernoulli's principle . . .
I'm sorry, but there are too many mistakes here. It starts at 1:15. The stagnation point at the leading edge is shown at the end of the chord line, but with an angle of attack like this, the stagnation point is further down. Secondly, the illustration shows the "equal transit time" hypothesis, which is the result of a poor understanding of Bernoulli's principle. Here is a link to the University of Cambridge, showing how it really works: www.eng.cam.ac.uk/news/how-wings-really-work
More:
This video only repeats very common misconceptions and invents a new one, as follows.
.
3:13 The low pressure above the wing allows higher pressure ahead of the wing to accelerate it to the higher speed. It is Newton. The force of pressure accelerates the mass of air.
The movement of the wing creates pressure gradients and as Euler reported to us in the mid 1700s, Pressure gradients accelerate fluids.
Bernoulli never said speed causes a pressure reduction. He only noted that the (static) pressure and velocity have an inverse relationship with no indication of cause and effect. This is a major, common misunderstanding.
Euler determined that pressure gradients accelerate fluids toward the lower pressure. That is the opposite of the common misconception.
...
3:29 The pressure difference top to bottom accounts for ALL THE LIFT. This 'a little of this and a little of that" is bad science. The same pressures that have the net upward lift force on the wing are the very same pressures that cause all accelerations around the wing including ahead, above, below, behind and around the tips.
The higher pressure under the wing pushes up on the wing AND down on the air below to contribute to the down-wash.
The lower pressure above the wing allows atmospheric pressure to push air above the wing downward, to also contribute to the down-wash.
..
NOTE: the whole upward force on the wing is equal to the force required to accelerate all the air in the down-wash. THAT is what satisfies Newton's Third Law. The upward 'push" (force) on the wing equals the downward 'push' (force) on the air accelerated downward.
The downward moving air does not push up on the wing. That air was pushed down by the pressures around the wing.
The down-wash also does not push the wing forward. You've invented a new a fallacy. The net force fore-aft is rearward and is called drag and is not caused by the down-wash as explained above.
When viewed from the still air frame of reference, the down-wash is moving slightly forward.
....
4:27 Bernoulli's Principle is again misused. The flow is not slowed under the wing which is NOT the cause of the higher pressure. . That view is valid only in the stationary wing, wind tunnel reference frame only.
In fact, REAL data from a REAL wing generating REAL lift flying through otherwise still air shows the lower air being moved forward in the direction of flight. This acceleration from still air is CAUSED BY the higher pressure at the lower surface. The increase in pressure at the surface is because the wing is pushing the air out of its way. This push increases the pressure, not the Bernoulli Principle Fallacy.
....
The pressure increase below the wing in combination with the decrease above the wing provides the ENTIRE lift force.
...
If by this magic, the down-wash did just happen to add to the lift, that "addition" would be exhibited as an increased pressure difference on the win...but it DOES NOT.
Bernoulli's Principle causes nothing in the generation of lift because the "speed-causes-pressures" is a fallacy.
It is all explained by Newton, BUT NOT with this ":reaction force" fallacy.
Newton's Third Law "reaction force" is not an originating force, but is a direct result of the originating force which, in this case, is from the pressures around the wing as described above.
....
At 7:11 Please listen to your words: “The high pressure area on the bottom of an airfoil pushes around the tip to the low pressure area on the top.”. This shows that you understand that pressure causes movement, but you fail to apply it on all the other parts of this and, therefore shows the problems with this explanation. The correct story uses this Pressure accelerated air in ALL aspects around the wing, because that I the real science.
The tip vortex does not ‘create the down wash”. You already explained the down-wash without reference to the tip vortex. This is a flaw in this explanation. The tip vortex is CONSISTENT with the wing generated down-wash moving against the still air outside the wing span. Masses of air sliding along each other create vorticity (vortices) along the boundary of the two masses.
…
At 7:47 Winglets DO NOT and CANNOT prevent the tip vortex from forming. They can only reduce the severity and the negative effect because they act to effectively lengthen the wingspan; longer wings have less severe vortices . See Doug McLean’s You Tube video on misconceptions for a full explanation.
ruclips.net/video/QKCK4lJLQHU/видео.html
…
Though well-meaning, the 'Pilot's Handbook of Aeronautical Knowledge.' has bad information in it as do so many other publications and on-line resources such as RUclips.
Here is the better explanation in a PDF from Cambridge:
www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwi97cSJp9DsAhXMm-AKHTQ3CKwQFjAaegQIKhAC&url=http%3A%2F%2Fwww3.eng.cam.ac.uk%2Foutreach%2FProject-resources%2FWind-turbine%2Fhowwingswork.pdf&usg=AOvVaw12sAqN9m4QZOvdGdrW5wHE
@@johnpombrio Yes, that is a good reference as is Doug McLean's. I'm well aware of Babinsky's papers, talks and videos and have conversed with him and other authorities in the field of aerodynamics. His is a good reference.
Here is his RUclips Video:
Dr Holger Babinsky, Cambridge University Engineering Department. Common misconceptions on lift.
ruclips.net/video/XWdNEGr53Gw/видео.html
You'll need his MISSING SLIDES from HERE (Click the Download Icon for the complete set of slides):
docs.google.com/file/d/0B0JABuFvb_G_MkpBZHJmRGo3UkU/edit?usp=sharing
Or here:
docs.google.com/file/d/0B0JABuFvb_G_MkpBZHJmRGo3UkU/edit
....
His equivalent article from PHYSICS EDUCATION magazine "How do wings work?", Holger Babinsky:
www.prirodopolis.hr/daily_phy/pdf/How%20do%20wings%20hork.pdf
..
Also:
This is a DIRECT link to that Babinsky paper:
www3.eng.cam.ac.uk/outreach/Project-resources/Wind-turbine/howwingswork.pdf
Shift of stagnation point is what sets off Piper aircraft stall vanes.
*This video only repeats misconceptions and bad science. I've already explained it in this and his other Theories in the Production of Lift video.*
If these descriptions on video were the reason planes fly, why DC-3 (which has totally symmetric airfoil) had flow and still flies so well... Please don't start explaining with airfoil modern planes don't have...
Summary:
The pressures changes created by the moving wing provide all the lift force *AND* also provides the force to accelerate the air downward. Those are two different results of the pressures, not two alternate ways to look at lift.
.....
This video only repeats very common misconceptions and invents a new one, as follows.
.
3:13 The low pressure above the wing allows higher pressure ahead of the wing to accelerate it to the higher speed. It is Newton. The force of pressure accelerates the mass of air.
The movement of the wing creates pressure gradients and as Euler reported to us in the mid 1700s, Pressure gradients accelerate fluids.
Bernoulli never said speed causes a pressure reduction. He only noted that the (static) pressure and velocity have an inverse relationship with no indication of cause and effect. This is a major, common misunderstanding.
Euler determined that pressure gradients accelerate fluids toward the lower pressure. That is the opposite of the common misconception.
...
3:29 The pressure difference top to bottom accounts for ALL THE LIFT. This 'a little of this and a little of that" is bad science. The same pressures that have the net upward lift force on the wing are the very same pressures that cause all accelerations around the wing including ahead, above, below, behind and around the tips.
The higher pressure under the wing pushes up on the wing AND down on the air below to contribute to the down-wash.
The lower pressure above the wing allows atmospheric pressure to push air above the wing downward, to also contribute to the down-wash.
..
NOTE: the whole upward force on the wing is equal to the force required to accelerate all the air in the down-wash. THAT is what satisfies Newton's Third Law. The upward 'push" (force) on the wing equals the downward 'push' (force) on the air accelerated downward.
The downward moving air does not push up on the wing. That air was pushed down by the pressures around the wing.
The down-wash also does not push the wing forward. You've invented a new a fallacy. The net force fore-aft is rearward and is called drag and is not caused by the down-wash as explained above.
When viewed from the still air frame of reference, the down-wash is moving slightly forward.
....
4:27 Bernoulli's Principle is again misused. The flow is not slowed under the wing which is NOT the cause of the higher pressure. . That view is valid only in the stationary wing, wind tunnel reference frame only.
In fact, REAL data from a REAL wing generating REAL lift flying through otherwise still air shows the lower air being moved forward in the direction of flight. This acceleration from still air is CAUSED BY the higher pressure at the lower surface. The increase in pressure at the surface is because the wing is pushing the air out of its way. This push increases the pressure, not the Bernoulli Principle Fallacy.
....
The pressure increase below the wing in combination with the decrease above the wing provides the ENTIRE lift force.
...
If by this magic, the down-wash did just happen to add to the lift, that "addition" would be exhibited as an increased pressure difference on the win...but it DOES NOT.
Bernoulli's Principle causes nothing in the generation of lift because the "speed-causes-pressures" is a fallacy.
It is all explained by Newton, BUT NOT with this ":reaction force" fallacy.
Newton's Third Law "reaction force" is not an originating force, but is a direct result of the originating force which, in this case, is from the pressures around the wing as described above.
....
At 7:11 Please listen to your words: “The high pressure area on the bottom of an airfoil pushes around the tip to the low pressure area on the top.”. This shows that you understand that pressure causes movement, but you fail to apply it on all the other parts of this and, therefore shows the problems with this explanation. The correct story uses this Pressure accelerated air in ALL aspects around the wing, because that I the real science.
The tip vortex does not ‘create the down wash”. You already explained the down-wash without reference to the tip vortex. This is a flaw in this explanation. The tip vortex is CONSISTENT with the wing generated down-wash moving against the still air outside the wing span. Masses of air sliding along each other create vorticity (vortices) along the boundary of the two masses.
…
At 7:47 Winglets DO NOT and CANNOT prevent the tip vortex from forming. They can only reduce the severity and the negative effect because they act to effectively lengthen the wingspan; longer wings have less severe vortices . See Doug McLean’s You Tube video on misconceptions for a full explanation.
ruclips.net/video/QKCK4lJLQHU/видео.html
…
Though well-meaning, the 'Pilot's Handbook of Aeronautical Knowledge.' has bad information in it as do so many other publications and on-line resources such as RUclips.
Aerobatic aircraft may have symmetrical wing. The angle of attack provides the slight change in camber. So they fly well even upside down.
@@flybobbie1449 indeed.. therefore the lift comes from the wings´s angle of attack.. of course wing profile means a lot especially low-speed flyiers..
@@dnjoncvichy This is why non sym. aerofoils are preferred, they produce lift even at slight negative angles of attack. Extreme attitude not req. for take off and guards against a tuck under when pitching down. DC3 starts it's take off very nose up.
The authors have two wrong scientific approaches: researching the creation of Lift force and Low pressure at upper side of the wing, relative to the ground surface and Earth. I explain the aerodynamic cavitation and existence of Lee side aerocavern, and creation of Aerodynamic force.
Hello Pilots,
Do I understand it right that,
Stall will happen when you have a large angle of attack at relative low speed?
But if, with the Same Angle of Attack, the speed is much higher, then stall won't happen. Right? And the plane will climb up of course. Right?
If not right, Then how come that fighter jets and other acrobatic planes can climb straight vertically?
I suppose this is because of their high speed, which provides enough lift, no matter in what direction or angle they move.
So why can't normal plans in a critical angle of attack give full thrust to gain more lift?
The air is the same everywhere in the sky. Why behaves the air different if we want to fly in an angle which is not parallel to the horizon?
A stall happens when the air on the wing becomes turbulent on the top side, resulting in much less lift. This can be caused by several factors, and can often be avoided by maintaining a higher airspeed, I recommend looking up "Vortex generator" videos, where they make a lot of very good examples and far better explanations than I ever could. (Samm Sheperd has a really good one)
Fighter jets and aerobatic aircraft can climb vertically with ease due to the ludicrous amount of power they have relative to their mass. When doing so, the wings are barely more than the fins on a rocket, helping them maintain control, instead of generating any lift.
Also something to note, the air isn't the same everywhere in the sky, thermals help gliders gain more lift, wind can cause severe turbulence and of course, the higher up you go the less dense it is.
Stall happens at same angle of attack. So could stall say 50kts or 100kts. Difference is loading. Make plane heavier stalls at higher speed. Heavier if more mass on board or high g loading say in a steep turn.
@@flybobbie1449
OK.
If you say that stall can happen at any speed, if the critical angel of attack is greater.
Suppose if a plane could climb in a very steep angel and with the flight path exactly in the direction of its nose,
would stall still happen?
@@sohail1855 No would not stall unless it reaches the critical angle. Pure thrust keeps you climbing like a rocket. Fast jets have a very small range of angle of attack, Cessna might be 15-18 degrees. A Tornado jet might only be 7-8 degrees. Starfighter jet must be very low critical angle, that climbs like a rocket. I would not like to suddenly pull back on the stick of a Starfighter.
Reason why it a rubbish dogfighter.
Stall occurs at about 15 degrees Angle of Attack regardless of airspeed. Repeat.
Regardless of airspeed.
.
Fly at high speed in a tight turn where you have high Gs and the apparent craft weight is high and you stall if you exceed that critical Angle of Attack.
You are at high speed, but also need high left because of the G loading.
.
As low speed you need the same lift to fly level, but low speed produces less lift from a wing, so you need to increase the AoA to get the needed lift.
When you are so slow that the lift needs that critical AoA, you are on the edge. Any slower and you can't get more lift and stall, or must descend to pick up speed to generate enough lift.
Another video giving wrong explanation of why low pressure at upper surface
as far as i know Bernoulli principle is not accepted anymore.
very informative video... nice...
There is no such thing as a negative pressure ;)
Yes there is. It is pressure below the local ambient atmospheric pressure This is a very common and well accepted concept. Look up gauge pressure and manifold pressure.
@@Observ45er Try to negatively press something and share how's that working for you.
@@My-Opinion-Doesnt-Matter
Winters Pressure Gauge, -30 to 15 psi Range, 1/4 in NPT, ±0.50% Gauge Accuracy
www.grainger.com/product/491A79
@@My-Opinion-Doesnt-Matter
Pressure Gauge, 0 to -100 kPa Vac, 0 to -30 in Hg Vac Range, 1/4 in NPT, ±3-2-3% Gauge Accuracy
www.grainger.com/product/4FLT5
@@My-Opinion-Doesnt-Matter Not only have I tried, but I got paid to do it while developing advanced night vision goggles, starting with one of these:
showcase.ulvac.co.jp/en/how-to/product-knowledge02/adsorption-pump.html
And finishing with one of these:
instrumentation.obs.carnegiescience.edu/FourStar/Documents/FourStar%20Commercial%20Manuals/Varian/ion-catalog.pdf
Bernoulli's principle is wrong
Correct.
when applied to the flow over an airfoil
@@ckusel123 No, Bernoulli's principle is correct there.
A lot of negative comments but no one offers a better solution!
See my complete explanation of all the errors in this video a year after that comment. About the time if this reply.
See my complete explanation of all the errors in this video, at this time.
+
Jason Bouchard
,
.
See my complete comment on all the errors at this time.
бред сивой кобылы , это работает совсем по другому .
03:00 - 03:12
This explanation of the lower pressure from the faster movement of the air above the wing has been given again and again and again. But it's wrong. THERE IS ABSOLUTELY NO NEED FOR AN AIR PARTICLE TO TRAVEL FASTER ALONG THE UPPER SURFACE THAN ANOTHER TRAVELLING ALONG THE LOWER SURFACE!
Indeed, an upside particle leaves a downside particle far behind. Two neighbouring particles splitting at the leading edge don't have to meet again at the trailing edge, and they don't. Period.
The air on the upside simply does travel faster, and there actually IS lower pressure on the upside, but the reasons are more complex.
If the camber was the only reason for lift, why does a flat airfoil fly? Why do Chinese kites fly? Why do you feel resistance that tries to move your hand aside when you stretch out your hand from a car window at higher speeds?
Okay, enough of that ... If you benefit from this video, congrats to you. Why not? But I don't.
You gotta be kidding.... it's nothing like that...at all
Wrong! Wrong! Wrong! And wrong again. It's now well established that Bernoulli effects have little to due with creating lift--flight. Neither does the Coanda effect. Lift is Newtonian, and comes about from pressure gradients due to the vacuum along the top-rear of an airfoil, not conservation of energy in air flows or Bernoulli pressure gradients.
Lift results from air accelerated by the vacuum on the top-rear surface of an airfoil. However, Bernoulli's formulas are a close approximation for designing wings and explaining lift, and so are often used for just that.
The formation of lift by an airfoil comes from the pressure gradient at the extreme vacuum found at the top-back surface of a wing. This vacuum accelerates the air just above the back surface of the wing down towards the back of the wing. This accelerated air in turn pulls down and accelerates more air from above the airfoil. The opposite and equal result of this pulling down, "scooping," of air and accelerating it downward is an upward force, lift. Lift is Newtonian.
Airfoil equipped aircraft are essentially horizontal rockets, but much more efficient because of their ability to utilize graviational energy to create lift.
The Coanda Effect is not the driver of lift either. It is caused by a weak electrical interaction between flowing fluid/air and the surface it is flowing over.
As lift is Newtonian, it follows that the vast majority of the energy that is used to create and sustain lift, and maintain a heavier than air aircraft in the sky, comes from gravity, not from the aircraft's engines. That is why aircraft have non-powered glide-ratios and helicopters auto-rotation. Autogyros are an extreme example of this fact. If the energy from an aircraft's engines were the sole source of energy generating lift, a plane, like a rocket, would not be able to sustain flight for more than a few minutes; Also why jet packs will remain elusive for the foreseeable future.
In the following video one can see the condensation in the vacuum induced low pressure area above the aircraft's wings. A closer look will reveal that this air is being pulled down, accelerated, and then pushed down at the back of the plane's wings:
ruclips.net/video/t2SZawBVSrQ/видео.html
Hate away, but them's the facts.
You've got it! ... except the lowest pressure is above and near the LEADING EDGE, not the rear. Is it about 25% of the way back.
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The above wing reduction gives folks the most trouble.
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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. A thumbs up on this video would be greatly appreciated:
*ruclips.net/video/3MSqbnbKDmM/видео.html\
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Regards.
again sjnsn iskaka jaa
Downwash is a result of the wing producing lift, not a cause.
I mean, aren't they both basically the same effect, it's just Newton's 3rd law isn't it?
Correct.
The wing's motion must push the air out if the way and let it flow back in behind it. This pushing and "pulling" i produces pressure changes around the wing. There is more under and less above. These pressures result in two things.
One the upward force holding the ewing up called lift - more under than above.
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The other thing it that these VERY SAME pressures cause is all the accelerations of air that we see around the wing: ahead, behind, above, below and around the tips.
The pressure reduction above contributes the most to the Top-bottom lifting pressure difference.
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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:
*ruclips.net/video/3MSqbnbKDmM/видео.html*
Regards.
@@FreyrDev If you saw hot, smoky air rising over a campfire would you claim the rising of the air is what made it hot?
@@niio111 My point was not that you had the causation backwards, but that you can't really say either causes the other. With the fire example I don't really care about that causative relationship, but more that if you tell me there is a column of hot air, I can assume its rising, and if you tell me there is a column of air rising, I can assume it's hotter than the surrounding air, and both of those would be valid ways of looking at the system. However I don't think its a great analogy in this situation, as with the fire I think you can probably view it as a system trying to find equilibrium, and thus you can assign a root cause to whatever is disrupting the equilibrium, i.e. the fire, but I don't think this works with a wing.
I think a better analogy would be to imagine firing two balls at each other so they collide, can you say that the statement "ball A causes ball B to ricochet away" is any more or less correct than "ball B causes ball A to ricochet away" (assuming neither ball comes to a stop in the collision), no, the resultant force must act on both balls equally in opposite directions. Similarly the wing being pushed up and the air being pushed down are caused by the same Newtonian reaction force, so it seems dumb to say that one caused the other.
Edit: Actually I think a more accurate way of describing why I dislike the fire analogy is that you're only analysing the result on one side, the air, whereas with the balls and the wing you have to analyse the result on both parts of the analogy.
Most of your lecture is incorrect bro... it started when u said the airflow over the top has to be faster because the upper surface is longer... seems you think molecules above and below are somehow entangled like quantum mechanics and need to return into each other’s arms... the transit times above and below are different bro... this is a gaseous fluid and there is nothing in aerodynamics that indicates fluids have to be the same after playing host to a transiting wing... pretending they have to be the same is not physics but a belief system such as religion is based on belief without good evidence...
if u don’t know bro just say so... BUT don’t churn BS to the uninitiated who will be none the wiser.
Another common fallacy is the faster bit.
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The air above the wing is faster, but that is *only* relative to the wing.
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Relative to the mass of relatively still air that the wing is flying through, that upper air is actually slower than the air below the wing. This is from measured tata I can provide.
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That fact blows the doors off this "faster air" nonsense myth.
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This faster air thing is the all too common misunderstanding of what Bernoulli's Principle actually says.
For a correct explanation of the *cause* of the lower pressure above a wing, see this short video:
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:
ruclips.net/video/3MSqbnbKDmM/видео.html
Regards.
Hahaha, nice grafics. Terrible, missleading content ..
Very poor explanation.. The worst part is the narrator sound like he knows what he is talking about. Awful! 😡
if you tilt an teardrop foil up it will produce a vacuum on the top of the wing which causes the air under the wing to try and fill in the vacuum pushing the wing up !!! its not negative pressure on the top of the wing its a partial vacuum over the top that produces lift !!a propeller on an air plane does not pull the air backwards it creates a vacuum on the front of the propeller to cause the air behind the propeller to push the air plane forward!! every thing in nature is pushed!!the only way you can pull an object is to change its inertia or with a magnet !!!
Totally reversed. the pressure will be higher above the wing since the area of stream air going through it will be smaller because of the concave shape.
This is not a matter for guessing. It has been measured and it is lower than the pressure farther from the wing. That 'pinching' effect is incorrect science. The air far above a wing is not a solid wall. It is very soft.
The changes in pressure changes at the wing's surfaces are caused simply by the fact that the wing must push the air around to move through it.
The air does not move "faster" over the wing, nor does it stagnate at the leading edge. Air does not move. An airplane has thrust. If wind tunnels were accurate there would be no such thing as porpoising in F1. If air moved at 150 mph, everything would fly. This is a lazy and ignorant way of explaining airfoils.
oh god not this again. Newtons 3rd law DOES NOT contribute to lift.
+jiunn wong You are correct.
Please explain your reasoning
Invisiblejihadi you cannot find a force the wing can exert on the free flow to change mass flow vector
I'm confused about your view. The wing creates pressure differences that push air downward.
Why not? Force is defined as a rate of change of momentum and in this case the momentum of the fluid flow is changed
D dude you just spend way too much time alone. 50 years flying and well over 25000 hours in the sky and the Bernoulli theory worked well. Speed over the top vs bottom equals lower pressure equals lift. Besides there is no such thing as gravity (Newton ) the earth just sucks... take up fly fishing...
Actually no difference which theory worked as long as planes were flying, as well as no difference if shaped charges were melting armour or not they were piercing it. Both shaped charges and planes were invented before people found out why they work
Bernoulli principle also predicts zero downward deflection of the air stream and no energy loss due to lift. Bernoulli is not wrong as much as it is incomplete. Lift is far more complicated. Anything short of partial equations using speed, friction, viscosity and density is bound to be a simplistic.
This video only repeats very common misconceptions and invents a new one, as follows.
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3:13 The low pressure above the wing allows higher pressure ahead of the wing to accelerate it to the higher speed. It is Newton. The force of pressure accelerates the mass of air.
The movement of the wing creates pressure gradients and as Euler reported to us in the mid 1700s, Pressure gradients accelerate fluids.
Bernoulli never said speed causes a pressure reduction. He only noted that the (static) pressure and velocity have an inverse relationship with no indication of cause and effect. This is a major, common misunderstanding.
Euler determined that pressure gradients accelerate fluids toward the lower pressure. That is the opposite of the common misconception.
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3:29 The pressure difference top to bottom accounts for ALL THE LIFT. This 'a little of this and a little of that" is bad science. The same pressures that have the net upward lift force on the wing are the very same pressures that cause all accelerations around the wing including ahead, above, below, behind and around the tips.
The higher pressure under the wing pushes up on the wing AND down on the air below to contribute to the down-wash.
The lower pressure above the wing allows atmospheric pressure to push air above the wing downward, to also contribute to the down-wash.
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NOTE: the whole upward force on the wing is equal to the force required to accelerate all the air in the down-wash. THAT is what satisfies Newton's Third Law. The upward 'push" (force) on the wing equals the downward 'push' (force) on the air accelerated downward.
The downward moving air does not push up on the wing. That air was pushed down by the pressures around the wing.
The down-wash also does not push the wing forward. You've invented a new a fallacy. The net force fore-aft is rearward and is called drag and is not caused by the down-wash as explained above.
When viewed from the still air frame of reference, the down-wash is moving slightly forward.
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4:27 Bernoulli's Principle is again misused. The flow is not slowed under the wing which is NOT the cause of the higher pressure. . That view is valid only in the stationary wing, wind tunnel reference frame only.
In fact, REAL data from a REAL wing generating REAL lift flying through otherwise still air shows the lower air being moved forward in the direction of flight. This acceleration from still air is CAUSED BY the higher pressure at the lower surface. The increase in pressure at the surface is because the wing is pushing the air out of its way. This push increases the pressure, not the Bernoulli Principle Fallacy.
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The pressure increase below the wing in combination with the decrease above the wing provides the ENTIRE lift force.
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If by this magic, the down-wash did just happen to add to the lift, that "addition" would be exhibited as an increased pressure difference on the win...but it DOES NOT.
Bernoulli's Principle causes nothing in the generation of lift because the "speed-causes-pressures" is a fallacy.
It is all explained by Newton, BUT NOT with this ":reaction force" fallacy.
Newton's Third Law "reaction force" is not an originating force, but is a direct result of the originating force which, in this case, is from the pressures around the wing as described above.
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At 7:11 Please listen to your words: “The high pressure area on the bottom of an airfoil pushes around the tip to the low pressure area on the top.”. This shows that you understand that pressure causes movement, but you fail to apply it on all the other parts of this and, therefore shows the problems with this explanation. The correct story uses this Pressure accelerated air in ALL aspects around the wing, because that I the real science.
The tip vortex does not ‘create the down wash”. You already explained the down-wash without reference to the tip vortex. This is a flaw in this explanation. The tip vortex is CONSISTENT with the wing generated down-wash moving against the still air outside the wing span. Masses of air sliding along each other create vorticity (vortices) along the boundary of the two masses.
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At 7:47 Winglets DO NOT and CANNOT prevent the tip vortex from forming. They can only reduce the severity and the negative effect because they act to effectively lengthen the wingspan; longer wings have less severe vortices . See Doug McLean’s You Tube video on misconceptions for a full explanation.
ruclips.net/video/QKCK4lJLQHU/видео.html
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Though well-meaning, the 'Pilot's Handbook of Aeronautical Knowledge.' has bad information in it as do so many other publications and on-line resources such as RUclips.