Hello everyone, I made this video after learning about lift in my high school physics class. Now I study engineering at Cornell University and I am taking an Aeronautics class because I wanted to know if what I was taught in high school was correct since I have many comments on this video saying that my explanation of lift using Bernoulli's principle is incorrect. Now I will try to respond to these comments based on what I have learned: First, in my video, I say that air travels faster over the upper surface because it has to cover a larger distance in the same amount of time as the air on the lower surface. This statement, also know as the equal transit time argument, is false! There is no physical principle that requires equal transit time and in reality, experiments have shown this is false. Furthermore, there are 2 popular lift theories, one relying on Newton's 3rd law, saying that airfoils deflect air downward and so the wing must experience a force upwards, and the second is based on Bernoulli's principle which correlates a difference in speed above and below the wing to a difference in pressures, causing lift, but it does not explain where the difference in speeds comes from. Therefore, both theories, used alone, are not necessarily incorrect, but they are incomplete. A more comprehensive and correct explanation of lift involves both theories, in which pressure differences along the airfoil are caused by a curved airflow (curved streamline). For straight flow, the pressure difference is zero, but for tight curvatures, there are large pressure differences along the surface. The non-uniform pressure distribution along the airfoil causes changes in the flow's direction and speed (Bernoulli's principle), where the air is accelerated from high pressure regions to low pressure regions. The pressure differences are only possible because air has mass and inertia and therefore resistance to movement. Airfoil surfaces are designed to deflect air downwards by using these pressure differences to accelerate air along the mostly downward sloping surface on the airfoil contour. The downward forced air then exerts an equal and opposite force (Newton's 3rd law) on the wing pushing it upwards. In summary, both principles are required to explain lift properly. Believe it or not, Wikipedia has a great explanation of lift if you read the first four sections (en.wikipedia.org/wiki/Lift_(force)). Hope this helps!"

Your ability to build this with things like pen housing for sleeves and the simplicity of design is brilliant!

Very nice for a first attempt but..... Experiments in a wind tunnel give much more accurate and repeatable data when done in laminar flow. By putting your ventilator in front of the model, you shoot a lot of very turbulent air onto the airfoil. The only thing you can really see here is that it actually moves. By moving the ventilator to the other side of the 'tunnel', and having it suck air *out* of the box, the flow around the airfoil will be less turbulent. Adding a honeycomb structure at the side where the air is sucked into the box, can reduce the turbulence even more, and create something which may start to look like laminar flow. The honeycomb structure should consist of small parallel pipes, similar to straws for drinking, placed in the direction of the flow of course, and cover the whole of the entrance. The walls of the straws should be thin compared to the diameter, to avoid introducing lots of drag. Pulling the rotor even further away from the airfoil (making the box much longer) will also help to improve laminar flow. I guess you will have learned this by now since the video is already 10 years old. But then my comment may help your viewers who would like to copy your setup. Just copying would be a bad idea if they want to create something that actually deserves to be called a wind tunnel.

Just what I was looking for, very cool.

Brilliant! Good job!

You should get a newton scale with a spring and attach it to measure the force produced.

Great project!

great video mate!!

clever design, well done

What a legend for thinking of this!! Amazing!!

This is so fucking cool dude, I’m making an engineering club for my highschool and I think this could be a rly fun project

Excellent example for lift force in aeroplane, thanks

Very nice...super.

Great project. Congratulations...but...the Bernoulli effect has very little effect on the production of lift on a wing. The Coanda effect of fluids acting on a curved surface creates a down-wash of the fluid, thus creating lift. So Newton's 3rd law of motion is the one "doing all the lifting", not Bernoulli's law. Great experiment!!!

Thnx ..great idea

Wow thank you!

Well done gentleman

good video thanks

Sick Erio!

He is a genius!great science fair project!

Very nice...super

Wing chord down: airplane Wing chord up: f1 car

That's a fantastic beginning, If you placed the vertical posts on the outside of the foil you could change the angle of attack into the wing giving you more than just flat flight but take off and landing. also you already have most of the RC equipment add a couple of rc flaps smoke generator and nozzles, maybe some threads on the surface, and possibly a tail.

Very good project and very well done!!! Nice presentation too!!! It looks like the angle of attack is higher on the airfoil shaped wing than it is on the flat wing but that may not be the case, it could be that it just appears that way from where I sit. If the angle of attack is less on the flat wing than on the airfoil shaped wing, then the comparison between the two wouldn't be fair, an "Apples to Apples" comparison for angle of attack would be required but again, they may just appear to be different from my perspective. Either way, your experiment clearly shows that an airfoil shape performs much better than a flat wing regardless of angle of attack. Lots of RC guys fly flat foam wing planes including me and they fly pretty good as long as they have enough power (like a 1.25 to 1 thrust to weight ratio or better). Give it enough power and almost anything will fly 😁. It is true that an airplane with the typical airfoil design does not need as much power to fly (when compared to a flat wing airplane). Although a flat wing airplane will fly, it will fly better and more stable with more lift if the wing has the typical airfoil shape because the air flowing across the wings adheres to the surface of the wing much better than it does over a flat wing with a square or blunt leading edge, the reduced pressure on top of the airfoil shaped wing certainly has an advantage over a flat wing with regards to lift. I fly full scale airplanes as well (got my PPL many years ago) and I certainly would not even attempt to fly a full scale airplane with flat wings 😮 I tried flying a model 3D foamy with square leading edges, then I flew another one where I rounded the leading edge to help keep the air attached to the wing and while there wasn't much difference in the overall performance, it did show improvement with stability, I assume it's because of reduced drag at the leading edge, anyway, it just seemed to be more controllable. BTW, I'm a halfa** 3D flyer!! I can do knife edges, inverted circuits and a few other things all day long but nowhere near good enough for anyone to go out of their way to watch 😴 One of the main reasons for using the typical airfoil shape (other than added lift as you have demonstrated), is the fact that air will adhere to the surface much better and it will have a much lower stall speed than a flat wing, a flat wing will have a much higher stall speed unless you use more wing surface area, this means that designers are trying to keep the wing loading as low as possible. The best wing loading range with flat wings is similar to a glider and is usually in the range of 10 to 14 ounces per square foot of wing area. I'm not familiar with what wing loading ranges are with full scale airplanes in terms of weight per square feet of wing area, I simply use the airplanes recommended weight and balance envelope from the operators handbook to make sure it's safe to fly. Even the rounded leading edge of an airfoil plays a very important role in keeping the air attached to the wing. The amount of lift produced by a typical airfoil is fairly low but certainly noticeable, going with that principle alone will require a higher airspeed or airflow to produce a good amount of lift. The total lift component of any airplane requires aerodynamic lift (with a typical airfoil) and angle of attack, it's not one or the other, it takes both but that is for maximum performance and efficiency. The total lift component for a flat wing is really just angle of attack and typically will require more power for thrust when compared to a good airfoil design (as you have demonstrated in this test), efficiency and stability is very low with a flat wing. Try another experiment with the same airfoil shape like the first wing you tested but this time try it with the bottom of the wing parallel to the table, I think it will take a lot more airflow to produce much lift but it would be very interesting to see what the results are. Are you up for the challenge? Maybe do another video comparing no angle of attack to the other various angles of attack? Maybe you could figure out a way to make the wing so it will pivot on the vertical slide tubes that run on the vertical rods in the tunnel? That way you could use just one airfoil wing. All full scale airplanes have some amount of positive angle of incidence to keep the fuselage level in flight, this is because it has to take angle of attack into account and the angle of incidence is the angle between the longitudinal axis of the fuselage and the chord line of the wing. As for spoilers, I think a better way to demonstrate the effects of spoilers would be to use that same wing but with a small spoiler mounted to the top side like you would see on a real wing. Inverting the wing as you did here just shows how it performs in inverted flight. Could you try demonstrating how that would work? Another thing to note in regards to your setup is that you have the bulk of the air coming from your PVC pipe flowing over the top of the wing, there is less air flowing under the wing than it is over the top of wing, great for creating lower pressure on the top of the wing but it doesn't seem like an accurate approach because in flight, there is always an equal amount of relative wind on both top and bottom. Notice that you have better results when you position the wing to the center-line of the PVC pipe, that allows the same amount of airflow over the top and under the bottom of the wing at the same time. Please know that I'm am only trying to give you "constructive" criticism, I'm not downing your experiment or your efforts at all!! Again, great experiment and well done!! Keep up the good work!!

nice video.. sensible explanation of the Bernoulli theory.. keep up the good work.. the lift is also related to surface area of the airfoil..more lift with large surface area.. try experimenting with it..

In the spoiler convention, could you put a scale under to measure the downforce or inverse lift?

This is a nice wind tunnel any chance of a step by step guide please

How did you make the airfoils?

How can you dislike this? It is informative if you don’t like it don’t click on it

Love the model. How did you make the wing? Or where did you make it from? You don't mention that in the materials section of your description too. Thanks.

Very good, but I think you should use slicker rods, there seems to be a lot of friction between your rods and pen caps when the wing moves.

Small correction: wing placed upside down is still a wing. Spoiler serves a different purpose it "spoils" the air flow which will cause lift it didn't, its the wing's job to create downforce. Anyway job well done.

Hai, I like your build, I have a similar project for school but i need a propeller where did you buy the propeller in the vid?

What material can you use for the airfoil?

Super super very nice...

Hi where did you find this fan and this motor?

Where did you get the toggle switch?

BTW, I have subscribed to your channel and I realize this is an older video but on KZfaq, they live forever :-)

Very nice. It is a good idea to use the RC motor and speed controller on the tunnel. The video does not show if you used an air straightening section to eliminate - reduce rotational flow. Usually this is done through air guides aiming to keep the flow parallel to the longitudinal axis. Assuming you did not, the flow pattern rotates heavily around the longitudinal axis. This has serious limitations on the type of experiments conducted.

What size sheets did you use?

did u measure pressure up and down side?

Have you tried using an EDF?

does it matter how many propeller blades there are?

Wow, that first wing looks suitable for my bicycle to ride at 345km/h.

Excellent project. keep on experimenting and sharing what you find. You are an inspiration to young upcoming scientists. great job,!!

can you list the specs of what you used

Hey just wondering, where did you get the wing from, or how did you make it. I am doing a similar project and would like to know. Thanks

how much rpm or kb is the motor?

thanks a lot man... I did really well..

ericinventor: You need a suction type generator which can produce more turbulent free air stream than the one you are showing. Your system is such that air is passing through the prop before it reaches airfoil. Such air stream is highly turbulent and does not give good results. Your experiment seems okay maybe because it is a video but in actual fact, the air is highly turbulent. For highly accurate result, let the air pass over airfoil first before reaching your propellers.

AWESOME.....which material did you use for the aerofoil?

Hey man... I liked the model and I'm making a similar one I just wanted to know what is the material you used for the aerofoil, is it very light ?

Can we use a 7000 rpm motor?

do you alsosell this project??

just a question what did u use to create your wing what fabric?

do you also sell this project??

That's neat but having a tube that graduates immediately to a larger box is going to create some backdraft into the box I would assume which does not make it ideal for tests.

hey eric i was wondering what size propeller and what size pvs pipe did you use, and what are the acrylic sheets for?

I've seen your wind tunnel... that's amazing! But I want to ask you a questions if you can... How much power does your air generator has? thanks friend :D

Hey, such an fabulous project, I am an 8th grade student and I’m trying to do something fairly similar but have a few questions. Where did you get such a powerful fan, my cheesy fan doesn’t seem to bring my styrofoam anywhere? And how did you manage to make the iron poles so perpendicular to the platform and parallel to each other, I tried my best to make them parallel but the styrofoam still gets stuck on the top. Thank you so much!

what kind of airfoil is this and what digit series?

What the material do you used to make an airfoil?

1st great job with the wind tunnel. Yes your explanation is semi-correct about Bernoulli. But 2 things, 1. the faster air on top of the wing reaches the trailing edge of the airfoil before the slower air at the bottom of the wing gets to the trailing edge causing a pressure gradient of low (top) and high (bottom) pressure. High pressure wants to go to low pressure (bottom wants to go to top) so the flow generates lift. The "reach the trailing edge at the same time" theory does not explain why flat plates can also be used as a wing/source of lift. 2. Remember Newton's third law, where there is an action, there is an opposite and equal reaction. So as the air from the top of the airfoil reaches the trailing edge of the wing 1st, the airflow is "thrown" downwards. Newton's law dictates an equal opposite force which results in lift.

may be a bit late), but if you change air wind direction in your tunnel, you will get significantly less disturbed air stream. try to use a smoke to visualize and see the difference when tunnel “pump” air and “suck”

What is the brand of your servo tester?

how to make airfoil balance?

Can you share how to make hole in airfoil?

Do you have the exact measurements for the materials?

I was wondering do u have some measurements for this wind tunnel I want to reproduce it

Hey eric, what sizes do you use for the airfoil?

another question. how did u make the stand for the wing?

Air on the upper surface of an airfoil arrives to the trailing edge in way smaller amount of time than air on its lower surface. I linked two GIFs depicting that. www.av8n.com/irro/animation/prosmo015.gif upload.wikimedia.org/wikipedia/commons/9/99/Karman_trefftz.gif

Well done, nice video. If you add some digital scales under the wing when it is upside down you can work out the amount of lift......dont ask me how though🤔, someone else on here will be able to tell you🤣

I need you help bro, can you reply to my comment the dimensions of this project pls? Thank you for this will help me for my project also

if you point the last model at a steeper angle back it will fly not every wing was based on the Bernoulli's principle the Wright brothers had flat wings they where just pointed back at a angle and also the Bernoulli's principle is not exactly the way everyone thinks in the first model. the air does fly over the top faster but they dont meet up at the same time with the bottom thats why planes can fly upside-down...THE MORE YOU KNOW

hey is there any alternative material that I can use to make the airfoil with please help me out!

Simple example

How many rpm is the motor

❤❤❤👏👏👏👏

You shouldn't use propeller to accelerate the air The air generated by propeller is in a spiral motion

Whats the rating of that fan bro??.......

very good?

Good job. Too much friction but still a nice experiment

Awesome, but here’s a tip, allow for more room In between the rod and the airfoil to slide more smooth

make a tutorial

Great video, however, there is one thing you should know, it is an extremely common misunderstanding that Bernouilli's Principle works because the air molecules on the top and the bottom have to get to the end at the same amount of time, but this statement is entirely false. The reality is that the air on top is compressed between the air above it and the wing below it, so its velocity increases, basically, it's like putting your thumb on the opening of a gardening hose, the same amount of water has to get through, but through a smaller aperture.

Incorrect lift theory #1, Bernoulli's isn't how airfoils generate lift Good vid tho

motor from traxas

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.

kawo kawo kawo

Need honeycomb or straws and a source of smoke

you can do it yourself ,just go to inplix page and learn how to make it.

120 dols for nothing, poor boy