How ducting a propeller increases efficiency and thrust

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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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aviationaerodynamicspropellersductsBernouilliliftthrustefficiencypowertheoryphysicswhite-boardcoanda effect




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RevAldea Day ago
Yes, sir, I'll take three bags full about this effect on, the now famous, the 'Oscosh' helicopter if you will, Please Sir. Thankyou!
happy 4 days ago
Fee 4 days ago
Stop all this “if you’re interested” crap and just give me the knowledge drugs
William Morrissey
Do these physics effects translate to boat propellers? Should we have ducted boat props?
William Morrissey
I’m going to guess...gyroscopic precession.
Piloto Z
Piloto Z 6 days ago
Oh! I wanna know what that effect was, for sure!
thecaveofthedead 7 days ago
This is the single best explanation of flight physics I've ever found.
3hacksTeam 7 days ago
Crap.... really good explanation for dummies - thank you !
mark booth
mark booth 8 days ago
Excellent tutorial I shared your enthusiasm ...please tell me...what were the multi-dynamic effects on the prototype helicopter rotor blades {ones which had additional duct ring} while trans-versing from an hover to full forward motion ?
MaxMorgan 9 days ago
Thx again, love all the info you give;)
Noetic333 9 days ago
You also have a torsion field making up for the extra 30% they can’t seem to account for in aircraft.
mrMacGoover 10 days ago
You make learning fun! I wouldn't have not failed so much if all my teachers would have taught as well as you did!
Hirantha Bandara
Hirantha Bandara 10 days ago
Can we improve it more by putting another lip at the bottom. Inside.
yahya Ibrahim
yahya Ibrahim 11 days ago
Thanx genious! I consider that the fuelless transportation is too late!! cars, planes, trains and ships... The use of fossil fuel should be terminated. I have conceptions and soutions which I couldn't apply... I live in an underdeveloped country... I am so sad....
John Beck
John Beck 11 days ago
But how do you convert a pot-controlled DC controller to one that has a receiver plug on it instead? They call them PWM dc controllers, so there must be some way to modify them. John B. (Minnesota, USA)
Yvon Rouillard
Yvon Rouillard 13 days ago
Great video tanks
Master Ivo
Master Ivo 13 days ago
Its like a loudspeaker, when its out of its box the air on the front and back creates a shortcut, around the speaker. resulting in loss of bass tones. By separating the front and back, there is no direct feedback any more, and more pressure can be build up, resulting in better bass responce.
Drone Pilot
Drone Pilot 14 days ago
Brilliant video!
STEVE JENNINGS 15 days ago
Real curious to know how and if this would improve a boat prop. Seems as though it would
Aldean Louis
Aldean Louis 13 days ago
I was wondering the same thing then I came across this comment. Please reply great teacher
Peter Cernjavski
Peter Cernjavski 15 days ago
It's clear, this is in fact acting like a winglet. But, it will create some drag when flying at high speed horizontally.
R3dp055um 16 days ago
He's a good explainer, but he needs to work on his English skills. His thick accent is hard to understand.
No One Unique
No One Unique 16 days ago
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
Fee 4 days ago
I want to knoowww
JourneyMan 17 days ago
What if the duct is fixed and spins with the prop? Awesome instruction easy to follow thanks
Edward Lewis
Edward Lewis 17 days ago
I would have to say he is intelligent, but use the correct terminology. Centrifugal force does not actually exist. The term is centripetal force. "A force that acts on a body moving in a circular path and is directed toward the center around which the body is moving."
Edward Lewis
Edward Lewis 14 days ago
Not trying to be like that at all. I just think if you are going to teach or instruct people in anything that you should use the correct terminology. Teach correct and use correct language. Other then that he is incredibly intelligent and a good teacher. Any person that dedicates time to teaching and instructing others for any reason gets an A in my book.
Virtual Willis
Virtual Willis 15 days ago
Don't be pedantic, you clearly understood exactly what he was talking about. At best you can correct the word for folks but you don't have to be an anus about it.
mixter7x7 17 days ago
8:20 centrifugal or centripetal - the force pulling outward is centrifugal. the force holding the rotating mass inward is centripetal. remember - there is ALWAYS an equal and opposite reaction. i'm going to also argue your reasoning for what's described as blade wash. the primary law of nature is - all things take the path of least resistance. when a propeller pushes the air - it's pushing air into a high pressure/ compressed area. air pressure around the tips is ambient / static or slightly lower than ambient .... all things in nature - including air - seek the path of least resistance and non ducted air washes off the blade tips instead of creating thrust by staying in the compressed air stream. the question of using a duct is .... does the weight of the duct cancel the added performance of ducting the propeller ? ducted propellers that are correctly balanced don't vibrate as badly as non ducted because there is very little blade tip oscillation. inlet ducts on aircraft begin to collect air around 150 mph. as an aircraft exceeds 200 mph the inlet begins to reach it's full " ram effect " . in ram effect a massive high pressure zone builds inside the inlet duct creating a large static high pressure force on the fan. this increases turbine engine performance exactly the same way a turbo charger effects piston engine performance.
Bobsunfire 17 days ago
Best theoretical physics teacher of all time.
CorrupT 18 days ago
With your whiteboard videos, you're never wasting any ones time mate.
greenman407 18 days ago
Fantastic !! Yes i would like to know why tilting a ducted fan causes a bad effect
David Broadfoot
David Broadfoot 18 days ago
yes i would love to see a video on the gyroscopic force effects that lower the control and fluid dynamics of a gymbled ducted fan drive ... looking forward to further of your videos,.. have shared these with others.
bledlbledlbledl 19 days ago
next, either propel a duck ... or duct an ape :P
steve00353 20 days ago
At 5:40, i realised he does not know how lift is generated. An aircraft is not pushed up, bernouilli principle
dgymboh 19 days ago
As he explains (and demonstrates), using the bernoulli principle, the greater pressure beneath an airfoil as air passes it literally does "push up" or "lift" the airfoil. As you don't believe this, what is your theory for lift?
Marsh 20 days ago
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.
cdreid9999 14 days ago
thanks man ive always wondered this
Michael Balls
Michael Balls 20 days ago
So, what happens if the propeller IS the duct? Would zero clearance be worth the additional skin friction? Offhand it seems like an interesting idea, but I get the feeling it's a big can of worms.
Richard Wallinger
Good stuff. keep breathing .. the hobby needs you .
Dax Chenier
Dax Chenier 21 day ago
Great job 👍
deltaxcd 22 days ago
Thet "debated" effect does not work. the only way to get a lift is by deflecting air down the way ho you do that does not matter If you think otherwise go ask for Nobel prize for inventiing reactionless drive. and as for why duct works (though pretty inefficiently) can be seen just by examining working propeller it does not only pushes air down but also behaves like a turbine and pushes it to the sides by centrifugal force and this is wasting lots of energy.
larry holbrook
larry holbrook 23 days ago
The aircraft is called the Marvel XV-11A, the upgraded version the Marvellet XAZ-1. Built by MS University and is now on display at the Air Museum it Atlanta, Georgia.
-IOI- 23 days ago
Or put the motor on the outside? Have the prop ‘tips’ in the central region?
Ob Server
Ob Server 23 days ago
Too many errors in this video.
Ryan Wingate
Ryan Wingate 24 days ago
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"
Kevin Taylor
Kevin Taylor 2 days ago
maybe the flapping of the duck wings might, umm sorta maybe ahm, help the turbine, no?
JS Mariani
JS Mariani 24 days ago
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.
Norman DeBoer
Norman DeBoer 15 days ago
Winglets reduce wingtip votices, not prevent...
xlcrlee 25 days ago
Several mistakes: the top and bottom flows do not meet "in pace" behind the airfoil, so the upper flow is NOT faster and spanwise flow is involved, creating tip vortices. When properly described the Newtonian and Bernoulli concepts give the same results, but confusion arises when incompletely and inaccurately described. Simpler just to describe what happens: spinning propeller moves/blows air, etc. Vortices scoot out, like breaking, rotating waves behind fast boat. "A little knowledge is a dangerous thing". Or just confusing, at best. Otherwise nice demo.
Nigel Ponsonby Smythe
But you can’t use swing props in a duct can you.
Ella Bella
Ella Bella 25 days ago
Tx. Excellent clarification of the fluid dynamics of the propeller. A thought: i suppose for higher speed applications, the flared lip could create a drag which at some point balances the lift it offers?
OrdnanceAnt 26 days ago
Excellent video
flynlow 27 days ago
Great explaination. What is the difference in the efficiencies of a propeller in a duct and one with the duct attached to the fan tips? If there is already a video, a link would be appreciated.
KC Roberts
KC Roberts Month ago
This a wonderful tutorial for anyone seeking the basic physics of the how's and why's an airplane can fly and propellers deliver forward motion. Implementing a "duct" on the propeller is aerodynamically ingenious. I would love to see a video, similar to this, testing and measuring the increase in efficiency of the "duct" propeller. Great video!
Moderate Fkr
Moderate Fkr Month ago
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.
Michael King
Michael King Month ago
Nice show
Mozart Telles
Mozart Telles Month ago
Excellent correct and simple explanation. The hard part is not teach but to simplify the instruction. E=MC^2
Mike Briggs
Mike Briggs Month ago
Nice one Bruce look forward to your explanation of the failure of fifty years ago. Cheers Baldrick
glen gillham
glen gillham Month ago
The presure is not lower, instead it is redirected to the direction the flow is going.
Chemicalvamp Month ago
You left me wanting to learn about a topic, but "you're not going to tell me what that is".
James Ball
James Ball Month ago
Yes, do tell what happens to the thrust when you rotate the ducted prop.
sumarianson Month ago
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!
Aren't I Adorable
Common dog sense would tell you that a duct will propell air into the direction the duct is facing.
John Harrington
John Harrington Month ago
Does the same apply to a ducted propeller in water? I’m interested in a hydrofoil surfboard but most seem to only use them for safety reasons not efficiency Great video by the way
bigfil1981 Month ago
I have no interest in RC but I've subbed.
U.S. PATRIOT Month ago
Why are'nt counter rotating EDF's used more? It can be done with only (1) motor, right? Here is an example: ruvid.net/video/video-fsHXWFrJfD4.html Thank you in advance!
TheDave570 Month ago
You forgot about the tapered shape of the duct! Forcing air or water through a restricted space causes the air or water to accelerate!! I say water and air because they both act as a fluid!
Anthony Propst
Anthony Propst Month ago
Do something!
Anthony Propst
Anthony Propst Month ago
Good Lord!
Robin Wells
Robin Wells Month ago
Not sure that you could waste my time if you tried! I have subscribed 😆
Simple Life
Simple Life Month ago
Sir i have one question 🙋 if 2 fan very close to etchother like a 2 jet engines so what should be duration of rotation flans ? If there is no Duckett in between to fans so what will happen ?
tewrgh Month ago
All nonsense, off course. NASA debunks this popular misconception here www.grc.nasa.gov/www/k-12/airplane/wrong1.html
Roberto Bheatcoker
Was a point where I guess you changed the direction of the flow thourgh the pipe, so, at the end of the video, the RED low press area on the blade should be on the other way. Right? :)
l p
l p Month ago
The duct prevents air to radial, forcing air in axial direction, thus efficiency increased. Say, what about putting a few tiny wings on the blade to curb arial air flow. I know it must increase the drag, but it might function like the duct without using the duct.
Austin Gamble
Austin Gamble Month ago
Funny, engaging and informative. I hope you made a career of teaching something you're interested in like seen in this video! 10/10
Thermal Flyer
Thermal Flyer Month ago
Fascinating. Thank you I have a question Please tell me why we don’t see coandant ducts attached to propellers on aircraft? I am not talking about a jet engine here! Bare with me. This idea would mean the duct rotates with the propellor, the blades would form the spokes / structure that support the duct. The whole thing rotates. This means zero gap between the propellor and the duct. The centrifugal affect on the wall of the duct would be enormous so there is a limint to how fast the propellor could turn but there will be a sweet spot where it works + more blades could be added to reduce the distance between the supports.
bledlbledlbledl Month ago
what an idea, ducttaping your propeller :P
John Thimakis
John Thimakis Month ago
Thanks for the explanation. 😎👌
Imustfly Month ago
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.
Elwood of Ardmore
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?
Joel Berson
Joel Berson Month ago
There is another source of thrust gain from the ducted prop. At the exit the air flowing through the duct is moving faster than the air surrounding the duct... lower pressure. The surrounding air is pulled into that airflow, but the airflow carries the outer air with it which results in a greater air mass flow which equates to more thrust.
Vishal Rander
Vishal Rander Month ago
Can we have a sub or ship without propeller using water suction technique.
Christian Gadisseur
Please make the next video (maybe you already did). So aren't there force resistance from the top of the lip pushing it down? that'd create a negative flow, no? however I agree that would be not significant while you already gained a second positive flow. great video. thank you so much.
duck Month ago
Minor error... at around 15 minutes he states that there is no drag created by the lip on the duct. That is incorrect, anytime you are pushing something through the air there is some degree of drag. If there was zero drag you would just put on ducts the size of elephants.
Steve Johnson
Steve Johnson Month ago
One suggestion. Using the blue pen for low pressure and the red pen for high pressure would make more sense to me and be easier to remember. Red = Hot = "H"igh = high pressure / Blue = Cold = lower = low pressure. I know, I'm nit picking a FREE educational video....it's just a thought. Thanks for the info. Sarcasm warning: It's totally worth re-recording the entire video to fix this issue. ;-)
Philip van der Waal
I wish my teacher where as passionate as this guy
routt ookc
routt ookc Month ago
physics makes sense...until you start adding numbers...
llib Month ago
hat about the pressure on the bottom of the other side of the propeller?
Blondie SL
Blondie SL Month ago
@2:19 >:)~ LOL But seriously, what would go great with this video would be a 3D printable file to be able to print it out and test it live and in color. :)
Mickie Hicks
Mickie Hicks Month ago
Top lesson. Helps alot.
Alan Campbell
Alan Campbell Month ago
Would a duct reduce the noise of a submarine propeller? [Need to re-watch Tom Clancy's Hunt For Red October]
clavo Month ago
You didn't quite cover the centrifugal force effect of the low pressure wad sliding off the end of the blade there. You do seem to clarify, for me anyway, why birds wings have all those microscopic eddies on their air foils. It appears to me that they have low speed ducting without the ducts by virtue of the hair like aspects in the feathers! Do you see it?
shamrai Month ago
Great stuff! Is there an equation to design the size of ducts in proportion with the propeller/s size?
His Word In Wood
I love this guy! What fun it would be to have him as a neighbor!
Michael The Atheist
This makes me happy!
Ben Month ago
I love this presentation.
leohobb leohobb
leohobb leohobb Month ago
alessdre Month ago
I would like to see the thrust test with ducted propeller and normal propeller because there is someone who says the ducted propellers are less efficiently. The theory looks make sense.
junior aroche_galindo
Wouldnt a design in the prepeler would give it more trust to go in rather then the blade being flat? I think at maximum capacity the blade would act as a repeller instead of a vacuum
CygnusX250 Month ago
question, can the duct be spinning as well ? Q2 on commercial jets the wings have a little fin at the end of it to keep the air from rolling off, i haven't seen this on propellers so i assume that it wont work...but curious to why
Andrew Stabback
Andrew Stabback Month ago
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.
Lee C
Lee C Month ago
I see you published this in July 2015. Did you do a follow-up video of the thrust of non duct and duct blades? You mentioned something about a military craft that failed. What was that? Thanks Lee
Marchel Andersen
actual answer @12:53 so skip to that part
Marchel Andersen
next time asume that we all know basic principels like a wing and make a second video that explaines it for those who dont understand it
Charles Burgess
Charles Burgess Month ago
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
TheDkjayjay Month ago
exactly the same principle is used when building loudspeaker cabinets: Separating low pressure space from high pressure space. Of-course loudspeaker cabinets also involves things as resonance chambers/channels. And talking about resonance, to make an optimum exhaustion system for a 2 stroke combustion engine, resonance is also a key issue. Thanks for sharing this educational and watch-worthy video.
Robert Holland
Robert Holland Month ago
Wonderfully informative Instructor!
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