How ducting a propeller increases efficiency and thrust
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- Опубликовано: 28 сен 2024
- By placing a propeller in a duct, the efficiency and maximum thrust can be increased, sometimes significantly. This video explains two of the mechanisms by which these improvements are obtained -- namely by reducing the losses due to the tip vortex which occurs when a propeller operates in free space and also by using an annular wing that harnesses the effects documented in Bernoulli's theorum.
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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
Yes please do explain what happens when you tilt a ducted fan, I thoroughly enjoy your videos, thank you
Absolutely interested! Plz do sir
ruclips.net/video/0stl1U9evzU/видео.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
What a great teacher! No fancy words, just a very economic explanation. What a pleasure to learn from you, sr.
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?
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 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.
What an inspiring teacher! Your explanations are stellar. I was interested from start to finish. You have a great teaching gift!
Yes please do another video about what you mentioned in this video, please.
the video: ruclips.net/video/0stl1U9evzU/видео.html
enjoy :)
@@GonEyal thank you!
This is the single best explanation of flight physics I've ever found.
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
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!
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.
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.
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 .
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!
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.
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.
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
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
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 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.
Who needs a University When you Get Teacher like him In *RUclips*
*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.
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.
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
excellent. Could you please explain the pros/cons between paddle-shaped and scimitar-shaped propellers?
Thank you for sharing your knowledge with us. You are a great teacher! People like you make this world a better place by inspiring our youth through education.
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.
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 RUclips 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
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
Idk how I always find your videos, I don’t even use rc stuff (apart from a mini drone I have) but I love your physics/electronics knowledge. Subscribed!
I was waiting for a external drive to external drive transfer to complete and I came across this, beats Neighbours any day. Entertaining ... and thanks for the physics
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
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).
He said that but I suppose it depends on the application. I can think of some ideas where weight wouldn’t matter. Not on a plane of course.
Thanks papa,you are such a good teacher,you just answered the questions that were holding me back from flying my own ultralight
I'd like to see that next video. thanks!
Brilliant work Bruce, looking forward to seeing it in action.
ATB Malc
Sir your teaching style is excellent.
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?
Sir,
You are a University in yourself. Lovely teaching style.
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.
Just excellent, both content and way of teaching with good speed and lots of enthusiasm! 👌👍
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.
Hmm, the Gyroscopic effect is a serious problem for Aircraft . Also any wanted change to rotational velocity (RPM) is delayed by the greater inertia,, plus extra weight, combine to make it less viable on Aircraft but acceptable on Ships.
On full size Aircraft , many have "variable pitch propellers" ; this would be structurally more difficult to accomplish with a ducted propeller as the torque would cause extreme stress upon the hub mechanism. Also with conventional type Helicopters, the necessary Cyclic pitch with rise & fall of "main Rotor blades" would make ducted versions non viable.
thanks man ive always wondered this
Wow! Such a great description, augmented by enthusiasm. Well done!
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
Nice one Bruce look forward to your explanation of the failure of fifty years ago.
Cheers Baldrick
I'd love to see a video on the affect of tilting a ducted fan
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
Sorry, love the show, your knowledge has helped me improve my RC planes. Just hate the adverts!
17:20... ok you've hinted at the question i was going to ask
So insightful! Thank you good sir! I learned so much!
Awesome explanation! Any high schooler can ynderstand it the way you explain it. Great introduction to understanding the basic running principles and variations!
You can not waste our time, We choose to watch ;)
I too would like to see a further video on the effect on the duct that was discovered in the US please.
I experimented with suction dredge propulsion styles one is called an infinity jet and what you're saying about the coriander effect and the bent lip of the tube is absolutely correct in practice I used half throttle on my thrust on my my pump motor for the same amount of suction.👍
That's the "Coanda effect," not to be confused with the coriolis effect that causes the latitude-dependent swirl of storm systems and water going down the drain, nor with the coriander spice popular in sausages and "southwest" cooking.
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 video my friend!! Your passion and knowledge and excited way of teaching really adds to the effectiveness of this video!! Well done, very good!!
Yes let us know the other principle you were talking about! Thank you for the video.
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
I wish my physics teacher was this talented! You make aerodynamics so much easier to understand!
You just blew my mind ! I would love to watch more of the videos on the same topic.
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)
Please do a video on the multi-rotor ducted tilt-rotor project that failed and the problems that caused the failure. Even if this is discussed elsewhere, your explanation promises to be clearer.
I wish i had a teacher like you , when i was attending school., i'would have been a jet pilot by now
N Ver he is wrong about air pressure....look it up.
That escalated quickly.
'c mon guys...it's all good..!
Yes and No. Bernoulli's theory is partly correct. if a wing is subjected opposite to an airstream, the relative airflow above an below the wings are different. faster above = lower pressure and slower under the wing = higher pressure. The air "tend" to move from HP to LP thus creating lift on the wings.
This effect also works with a flat plate which is subjected to an oncoming airstream. the exposed surface will be subjected to the force of the airstream pushing it upwards while the non -exposed side has no force acting on it. however if there is an increase in the angle to the airstream it will result in more drag and therefore no lift. same with the wing when the flaps are deployed, at a certain angle more lift (takeoff) at increased angles more drag (landing).
+Джейсон Хичкок see comment where I link NASA disproving that garbage, or better yet, Google Benrulli disproven. Then, read 3 articles explaining why...hint, it's physics dude... then come back and admit your wrong. Or, everyone else who reads this will do that and know you are!!!
Well, of COURSE! Inquiring minds want to know! Look forward to the next segment, and as always, thanks much for sharing.
Steve
My 7th grade Life Science teacher was kinda like this guy. Only difference was we were sitting in the classroom with him and if he is using something to show the concepts that is what each of us would have so we could all do it without passing around the 1 demo model lol. This teacher hated text books with a passion. You could almost see him cringe on the 1st day of class when he passed them out. He said he hated them but the all knowing "school board" said he MUST..... so he did..... They said he MUST use them..... so.... once a week we got a worksheet (if you can even call it that) to do. On single page was usually 8-10 multiple choice hand written questions on it. Beside each question there was a page # and paragraph # where the answer could be found. That was the ONLY homework/bookwork we EVER got in his class. It even came with a sketch he did every week of one of the students drawn as a pig. It took us a total of 5 minutes TOPS to do the ENTIRE WEEKS worth of "homework" for his class. Now...... lets say you managed to somehow NOT do your weeks "homework" your punishment for the next week was you did not get to participate in the class next week...... You got to do pull out the text book and do it the old fashoned way, crack the book and put pencil to paper while everyone else who took the 5 minutes out of their WEEK to write down the answers he was nice enough to give us got to participate in the actual "class" for the week. I mean what teacher can use NOT participating in the learning for a WEEK as an actual punishment and have the student wishing they spent that 5 mins and actually feel "bad" for not doing it.......
Mr Granderson on his own time would visit a slaughterhouse to pick up the days "equipment" for his lesson. Instead of reading how blood flows through the heart from the stupid books..... everyone was supplied with a thick coated looped & tied at the ends wire and 1 pigs heart. You did not look at a diagram with arrows and try to imagine how it all worked...... we put the wire through a heart the way the blood would flow through it.
For lungs we got a handy dandy straw with some masking tape around one end...... and a fresh set of rabbit lungs to play with. (he did warn us to make sure we dont use the straw for its "intended" purpose or we would not have plesent results lol). For intestines we got to get our lesson showed using cow intestines...... since it was huge we got a demonstration that day.
How best to learn genetics of plants and how the cross polinization process works..... we planted flowers and since there were no bees to polinate them..... we couldn't fill in for the bees and just do it without them..... we got toothpicks with actual dead bees. Just remove the abdomen more or less like so many has done with natures "glowsticks" and with bee part attached to toothpick, we polinated our other classmates flowers with our plants polen.
He was more of a "Mad Scientist" than a boring old teacher. The level of energy he put in was even more than this guy in the video. Of coarse what is a life science class without a couple 6 foot boa constrictors and a 4-5 foot ball python. Since we had the snakes, had to have the rats that he breed to feed the snakes. A green parrot (that was super asshole), Nice big harry tarantula (that I ended up picking up because we cant have the damn girls playing with it and letting it crawl on their face and shit..... peer pressure is a BITCH!!!!! lol).
The funnyest thing was at the end of the year when we turned in our "books". These books were like 3 years old, issued to 2 years classes before we got them....... and we were handing in BRAND NEW BOOKS..... they still had the high gloss on the covers, crisp mint condition pages, and almost even still had the NEW BOOK SMELL to them. Learned more in that class by not cracking a book than any traditional method of teaching.
He lived in Africa for a few years so we got cool stories from him too. One I remember was how they do the whole "death" thing. When someone dies over there in the more primitave parts (o ya, he wasnt a stay in the city type of guy) the funeral is pretty much THAT DAY or next day at the very latest. Not because of "beliefs" but because it was necessary as they did not have the refrigeration needed to store them or the embalming to preserve them. It was drop your day your going to a funeral in couple hours.
Simply AMAZING teacher that inspired and got even the "trouble students" excited about learning.
Sir I am interested to learn anything you are exited to share your thoughts about with so much clarity. Great lecture.
thank you sir. Lots of information here for the novice as am I. I appreciate you.
symmetrical wings also fly
Yes, and so do undercambered wings which REALLY destroys the Bernoulli explanation.
This helped me understand how a parachute is designed and how it works
Great explanation, Physics was always s my fav subject at school, because my teacher was as enthusiastic as you are. and i got a top grade, so at least he didnt fail because he made learning fun !
Fantastic video and an even better Lecturer. Thank you. It would be nice to see the practical thrust tests with and without ducting. Would a small wing-tip/winglet on the prop improve its efficiency?
Wow, i Think its the first time I disagree with you. You said that no drag is created by the ducts, how come not? When moving, an enormous drag is created by the duct, remember: anything that do not produces lift, produces drag. Also, we didn't consider the weight added, that also reduces the flight time.
Even tought you are right about the better efficiency created by the ducts, its weight and drag will make it not worth. A better solution would be propellers like tmotors, with curved tips, just like airplanes wingtips, this reduces the vortex.
Ricardo Iarossi you're right, drag created by duct is huge, but at high speed. Drag created by duct rises with the square of the speed (this fact is used to slow down airflow in turbofan engines), but I think Bruce wants to use it in a multirotor that moves relatively slow.
I agree that this will not work though - he would have to use a prop that has extremely small gap between tips and duct
Ricardo Iarossi My point was that the lip does not create any extra drag with respect to the air flowing into the duct. Obviously the duct itself will create drag once it starts moving through the air -- but in a hovering situation, the motor does not have to overcome any extra drag from the lip -- in fact the lip reduces the load on the motor.
Ricardo Iarossi
You should have watched the whole video before commenting as both of your (completely correct!) points where mentioned in the end.
Ricardo Iarossi It's not used on external propellers, I'm not sure why exactly. But in jet engines, the turbine blades often have a 'fence' at the outer end. You can buy one on ebay. :¬)
www.ebay.co.uk/itm/Rolls-Royce-Avon-Jet-engine-4-blade-Assembly-RAF-Lightning-Hunter-Turbine-/191624480262?pt=LH_DefaultDomain_3&hash=item2c9db58606
***** Any air moving over a surface is going to create drag just from friction alone.
i have always wondered about the effect of a duct around a propeller... your video was helpful in explaining how it works, which I had already kind of thought, but could never prove.
this system seems like it would be great as a stationary unit to move air more efficiently, BUT... my hobby is full sized boats, so....
how would this work on an outdrive that is moving THRU the water at 50mph?.... I am aware that at low speeds, the efficiency would be improved and probably most noticeable when turning tightly such as in a marina, because of the vectored thrust that an outdrive/outboard steers with... (as opposed to a "deflected" thrust from the use of a rudder)....
I think, at high speed the efficiency would be improved, but the drag caused by the duct thru the water would cancel out any possible gain, and quite possibly be REDUCED far below the point that using the propeller without the duct on it would have....
and im sure the length of the duct would have some effect on the efficiency, but obviously, there would be a happy medium somewhere in the length of it, as too short wont help much, and too long would cause more drag... what are your thoughts here?...
Good stuff, entertainment and educational. More please?
I want to know why the military test failed!
The vertical ducked fan was too stable and would instantly right itself even as the soldier was trying to fire his rifle,so his marksmanship was crap. It could only manage 16mph,he explains it in another video.
You swallowed that line? It is as old as human time and is just as wrong now as then. Militaries create fear and hatred, then get dim-witted fools to buy the "hero" line, then go do their killing for them. If you want peace, prepare for peace...if you want war prepare for war. You reap what you sow...etc
Good grief, what are they teaching kids these days? Look at what has happened all around the world during the last 8 years of Obama's withdrawl from influence and our unilarlteral disarmament while our adversaries have been increasing power and influence! If our enemies laid down their weapons, there would be peace. If we lay down our weapons, there will be genocide. If you want peace, prepair for war. Unless the good are powerful, evil will triumph. All it takes for evil to triumph, is for good men to do nothing. Pull your head out of your ass and look around at the real world, silly millenial.
Not the pace for this debate really, but I think you should do a bit more reading if you think Obama is withdrawing from anything or that Trump's war ethic will get us peace. Now I am really worried. p.s. I'm not a kid...I've been watching and studying the world and its antics go by for over sixty years. The mongers who profit by war will never cease their ministrations to the masses as long as it continues to work in their bank account's interest.
Gerry S..."I think you should do a bit more reading if you think Obama is withdrawing from anything"
^^^ I can't tell if serious, or trolling.
He went around the world apologizing for America, he bowed to our enemies and tried to appease them with endless concessions for nothing in return while betraying and disrespecting our allies who no longer trust our honor and resolve.
He coined the term: "Leading from behind".
We cut and ran from Iraq and Afghanistan with an unimaginable achievement of snatching defeat from the jaws of victory, and he drew a red line in Syria that he didn't enforce, all of which opened the doors and rolled out the red carpet for ISIS to fill the vacuum of power while Obama pretended they were the JV team that nobody needed to worry about.
He canceled the missile defense shield in Poland and cut all advanced missile defense programs.
He handed Iran the right build Nuclear Bombs.
He paid terrorist BILLIONS of dollars in untraceable cold hard cash in various world currencies delivered to them on pallets.
He signed the START2 treaty that reduced our nuclear warheads and delivery systems, prevents us from developing nuclear technology or modernizing our outdated nuclear missiles, all while allowing Russia to continue it's nuclear technology advancements and to increase their stockpile of warheads.
He has reduced Army manpower by 10%, marines battalions are down by 33%, our air force now has the smallest and oldest force of combat aircraft in its history.
Our defense budget was $917 billion under Carter, $1.1 trillion under Reagan, $624 billion under Clinton, $761 billion under George W. Bush, and Obama is only requesting $551 billion for 2017. Our defense budget as a percentage of GDP under Obama has not been this small since the end of WWII.
^^^ All that only scratches the surface of the damage that Obama has done to our power and influence in the world.
***Apparently you have been asleep for 60 years, because you need to do a LOT more reading!***
dailysignal.com/2015/07/26/weapon_system_revive/
www.washingtontimes.com/news/2016/mar/14/ed-feulner-obama-deep-cuts-to-defense-leaves-us-vu/
Why don't helicopters use ducts around their blades?
During cruise a helicopter flies forwards, not upwards and the rotor acts like a wing. A duct flying at almost 90 degree angle against the wind would badly disrupt airflow to the rotor and cause it to stall. A helicopter rotor would also need a very large duct which would cause a huge amount of drag.
tip jets work better for helo's
Rebals Reba during the cruise (by which I mean Vh) a helicopter, or indeed any other air vehicle, is producing enough lift so as to remain in level flight. Whilst it's true to say that adding a ducted fan outside the main rotor would induce unhelpful drag in the cruise it is false to say that the rotor "wing" would be stalled. It's very difficult to stall a helicopter because even when hovering helicopters create their own relative airflow. I would suggest that the real answer to the above question is simple: because it makes no sense. The extra drag, max takeoff weight and reduction in useful payload would outweigh any aerodynamic gain. If you look at the blue edge blades that we make in Airbus Helicopters you will see that there are better ways to improve rotor efficiency and to overcome the challenges of Vh flight, especially Vh at MCP, retreating blade stall etc than by adding a ducted fan. Nevertheless, check out our tail rotors... aha! Makes sense there. Google H160.
Mr Jay White sure, that's why there in use so widely 😂
you mean like a big circle around the tips of the propeller? for once, the blades are already heavy enough for the load they carry. for twice, the blades are so long that the loss along the blade probably disperses before reaching the tip.
You can make a dumb guy like me to be interested in physics.
Thats how talented you are in teaching !
wind turbines have been built similar to this and made a real improvement in power production in low winds , Airsynergy was one turbine mass produced
Terrific explanation. This made me think: you know how the wingtip of a 737 has a lip to reduce vortices? What if the propeller blade had an angled lip at the tip too? Will it have the same effect as a duct?
Thank you for this!! Took me ages to find a good explanation.
Why aren't all airplanes ducted?
Watch from 16:42 onwards. ;-)
ask this why arent helicopters hummm same can be aply to them to stop the centrifugal force the rotter has
shhhh et ufo
For the one reason he didn't mention. Drag.
Ducting works best when the velocity of the air through the ducting
is significantly greater than the aircraft airspeed, such as when
lifting an aircraft vertically, or with a turbo jet, but in normal horizontal flight the ducting around a more conventional prop presents a very large cross section of drag. There have been some notable attempts of ducted fans used in GA over the years, but none have lasted long.
Because they only improve efficiency in certain conditions. Once the airplane starts moving fast the duct creates more drag than it makes up for in increased efficiency.
the efficiency gained is not substancial, compaired to the added weight.
Sir you r a very good teacher ..keep it up ..I enjoy listening to u .👍
Well done sir. I'm discovering things that are new and exciting to me. Thank you so much for this content.
It is not a waste of time if we ( I ) learn from or can apply such knowledge .
Absolutely love instruction especially from someone who gets excited by the subject. I am about to change fan blade size on a refrigerator condenser at work so I'm brushing up on some knowledge. I suppose given this video the obvious question is why haven't i ever seen a crop duster with a duct around the prop, either connected to prop blades or affixed to plane? Something tells me I'll know why soon
Good video. I think for most people that you did a good job. However, technically speaking Bernoulli’s equations are only valid across a single stream line. Fluid moving over an air foil violates this assumption “Split flow”. To mathematically calculate why an air foil generates a pressure differential. You must use the Navier Stokes equations derived with respect to pressure. It is very common miss conception that Bernoulli’s equations can be used to calculate lift.
Peter Peel yup, no reason why the streamlines on the top and bottom have to meet at the trailing edge at the same time
Real curious to know how and if this would improve a boat prop. Seems as though it would
I was wondering the same thing then I came across this comment. Please reply great teacher
Drag is the drag
Fantastic teacher, very good explanation .
As always, very informative and colorful explanation.
Thank you very much for this video! I recently did a grade 12 research project on ducted fans after being introduced to them in this video. I wanted to talk about some of the things you mentioned in this video, could you please refer me to some of your sources so I could cite them as well?
Thank you again.
Thats really awesome video you made. I have a question; how do coaxial helicopter propellers work then? Two propellers rotate at the same time so bottom of the higher propeller has higher pressure but that’s where the lower propeller has lower pressure.
This man looks and radiates wisdom and knowledge.
Are you sure it is the pressure at the bottom that pushes it up? What I see is the force at the top pulls it up? Great video anyway. You should do more.
While ducted fans work as described - the demonstration blowing air over the paper is a bit misleading.
Here is excerpt from Wikipedia:
"Misapplications of Bernoulli's principle in common classroom demonstrations
There are several common classroom demonstrations that are sometimes incorrectly explained using Bernoulli's principle.[32] One involves holding a piece of paper horizontally so that it droops downward and then blowing over the top of it. As the demonstrator blows over the paper, the paper rises. It is then asserted that this is because "faster moving air has lower pressure".[33][34][35]
One problem with this explanation can be seen by blowing along the bottom of the paper: were the deflection due simply to faster moving air one would expect the paper to deflect downward, but the paper deflects upward regardless of whether the faster moving air is on the top or the bottom.[36] Another problem is that when the air leaves the demonstrator's mouth it has the same pressure as the surrounding air;[37] the air does not have lower pressure just because it is moving; in the demonstration, the static pressure of the air leaving the demonstrator's mouth is equal to the pressure of the surrounding air.[38][39] A third problem is that it is false to make a connection between the flow on the two sides of the paper using Bernoulli's equation since the air above and below are different flow fields and Bernoulli's principle only applies within a flow field.[40][41][42][43]
As the wording of the principle can change its implications, stating the principle correctly is important.[44] What Bernoulli's principle actually says is that within a flow of constant energy, when fluid flows through a region of lower pressure it speeds up and vice versa.[45] Thus, Bernoulli's principle concerns itself with changes in speed and changes in pressure within a flow field. It cannot be used to compare different flow fields.
A correct explanation of why the paper rises would observe that the plume follows the curve of the paper and that a curved streamline will develop a pressure gradient perpendicular to the direction of flow, with the lower pressure on the inside of the curve.[46][47][48][49] Bernoulli's principle predicts that the decrease in pressure is associated with an increase in speed, i.e. that as the air passes over the paper it speeds up and moves faster than it was moving when it left the demonstrator's mouth. But this is not apparent from the demonstration.[50][51][52]
Other common classroom demonstrations, such as blowing between two suspended spheres, inflating a large bag, or suspending a ball in an airstream are sometimes explained in a similarly misleading manner by saying "faster moving air has lower pressure".[53][54][55][56][57][58][59] "
Ducting a prop is is the TUBE version of putting winglets on wingtips, as it simply reduces the drag from wingtip vortices, thereby increasing the overall efficiency of the airfoil.