The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing. In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s. Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge. Also, it's Daniel Bernoulli. _ The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air. The lift is then the total pressure difference caused by the motion of the wing through the air. Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
I love how you put the short clips at the beginning of the videos. Every time I think to myself, ah, SIFT studying sucks I'm reminded what I'm studying for! Great video as always!
I'm a newly Aviation Mech in the Navy and this has been so helpful feeding my hunger for well explained information that I can't wait to be working in my MR-60R. Thanks a lot! 😁
The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing. In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s. Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge. Also, it's Daniel Bernoulli. _ The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air. The lift is then the total pressure difference caused by the motion of the wing through the air. Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
Actually Newton's 3rd law is complete if you take into account viscous effects and the fluid being forced downwards on the upper part of the airfoil. The Bernoulli effect is an obsolete explanation for lift due to the fact that for it to occur you assume that particles at the attack edge reach the end of the airfoil at the same time, which is not necessarily true. But good video!
Equal transit is observably false. . The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing. In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s. Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge. Also, it's Daniel Bernoulli. _ The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air. The lift is then the total pressure difference caused by the motion of the wing through the air. Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing. In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s. Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge. Also, it's Daniel Bernoulli. _ The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air. The lift is then the total pressure difference caused by the motion of the wing through the air. Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
Appealing to Bernoulli fails to work for a hydrofoil moving slowly through liquid helium. When the hydrofoil speeds up, flow is unable to double back round the trailing edge and a starting vortex is left behind in the flow. By the conservation of vorticity, there must be bound vorticity in the boundary layers around the hydrofoil, and this generates a transverse force, or lift, by the Magnus effect. We can switch back and forth between the Magnus effect and the Kutta-Joukowski circulation theorem by linear transformations. The starting vortex can actually be observed, and Bernoulli can be applied after the event of it being shed.
The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing. In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s. Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge. Also, it's Daniel Bernoulli. _ The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air. The lift is then the total pressure difference caused by the motion of the wing through the air. Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
Good job explaining the theories in an easy-to-understand way! However, some of the explanations contain common misconceptions. The second portion of the explanation was good because it utilized Newton’s law which was very similar to Doug McLean’s argument in chapter 7 of the Understanding Aerodynamics textbook. However, the first portion of the explanation utilized Bernoulli’s principle to explain the theory which was a misconception both the University of Cambridge professor Holger Babinsky as well as McLean explained. It sounds like the velocity change was causing the changes in pressure which would lead to the generation of lift when in reality velocity and pressure respond simultaneously. In addition, this utilized the venturi tube to explain the theory which McLean explained is another common misconception because external flows around airfoils don’t behave the same way internal flows do in solid surfaces such as venturi tubes because this pinching doesn’t always result in a pressure or velocity change which wouldn’t produce lift.
Great video! I like how you explained each theory and stated that neither theories by themselves are correct. One thing I would change is that the fluid particles do not meet back up at the trailing edge. In most cases, the air particles on top have left the trailing edge before the ones on the bottom do. Other than that, thanks for the good content!
The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing. In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s. Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge. Also, it's Daniel Bernoulli. _ The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air. The lift is then the total pressure difference caused by the motion of the wing through the air. Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
Bernoulies principal is totally wrong when explaining lift. What causes a boat propeller, for example, to move a boat forward is correct. Pushing water (fluid) rearward as the rotor basically screws its way through the water. It creates pressure reduction in water in front of rotor as the water is pushed back behind the rotor, water in front rushes in to fill the void creating pressure differential between front and rear of rotor. Same principal applies to a wing.
Thank you for making videos, im currently in helicopter flight school and these videos really help me understand the concepts in the book, its helped immensely in my ground schooling.
The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing. In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s. Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge. Also, it's Daniel Bernoulli. _ The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air. The lift is then the total pressure difference caused by the motion of the wing through the air. Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
The Venturi effect is also used on pressure washers to allow chemical injection. When you put an opening in the Venturi(the low pressure area) the low pressure creates a vacuum and will draw chemical(through a tube that is submerged in container of chemical) into the system and send it down stream.
Jacob, how do you feel about the Coanda Effect? I use Bernoulli's, Newton's, and the Coanda Effect to explain lift to my students. Do you have any thoughts on the matter? Thanks, Adam.
Adam Hough. Up to this point I had not heard of it. But I did some research on it. To me, it seems like this would explain laminar flow over an airfoil. I see where it can potentially increase speed of the airflow which seems more like Bernoulli’s principle. But I’m missing how it, by itself, produces lift. Can you elaborate more on it? Great question by the way! I’m going to keep researching it.
@@helicopterlessonsin10minut10 So the way that I explain it is that a fluid tends to stick(or adhere) to a curved surface(airfoil). I usually draw a picture of water going over one side of a beach sized ball. If you can imagine, the water will indeed stick to the surface of the ball, until it is overcome by gravity and then leaves the ball's surface. Bernoulli's is essentially based on pressure/velocity differences, so that is where the coanda effect differs. There is an amazing video that explains it better than I: ua-cam.com/video/AvLwqRCbGKY/v-deo.html You can see in the video that the curved surface of the spoon is representing the leading edge and upper camber surface of an airfoil. So, as an airfoil moves through the air it will continue to "adhere" to the fluid around it(air-since air is a fluid). As you raise collective the air will adhere at a steeper angle causing a lifting sensation. I was taught about this in an aerodynamics class, but it was brief and I've since done my own research on it. Your videos and instruction is TOP SHELF and I was curious what you would think about it. Thanks very much for your time Sir and thank you for your service. -Adam
Adam Hough. I watched the video and did some more research on the matter. It seems like the coanda effect is actually used for NOTAR helicopters and even jet aircraft to supplement to normal lift/thrust of an airfoil. It doesn’t seem to fully explain lift solely by itself but it does offer a supplement to the lift an airfoil is already producing. Very interesting stuff! I’ll keep researching it and trying to break it down into an easier to teach format that doesn’t get confused with surface tension too easily. Thanks again for brining it up! I’m always interested in other instructor teaching references and methods.
@@helicopterlessonsin10minut10 The Coanda Effect and what goes on above a wing are very similar, but they are not completely the same thing. In addition, the Coanda has a specific definition which the wing doesn't satisfy. It is a forced jet in otherwise still air. They do, however, both produce a lower pressure along the convex surface. If you want more lift science, I can provide better information that almost all other amateur explanations.
@@adamhough7941 The Coanda Effect and what goes on above a wing are very similar, but they are not completely the same thing. In addition, the Coanda has a specific definition which the wing doesn't satisfy. Coanda is a forced jet in otherwise still air. They do, however, both produce a lower pressure along the convex surface. .. The way Bernoulli is commonly used is also incorrect whether is is with the equal transit fallacy or the half-venturi fallacy. The Newton reaction fallacy grabs part of the science, but misapplies it. .. If you want more lift science, I can provide better information that almost all other amateur explanations.
The theories of lift that you discussed could only explain lift partially. The other theory that I think to take into account is the circulation theory of lift. Generally the explanation was easy to follow along, and had good information but there were some misconceptions stated in the video. Such as comparing the airfoil to a venturi nozzle, as well as not really explaining how the top surface contributed to the lift generation.
The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing. In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s. Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge. Also, it's Daniel Bernoulli. _ The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air. The lift is then the total pressure difference caused by the motion of the wing through the air. Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
I am currently studying for the Army SIFT test to go warrant and fly helicopters are there any particular videos I should focus on or is better to to study all your videos?
Kyle. I'd recommend having some general knowledge of aerodynamic concepts. You don't necessarily have to get into all of the details to pass the test. Although the more you know the more you understand when you begin flying. I'd recommend checking out the first 8 or so videos of my "All Videos in Order" playlist to get started. Those address the bare bones basics. Best of luck to you on your test!
Thank you very much for information I've been watching your videos and I'm currently on video 11 in that playlist but I'm still gonna watch the rest the videos have been very helpful with my studies for the test!
Another outstanding job, sir. Just a quick question... What is your opinion on how much lift is generated by the Magnus effect. Since it wasn't mentioned in this lesson I can only assume it would be negligible. Thanks again and you take care.
David Wallace. I'm no physicist but I haven't seen the Magnus Effect show applicability to a helicopter rotor blade. The basic explanation of the Magnus Effect is that a rotating body will produce lift due to creating a pressure differential much like Bernoulli's Principle. This explains a lot when you look at a curveball or a ping pong ball with a spin on it. But with a rotor blade, nothing is really spinning along the leading edge of the airfoil. There have been prototype airfoils on some planes that show that by adding a rotating leading edge to an airfoil lift can be increased. But I've yet to see anything applied to a helicopter. Good question.
The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing. In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s. Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge. Also, it's Daniel Bernoulli. _ The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air. The lift is then the total pressure difference caused by the motion of the wing through the air. Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
The venturi theory and the equal time theory are not able at all to explain lift .... But I still think for a layman it's ok , but the matter is combination of Bernoulli's and Newton's third law ( not the granular theory too , the one you did) , the flow is attached to the top and moves towards the trailing edge and get directed downward so the airfoil moves upward , but how? Here comes Bernoulli's principle and we know that the difference in pressure creates lift but why the air speeds up on the top ( not because of the camber, if it was so inverted flight woul be impossible ) here Bernoulli's principle needs an extra explanation which I still don't know. Besides all these , your videos are amazing , thanks ! You deserve to have much more subscribers .... Keep up !
The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing. In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s. Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge. Also, it's Daniel Bernoulli. _ The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air. The lift is then the total pressure difference caused by the motion of the wing through the air. Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
There are too many variables to answer this general of a question. I’d recommend start by researching the exact model of aircraft you want to understand more about.
Misconception using Bernoulli to explain lift in a 3 deminsional flowfield. Newton's first and third laws simplistically defines lift. F=ma Equal and opposite reaction Lift is a force L=ma m= air density a= 1/2 velocity squared. Simplistically air is captured across the surface area of the wing and accelerated and forced downward at the trailing edge, generating upward force. Bernoulli does not account for downwash, which basically is the causitive effect of lift in both fixed and rotary flight, not pressure differential. The whole concept of boundary layer, circulation theory, and vorticity comes into play in actual 3d flight. Bernoulli theory works in the wind tunnel (2 deminsional flow) but falls apart in 3 deminsional.
OK. But what is is that causes the air to accelerate? "Capture" hardly is a physics term. .. Problem: Also, if the air is "forced downward at the trailing edge" why do we measure the lift centered toward the leading edge?
The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing. In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s. Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge. Also, it's Daniel Bernoulli. _ The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air. The lift is then the total pressure difference caused by the motion of the wing through the air. Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
Help me understand. When in auto rotation, specifically in a gyroplane, the rotational speed of the rotor is determined by the condition of the atmosphere and the gross weight of the aircraft. Typically a two place machine with two passengers, the rotor speed will be in the neighborhood of 350 rpm. We also will not see more than a 10% change of rotor rpm during the entire flight envelope. This is not true during the flare as the g-loading will increase causing an increase of rotor rpm prior to landing. Is the limiting factor of rotor rpm due to induced and parasitic drag of the airfoil? I also tend to view lift as a factor of rrpm and tend to ignore airspeed as an equal component of the total lift. As a gyroplane is already in auto rotation we will descend for fun at zero airspeed until a decision height which at that time we will lower the nose and accelerate to our best glide speed for landing. We could hold that zero airspeed descent and probably survive but destroying the aircraft. We nose the aircraft over to store energy in the blades or so that term is used. But if the rotor rpm really doesn’t change all that much what is the extra airspeed really gaining? Is it energy stored in the spinning rotor or is the aircraft benefiting from additional lift from more airflow over the disk? Let’s say a hypothetical disk is achieving 300 mph in the driven area and it is moving into a 65 mph forward speed generated wind. The advancing blade benefits and shares this with the retreating blade via teetering. Although the rrpm has not substantially increased, has the total lift increased because of flow or because of the resistance of the viscosity of more air trying to move through the rapidly rotating rotor. Are we too obsessed about rrpm and not so much airspeed, when airspeed might be our better friend when in auto rotation once our desired rrpm is achieved?
Helicopter Lessons In 10 Minutes or Less I knew it! Just spent a month out there for field training won’t forget it. Very helpful video. You do an excellent job of breaking things down so that they’re easier to retain.
No. Air pressure pushes air against the surfaces; all surfaces, top and bottom; all the time. .. The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing. .. In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s. . Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge. Also, it's Daniel Bernoulli. _ The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air. The lift is then the total pressure difference caused by the motion of the wing through the air. Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
I think Bernoulli principle doesn't make sense in lift force because how one can prove that fluid particles over lower and upper side of airfoil reach trailing edge at the exact same time. so, coanda effect make sense for lifting force.
+ evanleebodies , He is not using the equal transit fallacy. He is using the half-venturi fallacy. The Coanda Effect is similar to what happens above a wing, but not correct. Coanda is for a forced jet into otherwise still air.
The Newton explanation is not very good, the air over the top of the wing is accelerated and leaves the wing at an angle approximately in line with the wing chord with a positive angle of attack with respect to the ground. Therefore with respect to Newton’s third law the direction is upwards. Otherwise a fully symmetrical wing would not creat lift.
Jacob: "Hey, here's two concepts that help explain lift. Just keep in mind neither is a complete explanation for lift and this is also a simplified overview." YT commenters: "ACkShEwaLLy..."
@@helicopterlessonsin10minut10 NO! it is wrong. It is one of many guesses by amateur scientists. . The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing. . In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s. . Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge. Also, it's Daniel Bernoulli. _ The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air. The lift is then the total pressure difference caused by the motion of the wing through the air. Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
+ evanleebodies , You're using the wrong intuition. The narrow section is a restriction in the flow which causes the pressure to go up UP STREAM of the narrowing; in the wide section to the left. This increased pressure is what accelerates the mass of the fluid into the narrow section. The narrow section is like a hole in a pressurized tank. .. This is exactly like putting your finger on the end of a garden hose. It squirts farther *because* the pressure went up IN THE hose BEFORE your finger..
@@evanleebodies Thank you. However it isn't brilliant, it is just correct. . Because I took responsibility for a full cockpit Boeing 737 flight simulator at a science center several years ago, I decided to look up lift since I'd be asked to explain anything and found all the nonsense people are trying to explain while violating this or that fundamental principle. ... The air over a wing is accelerated *BECAUSE OF* the lower pressure. Euler taught us in the mid 1700s that Pressure Gradients accelerate fluid, just like force accelerates mass as Newton taught us... . Those Pressure Gradients around a wing are caused by the simple fact that the wing (just like anything moving through a fluid) must move the air around so it can get through. This and only this causes high and low pressures at the surfaces and that is the lift. These pressures are to our advantage for flight, but I won't go into more detail here. *Everything else* can be easily shown to be caused by these pressures...including the down-wash (diverted air). . To test my understanding and clear up a few more things I actually contacted Boeing's Doug McLean (see his UA-cam misconceptions video) and Embry-Riddle's Charles Eastlake. So I know this stuff is correct and the only thing that makes sense when you keep all the fundamentals in view at all times (if you know them and can). .. The pinching/narrowing thing is wrong because the air far above is not a hard surface and if you care to look, there is another "narrowing" below the trailing edge: *BUSTED!* .. So many people that are well-meaning, but wrong.
I take my cfi check ride in a few weeks and I can’t tell you how helpful your videos have been to really smooth out my presentations.
The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing.
In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s.
Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge.
Also, it's Daniel Bernoulli.
_
The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air.
The lift is then the total pressure difference caused by the motion of the wing through the air.
Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
I love how you put the short clips at the beginning of the videos. Every time I think to myself, ah, SIFT studying sucks I'm reminded what I'm studying for! Great video as always!
I'm a newly Aviation Mech in the Navy and this has been so helpful feeding my hunger for well explained information that I can't wait to be working in my MR-60R. Thanks a lot! 😁
The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing.
In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s.
Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge.
Also, it's Daniel Bernoulli.
_
The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air.
The lift is then the total pressure difference caused by the motion of the wing through the air.
Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
Actually Newton's 3rd law is complete if you take into account viscous effects and the fluid being forced downwards on the upper part of the airfoil. The Bernoulli effect is an obsolete explanation for lift due to the fact that for it to occur you assume that particles at the attack edge reach the end of the airfoil at the same time, which is not necessarily true. But good video!
Equal transit is observably false.
.
The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing.
In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s.
Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge.
Also, it's Daniel Bernoulli.
_
The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air.
The lift is then the total pressure difference caused by the motion of the wing through the air.
Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
Nice video mate and your explanation in the description is always good.
Thanks for that
Always appreciate your videos.
The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing.
In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s.
Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge.
Also, it's Daniel Bernoulli.
_
The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air.
The lift is then the total pressure difference caused by the motion of the wing through the air.
Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
Appealing to Bernoulli fails to work for a hydrofoil moving slowly through liquid helium. When the hydrofoil speeds up, flow is unable to double back round the trailing edge and a starting vortex is left behind in the flow. By the conservation of vorticity, there must be bound vorticity in the boundary layers around the hydrofoil, and this generates a transverse force, or lift, by the Magnus effect. We can switch back and forth between the Magnus effect and the Kutta-Joukowski circulation theorem by linear transformations. The starting vortex can actually be observed, and Bernoulli can be applied after the event of it being shed.
Thanks a lot friend you helped me a lot. Keep up the work😄
The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing.
In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s.
Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge.
Also, it's Daniel Bernoulli.
_
The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air.
The lift is then the total pressure difference caused by the motion of the wing through the air.
Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
Good job explaining the theories in an easy-to-understand way! However, some of the explanations contain common misconceptions. The second portion of the explanation was good because it utilized Newton’s law which was very similar to Doug McLean’s argument in chapter 7 of the Understanding Aerodynamics textbook. However, the first portion of the explanation utilized Bernoulli’s principle to explain the theory which was a misconception both the University of Cambridge professor Holger Babinsky as well as McLean explained. It sounds like the velocity change was causing the changes in pressure which would lead to the generation of lift when in reality velocity and pressure respond simultaneously. In addition, this utilized the venturi tube to explain the theory which McLean explained is another common misconception because external flows around airfoils don’t behave the same way internal flows do in solid surfaces such as venturi tubes because this pinching doesn’t always result in a pressure or velocity change which wouldn’t produce lift.
Great video! I like how you explained each theory and stated that neither theories by themselves are correct. One thing I would change is that the fluid particles do not meet back up at the trailing edge. In most cases, the air particles on top have left the trailing edge before the ones on the bottom do. Other than that, thanks for the good content!
Omg thank you so much for your videos, you're God send, it helps me so much to help study these topics! Thank YOU 🙏🏼👍👏😍
The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing.
In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s.
Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge.
Also, it's Daniel Bernoulli.
_
The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air.
The lift is then the total pressure difference caused by the motion of the wing through the air.
Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
Bernoulies principal is totally wrong when explaining lift. What causes a boat propeller, for example, to move a boat forward is correct. Pushing water (fluid) rearward as the rotor basically screws its way through the water. It creates pressure reduction in water in front of rotor as the water is pushed back behind the rotor, water in front rushes in to fill the void creating pressure differential between front and rear of rotor. Same principal applies to a wing.
You're amazing
Thank you for making videos, im currently in helicopter flight school and these videos really help me understand the concepts in the book, its helped immensely in my ground schooling.
The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing.
In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s.
Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge.
Also, it's Daniel Bernoulli.
_
The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air.
The lift is then the total pressure difference caused by the motion of the wing through the air.
Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
I believe Bernoulli's can perfectly explain lift, where it went wrongs?
ua-cam.com/video/w78JT6azrZU/v-deo.html
This will enlighten you!!
The Venturi effect is also used on pressure washers to allow chemical injection. When you put an opening in the Venturi(the low pressure area) the low pressure creates a vacuum and will draw chemical(through a tube that is submerged in container of chemical) into the system and send it down stream.
Jacob, how do you feel about the Coanda Effect? I use Bernoulli's, Newton's, and the Coanda Effect to explain lift to my students. Do you have any thoughts on the matter? Thanks, Adam.
Adam Hough. Up to this point I had not heard of it. But I did some research on it. To me, it seems like this would explain laminar flow over an airfoil. I see where it can potentially increase speed of the airflow which seems more like Bernoulli’s principle. But I’m missing how it, by itself, produces lift. Can you elaborate more on it? Great question by the way! I’m going to keep researching it.
@@helicopterlessonsin10minut10 So the way that I explain it is that a fluid tends to stick(or adhere) to a curved surface(airfoil). I usually draw a picture of water going over one side of a beach sized ball. If you can imagine, the water will indeed stick to the surface of the ball, until it is overcome by gravity and then leaves the ball's surface. Bernoulli's is essentially based on pressure/velocity differences, so that is where the coanda effect differs. There is an amazing video that explains it better than I: ua-cam.com/video/AvLwqRCbGKY/v-deo.html You can see in the video that the curved surface of the spoon is representing the leading edge and upper camber surface of an airfoil. So, as an airfoil moves through the air it will continue to "adhere" to the fluid around it(air-since air is a fluid). As you raise collective the air will adhere at a steeper angle causing a lifting sensation. I was taught about this in an aerodynamics class, but it was brief and I've since done my own research on it. Your videos and instruction is TOP SHELF and I was curious what you would think about it. Thanks very much for your time Sir and thank you for your service. -Adam
Adam Hough. I watched the video and did some more research on the matter. It seems like the coanda effect is actually used for NOTAR helicopters and even jet aircraft to supplement to normal lift/thrust of an airfoil. It doesn’t seem to fully explain lift solely by itself but it does offer a supplement to the lift an airfoil is already producing. Very interesting stuff! I’ll keep researching it and trying to break it down into an easier to teach format that doesn’t get confused with surface tension too easily. Thanks again for brining it up! I’m always interested in other instructor teaching references and methods.
@@helicopterlessonsin10minut10 The Coanda Effect and what goes on above a wing are very similar, but they are not completely the same thing. In addition, the Coanda has a specific definition which the wing doesn't satisfy. It is a forced jet in otherwise still air.
They do, however, both produce a lower pressure along the convex surface.
If you want more lift science, I can provide better information that almost all other amateur explanations.
@@adamhough7941 The Coanda Effect and what goes on above a wing are very similar, but they are not completely the same thing. In addition, the Coanda has a specific definition which the wing doesn't satisfy. Coanda is a forced jet in otherwise still air.
They do, however, both produce a lower pressure along the convex surface.
..
The way Bernoulli is commonly used is also incorrect whether is is with the equal transit fallacy or the half-venturi fallacy.
The Newton reaction fallacy grabs part of the science, but misapplies it.
..
If you want more lift science, I can provide better information that almost all other amateur explanations.
The theories of lift that you discussed could only explain lift partially. The other theory that I think to take into account is the circulation theory of lift. Generally the explanation was easy to follow along, and had good information but there were some misconceptions stated in the video. Such as comparing the airfoil to a venturi nozzle, as well as not really explaining how the top surface contributed to the lift generation.
Great explanation as usual, thanks.
The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing.
In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s.
Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge.
Also, it's Daniel Bernoulli.
_
The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air.
The lift is then the total pressure difference caused by the motion of the wing through the air.
Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
I am currently studying for the Army SIFT test to go warrant and fly helicopters are there any particular videos I should focus on or is better to to study all your videos?
Kyle. I'd recommend having some general knowledge of aerodynamic concepts. You don't necessarily have to get into all of the details to pass the test. Although the more you know the more you understand when you begin flying. I'd recommend checking out the first 8 or so videos of my "All Videos in Order" playlist to get started. Those address the bare bones basics. Best of luck to you on your test!
Thank you very much for information I've been watching your videos and I'm currently on video 11 in that playlist but I'm still gonna watch the rest the videos have been very helpful with my studies for the test!
Another outstanding job, sir. Just a quick question... What is your opinion on how much lift is generated by the Magnus effect. Since it wasn't mentioned in this lesson I can only assume it would be negligible. Thanks again and you take care.
David Wallace. I'm no physicist but I haven't seen the Magnus Effect show applicability to a helicopter rotor blade. The basic explanation of the Magnus Effect is that a rotating body will produce lift due to creating a pressure differential much like Bernoulli's Principle. This explains a lot when you look at a curveball or a ping pong ball with a spin on it. But with a rotor blade, nothing is really spinning along the leading edge of the airfoil. There have been prototype airfoils on some planes that show that by adding a rotating leading edge to an airfoil lift can be increased. But I've yet to see anything applied to a helicopter. Good question.
Thanks for your reply and keep em flying sir!
Great! Thumbs up, Thank you
The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing.
In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s.
Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge.
Also, it's Daniel Bernoulli.
_
The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air.
The lift is then the total pressure difference caused by the motion of the wing through the air.
Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
Your videos are amazing!!! Can we get more?))))
Working on it. I’m busy right now doing the magic this aircraft was truly meant to do.
The venturi theory and the equal time theory are not able at all to explain lift .... But I still think for a layman it's ok , but the matter is combination of Bernoulli's and Newton's third law ( not the granular theory too , the one you did) , the flow is attached to the top and moves towards the trailing edge and get directed downward so the airfoil moves upward , but how? Here comes Bernoulli's principle and we know that the difference in pressure creates lift but why the air speeds up on the top ( not because of the camber, if it was so inverted flight woul be impossible ) here Bernoulli's principle needs an extra explanation which I still don't know.
Besides all these , your videos are amazing , thanks ! You deserve to have much more subscribers .... Keep up !
The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing.
In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s.
Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge.
Also, it's Daniel Bernoulli.
_
The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air.
The lift is then the total pressure difference caused by the motion of the wing through the air.
Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
What fraction of the lift is provided by AOA vs wing shape, for a typical airliner, at typical cruise speed and altitude?
There are too many variables to answer this general of a question. I’d recommend start by researching the exact model of aircraft you want to understand more about.
Misconception using Bernoulli to explain lift in a 3 deminsional flowfield.
Newton's first and third laws simplistically defines lift.
F=ma
Equal and opposite reaction
Lift is a force
L=ma
m= air density
a= 1/2 velocity squared.
Simplistically air is captured across the surface area of the wing and accelerated and forced downward at the trailing edge, generating upward force.
Bernoulli does not account for downwash, which basically is the causitive effect of lift in both fixed and rotary flight, not pressure differential. The whole concept of boundary layer, circulation theory, and vorticity comes into play in actual 3d flight.
Bernoulli theory works in the wind tunnel (2 deminsional flow) but falls apart in 3 deminsional.
OK. But what is is that causes the air to accelerate?
"Capture" hardly is a physics term.
..
Problem:
Also, if the air is "forced downward at the trailing edge" why do we measure the lift centered toward the leading edge?
Good vídeo 👍🏾🚁
The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing.
In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s.
Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge.
Also, it's Daniel Bernoulli.
_
The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air.
The lift is then the total pressure difference caused by the motion of the wing through the air.
Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
Newton’s 3rd law. It is not only the airflow below the wing but the flow above the wing also makes lift.
Help me understand. When in auto rotation, specifically in a gyroplane, the rotational speed of the rotor is determined by the condition of the atmosphere and the gross weight of the aircraft. Typically a two place machine with two passengers, the rotor speed will be in the neighborhood of 350 rpm. We also will not see more than a 10% change of rotor rpm during the entire flight envelope. This is not true during the flare as the g-loading will increase causing an increase of rotor rpm prior to landing. Is the limiting factor of rotor rpm due to induced and parasitic drag of the airfoil? I also tend to view lift as a factor of rrpm and tend to ignore airspeed as an equal component of the total lift. As a gyroplane is already in auto rotation we will descend for fun at zero airspeed until a decision height which at that time we will lower the nose and accelerate to our best glide speed for landing. We could hold that zero airspeed descent and probably survive but destroying the aircraft. We nose the aircraft over to store energy in the blades or so that term is used. But if the rotor rpm really doesn’t change all that much what is the extra airspeed really gaining? Is it energy stored in the spinning rotor or is the aircraft benefiting from additional lift from more airflow over the disk? Let’s say a hypothetical disk is achieving 300 mph in the driven area and it is moving into a 65 mph forward speed generated wind. The advancing blade benefits and shares this with the retreating blade via teetering. Although the rrpm has not substantially increased, has the total lift increased because of flow or because of the resistance of the viscosity of more air trying to move through the rapidly rotating rotor. Are we too obsessed about rrpm and not so much airspeed, when airspeed might be our better friend when in auto rotation once our desired rrpm is achieved?
Was your intro clip taken at Graff?
Jaime Olague. Yep. It was.
Helicopter Lessons In 10 Minutes or Less I knew it! Just spent a month out there for field training won’t forget it. Very helpful video. You do an excellent job of breaking things down so that they’re easier to retain.
Super
3:21 isnt the reason of airflow sticks on the airfloil no slip condition?
No. Air pressure pushes air against the surfaces; all surfaces, top and bottom; all the time.
..
The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing.
..
In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s.
.
Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge.
Also, it's Daniel Bernoulli.
_
The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air.
The lift is then the total pressure difference caused by the motion of the wing through the air.
Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
I think Bernoulli principle doesn't make sense in lift force because how one can prove that fluid particles over lower and upper side of airfoil reach trailing edge at the exact same time. so, coanda effect make sense for lifting force.
+
evanleebodies
,
He is not using the equal transit fallacy. He is using the half-venturi fallacy. The Coanda Effect is similar to what happens above a wing, but not correct. Coanda is for a forced jet into otherwise still air.
Is that Germany in the opening clip? I did a crap ton of Land Nav there as a private, ha!
Why flow over airfoil faster than below
@@cosaosa2855
Wrong explanation
U talk about a wrong theory called transit time or equal path
And its wrong
Nonsense. There is no restriction above the wing
The Newton explanation is not very good, the air over the top of the wing is accelerated and leaves the wing at an angle approximately in line with the wing chord with a positive angle of attack with respect to the ground. Therefore with respect to Newton’s third law the direction is upwards. Otherwise a fully symmetrical wing would not creat lift.
Jacob: "Hey, here's two concepts that help explain lift. Just keep in mind neither is a complete explanation for lift and this is also a simplified overview."
YT commenters: "ACkShEwaLLy..."
You are Wrong to explain lift using the bernoulli principle...
It’s one of the many theories
@@helicopterlessonsin10minut10 NO! it is wrong. It is one of many guesses by amateur scientists.
.
The “Bernoulli Principle half-venturi” explanation is false. The air far above the wing is not a hard boundary and the air does not speed up because of this. If that was valid, then there would be an equally low pressure under the wing because you can easily see that the trailing edge produces a similar ‘narrowing’ below the wing.
.
In addition, a pressure difference between two regions, called a pressure gradient, is what speeds up the fluid in the venturi. Air has mass and Newton tells us that a force is required to accelerate a mass and in a fluid, a pressure difference accelerates fluid. Pressure is the force that accelerates air. The fluid does not magically speed up in the venturi narrowing without the force provided by the pressure difference. Pressure difference causes acceleration in fluids. Euler figured this out in the mid 1700s.
.
Above a wing, it is the curved flow that creates a lower pressure and the low pressure accelerates that air toward the trailing edge.
Also, it's Daniel Bernoulli.
_
The common Newton explanation is incorrect because the air does not bounce off the bottom, but the flow is curved to flow downward, but along the lower surface. That causes an increase in pressure at the lower surface. The wing moving toward the air increases the pressure. This increased pressure under the wing pushes up on the wing and down on the air.
The lift is then the total pressure difference caused by the motion of the wing through the air.
Those two explanations are incorrect, but it is the pressure difference top-to-bottom which is the lift.
No, not wrong. Maybe just not complete.
Seems counter-intuitive.....air flow being lower pressure when its going through a constriction in a tube
+
evanleebodies
,
You're using the wrong intuition. The narrow section is a restriction in the flow which causes the pressure to go up UP STREAM of the narrowing; in the wide section to the left. This increased pressure is what accelerates the mass of the fluid into the narrow section. The narrow section is like a hole in a pressurized tank.
..
This is exactly like putting your finger on the end of a garden hose. It squirts farther *because* the pressure went up IN THE hose BEFORE your finger..
@@Observ45er Ahaaa!! brilliant explanation...thanks
@@evanleebodies Thank you. However it isn't brilliant, it is just correct.
.
Because I took responsibility for a full cockpit Boeing 737 flight simulator at a science center several years ago, I decided to look up lift since I'd be asked to explain anything and found all the nonsense people are trying to explain while violating this or that fundamental principle.
...
The air over a wing is accelerated *BECAUSE OF* the lower pressure.
Euler taught us in the mid 1700s that Pressure Gradients accelerate fluid, just like force accelerates mass as Newton taught us...
.
Those Pressure Gradients around a wing are caused by the simple fact that the wing (just like anything moving through a fluid) must move the air around so it can get through. This and only this causes high and low pressures at the surfaces and that is the lift. These pressures are to our advantage for flight, but I won't go into more detail here. *Everything else* can be easily shown to be caused by these pressures...including the down-wash (diverted air).
.
To test my understanding and clear up a few more things I actually contacted Boeing's Doug McLean (see his UA-cam misconceptions video) and Embry-Riddle's Charles Eastlake. So I know this stuff is correct and the only thing that makes sense when you keep all the fundamentals in view at all times (if you know them and can).
..
The pinching/narrowing thing is wrong because the air far above is not a hard surface and if you care to look, there is another "narrowing" below the trailing edge: *BUSTED!*
..
So many people that are well-meaning, but wrong.