He did a great job. All good for school children. The title was click bait for adults... It should have been titled: What your clueless 8 year old needs to know about ducted propellers...
@@barking.dog.productions1777 a lot of dumb ass adults need this! Lol. Some engineers don't know that cos they don't get taught or too stupid to remember 😂
Gyroscopic effect. Take a bicycle wheel and hold it by the axle as it's spinning, then try to rotate it on its axis. It will fight to keep its current plane. Well, looks like I was wrong. Hmm
A teacher who can explain what others would deem as complex in a simple and easy to follow way. My 10-year-old daughter can understand this! Great presentation!
I worked for a major industrial fan mfg'r, axial and centrifugal equipment with 40-100 hp motors; every design factor discussed here was critical for performance. This was all spot on.
Interesting comment, ...I'm currently researching designs for a stationary duct for manned electric copter,. Do you think the duct has a negative affect on vehicle speed when rotating the blades?
I was researching about propellers for my project, I have spent many hours on understanding how it works but this video is the summarisation of all my understanding. You have amazing teaching skills sir.
@@EngineerHank You don't need "the course". We get all the books and classes on online. Indeed, anything that you "learn" in college is already in books but you are too lazy. I bet that you had read no books in college. Only sat there your f@t @ss listening thinking that learn is some passive action of absorption. Learning is active.
You are amazing. I really appreciate the efford you put into this. You are the only one so far, who can actually explain the science behind flying. I needed this info for my custom drones! Cant wait to see more about this!!! Thank you soo much.
I like your videos because they are very informative and easy to understand, you have a passion for your subject and you often make complex subjects real easy to get to grips with.
You are a great amazing energetic teacher. Not just learning the knowledge you teach. But also the way u deliver the knowledge.... Thank you. Learn a lot from you. Will watch all your class.
I want to build something at home, my two sons dont believe I can make it, but if I have to watch this videos a thousand times, I'll do it, I know a good result can be achieve .I'm learning a lot from all this information.thank you.
4:45 This is the first video I've seen of yours, and I was trying to prepare myself for you to only mention the Bernoulli effect on its own (in regards to lift) and I am so glad that you didn't! Happens so much by people who want to sound smart. Great video, thank you for the effort you put into it!
Brilliant!!! Although you broke my heart saying that it was a failure due to tilt. I was thinking "why aren't all choppers made like this", then you dropped the bombshell. Great video though, thoroughly enjoyed it, well done and thx
Great video Bruce! Thanks. I'm gonna assign it as required watching to my physics and engineering students. We'll see if they spot the centrifugal/centripetal thing. Should make for an interesting discussion. After your last video I created a project for them to design and 3D print guards for the 450 quad they are building and programming from scratch. These propeller guards are what we needed to make the testing safer for them. As usual, great job. I'm looking forward to the bench test, but I may not show them that one. They'll need to generate the numbers themselves to compare the efficiency of their different designs. BTW...you are getting quite famous at University of the Pacific in California and the feeder high schools in the area. Keep 'em coming!
The important problem with people's understanding of the pressure explanation is that the air doesn't have to end up at the same place at the same time. The air DOES move faster over the top of the wing, but not because of any need to get to the other side at the same time. Similarly, the idea that it's A and B is misses the important bit that you can ENTIRELY model wing physics by either looking at deflections of mass, or entirely by looking at pressure. Wings deflect air downwards, both below and over the wing. At the same time, you can equally say that wings work by generating lower pressure over the wing and higher pressure under the wing. They're not separate. They're two ways of describing the same thing.
It's just not as intuitive for people to understand ideas like that the wing can cause air that passes OVER it to be deflected downwards too, or to think of the air being deflected under the wing as creating a high pressure zone. Honestly, it took me a lot of time and reading stuff on the NASA website, research papers, etc. to really feel like it made sense to me, so I don't exactly blame people.
Not up on the engineering and maths of this by far, but my intuitive reasoning says of course it deflects the upper flow, because it creates drag - the air will slow closer to the surface, (and that will slow the air above it a bit and so on) and (just like with water or light,) slowing one side of a stream will bend the airflow. Am I on track or way off base here?
The1stImmortal It's actually the opposite. It increases the speed of flow over the top of the wing. Remember that I said it decreases the pressure above the wing. If it slowed the air, it would be increasing the pressure above the wing.
I meant in the context of deflecting the air above the wing as well as below. What's the mechanism by which the airflow is sped up over the wing btw, since equal transit's bs?
The1stImmortal It has to do with the shape of the wing. As the wing passes through the air, it generates a low pressure region over the wing, and a high pressure region under the wing. Fluids flow from high pressure to low pressure, so air entering the high pressure area under the wing slows down, and air entering the low pressure area above the wing speeds up. The simplest way to understand this I can think of, is imagining shooting tennis balls at a large inclined board. When they hit the bottom, they get deflected down, but there's a region behind the top of the board where no balls pass through because they'd be blocked by the board. That region is a low pressure zone, and the surrounding air pushes into it. It gets complex after that, because air isn't like a bunch of tennis balls being shot at the wing, and is really like an uncountable number of tiny tennis balls whizzing around in every direction really really fast that the wings are slamming through. Which is why the air can push in behind the wing whereas the tennis balls aren't going to just get sucked in behind the board. Also, the air is all like this, so the regions of pressure change and air speed change are substantially larger than you'd expect thinking of it like a bunch of tennis balls, since air getting sucked into a low pressure zone is leaving it's own low pressure zone behind, which then gets filled by the surrounding air, creating a pressure gradient "bubble." This also is a great way to discuss the other important thing to understand. While wings can deflect air/generate pressure differences by being inclined as they pass through the wind, they can also be made curved, which does basically the same thing, but without having to angle the board.
I was actually searching for dust collection duct work and stumbled across your video - watched the whole thing and now I have learnt something new - well done
Woah, I've been trying to understand these concepts for years, and just like that, in about 20 minutes, everything about aerodynamics, drag coefficients, etc has suddenly made sense. It was an epiphany among epiphanies for me in aviation
I have struggled for years trying to understand how a wing works, You took a few minutes and now I see it,and so much more, THANK YOU sooo much mate :)
Bloody good lesson mate !! Well explained !! I just bought an electric jet unit for my kayak which operates exactly as you explained , a prop in a tube/nozzle, I was curious as to why it was more efficient, Thank you
BTW turbine blade tip clearance for a 12 inch turbine should be between 0.020" and 0.033". That's about 0.3% of total diameter. For a 5 inch prop you wouldn't want more than 0.015" inch of a gap. Here's a trick for achieving that, paint some thick but soft material in your duct at the place where the prop would be. This is an abradable seal. The prop itself will machine the duct surface until you get the tightest gap that your structural integrity can handle.
Excellent video. Thank you. It is always a pleasure to listen to someone explain things well, even if you already understand the principal. I look forward to seeing your test results. But even more so, I look forward to hearing about how all of this relates to multirotors. As I was watching this video I was wondering to myself how these principals are effected by the aerodynamics of a tilted vehicle in fast forward flight. I am unaware of the related military history lesson you mentioned and look forward to hearing all about it in a future video.
It has been obseved that in FF Flight the two rear motors have to work harder. There has not been a satisfactory scientific explanation for this. Probably has to do with the aero dynamics of a tilted multirotor
Wingtip vortices occur without spinning as mentioned in the video, if I understand him correctly. Some modern airliners use winglets to prevent this, thus improving efficiency.
Back during my seafaring days, my ship had a ducted bow thruster. I always thoght the duct was simply to prevent the prop from being damaged in case it hit the bottom (we used it a lot for mooring at the pier or getting underway - it eliminated the need to use tugboats) in shallow water. Now I know better. Thanks so much for making me one of 'today's 100,000'.
bro dont confuse hearing with understanding hypothetical theories, because later after you had lunch ... you forgot everything. Thats what i call hearing. You heard the man but not able to reproduce or use his knowledge. And it makes you look silly, Some of it its really wrong. Why dont we use tease blade yet? not because o people like you or him but because of real science. chhers.
Thanks for taking the time to produce your videos. Very intersting! However, after having taught the principles of aerodynamics to children (young and old), I have found that most people have the most difficulty with grasping the concept of atmospheric pressure. Simply put, it is the weight of the mass of air above you, about sixty miles high at sea level. A collum of the air we breathe which is one sqare inch at its base, and sixty miles high, weighs almost 15 pounds. The most important thing to realise is that we experience this weight as pressure because we are inside of the air. It's called "internal sideways pressure". NASA's "new" theory of lift is just a matter of angle of attack. Bernoulli's theory holds the most water with me because it best explains how turbulateors work to increase lift without increasing airfoil airspeed. And, the reason why you don't readily feel the pressure is just because you're used to it. Don't try living without it, your blood will boil!
Brilliant explanation. What if the prop tips were embedded into a ring that spun around as part of the propeller? This ring could be recessed within a groove in the inner circumference of the tube portion of the duct, thereby maintaining the general integrity of the tube inner shape. Yet, there would be zero blow-by because the tips would be embedded.
Propellers with rings cause another problem: they add a lot of extra surface area that produces a lot of drag, which in turn puts more load on the motor driving the prop.
What if the medium that the ringed propeller was using was water instead of air, would this be a beneficial use for say a submarine? I would think that since you don't need to move a water/submerged prop as near as fast as a air prop that the extra resistance from the ring would be worth it for less cavitation creating a quiter and significantly improved drive system for a submarine or is this theory incorrect as well? Just whondering because I want a really efficient propeller for the sub I plan on building.
@@spectre2466 You may be interested in the fact that the US Navy constructed and tested a full scale propulsor in the late 1970s and into the early 1980s. It was fit to a couple of Submarines. It was also tested in a smaller scale for possible use on torpedoes. Good insight on your part!
@@BrightBlueJim Another practical problem is that making the ring thin enough will make them very weak and the segments between the blades will bow out. This will cause even more turbulence/drag plus pumping losses if it's tightly enclosed in a shroud.
Very interesting! Thank you for sharing your knowledge. I knew ducted propellers will give the Lilium evtol an advantage but now I’m more confident that they will simply beat everyone once batteries become better and better!
Yes, you are a great, amazing teacher and man. I showed your video to my teatcher wife and she was so proud, and amazed too; Loved the explanation. Congrats.
Have you made a video on the effects of the angle of attack issues with the ducts yet? I’m working with a ducted drone and I’m looking for more information like this to expand my knowledge on this subject. Thank you for all you do for the community. 🙏🤟🏽🔥
if the duct is tilted relative to the air flow, then a low pressure bubble develops inside the air intake. when the propeller reaches it, will loose load and when it exits will get loaded back. vibration, unsteady air flow. engine surges gasping for air, then it chockes with too much. no project ever tilted the air intake.
Trevor Hurd it was called the Avro Car I believe. When the vehicle began forward motion by tilting what in effect was a giant duct, the vehicle lost lift. No matter how much energy was applied, all efficiency was lost and it could not conquer the smallest ground based obstacles.
how much tilt are we talking about? a drone tilts about 45 degrees. Is that enough to produce this counter effect? can ducts still be used efficiently in copters without tilting ducts?
Simply amazing ! Thank you for taking the time to compose this video as well as all of the other videos in your channel. They have been very informative and educational for my current endeavor.
Yes please do a video on why ducted fans don't travel well in fast forward flight. I remember seeing that project and always wondered why it didn't work. I have always wanted to bould a flying wing with twin ducted fans. Something like the FT Crackin with the Jets in the middle of the wings. I know that if the wing is stalling or producing a lot of left, the fans can cut out due to lack of air from the low pressure zone above the wing and you need to duct air from underneath the wing to keep the thrust up. Can you do a video on that and other physics related aircraft issues More airplanes please...and drones, and drone airplane hybrids Sincerely Adam in Iowa
I was talking more about the vacuum above the wing interfering with the inlet of an EDF. Also things like a forward sweeped wing can be more stable then a straight or rear sweeped wing. Or how a Canard doesn't add much more lift surface but dose add a lot more lift.
Adam Sparrow id also be interested in why we dont build props with winglets on them, effectively making it a self contained ducted prop.... probably materialstrength.
Mendoza Bracken Hartzell makes a Q-Tip propeller with winglets. The problem is that propellers are already under a LOT of strain along the radius and the added structure needed to support a significantly bent tip adds a lot of weight and cost. Hartzell says they are more efficient but also a lot more expensive.
Awesome video RCModel Reviews, I love the way you teach... Your information on this Topic.. a very funny way of learning... Thanks Mate.. Keep up the Great Work...
Very simple and clear explanation. Your love to teach is part of you. Only two questions: what's the right space between propeller and duct and what's the percentage of efficiency of this system? I'm looking forward to your next video on these questions. Be good.
I would like to thank you for this lesson, its something I should have known long ago, after all most of us have flown on jets throughout our lives. Thanks again
The vortex bit is wrong, the low pressure region does not get flung out, I suppose you could argue that the high pressure does, but circulation at the tip occurs because the high pressure region towards the tip trailing edge trys to flow around the tip and gets left behind by the advancing blade, also the "packet of air" principle with curved aerofoils is flawed, there is no reason that the air above and below have to meet up again, it's better to consider the pressure distribution around the entire cross-section not just the top.
Leon Hostad yes, there has been some debunking of the effect that Bernoulli's theorem plays in how a wing creates lift but the spanwise flow of air (induced by centrifugal force) does see a flow between the low and high pressure sides of the propeller at the tip -- and a resulting vortex being formed.
Got to disagree about how that spanwise movement is caused, it's not down to centrifugal force, but down to the pressure difference; under the wing or prop you have higher than atmospheric pressure, and at the tips normal pressure and above less than atmospheric, the difference between under and tips causes a spanwise flow out, and the difference between the tip and the upper causes a spanwise flow in, that causes a rotating airflow, if it was down to centripital forces then tip vortexes on wings wouldn't form, but we know they do.
Leon Hostad Yes, it's primarily a pressure differential but there is still a centifugal effect. Spin a flat disk and watch the airflow across the face of that disk -- you'll see that centrifugal effect plays a part because there is a pronounced flow from the center of the disk towards the edge. This is in fact (partly) how Tesla turbines work.
Never said it wasn't, I only said that centrifugal force is negligible, so much so it can be ignored, the main reason for circulation around the tip is the pressure distribution below the wing, around the tip, and above the wing.
You are such a great teacher. Thank you! Whiched I had you in school ...would have been so much more fun and open new possibilities. But I am here now to learn. Better late than never.
Great, great video my friend. I have been testing many EDF units lately and their thrust and this video is perfect for me to understand some things about how the exhaust of EDF unit should be. Thanks for making this video and big salute from Slovenia, Pilot Robert
As an empiric learner, very few people can teach me. But I've learned a great deal from your vid. Thank you. What effect does narrowing the tube towards the outlet have on thrust? And would you be able to create a semi turbine effect if you had dual counter rotating truncated props in a tapered tube? What I have in mind is a medium pitch 3 or 4 blade prop I'm the front, with a similarities aggressively pitched prop behind. They would need to be specially made props with their pitches finishing at squared off ends that fit tightly in the tube, and also exactly mimicking the taper. This might make it easier to calibrate the clearance tolerances by varying the motor/prop mountings using shims. Have been thinking about this idea since before I watched your vid the first time - about three years ago! Would really appreciate your thoughts on this proposal.
宋泰成 ducks are not that heavy, birds have hollow bones, so I'm surprised they're not the primary source of thrust for drones and flying devices in general.
Great video! Loved the content, however one thing to realise is that the lift provided by a wing and therefore the thrust produced by a propeller is mainly due to the Coanda effect which we have recently acknowledged that proves that the flow of fluids conform to the shapes they are moving against, so the air gets deflected down because of the airfoil shape and in Newton's 2rd law, every force has an equal and opposite reaction, creating lift.
thanks for the comment, i was wondering about that...I'm currently researching designs for a stationary duct for manned electric copter,. Do you think the duct has a negative affect on vehicle speed when rotating the blades?
The fact that the equal transit time theory is false doesn't mean that Bernouli is wrong. The Bernouli principle is obviously true. But, there are absolutely no reason for a bunch of atom to go faster to meet their buddies on the other side of the airfoil at the same time. None. And, indeed, they don't.
The "knobs" do something called "tripping the boundary layer" which can be very helpful when form drag is a large portion of the total drag on a system. Form drag is the drag caused by the wake of the object. This type of drag is dependent on the largest cross sectional area of the object defined by a plane normal to the flow direction. Another large contribution to drag is "skin drag" which can be thought of just like friction between two solids. Skin drag is dependent on surface area exposed to the flow. A good example of this trade-off is a golf ball vs. an airplane wing. Without going into too much detail, tripping the boundary layer changes the flow from laminar to turbulent which reduces the flow's tendency to resist a change in direction. This allows the size of the wake to lessen, which reduces form drag, but the cost is an increase in skin drag. In summary, adding dimples or "knobs" to a surface in a flow can decrease it's drag if the drag is dominated by form drag and form drag is dominant when the object has a large cross sectional area when compared to its surface area. Propellers are much like wings in that their drag is not greatly defined by form drag, so dimples would be detrimental, but some sections of a fuselage might benefit from dimpling. Speed and other things have effects on this phenomenon, but I think that is beyond the scope of a TH-cam comment.... If you are interested in the topic, look up some of these keywords: Form Drag Skin Drag Induced Drag Boundary Layer Laminar Flow Turbulent Flow
Could listen to your teaching and enthusiasm all day - such clarity and zest - pity we aint got teachers like this in the UK (theyre only interested in the dosh )
***** Not me. I don't care if ducts increase efficiency (which, without a specially designed fan, I doubt they do enough to make up for their weight), they just don't look manly enough. Ducts are for girls. (I'm kidding, folks) (kind of)
you have a larger rotating mass with more gyroscopic effect and a less responsive and more stable quad... you also eliminate all the losses of the gaps between the propeller and the duct, but you increase the load on the motor since higher rotating mass... dunno if its worth it tbh since no one ever went into production with a patent like that.
As an aero engineer by education, a fighter pilot by trade, and an RC pilot by hobby, I can say with certainty that the RC community as a whole has more practical design knowledge, derived from the physics lab in the sky known as the real world, than all of global industry's aero engineers, combined. We have limitless real world data on ducted fans--none are real-world efficient. They are too heavy, too draggy, practical implementations have airfoils with too low aspect ratio to control back-pressure, and they need extreme RPM to produce comparable thrust to a prop that puts the same weight and power into a larger, lower aspect ratio, traditional design. All you have to do is listen to them to know they convert a lot more electricity into sound than an efficient, quiet, high thrust prop. What they do provide is terribly power hungry, higher speed solutions. Much like any jet vs. prop trade study. At 1:1 scale, props without ducts are as much as an order of magnitude cheaper to operate in the real world, empirically captured by gathering cost per flying hour stats. It's why the USAF is interested in LAA, and why they switched from the T-37 back to the T-6 II. If you have a req to go faster, they can make sense given power to burn.
Absolutely right, sir! Through aviation history, there have been maybe 10 ducted propeller aircraft that has reached production, none very successfully. it was thought for a while to be a great way to control noise, but it was proved that low-rev propellers were more efficient and much lighter.
@Jerry Moody If you mean turbofan jet engines, the duct does improve efficiency because it increases mass flow of air (thrust) - although this isn't true for higher possible speeds, which is why fighters don't use them. However, this would happen even if there wasn't a shroud around the fan, (as in turboprops) but the duct does multiple duty in controlling/slowing the inlet air necessary for the engine and fan, protecting the fan, and containing broken blades.
With the piece of paper he actually demonstrated the Coanda effect. To demonstrate the Bernoulli effect you would have to use an actual rigid flat plate.
I'm guessing if he had used a rigid plate, it wouldn't have risen no matter how hard he could blow? Like if he hung the paper straight down with no curve and blow on one side, it would just push the paper away from you and it wouldn't move towards where you are blowing, basically the opposite of what he is claiming?
One can NOT apply the Bernoulli principle on two seperate airflows. The airflow over and the airflow under the paper are two different flows. The paper was lifted because of the reaction force generated on it to the downwards routed (turned) airflow. i.e. the air was forced to go down whereas the paper (wing) forced to go up ....as a reaction.
@@DavidL-qb8cl yes. Blowing trough the upper surface created a downwards routed airflow (due to the initial downwards deflected paper) . An upwards reaction force was generated on the paper. Similar to how aircraft wings generate lift.
A very good video sir thank you for taking the time to make it. Please so talk about the American experiment. I think I know which one but want to know for sure. Your teaching method is a lot of fun and your obvious enjoyment of doing so makes you a truly good teacher. I look forward to many more videos.
Heya, Yeah i would like to know what happens when moving lateral with a ducted fan said. what was the US Project name from the 50s. I think Canada had something similar also
Someone should pick such people off the internet and just treasure them in one big reputed university. you won't require any sorts of ppt or high graphics 3d animation just to teach the students, rather only by this simple method of teaching, you would get some exceptionally highly skilled people on this planet Earth.
Design idea: what if you enclose the propeller fully in a very short tube, but have zero gap between tube and outside edge of the propeller. So when it spins the entire tube spins. Then no chance of vortices at the outer edge of propeller. Just an idea. I don't know how well it would work in practice.
So, this is going to be more difficult in smaller models to find a clearance between propeller and duct wall which makes for significant gain. And if the propeller edge is too close to the wall, it catches and gums up the works. As soon as you begin increasing the distance between propeller and wall the benefit drops off. But the propeller won't move well, won't go without friction and power loss, when the blades connect with the wall. You can't connect the propeller to the wall and get good thrust. Or can you? What if the propeller and the wall are one piece? Or rather a section of the wall or a ring is one with the propeller but separate from the rest of the wall. Flush with the main wall the ring portion of the propeller has free movement. Mounted as of a bearing.
What about : (i) The additional drag caused by the duct? (ii) The additional weight of the craft due to the duct itself? Will this not offset the effect of the energy saved by deploying the duct to begin with?
When I clicked, I only planned to watch a few mins, but your enthusiasim is contagious
Great explanation on Ducted Fan operation.
Likewise! This wasn't even what I was looking for but couldn't stop watching and learned a ton!
What a terrific teacher this guy is! Can't beat a guy who gets excited by what he's teaching.
Marc Draco h
Must be a Kiwi guy, as he also said "ear preesure".
He did a great job. All good for school children.
The title was click bait for adults...
It should have been titled: What your clueless 8 year old needs to know about ducted propellers...
@lil Oofy guGhGGHGhHhhZZUGzGhuGHHUZHhzU zu ZzHuGZGzZHgzzhUGGHHFFhGgHhGgZfuYhuGzGgGuG7GUHHGGGGHF uhh UGGghHgzuGHHhZHUHghZzGffUghHGYgHHhgZGHZuyzFhuzUHhuggZUhHgzZg8GgGHHFhGGgGgGGZfGHyzG uGzFUgGZZHZHuHUUZyUFHG
@@barking.dog.productions1777 a lot of dumb ass adults need this! Lol. Some engineers don't know that cos they don't get taught or too stupid to remember 😂
This guy would have made me love to go to school when I was a kid. I'm old, and he makes me want to go now. Well done mate!
Go
What a great teacher! No fancy words, just a very economic explanation. What a pleasure to learn from you, sr.
Yes please do explain what happens when you tilt a ducted fan, I thoroughly enjoy your videos, thank you
Absolutely interested! Plz do sir
th-cam.com/video/0stl1U9evzU/w-d-xo.html
@@nathanbanks2354 thanx Nathan
Upvoting!!!!
Gyroscopic effect. Take a bicycle wheel and hold it by the axle as it's spinning, then try to rotate it on its axis. It will fight to keep its current plane.
Well, looks like I was wrong. Hmm
A teacher who can explain what others would deem as complex in a simple and easy to follow way. My 10-year-old daughter can understand this! Great presentation!
I worked for a major industrial fan mfg'r, axial and centrifugal equipment with 40-100 hp motors; every design factor discussed here was critical for performance. This was all spot on.
Interesting comment, ...I'm currently researching designs for a stationary duct for manned electric copter,. Do you think the duct has a negative affect on vehicle speed when rotating the blades?
You sir are an asset to this planet. Thank you for this video. Your love for the subject is apparant. Profess on.
Too bad he teaches misconceptions...
You've got a way that makes seemingly complicated theory understandable, and your enthusiasm is infectious - something my teachers lacked!
The enthusiasm is mesmerizing and contagious. What a great lesson!
Ok Bruce let us all in on the military failure....Great learning video thanks for taking the time out to teach us! Keep up the awesome work!!
I was researching about propellers for my project, I have spent many hours on understanding how it works but this video is the summarisation of all my understanding. You have amazing teaching skills sir.
Who needs a University When you Get Teacher like him In *TH-cam*
*Love* Form 3rd World. 👍👍
@@petemiller519 But without the course, one cannot calculate the shapes and sizes needed making the project cut and try and very expensive.
@@petemiller519 in their pay chk
YT is actually YTU. Two Russian guys. TY Russia! Dopamine hit for them.
👍👍👍
@@EngineerHank You don't need "the course". We get all the books and classes on online. Indeed, anything that you "learn" in college is already in books but you are too lazy. I bet that you had read no books in college. Only sat there your f@t @ss listening thinking that learn is some passive action of absorption. Learning is active.
You are amazing. I really appreciate the efford you put into this. You are the only one so far, who can actually explain the science behind flying. I needed this info for my custom drones! Cant wait to see more about this!!! Thank you soo much.
I was most impressed with the explanation of why ducting a propeller increases efficency and thrust. Best explanation I have ever heard. Thanks
I like your videos because they are very informative and easy to understand, you have a passion for your subject and you often make complex subjects real easy to get to grips with.
You are a great amazing energetic teacher. Not just learning the knowledge you teach. But also the way u deliver the knowledge.... Thank you. Learn a lot from you. Will watch all your class.
I want to build something at home, my two sons dont believe I can make it, but if I have to watch this videos a thousand times, I'll do it, I know a good result can be achieve .I'm learning a lot from all this information.thank you.
What an inspiring teacher! Your explanations are stellar. I was interested from start to finish. You have a great teaching gift!
4:45 This is the first video I've seen of yours, and I was trying to prepare myself for you to only mention the Bernoulli effect on its own (in regards to lift) and I am so glad that you didn't! Happens so much by people who want to sound smart.
Great video, thank you for the effort you put into it!
Brilliant!!! Although you broke my heart saying that it was a failure due to tilt. I was thinking "why aren't all choppers made like this", then you dropped the bombshell. Great video though, thoroughly enjoyed it, well done and thx
Great video Bruce! Thanks.
I'm gonna assign it as required watching to my physics and engineering students. We'll see if they spot the centrifugal/centripetal thing. Should make for an interesting discussion.
After your last video I created a project for them to design and 3D print guards for the 450 quad they are building and programming from scratch. These propeller guards are what we needed to make the testing safer for them.
As usual, great job. I'm looking forward to the bench test, but I may not show them that one. They'll need to generate the numbers themselves to compare the efficiency of their different designs.
BTW...you are getting quite famous at University of the Pacific in California and the feeder high schools in the area.
Keep 'em coming!
The important problem with people's understanding of the pressure explanation is that the air doesn't have to end up at the same place at the same time. The air DOES move faster over the top of the wing, but not because of any need to get to the other side at the same time.
Similarly, the idea that it's A and B is misses the important bit that you can ENTIRELY model wing physics by either looking at deflections of mass, or entirely by looking at pressure. Wings deflect air downwards, both below and over the wing. At the same time, you can equally say that wings work by generating lower pressure over the wing and higher pressure under the wing.
They're not separate. They're two ways of describing the same thing.
It's just not as intuitive for people to understand ideas like that the wing can cause air that passes OVER it to be deflected downwards too, or to think of the air being deflected under the wing as creating a high pressure zone.
Honestly, it took me a lot of time and reading stuff on the NASA website, research papers, etc. to really feel like it made sense to me, so I don't exactly blame people.
Not up on the engineering and maths of this by far, but my intuitive reasoning says of course it deflects the upper flow, because it creates drag - the air will slow closer to the surface, (and that will slow the air above it a bit and so on) and (just like with water or light,) slowing one side of a stream will bend the airflow.
Am I on track or way off base here?
The1stImmortal It's actually the opposite. It increases the speed of flow over the top of the wing. Remember that I said it decreases the pressure above the wing. If it slowed the air, it would be increasing the pressure above the wing.
I meant in the context of deflecting the air above the wing as well as below.
What's the mechanism by which the airflow is sped up over the wing btw, since equal transit's bs?
The1stImmortal It has to do with the shape of the wing. As the wing passes through the air, it generates a low pressure region over the wing, and a high pressure region under the wing. Fluids flow from high pressure to low pressure, so air entering the high pressure area under the wing slows down, and air entering the low pressure area above the wing speeds up.
The simplest way to understand this I can think of, is imagining shooting tennis balls at a large inclined board. When they hit the bottom, they get deflected down, but there's a region behind the top of the board where no balls pass through because they'd be blocked by the board. That region is a low pressure zone, and the surrounding air pushes into it. It gets complex after that, because air isn't like a bunch of tennis balls being shot at the wing, and is really like an uncountable number of tiny tennis balls whizzing around in every direction really really fast that the wings are slamming through. Which is why the air can push in behind the wing whereas the tennis balls aren't going to just get sucked in behind the board. Also, the air is all like this, so the regions of pressure change and air speed change are substantially larger than you'd expect thinking of it like a bunch of tennis balls, since air getting sucked into a low pressure zone is leaving it's own low pressure zone behind, which then gets filled by the surrounding air, creating a pressure gradient "bubble."
This also is a great way to discuss the other important thing to understand. While wings can deflect air/generate pressure differences by being inclined as they pass through the wind, they can also be made curved, which does basically the same thing, but without having to angle the board.
I was actually searching for dust collection duct work and stumbled across your video - watched the whole thing and now I have learnt something new - well done
Woah, I've been trying to understand these concepts for years, and just like that, in about 20 minutes, everything about aerodynamics, drag coefficients, etc has suddenly made sense. It was an epiphany among epiphanies for me in aviation
Yes please do another video about what you mentioned in this video, please.
the video: th-cam.com/video/0stl1U9evzU/w-d-xo.html
enjoy :)
@@GonEyal thank you!
I have struggled for years trying to understand how a wing works, You took a few minutes and now I see it,and so much more, THANK YOU sooo much mate :)
Do you have a video comparing thrust, before and after the ducting? I am very interested in the actual gain or loss in efficiency. Thanks!
This is the single best explanation of flight physics I've ever found.
Bloody good lesson mate !! Well explained !! I just bought an electric jet unit for my kayak which operates exactly as you explained , a prop in a tube/nozzle, I was curious as to why it was more efficient, Thank you
60 years after I could have really benefited from a teacher like this!
they say 90% of failure is operator error.....
BTW turbine blade tip clearance for a 12 inch turbine should be between 0.020" and 0.033". That's about 0.3% of total diameter.
For a 5 inch prop you wouldn't want more than 0.015" inch of a gap.
Here's a trick for achieving that, paint some thick but soft material in your duct at the place where the prop would be.
This is an abradable seal. The prop itself will machine the duct surface until you get the tightest gap that your structural integrity can handle.
How much more air should we expect for a given prop if it's ducted?
@@ChristianNally That will depend very much on the aspect ratio of the prop blades, number of blades, and rotational velocity.
I have watched you on Xjet for years and enjoyed all the banter on the field with your buddies but didn't realize you are such a great teacher !!
Excellent video. Thank you. It is always a pleasure to listen to someone explain things well, even if you already understand the principal. I look forward to seeing your test results. But even more so, I look forward to hearing about how all of this relates to multirotors. As I was watching this video I was wondering to myself how these principals are effected by the aerodynamics of a tilted vehicle in fast forward flight. I am unaware of the related military history lesson you mentioned and look forward to hearing all about it in a future video.
It has been obseved that in FF Flight the two rear motors have to work harder. There has not been a satisfactory scientific explanation for this. Probably has to do with the aero dynamics of a tilted multirotor
zenman8269 I've noticed this with my "toy" grade quadcopters with brushed motors. The rear motors burn out long before the front ones.
Phillip Toone Its a bit of a mystery I guess, how and why the high pressure and low pressure areas are arranged on a multirotor in FFF .
Wingtip vortices occur without spinning as mentioned in the video, if I understand him correctly. Some modern airliners use winglets to prevent this, thus improving efficiency.
Winglets reduce wingtip votices, not prevent...
Back during my seafaring days, my ship had a ducted bow thruster. I always thoght the duct was simply to prevent the prop from being damaged in case it hit the bottom (we used it a lot for mooring at the pier or getting underway - it eliminated the need to use tugboats) in shallow water. Now I know better. Thanks so much for making me one of 'today's 100,000'.
man he'd make a really good fast teacher lol. their wasn't one thing he said that i didn't understand.
It's the New Zealand accent. : )
Lakario Davis there is one thing i don't understand!
Lakario Davis I agree. Easily explained what would otherwise be a complex topic. If he was never a science teacher, he missed his calling!!
bro dont confuse hearing with understanding hypothetical theories, because later after you had lunch ... you forgot everything. Thats what i call hearing. You heard the man but not able to reproduce or use his knowledge. And it makes you look silly, Some of it its really wrong. Why dont we use tease blade yet? not because o people like you or him but because of real science. chhers.
@@videos40058 what's a tease blade. you'll have to message me, and I'll take months to read that.
excellent. Could you please explain the pros/cons between paddle-shaped and scimitar-shaped propellers?
Hes either a Kiwi or lived in South Australia for too long but what a great teacher.Id love to learn from him all day! Great passion.
Thanks for taking the time to produce your videos. Very intersting!
However, after having taught the principles of aerodynamics to children (young and old), I have found that most people have the most difficulty with grasping the concept of atmospheric pressure. Simply put, it is the weight of the mass of air above you, about sixty miles high at sea level. A collum of the air we breathe which is one sqare inch at its base, and sixty miles high, weighs almost 15 pounds.
The most important thing to realise is that we experience this weight as pressure because we are inside of the air. It's called "internal sideways pressure".
NASA's "new" theory of lift is just a matter of angle of attack. Bernoulli's theory holds the most water with me because it best explains how turbulateors work to increase lift without increasing airfoil airspeed.
And, the reason why you don't readily feel the pressure is just because you're used to it. Don't try living without it, your blood will boil!
When flying at cruise in a fixed wing airplane you usually have a negative nose down attitude. Negative aoa
Brilliant, you are! You should have your own channel doing just this! Encore! Bravo! Well done!
Thank you for being the most enthusiastic entertaining person to ever talk about aerodynamics
i wish to say I appreciate this gentleman explnations and why you must be a teacher good job
Not really, i think it's a load of rubbish.
Brilliant explanation.
What if the prop tips were embedded into a ring that spun around as part of the propeller? This ring could be recessed within a groove in the inner circumference of the tube portion of the duct, thereby maintaining the general integrity of the tube inner shape. Yet, there would be zero blow-by because the tips would be embedded.
bobert4him exactly what i was thinking. ive seen these on toy helicopters
Propellers with rings cause another problem: they add a lot of extra surface area that produces a lot of drag, which in turn puts more load on the motor driving the prop.
What if the medium that the ringed propeller was using was water instead of air, would this be a beneficial use for say a submarine? I would think that since you don't need to move a water/submerged prop as near as fast as a air prop that the extra resistance from the ring would be worth it for less cavitation creating a quiter and significantly improved drive system for a submarine or is this theory incorrect as well? Just whondering because I want a really efficient propeller for the sub I plan on building.
@@spectre2466 You may be interested in the fact that the US Navy constructed and tested a full scale propulsor in the late 1970s and into the early 1980s. It was fit to a couple of Submarines. It was also tested in a smaller scale for possible use on torpedoes.
Good insight on your part!
@@BrightBlueJim Another practical problem is that making the ring thin enough will make them very weak and the segments between the blades will bow out. This will cause even more turbulence/drag plus pumping losses if it's tightly enclosed in a shroud.
Excellent presentation with no unnecessary drivel. Learned so much in such a short period of time.
Loved your video. I found it by pure chance thinking it was something completely different. I'm looking forward to watch more of them.
Very interesting! Thank you for sharing your knowledge. I knew ducted propellers will give the Lilium evtol an advantage but now I’m more confident that they will simply beat everyone once batteries become better and better!
Yes, you are a great, amazing teacher and man. I showed your video to my teatcher wife and she was so proud, and amazed too; Loved the explanation. Congrats.
Have you made a video on the effects of the angle of attack issues with the ducts yet? I’m working with a ducted drone and I’m looking for more information like this to expand my knowledge on this subject.
Thank you for all you do for the community. 🙏🤟🏽🔥
Great video. I'd like to see a whole series like this on various topics:)
Dude, you are probably one of the most enthusiastic presenters I have seen in a very long time!
Great presentation and very informative!
I love this guy! What fun it would be to have him as a neighbor!
Definitely do the tilted duct video , thanks for the video it was very interesting
I had Aerodynamics teachers in Air Force Academy but you are much better the way you explain the subject.
Could you make the duct spin or mold it so it was part of the propeller?
So what happened to the ducted project that failed for tilting the duct?
if the duct is tilted relative to the air flow, then a low pressure bubble develops inside the air intake. when the propeller reaches it, will loose load and when it exits will get loaded back. vibration, unsteady air flow. engine surges gasping for air, then it chockes with too much.
no project ever tilted the air intake.
Alexandru Vatamanu wow.. i was way off. i was talking about gyroscopic forces 😂
Trevor Hurd it was called the Avro Car I believe. When the vehicle began forward motion by tilting what in effect was a giant duct, the vehicle lost lift. No matter how much energy was applied, all efficiency was lost and it could not conquer the smallest ground based obstacles.
how much tilt are we talking about? a drone tilts about 45 degrees. Is that enough to produce this counter effect? can ducts still be used efficiently in copters without tilting ducts?
Also interesting for me, but never saw a single ducted multirotor or even a project of it
Simply amazing ! Thank you for taking the time to compose this video as well as all of the other videos in your channel. They have been very informative and educational for my current endeavor.
Yes please do a video on why ducted fans don't travel well in fast forward flight. I remember seeing that project and always wondered why it didn't work.
I have always wanted to bould a flying wing with twin ducted fans. Something like the FT Crackin with the Jets in the middle of the wings. I know that if the wing is stalling or producing a lot of left, the fans can cut out due to lack of air from the low pressure zone above the wing and you need to duct air from underneath the wing to keep the thrust up. Can you do a video on that and other physics related aircraft issues
More airplanes please...and drones, and drone airplane hybrids
Sincerely Adam in Iowa
Adam Sparrow there have been videos of ft versa wings with edf's on them
I was talking more about the vacuum above the wing interfering with the inlet of an EDF. Also things like a forward sweeped wing can be more stable then a straight or rear sweeped wing. Or how a Canard doesn't add much more lift surface but dose add a lot more lift.
Adam Sparrow id also be interested in why we dont build props with winglets on them, effectively making it a self contained ducted prop.... probably materialstrength.
Mendoza Bracken Like aircraft wings now.
Mendoza Bracken Hartzell makes a Q-Tip propeller with winglets. The problem is that propellers are already under a LOT of strain along the radius and the added structure needed to support a significantly bent tip adds a lot of weight and cost. Hartzell says they are more efficient but also a lot more expensive.
Please make a video of why tilting the ducted fan proves fatal ??
You make the whole teaching process very fulfilling.
My wife heard the video and said she wanted to see how adding ducks helped the wind turbine XD then frowned when I said "ducts"
maybe the flapping of the duck wings might, umm sorta maybe ahm, help the turbine, no?
adding ducks sounds great
Voiceless consonants can be a problem. Imagine doubling them.
that's because your wife thinks on a higher plain than you do, she already knew the common sense answer, she wasn't expecting such a dumb answer.
Lol. Mine sat on the hoover´s duct and off she went, quacking through the window. XD
Awesome video RCModel Reviews, I love the way you teach... Your information on this Topic.. a very funny way of learning... Thanks Mate.. Keep up the Great Work...
why not drones/multicopter use ducting fan ?? ..it would be safer for people ...right ??
@@pooorman-diy1104 A lot of multicopters actually use ducting fans
@@mickael9662 thats safer drones .. and more efficient 'i believe
Very simple and clear explanation. Your love to teach is part of you. Only two questions: what's the right space between propeller and duct and what's the percentage of efficiency of this system? I'm looking forward to your next video on these questions. Be good.
I'd like to see that next video. thanks!
I would like to see a video of what you were talking about with multirotors and ducts. And the American experiment with them.
I would like to thank you for this lesson, its something I should have known long ago, after all most of us have flown on jets throughout our lives. Thanks again
The vortex bit is wrong, the low pressure region does not get flung out, I suppose you could argue that the high pressure does, but circulation at the tip occurs because the high pressure region towards the tip trailing edge trys to flow around the tip and gets left behind by the advancing blade, also the "packet of air" principle with curved aerofoils is flawed, there is no reason that the air above and below have to meet up again, it's better to consider the pressure distribution around the entire cross-section not just the top.
Leon Hostad yes, there has been some debunking of the effect that Bernoulli's theorem plays in how a wing creates lift but the spanwise flow of air (induced by centrifugal force) does see a flow between the low and high pressure sides of the propeller at the tip -- and a resulting vortex being formed.
Got to disagree about how that spanwise movement is caused, it's not down to centrifugal force, but down to the pressure difference; under the wing or prop you have higher than atmospheric pressure, and at the tips normal pressure and above less than atmospheric, the difference between under and tips causes a spanwise flow out, and the difference between the tip and the upper causes a spanwise flow in, that causes a rotating airflow, if it was down to centripital forces then tip vortexes on wings wouldn't form, but we know they do.
Leon Hostad Yes, it's primarily a pressure differential but there is still a centifugal effect. Spin a flat disk and watch the airflow across the face of that disk -- you'll see that centrifugal effect plays a part because there is a pronounced flow from the center of the disk towards the edge. This is in fact (partly) how Tesla turbines work.
Leon Hostad sorry but that part of his theory is right. the air wants to travel from the high pressure to the low.
Never said it wasn't, I only said that centrifugal force is negligible, so much so it can be ignored, the main reason for circulation around the tip is the pressure distribution below the wing, around the tip, and above the wing.
Brilliant work Bruce, looking forward to seeing it in action.
ATB Malc
You are such a great teacher. Thank you! Whiched I had you in school ...would have been so much more fun and open new possibilities. But I am here now to learn. Better late than never.
I am interested to know what military aircraft failled because of tilting duct fan? Thank you
yeah me too
ditto
It was the Avero Car project
Who said it was an AIR craft?
@@SaltiDawg2008 lol
The weight of the duct will need to be lesser than lift force gained.
Alan Fok just thinking the same thing
No really? Maybe that's why my super aerodynamic lead car was such a failure.
Yes, they're made of "Duct Tape"
+Völundr Frey Maybe a concrete car instead. A concrete model aeroplane could fly (Mythbusters, TV programme).
Great, great video my friend. I have been testing many EDF units lately and their thrust and this video is perfect for me to understand some things about how the exhaust of EDF unit should be. Thanks for making this video and big salute from Slovenia, Pilot Robert
As an empiric learner, very few people can teach me. But I've learned a great deal from your vid. Thank you.
What effect does narrowing the tube towards the outlet have on thrust?
And would you be able to create a semi turbine effect if you had dual counter rotating truncated props in a tapered tube? What I have in mind is a medium pitch 3 or 4 blade prop I'm the front, with a similarities aggressively pitched prop behind.
They would need to be specially made props with their pitches finishing at squared off ends that fit tightly in the tube, and also exactly mimicking the taper. This might make it easier to calibrate the clearance tolerances by varying the motor/prop mountings using shims.
Have been thinking about this idea since before I watched your vid the first time - about three years ago!
Would really appreciate your thoughts on this proposal.
Check out the videos by Agent JayZ on turbine engine compressor sections.
I want to propel my drone with ducks. Would that be efficient?
Very. You'll get around 40 hours of propulsion with a loaf of old bread.
not efficient cuz duct are too heavy
宋泰成 ducks are not that heavy, birds have hollow bones, so I'm surprised they're not the primary source of thrust for drones and flying devices in general.
Jose Díaz Are you gonna pay the ducks? They do a lot of hard labor
Between the SPCA and PETA, would the trouble be worth it?
Great video!
Loved the content, however one thing to realise is that the lift provided by a wing and therefore the thrust produced by a propeller is mainly due to the Coanda effect which we have recently acknowledged that proves that the flow of fluids conform to the shapes they are moving against, so the air gets deflected down because of the airfoil shape and in Newton's 2rd law, every force has an equal and opposite reaction, creating lift.
thanks for the comment, i was wondering about that...I'm currently researching designs for a stationary duct for manned electric copter,. Do you think the duct has a negative affect on vehicle speed when rotating the blades?
Oh! I wanna know what that effect was, for sure!
See here: th-cam.com/video/0stl1U9evzU/w-d-xo.html
Oh brother the equal transit theory is back...
The fact that the equal transit time theory is false doesn't mean that Bernouli is wrong. The Bernouli principle is obviously true. But, there are absolutely no reason for a bunch of atom to go faster to meet their buddies on the other side of the airfoil at the same time. None. And, indeed, they don't.
I always worry a bit when someone is so....absolute. Natural reflex.
The "knobs" do something called "tripping the boundary layer" which can be very helpful when form drag is a large portion of the total drag on a system. Form drag is the drag caused by the wake of the object. This type of drag is dependent on the largest cross sectional area of the object defined by a plane normal to the flow direction. Another large contribution to drag is "skin drag" which can be thought of just like friction between two solids. Skin drag is dependent on surface area exposed to the flow. A good example of this trade-off is a golf ball vs. an airplane wing. Without going into too much detail, tripping the boundary layer changes the flow from laminar to turbulent which reduces the flow's tendency to resist a change in direction. This allows the size of the wake to lessen, which reduces form drag, but the cost is an increase in skin drag.
In summary, adding dimples or "knobs" to a surface in a flow can decrease it's drag if the drag is dominated by form drag and form drag is dominant when the object has a large cross sectional area when compared to its surface area. Propellers are much like wings in that their drag is not greatly defined by form drag, so dimples would be detrimental, but some sections of a fuselage might benefit from dimpling. Speed and other things have effects on this phenomenon, but I think that is beyond the scope of a TH-cam comment....
If you are interested in the topic, look up some of these keywords:
Form Drag
Skin Drag
Induced Drag
Boundary Layer
Laminar Flow
Turbulent Flow
I always hate seeing that ruin an otherwise great explanation. It's such a common misconception.
Actually its the parasites on the humpback, the knobs... counter ..the parasitic draaagggggg pfffffff
Could listen to your teaching and enthusiasm all day - such clarity and zest - pity we aint got teachers like this in the UK (theyre only interested in the dosh )
15:35 now be honest viewers, how many of you tried that yourself
***** Not me. I don't care if ducts increase efficiency (which, without a specially designed fan, I doubt they do enough to make up for their weight), they just don't look manly enough. Ducts are for girls. (I'm kidding, folks) (kind of)
Jeff Morris lol, and quads are for nerds :)
Vic Prk nerds rule the world lol ;-)
WorksopGimp and the world is sheit, weve come full circle......with a duct.
***** not me! (until now :O)
What happens if the duct is attached to the outside of the prop blades and spins with the prop?
Great question.
you have a larger rotating mass with more gyroscopic effect and a less responsive and more stable quad... you also eliminate all the losses of the gaps between the propeller and the duct, but you increase the load on the motor since higher rotating mass... dunno if its worth it tbh since no one ever went into production with a patent like that.
I think it will have more drag/friction... and also motor load will be increased
If you throw a spinning baseball, it will curve, right? Well, a spinning duck will act the same. Your RC plane will try to go side way.
sok8888 instructions unclear and now my duck is angry with me.
that first bit was the best and quickest explanation of lift i have ever heard
As an aero engineer by education, a fighter pilot by trade, and an RC pilot by hobby, I can say with certainty that the RC community as a whole has more practical design knowledge, derived from the physics lab in the sky known as the real world, than all of global industry's aero engineers, combined.
We have limitless real world data on ducted fans--none are real-world efficient. They are too heavy, too draggy, practical implementations have airfoils with too low aspect ratio to control back-pressure, and they need extreme RPM to produce comparable thrust to a prop that puts the same weight and power into a larger, lower aspect ratio, traditional design.
All you have to do is listen to them to know they convert a lot more electricity into sound than an efficient, quiet, high thrust prop. What they do provide is terribly power hungry, higher speed solutions. Much like any jet vs. prop trade study.
At 1:1 scale, props without ducts are as much as an order of magnitude cheaper to operate in the real world, empirically captured by gathering cost per flying hour stats. It's why the USAF is interested in LAA, and why they switched from the T-37 back to the T-6 II.
If you have a req to go faster, they can make sense given power to burn.
Absolutely right, sir! Through aviation history, there have been maybe 10 ducted propeller aircraft that has reached production, none very successfully. it was thought for a while to be a great way to control noise, but it was proved that low-rev propellers were more efficient and much lighter.
Amen
@Jerry Moody If you mean turbofan jet engines, the duct does improve efficiency because it increases mass flow of air (thrust) - although this isn't true for higher possible speeds, which is why fighters don't use them.
However, this would happen even if there wasn't a shroud around the fan, (as in turboprops) but the duct does multiple duty in controlling/slowing the inlet air necessary for the engine and fan, protecting the fan, and containing broken blades.
With the piece of paper he actually demonstrated the Coanda effect. To demonstrate the Bernoulli effect you would have to use an actual rigid flat plate.
I'm guessing if he had used a rigid plate, it wouldn't have risen no matter how hard he could blow? Like if he hung the paper straight down with no curve and blow on one side, it would just push the paper away from you and it wouldn't move towards where you are blowing, basically the opposite of what he is claiming?
One can NOT apply the Bernoulli principle on two seperate airflows. The airflow over and the airflow under the paper are two different flows.
The paper was lifted because of the reaction force generated on it to the downwards routed (turned) airflow.
i.e. the air was forced to go down whereas the paper (wing) forced to go up ....as a reaction.
@@vatandas1542 he was blowing on top of the paper, not on the bottom
@@DavidL-qb8cl yes. Blowing trough the upper surface created a downwards routed airflow (due to the initial downwards deflected paper) . An upwards reaction force was generated on the paper. Similar to how aircraft wings generate lift.
A very good video sir thank you for taking the time to make it. Please so talk about the American experiment. I think I know which one but want to know for sure. Your teaching method is a lot of fun and your obvious enjoyment of doing so makes you a truly good teacher. I look forward to many more videos.
Love it - thanks! Would love to hear about how the US Military "duct up" in its design
Heya, Yeah i would like to know what happens when moving lateral with a ducted fan said. what was the US Project name from the 50s. I think Canada had something similar also
I want to knoowww
Hiller VZ-1 Pawnee
Someone should pick such people off the internet and just treasure them in one big reputed university.
you won't require any sorts of ppt or high graphics 3d animation just to teach the students, rather only by this simple method of teaching, you would get some exceptionally highly skilled people on this planet Earth.
10:19 The winglets on the end of modern aircraft serve the same purpose.
Design idea: what if you enclose the propeller fully in a very short tube, but have zero gap between tube and outside edge of the propeller. So when it spins the entire tube spins. Then no chance of vortices at the outer edge of propeller. Just an idea. I don't know how well it would work in practice.
I guess the raised tip on the far end of passenger jet wings is to help this same issue of vortices spiraling off the end of the wing/propeller.
Simple stuff, not so simple to understand, explained simply. Well done.
so wouldnt it be best, for all, or at least most, non ductable props and rotors to have winglets on the ends?.
No, answer, just want a notification when someone gives one :)
know what? might not be a bad idea to find some cheap slightly oversized plastic props - mildly heat and bend down the tips
that has been done, google Q-tipped propellers
Martin Baadsgaard I posted the answer but it's been blocked. He made a video explaining why it doesn't work.
it was done on a british design of helicopter rotor which I think was taken up my US military (the technology, that is)
Why don't they duct helicopter propellers? Even if it is just to save the main and back rotors, if the rotors touch the ground or trees?
Weight becomes an issue. The tail rotors on some models are housed within the tail.
The main rotor has to be able to decapitate zombies.
Some tail rotors are indeed ducted for this reason... for a main rotor it adds far too much weight to be worth doing though
They did in Avatar..cool looking!
Can't wait for graphene..
img.gta5-mods.com/q95/images/sa-2-samson-from-the-movie-avatar/b2684f-GTA5%202016-04-13%2011-02-17-60.jpg
Excellent Presentation. You are a joy to watch and have helped me understand my drones better.
You can not waste our time, We choose to watch ;)
So insightful! Thank you good sir! I learned so much!
You are really a best teacher to teach about duct propulsion
Amazing, can the wingtips be a bit more practical than a duct?
New wing design have winglets on the end to suppress the vortex and make the wing lift more efficiently
Great work mate. Thanks for your thorough explanations. Please don't hang us on a cliff though :D What happens when it's tilted?
That's the magic of good vloggers! He's selling us a little bit and I'm not even mad because he's got a lot of amazing knowledge to dish out.
So, this is going to be more difficult in smaller models to find a clearance between propeller and duct wall which makes for significant gain. And if the propeller edge is too close to the wall, it catches and gums up the works. As soon as you begin increasing the distance between propeller and wall the benefit drops off. But the propeller won't move well, won't go without friction and power loss, when the blades connect with the wall. You can't connect the propeller to the wall and get good thrust.
Or can you?
What if the propeller and the wall are one piece? Or rather a section of the wall or a ring is one with the propeller but separate from the rest of the wall. Flush with the main wall the ring portion of the propeller has free movement. Mounted as of a bearing.
What about : (i) The additional drag caused by the duct? (ii) The additional weight of the craft due to the duct itself? Will this not offset the effect of the energy saved by deploying the duct to begin with?