+Eduardo Maltauro: Bernoulli's Principle is *not* false. It is the incorrect interpretation and application of Bernloulli's Principle that has been used to incorrectly explain lift too many times in the past and now. Very refreshing to see this.
Stunt planes have symmetrical wings, so no Bernoulli. And many planes can fly upside down so again, the B effect is not really important. Its all about flow turning. If there is a B effect, its only helping create a small amount of upwards force, but not enough to actually lift anything .
+Quillons1 RE: "when a fluid accelerates, it creates low pressure against a surface ". Actually, it is the other way around. The low pressure (caused by the convex curved shape) causes air to accelerate from higher to lower pressure. In the case of the upper surface, the acceleration is more of a radial acceleration - that is, acceleration being a change in velocity making it curve.
If done carefully, this same explanation works just as well when using the wing moving past the air. While I could pick on a few choices of words, this essentially explains lift correctly. "drag along" = Entrains due to viscosity "Stationary air" = Air at that point "small vacuum" = lower pressure "pulls the airstream towards the wing" = higher pressure above pushes it towards the wing.
As a wing moves through the air at a positive AOA, the lower surface pushes the air forwards and downwards creating lift component 1. The pressure bow wave in front of the lower leading edge then pushes the air up and over the wing. Normal static air pressure holds the air close to the wing's surface. The skin friction (form drag) causes the air to be pulled forwards in the direction of the wing's movement and downwards parallel to the upper surface. Change of direction =Force. F=Ma = Lift.
Sorry Naked Science people. The Coanda effect does not exist (if at all) in un-accelerated flows. It is typically described as being the 'effect' present in upper surface blowing but some scientists do not think it really exists as an effect distinct from viscosity/ form drag that are responsible for the boundary layer. The air over the upper surface is pulled forwards in the direction of the wing's movement and bent downwards by static air pressure. (no vacuums in normal space)
+Quillons1 It also is not technically the Coanda effect. Though similar, that term is used to describe a high speed jet, or sheet of air that is faster than the prevailing airflow, not the ordinary action of the surface moving through air. Sounds like a nit, but true.
Basically the same effect. You can produce lift with a plane plate by having shown angle against the air, much like sticking your hand out of the car window while driving. In inverted flight state a profile like the shown one will still produce lift, but much less than in normal position, as it is designed to be more effective that way. This and the quite high number of passengers who would dislike inverted flight usually stops commercial pilots from flying this way ;-)
+MaverickX2k5 Regarding the statement: "Higher velocity results in a lower pressure!" This is the common misapplication of Bernoulli and has it backwards. Air changes velociry *because of* a difference in pressure. It is that precise bad interpretation of Bernoulli that has been incorrectly used to explain lift. LISTEN CAREFULLY, the video says @1:40 that the curve causes a low pressure (tiny vacuum) that puls the air down. Ok the pressure above pushes it down.
+Quillons1 Finally, Bernoulli describes both the upper and lower. It is a pressure fifference that causes the curved air path in both. Below, the wing's curve creates the higher pressure and above, the lower pressure as she describes.
This is very much it: A fluid has a certain amount of energy in the current state, which is a sum of temperature, pressure and velocity. If you don't put energy into the fluid, the amount has to stay the same, but you can change the parts: Higher velocity results in a lower pressure! Don't mix this up with higher velocity of engine exhaust: you put very much energy into the fluid here!
Why not? it is the very same principle, just that the wing is upside down. A wing must not be shaped like the ones of a commercial airliner. In fact, commercial airliners create much less lift when upside down as they are designed to be more effective in normal flight state
Let us try to explain the physics of lift and control and let the readers ponder about it. Assume the space around us is filled with a voluminous mass of fluid at atmospheric pressure. 1. If one bashed a voluminous lump of very fast heavy fluid against the surface area of a heavy body, then on impact ,there will be created zones of high compression (high pressures) and any reflected, or bouncing sheets of fluid, which will try and separate from the surface of the body, they will create between them and the surface of the body, zones of partial vacuum or low pressure. So bashing volumes of fluid on to a solid body can create zones of high pressure, while trying to reflect and separate fluid sheets from surfaces of a body, will form zones of low pressure . 2. A heavy body can be made to levitate and move and be made directional in a fluid, by arranging for the body itself to throw volumes of fluid at itself, in selected directions and through shaping the outer contours of the body, the compression and partial vacuum zones can be made unsymmetrical such that its body lifts itself, while its direction is selected through the controlled throwing of more fluid moving along various angled surfaces. 3. It is best to keep the adjacent flows of the fluid to have little differential velocities, but if these differential velocities are high then one can circulate the faster streamlines to take the form of a helix rotating around the slower one where the axial velocity of the spiralling helix will be the same as the slower straight streamline, till they mix and equalise in pressure and velocity. There is all of micro detail in that, but better to keep to the basic principles to start with.
If this is a scientific presentation, then why no mention of the starting vortex? Any scientist who is presented with a handwaving explanation of lift should ask themselves if it will work in liquid helium.
+Quillons1 Not really "right on". Not terrible, but not great. Accelerating fluid creating low pressure is the all too common misconception. The way she describes the cause of the upper surface lower pressure is essentially correct except for the word "pull". The lowered pressure above the wing does not actually pull the difference is the lift force.. It takes a force to accelerate a mass. This applies to a mass of air and the force available is pressure. There's more but no space here.
If you imaging a wing under water (air is a gas that behaves like a fluid) it is easy to see why the air behaves as it does. No need for silly explanations... Search Cambridge University-How wings Work or NASA - Incorrect Lift Theory for more.
Sorry, but Bernoulli is *always* part of ther whole lift story, __when used correctly__ ; which it rarely is. It takes a force (pressure) to accelerate a mass of air just like any other mass "Flow turnig" is the result of the pressure difference of a moving airfoil producing lift.
Oh, and air DOES NOT ACCELERATE over the upper surface of a wing. Another myth. In fact relative to free stream air, it SLOWS DOWN as is must because of viscosity and form drag and because it is being pulled in the direction of movement of the wing. Again, watch the Cambridge video pulsed smoke section and see the myths explode!
The only argument you'll get is the Coanda part. While it looks sthe same, Coanda is considered to be the effect when a *Forced, high pressure jet, or sheet of air* is directed over a convex surface to develop, or improve lift - rather than the air moving as the result of a convex surface moving through air.
*If you are careful* this explanation can be made just as well when considering that the wing is moving through the air, not air moving past the wing. THIS IS THE CORRECT EXPLANATION OF LIFT. ... Very refreshing to see...
Finally a video with the correct explanation. You usually get the explanation that the air travels faster on the top of the curved wing and therefor creates a lower pressure that creates the lift. Actually its the other way round: the pressure difference created by the wing as seen in the video creates the speed difference
+Eduardo Maltauro: Bernoulli's Principle is *not* false. It is the incorrect interpretation and application of Bernloulli's Principle that has been used to incorrectly explain lift too many times in the past and now.
Very refreshing to see this.
Stunt planes have symmetrical wings, so no Bernoulli. And many planes can fly upside down so again, the B effect is not really important. Its all about flow turning. If there is a B effect, its only helping create a small amount of upwards force, but not enough to actually lift anything .
I was high and this question popped into my head, thanks
+Quillons1 RE: "when a fluid accelerates, it creates low pressure against a surface ".
Actually, it is the other way around. The low pressure (caused by the convex curved shape) causes air to accelerate from higher to lower pressure. In the case of the upper surface, the acceleration is more of a radial acceleration - that is, acceleration being a change in velocity making it curve.
If done carefully, this same explanation works just as well when using the wing moving past the air.
While I could pick on a few choices of words, this essentially explains lift correctly.
"drag along" = Entrains due to viscosity
"Stationary air" = Air at that point
"small vacuum" = lower pressure
"pulls the airstream towards the wing" = higher pressure above pushes it towards the wing.
As a wing moves through the air at a positive AOA, the lower surface pushes the air forwards and downwards creating lift component 1. The pressure bow wave in front of the lower leading edge then pushes the air up and over the wing. Normal static air pressure holds the air close to the wing's surface. The skin friction (form drag) causes the air to be pulled forwards in the direction of the wing's movement and downwards parallel to the upper surface. Change of direction =Force. F=Ma = Lift.
The blowing effect over paper is also a myth as far as lift is concerned. What you have described is normal viscosity.
Sorry Naked Science people. The Coanda effect does not exist (if at all) in un-accelerated flows. It is typically described as being the 'effect' present in upper surface blowing but some scientists do not think it really exists as an effect distinct from viscosity/ form drag that are responsible for the boundary layer. The air over the upper surface is pulled forwards in the direction of the wing's movement and bent downwards by static air pressure. (no vacuums in normal space)
+Quillons1 It also is not technically the Coanda effect. Though similar, that term is used to describe a high speed jet, or sheet of air that is faster than the prevailing airflow, not the ordinary action of the surface moving through air. Sounds like a nit, but true.
Basically the same effect. You can produce lift with a plane plate by having shown angle against the air, much like sticking your hand out of the car window while driving.
In inverted flight state a profile like the shown one will still produce lift, but much less than in normal position, as it is designed to be more effective that way. This and the quite high number of passengers who would dislike inverted flight usually stops commercial pilots from flying this way ;-)
+MaverickX2k5 Regarding the statement: "Higher velocity results in a lower pressure!"
This is the common misapplication of Bernoulli and has it backwards. Air changes velociry *because of* a difference in pressure.
It is that precise bad interpretation of Bernoulli that has been incorrectly used to explain lift. LISTEN CAREFULLY, the video says @1:40 that the curve causes a low pressure (tiny vacuum) that puls the air down. Ok the pressure above pushes it down.
+Quillons1 Finally, Bernoulli describes both the upper and lower. It is a pressure fifference that causes the curved air path in both. Below, the wing's curve creates the higher pressure and above, the lower pressure as she describes.
This is very much it: A fluid has a certain amount of energy in the current state, which is a sum of temperature, pressure and velocity. If you don't put energy into the fluid, the amount has to stay the same, but you can change the parts:
Higher velocity results in a lower pressure!
Don't mix this up with higher velocity of engine exhaust: you put very much energy into the fluid here!
Why not? it is the very same principle, just that the wing is upside down. A wing must not be shaped like the ones of a commercial airliner. In fact, commercial airliners create much less lift when upside down as they are designed to be more effective in normal flight state
Let us try to explain the physics of lift and control and let the readers ponder about it. Assume the space around us is filled with a voluminous mass of fluid at atmospheric pressure.
1. If one bashed a voluminous lump of very fast heavy fluid against the surface area of a heavy body, then on impact ,there will be created zones of high compression (high pressures) and any reflected, or bouncing sheets of fluid, which will try and separate from the surface of the body, they will create between them and the surface of the body, zones of partial vacuum or low pressure. So bashing volumes of fluid on to a solid body can create zones of high pressure, while trying to reflect and separate fluid sheets from surfaces of a body, will form zones of low pressure .
2. A heavy body can be made to levitate and move and be made directional in a fluid, by arranging for the body itself to throw volumes of fluid at itself, in selected directions and through shaping the outer contours of the body, the compression and partial vacuum zones can be made unsymmetrical such that its body lifts itself, while its direction is selected through the controlled throwing of more fluid moving along various angled surfaces.
3. It is best to keep the adjacent flows of the fluid to have little differential velocities, but if these differential velocities are high then one can circulate the faster streamlines to take the form of a helix rotating around the slower one where the axial velocity of the spiralling helix will be the same as the slower straight streamline, till they mix and equalise in pressure and velocity.
There is all of micro detail in that, but better to keep to the basic principles to start with.
It's a good video learning process shows, thanks.
It's me,
Sule Shangodoyin.
If this is a scientific presentation, then why no mention of the starting vortex? Any scientist who is presented with a handwaving explanation of lift should ask themselves if it will work in liquid helium.
they know how design of plane stays aloft. but equations don't explain how aerodynamic lift occurs.
What's that situation is called...
I want to know the technical word of that condition
+Quillons1 Not really "right on". Not terrible, but not great.
Accelerating fluid creating low pressure is the all too common misconception. The way she describes the cause of the upper surface lower pressure is essentially correct except for the word "pull". The lowered pressure above the wing does not actually pull the difference is the lift force.. It takes a force to accelerate a mass. This applies to a mass of air and the force available is pressure. There's more but no space here.
If you imaging a wing under water (air is a gas that behaves like a fluid) it is easy to see why the air behaves as it does. No need for silly explanations... Search Cambridge University-How wings Work or NASA - Incorrect Lift Theory for more.
Coanda is irrelevant. Air is pulled down due to pressure differential, but it is not the Coanda effect.
How does a plane stay in flight upside down?
+General: Not true. The upper flow separates in a stall.
Sorry, but Bernoulli is *always* part of ther whole lift story, __when used correctly__ ; which it rarely is. It takes a force (pressure) to accelerate a mass of air just like any other mass "Flow turnig" is the result of the pressure difference of a moving airfoil producing lift.
one awser gravity
thanks mam
did you know there's nothing called safely landing on the water? its called crashing into the sea
it doesnt
@Task5003 No duh.
thats not real theory!
Where is Bernoulli's principle? This video is false
How a Wing Actually Works: /watch?v=aFO4PBolwFg
Oh, and air DOES NOT ACCELERATE over the upper surface of a wing. Another myth. In fact relative to free stream air, it SLOWS DOWN as is must because of viscosity and form drag and because it is being pulled in the direction of movement of the wing. Again, watch the Cambridge video pulsed smoke section and see the myths explode!
they know how design of plane stays aloft. but equations don't explain how aerodynamic lift occurs.
The only argument you'll get is the Coanda part. While it looks sthe same, Coanda is considered to be the effect when a *Forced, high pressure jet, or sheet of air* is directed over a convex surface to develop, or improve lift - rather than the air moving as the result of a convex surface moving through air.
*If you are careful* this explanation can be made just as well when considering that the wing is moving through the air, not air moving past the wing.
THIS IS THE CORRECT EXPLANATION OF LIFT.
... Very refreshing to see...
I'm not the only one who held a piece of paper to their lips only to be disappointed that nothing happened...right?
The best and simply explained lift
don't no real thing and shouting too much!
Finally a video with the correct explanation. You usually get the explanation that the air travels faster on the top of the curved wing and therefor creates a lower pressure that creates the lift. Actually its the other way round: the pressure difference created by the wing as seen in the video creates the speed difference
With a higher angle of attack...
hello what ur saying about coanda effect to try at home is wrong that's due to bernoully's eqation