Part 2 - Coanda effect, Bernoulli's Principle and Lift
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- Опубліковано 28 лип 2024
- In this video i continue to describe how lift is created using Bernoulli's principle, the coanda effect, the motion of air over curved surfaces and more. if you REALLY want to understand how these things are related watch this video!
Excellent and clear explanation, thanks.
That’s great explanation!! The fact that it works with water, it mean water is a fluid!
that is actually how we steer submarines yes! we use the tails to make an "angle of attack" with the water to lift the submarine up or suppress it down.
Great explanation, tying together Bernoulli's, Coanda effect and curved motion of the streamlines, and the effect they have on lift. I would suggest a couple of points to clear things up. While the curve of the airfoil does cause the streamline to speed up it does so specifically because of circulation. This along with the coanda effect and centrifugal force causes a force that pitches the airfoil up meaning that at the trailing edge of the airfoil the streamlines should be deflected downward instead of continuing in a straight path like your graphic show.
FINALLY !!!
It appears that you've improved this video since I last commented. It hits the important points rather well.
Lift is the lower / upper pressure difference.
The curved flow above is the cause of the lowered pressure.
[curved flow is also the cause of the higher pressure below]
..
HOWEVER, those red streamlines above the wing at 7:37 should curve downward behind the trailing edge.
Also,m it would be much better to refer to the upper pressure as Pupper because Pdown can be confused with the bottom pressure. Likewise for the Pup --> Pbelow.
Otherwise, GOOD JOB!
FINALLY a video by someone who gets it !!
Here is a summary of the physical effects that are taking place. Go to diagram at 03:29. Neglect, friction, viscosity, meniscus, surface tension and gravitational pull, electrostatics between fluid and mass of solid profile being used, any flying due to fluid sheets.
1, The fluid particles rushing from the left towards the cylinder will cause a very high pressure zone on the left hand side.
2. The high speed moving particles of fluid away/lateral from the centre line will experience a higher pressure on one side and they will be gradually aligned and vectored up and down about the centre line, in this case. (another position with aerofoil sections,)
3. Those group of particles forming a relatively wide sheet, now going up at high speed will tend to leave the receding surface with their momentum, but leaving the surface would create a partial vacuum with the surface, which will pull the particles towards the surface. Here it must be noted that putting one thin streamline of water or smoke will not create the higher vacuum that a whole sheet of fluid going over the solid surface of a ball or an aerofoil section. So for better understanding we shall stick to a sheet of fluid flowing over the whole surface, and not one narrow stream line.
4. The sheet of fluid will keep trying to continuously separate from the surface by its momentum, but will be restricted, by the partial vacuum created with the surface and also the atmospheric pressure above it in this case. So the particle will curve around creating centrifugal force.
5. The fluid sheet, note , a relatively wide sheet, will try to keep separating from the curved receding surface with its remaining momentum, but, the partial vacuum created by itself will still be formed to pull it to the surface, the atmospheric pressure will keep pushing it to the surface, while the centrifugal force will also be present.
6. This is the reason why the sheet of fluid will keep attaching itself to the body in question till there comes a location where it could separate for other states coming into action. These are the physics that are going on in the Coanda Effect and in any aerofoil section.
7. In a symmetrical body, all the above is occurring above and below and to the left or the right in the case of a ball or a torpedo or a ring.
8. In an aerofoil section which is not symmetrical and with or without an angle of attack, the high pressure and low pressure zones (bubbles) pushing or pulling the sheet of fluid to the surfaces of the solid body these can be controlled by the design of the profile of the airfoil section or its angle of attack and the speed of the fluid itself. In an airplane the sheet of fluid above the wing is made to try and continuously separate along the top surface through receding the surface down while that below the wing is made to be pushed through also angling down the lower surface down through the angle of attack so that its velocity downwards will push the fluid sheet all the time hence compression rather than a separation and partial vacuum.
9. The unequal velocities that occur at the trailing edge in an unsymmetrical aerofoil section with or without angle of attack have no option but to disturb each other and form a helix where the lower velocity will at first travel inside the helixes and vortexes and circulations which will eventually stir the fluid up to equalise the velocities hence pressures by bleeding into the turbulent bubble an atmospheric pressure on the top surface of the wing where it could stall for higher angles of attack.
I believe, Coanda Bernoulli, Newton, should get together and try and agree on the explanation and in the meantime to consider what I contributed.
I learned more from this then the vid!
Here's an idea.. why don't you make YOUR OWN video! That way, you wont be an Ass.. jamming-in 'your' way of explaining something that was already very informative.
@@philip6419 informative but wrong. As many popular explanations of lift are.
See docshare01.docshare.tips/files/3422/34223648.pdf
@@kramrle A & E aren't too bad. They have a few rough spots, but better than most amateurs.
finally someone who bothered to understand inertia effect and give a more complete still simple explanation. excellent explanation!
secondary, not important for this but possibly misleading small errors
coanda effect- coanda exact word was fluid (any fluid) not just air
bernoulli - bernoulli principle is working here but not formula, formula assume incompressible fluids
Your explanation is very clear and really easy to be understood, thank you
why is the pressure lower on the top of the wing?
Did you try the coanda effect with water over Teflon tube?
why is the pressure lower on the top of the wing?
You are great teacher. Thank you 🙏🏾💯 Shalom!
And you have a new subscriber 😊
Curvature of streamlines accounts for drop in pressure...also speed (scalar) and velocity (vector) should not be used interchangeably. Streamlines are tangent lines to velocity vector at any instant. Example - as combustion air is drawn into a furnace or boiler there is a slight pressure drop from ambient atmospheric conditions.
Great sir
Very clean explanation, thanks. One simple addition into the equations though, might be using 'with velocity' and 'when at rest'.
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Check out my Archimedes' principle video: ua-cam.com/video/fTXlID-8QGE/v-deo.html
Let me know if you'd like to have videos on other subjects
Lift is action and reaction.
The action is the deflection of air molecules downwards, the reaction is the wing being pushed upwards. Pressure differences are secondary. If there is no downflow of air from the wing, there is no lift.
R
awsome man
i have a question. about that tornado. when air moves a longer distance the pressure will go down but here you said the highest pressure was on the outside of the tornado. but that is the oppisit of that.
no in the center there is low pressure and in outside the pressure is high
The question is why pressure differential increases as speed increases? As aircraft speed increases, velocity on bottom and top of wings increases too. Then, pressure on top and bottom of wings decreases too. Why does a pressure differential comes up and lift force increases?
TNX
so what ? the high pressure just goes through the wing to the low pressure?
Consider a hydrofoil moving through liquid helium as compared to the same hydrofoil moving through liquid sodium. The hydrofoil is slightly inclined and the geometry or kinematics is exactly the same between the two cases.
In the case of the sodium, there will be a transverse force, also known as lift. There is no transverse force in the case of the helium. Not sure how talk about Newton or Bernoulli or the Coanda effect can explain this. It can be explained in terms of the Kutta condition and the Kutta-Joukowski circulation theorem.
It can be visualised as well. If a hydrofoil is moved with an intermittent stop-start action, it will generate a vortex street which we can see. While vorticity is bound with the hydrofoil, it generates lift by the Magnus effect, which is the same thing as KJ.
can someone explain aerodynamic on f1 car?
because we know that f1 is flat in the bottom, but the air move faster than upper part. meanwhile the aerofoil wing has the same thing, curved on upper part, and created a lift, not downforce.
🤔🤔🤔
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 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 occus 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
Actually, about the Coanda effect. You are stating that it applies to air or gas and not to water. In fact water and air are both fluids and the effect applies (to some extent) to all fluids, such as water.
infact, we have hydrofoils
Yes, it is. I have tested with water drop from a tap to the back side of a food spoon, and proved that it work.
In fact, Coanda himself discovered this effect by playing with water droplets from the tap, while taking a long bath.. He said that in an interview. :)
They are both 'fluid' in movement and the effect does occur in regards the spoon, ONLY because the spoon is not submerged. As a HVAC State Contractor, I see ignorant engineers trying to use the Coanda effect using liquid to design ductwork, only to have the entire systems torn out and replaced. THIS because, [in this case], liquid does NOT produce the same results as a gas.
The reason they usually do not attribute this effect to water is beacuse you can argue that water viscosity causes it to "stick" to the tube and not an external force. while air do have some viscosity its usually really small in comperison
thank you
Ty
I was expecting the mechanism behind it...already knew the statement.
Why is Pdown greater than Patm1? I dont get this. Wouldnt the air at Pdown be travelling faster then at Patm1, therefore be of less pressure?
What software or app to produce a video like this?
I have the same question!
The flow of a liquid or gas following along the outside of a curved surface is the COANDA EFFECT!
If you assume P(ATM)=P(atm1)=P(atm2)
Why do you say P(atm1)
Yes, it's incorrect. This would only be true, if an undercambered airfoil would be used.
@@worroSfOretsevraH This fundamental explanation applies to ALL wings. ALL!
Wao sir 🙋👍🌟💛
The distance between Patm1 and Patm2 is *_FEET_*.
does coanda effect happens because of bernouli's law? is it?
No, Coanda effect is related to fluid viscosity
If Bernoulli actually gave lift in air, how can planes fly upside down? Wouldn't the faster air over the curve (now on the bottom of the wing) cause the plane to lose lift and dive? Yes, Bernoulli applies... but it's not strong enough to generate lift in air.
Yes, Bernoulli is not the only explanation for the lift, but planes fly upside down because of the higher angle of attack of the plane in relation to incoming air when flying inverted. Fighter planes with high T/W ratio can climb vertically at 90 deg nose high and in that case the plane is flying at certain AoA where it is not producing lift. In other words, upper and lower part of the wing/plane are in pressure equilibrium at that given angle of attack.
@@Semendrija123 agreed... but I think you missed the main point, which is that if the Bernoulli Effect was the reason airplanes stayed in the air planes could not fly upside down.
My friend, Bernoulli only works in a single streamline not across a pressure gradient. This is a common error.
A wing is not a venturi as there is no constraint of the fluid and therefore no requirement to preserve pressure.
Cut a venturi in half and it doesn't work.
Any explanation has to work for a flat plate wing (no camber) because we know flat plate wings work very well.
Also all airliners have super-critical wings that are flat on top and curved underneath.
The effect you are talking about with the curved surface is viscosity and attachment not Coanda. Coanda does not work in non-accelerated flows if at all.
Aerodynamics IS fluid dynamics. The same rules apply. air is considered in compressible below M0.4.
Centrifugal force doesn't exist. It is angular momentum.
Lift is caused by turning a fluid. The amount is varied by airspeed or AOA F=MA
The pressure differences are caused by effective AOA.
The pressure below the wing is greater because it combines static and dynamic pressure.
If your explanation is not correct for a flat wing it is not correct. Period.
@Deos He's right, completely right. Not all wings are curved at the top surface.....
@Deos Indeed, for 'normal' aircraft you are right and Aerogeek got that wrong. However, and that is is main point: Curvature is completely non-essential to the principles of generating lift. Only AOA matters. Curvature serves only one purpose: To enable higher AOA without introducing airflow separation. Also, people always get Bernoulli wrong. It is a mathematical relationship that says *nothing* about the *cause* of the relationship. Thinking about the cause, however, it follows from Newton that in order for anything to accelerate, a force has to act upon it. Therefore higher/lower relative pressures *cause* the changes in relative flow speeds, not the other way round.
@@woodwind314 No, in general a more cambered airfoil decreases stall angle of attack but increases lift coefficient at zero angle of attack. Curvature is essential to the principles of generating lift because pressure must decrease as you move radially inward along curved streamlines - so there is a low pressure zone above the airfoil, which helps lift significantly.
The pressure difference between the bottom of the wing and the top is what causes lift. Upwash, downwash, the Coanda effect and turning of the flow are all caused by this pressure difference. They are effects, not causes. The low pressure on the top of the wing is caused by the particles interacting with each other and with the wing. Such interactions are ignored in the fluid approximation so it is not warranted near the wing’s surface. The reason for the low pressure on the top of a cambered wing is that the boundary layer there is depopulated by these interactions. This explains the purpose of the blown flaps on an aircraft carrier’s supersonic fighters.
P up must be greater than pp down according to fig
*Nope!* Look more carefully. Pup is the UPPER pressure which is lower than Pdown under the wing. His labels are confusing.
Why can planes fly upside down?
I'm searching for the reason that the pressure above the wing is lower than the pressure below. (I know it is, and I know that the pressure difference causes lift). Saying it's due to the increased airspeed over the wing is a CIRCULAR ARGUMENT! The speed above greater than the speed below because it's moving from high pressure to low pressure. That's a circular argument which is missing an independent explanation either for the speed difference or the pressure difference. And invoking Bernoulli to explain how increased speed induces low pressure is just a mathematical relationship between speed and pressure. Can someone, please explain the reason that there's a difference between the air over the two surfaces. (it's nothing to do with path lengths!)
Alan,
You're on the right track.
In short: the upper air is at a lowered pressure because of the curved (radially accelerated) flow.
..
A summary in basic concepts is that the wing must push air out of the way to get through it -- and the air pressure pushing inward all around the wing causes it to flow back in around the wing to "fill-in" behind it, wherever needed ti enclose the wing again.
.
Where the wing advances into the air, this pushes on the air and this increases the pressure. Where the air flows in to "fill the void" sort of behind the wing, this lowers the pressure allowing higher pressure regions to push it back in. The air around the wing then moves (accelerates) from higher pressures to lower pressures.
.
This explains it step-by-step: *www.quora.com/q/rxesywwbdscllwpn*
Of all the potential inviscid flows possible, on one meets the Kutta condition as soon as viscosity is introduced. That’s why the stream paths follow a curved path. The curvature causes pressure differences. The pressure differences cause accelerated flow.
@@fredericborloo1910 That says essentially the same thing.
Had the same issue from the explanation, thank you for asking it!
well, I think this expression is more rational and precise than Bernoulli's principle
Well you don't explain why the Coanda effect creates low pressure against the upper foil surface. Instead ,you present a circular argument, in which the curved flow creates centrifugal force which creates curved flow = circular argument.
Coanda effect occurs because an air flow travelling over the upper foil surface attracts the air surrounding the flow, towards the flow.
This results in a sleeve of low air pressure adjacent to the flow.
The sleeve of low pressure closest to the foil surface cannot be filled by surrounding air, due to the presence of the foil. The sleeve of low pressure on the upper surface of the flow can be filled quicker from adjacent air above. This results in a a tendency for the flow to move closer to the upper foil surface. i.e. low pressure adjacent to the foil below the flow, normal pressure above the flow. This is the Coanda effect.
The flow close to the foil is also facilitated by the angle of attack and foil shape creating a low pressure above the foil. As the foil moves at a positive angle of attack through the air, flow that would have traveled horizontal is forced down under the foil. This creates a relative low pressure behind the top foil surface. This low pressure attracts the flows going over the foil towards it.....and at greater speed due to less resistance from the low pressure.
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. Low pressure creates force normal to the cord (contact surface), and it name is "aerodynamic force" because is made from the air (aero) in motion (dynamic), or wind relative to the wing (object).
The equal time argument's wrong
Coanda effect and bernoulli principle does not give proper explanation to lift generation over airfoil rather they have their own limitation for explaining the lift generation.
The flaw is not working from velocity of the wing to lift. Invoking pressure reduction as the cause of lift is fine but then blaming pressure reduction on bernoulli/coanda is again problematic without reference to weight and gravity AND a wing moving in the open rather than a fluid driven through a tube. Furthermore conservation laws have zero relevance to incompressability of a fluid moving under a pressure differential thru a pipe.
To many false equivalences invoking laws used incorrectly bro
centrifugal force doesn't exist.
RE: your Part #2.
Your explanation is simplistic, but, unfortunately, actually, it is quite incorrect science. You have much correct here, but there are errors that are very significant.
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When the air that reaches the curved surface "kind-of pushes away the air molecules that were already there" this clearly indicates that there is a *_HIGHER_* pressure there! Higher pressure pushes toward lower pressure. The lower pressure as you describe makes no sense, science-wise, that is.
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This increased pressure is actually the case, but that higher pressure actually has the effect of accelerating that air stream in the curved path that changes direction to upward at about a 45 degree angle as you show in *_BLACK_* @2:40. That initial sharp curve requires a force and it is the increased pressure, caused by the air's motion against the solid object, at that point of first contact.
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The fact is that High pressure pushes toward lower pressure.
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Moving in that new direction, its inertia _*would carry it* along that same BLACK line. The fact that the air tries to move away from the surface reduces the pressure; not the sucking action of the pushed-away air you describe.
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As stated in another comment, Coanda applies to all fluids.
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Your curved path (which is an acceleration) explanation with the inward force being greater is correct. This is also why satellites orbit. This MUST be the same thing that happens at the point above at time 2:40 I mention above. Please review your earlier explanation with this in mind.
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At time 7:32, the upper air should be shown moving downward just as the lower air is.
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Finally, A very careful and correct analysis of the pressures that you correctly describe all motions around trhe wing and will ALSO be shown to be the very cause of the downwash. I now move on to your Video #3 to see what you say because there are NO OTHER factors...
--
Regards, ScienceAdvisorSteve
challengerillinois/org
@Castlegrad seriously ,i have been watching videos and reading for straight two days , still cant find clear answer for why the air flows faster over the top surface of the airfoil . if you had found it , kindly help
does coanda effect happens because of bernouli's principle?
@@vshankarfulFrom a physicist.That is closer to the truth. ua-cam.com/video/PF22LM8AbII/v-deo.html
@@vshankarful ua-cam.com/video/Gg0TXNXgz-w/v-deo.html
No one:
Absolutly no one :
UA-cam : Here, have some hebraic subtitles !
WTF?
7:30 thank me later
Confused nonsense with no actual explination or proof.
Great another equal transit myth
Lol