Coanda effect Flying Saucers what does works...

[jamesatwork]

Coanda effect flying saucers

Hi all I'm looking to make a Coanda based flying saucers. I was wounder what are the factors important for sizing calcs, the common stuff like appropriate power to weight. But also if any info on actual performance such as for the profile of hull that would be so much appreciated.

Many thanks

James

[adamdb]

Here is the only one I know of that's been done:

http://jlnlabs.online.fr/gfsuav/index.htm

[eflightray]

James, have a look at the following two threads, they're in the Foamies (Scratchbuilt) forum -

Coanda UFO v2.0 - a different approach (http://www.rcgroups.com/forums/showthread.php?t=667204)

Coanda effect UFO (foamy contest build) (http://www.rcgroups.com/forums/showthread.php?t=653166)

You will probably also find links within them to other threads and information.

[mnowell129]

You're kidding right?
You never get more lift than the propeller would make by itself, because that's the total amount of energy being input.
This is like Wile E. Coyote mounting a fan on his sailboat car to blow air at the sail to catch the road runner....

[Brandano]

Indeed. If a coanda effect saucer would get more lift from the prop than what was there to start with, then you'd get more speed out of a Gee Bee racer by fitting a smaller prop to it

[jamesatwork]

but coanda effect does not rely on direct thrust, but in a similar way to a convetional wing from making lift perpendicular to a high velocity air stream by creating a pressure diferntial, between the upper and lower aerofoil surfaces via the cuved profile on the top surface, coanda by veloctiy differntial. while there are other factors ithat are important this principle this principle is much more efficent than just an angled surface in terms of lift to drag ratio because you not creating a large cross sectional area with out the beifits of a domed profile.

as far as the Gee Bee racer there would be an effect acting in a directon perpendicular to the surface eg radial outwards in all direction creating no net lift for the aircraft. there would be an incresed pressure differntial between the inside and outside fluctuating with speed, all it would do is run through the fatigue life of the fuslarge skins a bit quicker

[mnowell129]

but coanda effect does not rely on direct thrust, but in a similar way to a convetional wing from making lift perpendicular to a high velocity air stream by creating a pressure diferntial, between the upper and lower aerofoil surfaces via the cuved profile on the top surface, coanda by veloctiy differntial. while there are other factors ithat are important this principle this principle is much more efficent than just an angled surface in terms of lift to drag ratio because you not creating a large cross sectional area with out the beifits of a domed profile.

But the net thrust is always less than the thrust that would be made by the propeller or fan that blows the air, if it were just blowing straight down.

[eflightray]

Hey, I got mine to hover. I didn't realize I had it up side down to start with, it kept digging tunnels.

[Stef]

A plane is not sucked up into the air by lower pressure on the upper wing surface.

[Brandano]

Stef, a plane is kept up in the air by the energy it puts in the air to move it downwards. Now, this can be explained in several ways, and the "difference in pressure" between the top and bottom surface just happens to work perfectly well for this purpose, allows you to consider the plane/air ensemble as a sort of closed static system and still match real world measurements. When a plane is flying, the air under the wing has a pressure higher than that of the atmosphere the plane is flying into. The air above the wing has a pressure that is MUCH lower than that of the atmosphere surrounding the plane. This is in some way due to the fact that the plane is moving air downwards, and creating a pressure difference. so there you have it, you can explain lift as a result of reaction or as a result of a pressure difference, however saying that either of the two "theories" is false is a mistake.

[Stef]

The point I was trying to make is that no matter how hard you blow across a surface with an attached device it will not rise it will not be "sucked" up into the sky. i don't even want to start discussing the question of Bernoulli's principal as it applies to a wing. You can learn more about how a wing works by "playing" with the air with your hand sticking out a car window at 40mph than with most text books.

[KaneTheMediocr]

You're kidding right?
You never get more lift than the propeller would make by itself, because that's the total amount of energy being input.
This is like Wile E. Coyote mounting a fan on his sailboat car to blow air at the sail to catch the road runner....

You might be right in this case, but your argument has a hole in it.

Energy is conserved, and you certainly cannot (with a coanda setup or any other) get more energy output than input, but lift is a FORCE, not an energy. Two rotors with the same power can produce dramatically different thrust if they have different areas, this is why helicopters have huge blades (they couldn't fly if they had an airplane sized rotor). Airplanes fly with less than 1:1 thrust-to-weight because they convert a small force times a large velocity to a large force at a low (vertical) velocity with their wings. (Power = force times velocity, if they are the same direction).

[Stef]

yes but the small prop makes up the equation by providing much higher velocity (pitch speed). If your prop and motor combo in a coanda setup dpes not provide more thrust than the total weight of the craft it will not vtol. Do some testing (no pie in the sky, you can't stand in a shopping bag and lift yourself by the handles a lot of coanda proponents believe you can).

[mnowell129]

You might be right in this case, but your argument has a hole in it.

Energy is conserved, and you certainly cannot (with a coanda setup or any other) get more energy output than input, but lift is a FORCE, not an energy. Two rotors with the same power can produce dramatically different thrust if they have different areas, this is why helicopters have huge blades (they couldn't fly if they had an airplane sized rotor). Airplanes fly with less than 1:1 thrust-to-weight because they convert a small force times a large velocity to a large force at a low (vertical) velocity with their wings. (Power = force times velocity, if they are the same direction).
I don't see the hole. I'm familiar with rotor efficiency equations and the efficiency of converting HP to lift with larger diameter.
But my point was that if you had a prop making 1 lb of lift by itself and instead you blew the air over a "coanda" device you would get less than one 1lb of lift.

[Brandano]

I believe that the theory behind the coanda device is that the high energy flow from the prop traps extra air from outside the prop edges, increasing mass flow at the expense of speed, and therefore increases static trust. I am not sure how well this actually works. It's pretty much the same principle used in thrust augmenters for pulse jets, and in compressor driven vacuum pumps. However, I am ready to give it the benefit of doubt. That said, driving a larger rotor will probably be more efficient anyway.

[Stef]

mnowell you've got it right. The coanda effect uses a high speed jet to entrain more air in the right circumstances. Air blown by a prop isn't fast enough to do much entraining. The best you can hope for is small losses and turning the air stream downwards efficiently to give you lift. If you look at the current model of the GFS you will see that the duct and the coanda body are much closer to being the same diameter than the earlier models and he's using a fan that provides gyroscopic effect.
With the wider coanda body he was getting to many losses and not turning airstream efficiently.

[Thomas B]

Many years ago, (Circa 1978, I think) Robbe had a flying saucer type kit called the Turboplan that was using Coanda effect for some of the lift, along with direct prop lift.

Pic of kit box below. Power was a glow .61. Diameter is 36" overall.

I found a small pic of one flying, as well.

[Stef]

There is still info on the turboplan on the net. The foam body did not provide anything in the way of lift (just wishful thinking) it did provide stabilization through gyroscopic action.

[underthefloor]

I don't see the hole. I'm familiar with rotor efficiency equations and the efficiency of converting HP to lift with larger diameter.
But my point was that if you had a prop making 1 lb of lift by itself and instead you blew the air over a "coanda" device you would get less than one 1lb of lift.

Do you know this for a fact or are you just making stuff up?

If you don't know for sure what you are talking about don't pretend like you are an authority.

By your logic, an airplane that can't climb vertically can't fly at all.

[mnowell129]

Do you know this for a fact or are you just making stuff up?

If you don't know for sure what you are talking about don't pretend like you are an authority.

By your logic, an airplane that can't climb vertically can't fly at all.
You're kidding right?
An airplane doesn't fly by blowing prop air over it's wing, like you are implying.
I think I'll stop here and not waste any more keystrokes on

[underthefloor]

You're kidding right?
You never get more lift than the propeller would make by itself, because that's the total amount of energy being input.
This is like Wile E. Coyote mounting a fan on his sailboat car to blow air at the sail to catch the road runner....


Im not implying that an airplane generates lift by blowing the prop wash over the wings.

You are claiming that you can never get more lift than a propeller would make by itself because of conservation of energy. If this was true, most airplanes would not be able to fly. An airplane generates more downward thrust (lift) than is produced by the propeller.

[nmasters]

An airplane doesn't fly by blowing prop air over it's wing
A Custer channel wing does. So do blown flap systems. Neither are particularly efficient but they do have applications. I'm not saying that I think Naudin's toy works mind you :rolleyes:

[Thomas B]

There is still info on the turboplan on the net. The foam body did not provide anything in the way of lift (just wishful thinking) it did provide stabilization through gyroscopic action.

I dunno..I'd like to see some yarn tufts on the ring when it flys...I know tha the prop is supplying most of the lift, but I predict some lift is indeed coming from the flow over the upper surface of the ring into the prop, which in effect working in a venturi with the upper ring surface forming a shallow bell mouth.

[mnowell129]

Im not implying that an airplane generates lift by blowing the prop wash over the wings.

You are claiming that you can never get more lift than a propeller would make by itself because of conservation of energy. If this was true, most airplanes would not be able to fly. An airplane generates more downward thrust (lift) than is produced by the propeller.
Actually I'm not claiming that point at all and you seem to be mixing force, energy and power. It comes down to lift force per HP.
I think you are missing a major point. The mass of air moving through a propeller disk is what makes the lift force (the m in f = ma). The wing of an airplane flying through the air moves a substantially larger mass of air than the propeller disk, hence the substantially larger lift force for the same HP.

If you examine the efficiency equations for hovering flight you will see that the most efficient lift comes from accelerating the largest mass of air with least delta velocity, hence a bigger rotor makes more lift per hp than a smaller one, with a wing obviously being a very large rotor in the extreme case. So it's mathematically obvious how the power from a prop can provide enough power to make an airplane fly, yet not be enough to hover on the prop. An analogous situation is using a small prop at the tip of a large rotor to make it spin. The small prop isn't enough to hover the rotor but is sufficient to make the big rotor spin fast enough to make it hover. An airplane is in a sense a very large rotor being spun by a tip propeller that happens to be in the middle of the rotor blade and is just spinning in a very large circle. (Aside, likewise a gyrocopter is some gliders flying in very small circle.. :) )
This is well known, commonly accepted fact in aerodynamics. This is why the human powered helicopters can fly, very large diameter rotors (which, by the way, are turned by tip props). When you understand that a very small prop turned by a human cannot lift a human, but a very large rotor pulled in a circle by the same small prop can lift the same human you will also understand why a coanda effect aircraft is hooey from a thrust efficiency perspective.
Once you have accelerated a mass of air with a propeller, compressor or whatever you've set the basic parameters for how much lift it will make per HP and blowing that air over a bowl, a conehead or dyson vacuum, doesn't change how much mass got accelerated at what delta V.

[mnowell129]

A Custer channel wing does. So do blown flap systems. Neither are particularly efficient but they do have applications. I'm not saying that I think Naudin's toy works mind you :rolleyes:
Blown flap systems are about adding energy to the boundary layer to make it stay attached to the flaps. The same effect can be achieved by sucking the boundary layer away with pinholes on the upper surface (Reference XV11 Marvel ). I agree there is some net lift from upper surface blowing following the flap but the major component is keeping the boundary layer energy up so the flow stays attached.
The custer channel wing is also a circulation control device, same basic idea is to force attached flow in an otherwise detached flow condition , thus allowing the wing to work much more efficiently.

[underthefloor]

...blowing that air over a bowl, a conehead or dyson vacuum, doesn't change how much mass got accelerated at what delta V.

I think that is the point of the coanda craft, the air mass and delta v are changed.

[Stef]

An airplane wing is not generating lift while standing still. It generates lift by moving through the air affecting in some cases tons of air per second. Blown flaps worked by directing the airstream from the engines downward therefore providing some control at slower speeds. Flight is a reaction to an action. Forcing airflow over the wing downward, action air down, reaction wing up. The coanda saucer needs lift (VTOL) without foward motion therefore only prop thrust is applied to lift.

[mnowell129]

I think that is the point of the coanda craft, the air mass and delta v are changed.
How can it? Draw me the diagram showing where the coanda device adds mass to the airflow or adds velocity to the airflow. At the exit to the impeller the mass flow rate is the same as the entrance to the coanda device which is the same mass flow rate at the exit of the device (minus losses). The fact that you think this devices somehow magically adds energy to the air by turning it leads me to conclude that I'm making myself look like the fool for arguing with you about it.
So I'm going to stop doing that.

[Brandano]

mnowell, I think the theory is that the thin film of high energy air that sticks to the bell shape due to the coanda effect causes more air to follow it by viscous friction, trading speed and energy for mass. Doesn't really add more energy to that the prop or centrifugal compressor can provide (actually wastes quite a lot due to surface friction with the bell, I think) but trades impetus for mass flow, essentially the same effect as using a larger, slower prop. I am not a believer in free energy, but I can see how this sort of device could be useful to obtain a controllable hover using a smaller prop. However, as I stated before, an helicopter rotor will likely be more efficient. The tradeoff here is complexity.

[HugePanic]

here are some results i made in a 2.35minute test!

i don't know exactly that this experiment is relevant for the coanda effect, so i let you guys analyse the results:

i just grabbed the first-best ufo available (there are zillons sold of them...) and mounted the second best foamy just on top of it. the motor cables were inversed, so that i pushed air over the ufo.

the ufo itself was mounted on a lightweight aerostructure type of stand on my precision scales! (same manufaktuer as the ufo!!!)

now it is simple: power on an read the scales!
what do i read??? a NEGATIVE value! this means my ufo is creating a type of anti gravitation! :)
it was not much, but more than "by accident" and NO mistake! the scales were reading -15grams at full throttle (about .5 oz).

is this a relevant experiment???

(my results: it is not proven that the summ of the lift is raised due to the ufo. maybe the drop in propeler effeciency is more the the ufos lift)

[mnowell129]

... to the coanda effect causes more air to follow it by viscous friction, trading speed and energy for mass. Doesn't really add more energy to that the prop or centrifugal compressor can provide..
Then why doesn't a stream of high pressure air from, say a turbojet, cause more air to follow it because of viscous friction? I think in your mind you know this is bogus. And if it doesn't add more energy where does the lift come from? The point that is being missed is that the power that was wasted to make the lift in the small prop/compressor is gone by-by when the little prop makes it, never to be seen again and not recoverable. The conversion of shaft horsepower to lift has an efficiency factor that occurs based on the disk size. Once you make that conversion and take that loss, you never get it back. You can do whatever you want downstream from that but unless you add more energy somehow all you are going to see is losses. If this really worked don't you think that Sikorsky would have a big efficient heavy lift aircraft that was a jet engine blowing a colander?
The coanda effect is that a high energy low thickness stream will follow a curved path and not detach due to adverse pressure gradient. The upper surface blowing that has been referred to is used to make a flow (the normal airflow over a wing) stay attached to flaps to increase the overall Cl to make STOL more effective. The same thing has been done with upper surface suction and in fact is the principle used on slotted flaps on commercial aircraft. And by the way is how some of the NOTAR tail boom lift is created. The coanda effect allows you to control a larger airflow that is causing the lift, not cause the lift in the first place. The coanda effect flying saucer might be more efficient once it started to translate and the effect was used to keep the flow attached, but as to making lift directly, I still think this is horse hooey. It's a funny effect that people who don't understand momentum theory get all caught up in.
Just for the record having a prototype that kinda "works" doesn't change physics. The moller sky car is one example of a guy who doggedly pursues an idea that will never work because the rotor disks are so small that the fuel efficiency will never allow the aircraft to be financially viable. The world is full of passionate people who believe in ideas that are impossible, but they hang on to the George Foreman theory that anybody can be an inventor if you just believe in your invention strongly enough. Watch the American Inventor shows for pitiful examples of this behavior. :)

[mnowell129]

is this a relevant experiment???


Relevant but incomplete.
Remainder of test:
1) Mount motor to alumium test structure, rig for forward running.
2) Run motor.
3) Watch motor/prop and test structure fly away into ceiling.
4) Reach conclusion that prop blowing on colander makes less lift than
prop alone, proving hypothesis that colander device does not make extra thrust compared to prop alone.

Test 3:
1) Fly airplane, measure vertical climb rate as estimate of thrust production.
2) Mount colander to airplane, attempt to re-measure climb rate.
3) Reach conclusion (again) that colander device does not make extra thrust compared to prop alone.

[Brandano]

Then why doesn't a stream of high pressure air from, say a turbojet, cause more air to follow it because of viscous friction?
Oh, it does, and it has been used too in some places, just google "thrust augmenters". However it does so at the expense of speed, and if you are using a jet engine and then trade speed for static thrust then why are you using a jet engine in the first place?
http://www.aiaa.org/tc/vstol/augmented.html

...Rockwell International's XFV-12A
Lab tests were interpreted to show that 55% augmentation could be anticipated, but differences from the lab models to the full scale system caused the actual augmentation to be onlu 19% for the wing and 6% for the canard....

[Stef]

In your test setup up you are acting on the colander with an an outside force, like the wind blowing on a sailboat. If the motor and prop were part of the colander you would not get the same results, like sitting in the sailboat blowing on the sail.

[HugePanic]

In your test setup up you are acting on the colander with an an outside force, like the wind blowing on a sailboat. If the motor and prop were part of the colander you would not get the same results, like sitting in the sailboat blowing on the sail.

yes, i know this. but on the other hand it shows the isolated effect that the lift is larger than the applied impact pressure. this fact is sth I wouldn't have expected!

maybe if am bored this week i will mount a motor on it.
one test with motor on scales alone
one test with motor on the ufo on scales...

[biber]

If the effect is really there and has just gotten largely underestimated,
why don't I see one working example of an aircraft based on that particular principle
that comes close to the efficiency of conventional setups?

Why all the mumbo jumbo?

The coanda effect isn't any special but just compliant with the well established laws of fluid dynamics, after all, isn't it?

What mnowell129 said.
There is no free lunch.

biber

[mnowell129]

There is no free lunch.

biber
but there's always someone trying to get one.... :D

[Stef]

AMEN.... Please pass the potatos

[nmasters]

but there's always someone trying to get one.... :D
Or trying to sell one. It wouldn't be the first time for J. L. Naudin

[KaneTheMediocr]

Then why doesn't a stream of high pressure air from, say a turbojet, cause more air to follow it because of viscous friction? I think in your mind you know this is bogus. And if it doesn't add more energy where does the lift come from? The point that is being missed is that the power that was wasted to make the lift in the small prop/compressor is gone by-by when the little prop makes it, never to be seen again and not recoverable. The conversion of shaft horsepower to lift has an efficiency factor that occurs based on the disk size. Once you make that conversion and take that loss, you never get it back. You can do whatever you want downstream from that but unless you add more energy somehow all you are going to see is losses. If this really worked don't you think that Sikorsky would have a big efficient heavy lift aircraft that was a jet engine blowing a colander?
The coanda effect is that a high energy low thickness stream will follow a curved path and not detach due to adverse pressure gradient. The upper surface blowing that has been referred to is used to make a flow (the normal airflow over a wing) stay attached to flaps to increase the overall Cl to make STOL more effective. The same thing has been done with upper surface suction and in fact is the principle used on slotted flaps on commercial aircraft. And by the way is how some of the NOTAR tail boom lift is created. The coanda effect allows you to control a larger airflow that is causing the lift, not cause the lift in the first place. The coanda effect flying saucer might be more efficient once it started to translate and the effect was used to keep the flow attached, but as to making lift directly, I still think this is horse hooey. It's a funny effect that people who don't understand momentum theory get all caught up in.
Just for the record having a prototype that kinda "works" doesn't change physics. The moller sky car is one example of a guy who doggedly pursues an idea that will never work because the rotor disks are so small that the fuel efficiency will never allow the aircraft to be financially viable. The world is full of passionate people who believe in ideas that are impossible, but they hang on to the George Foreman theory that anybody can be an inventor if you just believe in your invention strongly enough. Watch the American Inventor shows for pitiful examples of this behavior. :)

I was wondering if anyone else had noticed that problem with the Moller guy. That said, he has made a LOT of money on flying cars. Hasn't sold any, hasn't built any, but lots of foolish investors give him money. He put up public stock, and raised about $4 million without having a sellable product. He was fined by the SEC for this (about 250,000 if I remember correctly) since you're supposed to have sold a product before listing public stock, but thats a net profit of $3,750,000.

American ingenuity at its best.

[mnowell129]

The deal with Moller is he already started a successful company. He invented SuperTrapp mufflers ( I had one on my Honda 185, way back when) and made a bunch of money when the company sold. So investors are likely to see a successful entrepreneur in the guy, and he's got a PHd so he has all the credentials. Problem is that he doesn't understand the one piece of physics that stops his skycar from ever working (or he does and just can't get off the money train). I noticed that he's started to spin off other companies based on his engine development, maybe he's looking for a golden parachute....

[macboffin]

The point I was trying to make is that no matter how hard you blow across a surface with an attached device it will not rise it will not be "sucked" up into the sky. i don't even want to start discussing the question of Bernoulli's principal as it applies to a wing. You can learn more about how a wing works by "playing" with the air with your hand sticking out a car window at 40mph than with most text books.
If that were so, then the Custer "Channel Wing" aircraft could not fly. They did so very well!

[mnowell129]

If that were so, then the Custer "Channel Wing" aircraft could not fly. They did so very well!
Not without forward airspeed. The Channel Wing was a circulation control wing. It made the wing work better, but the channel wing still had to move forward to make it fly.

[Texas Buzzard]

If this Coanda effect flying device was effecient don't you think an A/C company such as Lockheed would have built a prototype?

[underthefloor]

If this Coanda effect flying device was effecient don't you think an A/C company such as Lockheed would have built a prototype?

Well, they wouldn't know how efficient it really was unless they or someone builds a prototype. Even if a Coanda craft had the potential to be efficient it is likely that it would still take a lot of development to get it there. I suspect that aircraft companies don't develop Coanda crafts because there is already a highly developed alternative in the helicopter and because of people like mnowell129 who use bad logic to dismiss innovations offhand.

I don't know how much potential Coanda crafts actually have but Im not going to dismiss them without knowing for sure that they can't work well.

[mnowell129]

people like mnowell129 who use bad logic to dismiss innovations offhand.

What bad logic are you referring to?
There's no such thing a perpetual motion. In a closed system energy cannot be created or destroyed. The universe tends toward entropy. No energy conversion is 100% efficient. And you can't run a car on hydrogen made from water that you crack with electrolysis off the battery that you charge by running the engine. And a coanda device, when it's not moving, cannot make more lift than the lift made by the device blowing on it. The coanda effect does allow you to control the flow of air on a moving surface and force it to be more efficient. But saying that the coanda device can make more lift than the air that is blown on it implies more than 100% efficiency.
I'm not anti-innovation, just anti-urban-myth-based-on-a-misunderstanding-of-basic-physics.

[underthefloor]

Im referring to the logic you just used in your post.

Im not claiming that a coanda is a perpetual motion machine by the way. That doesn't have anything to do with this discussion.

An airplane is able to use a relatively small amount of thrust from its propeller to sustain flight. All the energy going into the system goes through the inefficient propeller. If you take the same engine and propeller that can make an airplane fly and apply it to other types of aircraft, it may be possible to generate more lift than the propeller produces just like with the airplane. You can't use entropy or conservation of energy to offhand dismiss the possibility of a coanda craft producing more lift than the propeller that drives it does. Conservation of energy does not equal conservation of lift.

[underthefloor]

Seriously, you are claiming that a coanda craft would violate conservation of energy unless its moving? Having the craft move somehow lets you off the hook regarding thermodynamics?

You seem like a smart guy but you are mis-applying physics.

[Stef]

mnowell129
Hallelujah.... Praise the Lord!!!!! I've been preaching this for years but pie in the sky is hard to deny.

[MarkusN]

mnowell129
Hallelujah.... Praise the Lord!!!!! I've been preaching this for years but pie in the sky is hard to deny.
By that Argumentation a plane with a propeller up front can't fly if the thrust of its propeller is less than its weight.

As others have pointed out: There is no law of preservation of thrust, just one of preservation of energy. And that fails to describe hovering objects, as hovering per se needs no energy.

For example: let that propeller blow air into a gasometer. It can lift a huge weight. Or look at pneumatic domes. Same principle. Or even closer: a hovercraft.

If a coanda principle disk can achieve the necessary efficiency of lift conversion is another matter altogether. That remains to be seen.

[mnowell129]

A helicopter uses less energy in forward flight than hover. In a hover the rotor is supplying 100% of the energy to support the craft, same as forward flight. So how come it takes less energy to fly forward?
The volume of air that you interact with changes when the craft is moving, therefore the efficiency changes. A prop/turbine's static thrust is lower than the dynamic thrust because of the same reason. This is the subtle piece of aerodynamics/physics that you are ignoring. The coanda effect is using a stream of high velocity air to control a larger flow of air, like the notar tail boom and the upper surface blowing on some cargo aircraft. The larger flow being the rotors downwash and the wings motion. In the absence of the larger flow of air the coanda air is all the supplied thrust and blowing that at disk doesn't change the amount of net thrust produced.
Here's the scientific measurement. Build the coanda saucer, hover for a fixed period of time and measure the fuel consumed. Build the same weight craft, but instead of the coanda device use a rotor of the same diameter as the coanda device. Measure the fuel consumed. Compare.
The coanda addicts don't want to run this test any more than Moller wants to run the test, because they know the outcome.

[mnowell129]

ply it to other types of aircraft, it may be possible to generate more lift than the propeller produces just like with the airplane. You can't use entropy or conservation of energy to offhand dismiss the possibility of a coanda craft producing more lift than the propeller that drives it does. Conservation of energy does not equal conservation of lift.
This misses an important point. The conversion of mechanical energy to lift in air takes place with a certain efficiency. In an airplane that conversion takes place between the wing and the air that it is moving in. This conversion takes place no matter what the reason you are being pulled through the air, gliding for example or shot from a bungee, or dragged on a cable behind a car.
The prop on an airplane is just providing the motivation to move the wing through the air. The efficiency goes up with the span.
When the prop is turned vertically and used to make thrust, the conversion from mechanical to lift takes place at the small diameter prop. The efficiency of the system is set right at that point. Whatever you do with the airstream at that point and beyond never gets the efficiency back out of the prop compared to a much larger span conversion device. The efficiency of your system is related to the diameter of your mechanical to lift conversion device. In an airplane the prop is not the conversion device, it is the propulsion device. In the coanda saucer the prop is the conversion device and therefore governed by the efficiency of the small diameter, so the overall efficiency of the system is never going to be better than the small prop.

Airplanes flying at a thrust to weight of less than 1:1 is possible simply because the wing is providing the lift by efficiently interacting with a large volume of air and the only energy required is that of dragging that wing through the volume of air.

I guess we are going to have to disagree on this one...

[Stef]

You cannot convince someone if they have their eyes and mind closed!
One thing I have seen on the boards here is someone will come up with the blown wing VTOL idea (AGAIN) not seeing the fact that the wing needs to move through the air. They talk it up and argue that it will work has to work lower pressure on top surface higher pressure on bottom, Bernoullis principal yada..yada..yada.. then after an initial flurry no more posts, to embarrassed to come back and say gee guess I was wrong. I still don't see any VTOLs with a purely blown wing wonder why?

[mnowell129]

I still don't see any VTOLs with a purely blown wing wonder why?
At least you and I don't have to wonder.....

[MarkusN]

Maybe ten (could also be 20) years ago a new modelcraft was hyped. It had a toroidal wing with a 0.61 engine set in the center blowing down into the hole. It was said to fly by the air drawn over that wing and to to do so remarkably stable (more so than the notoriously difficult to control helicopters). Anybody remember this? I couldn't turn anything up with a quick google.

[mnowell129]

It was called the turboplan.
Stable, maybe, efficient, no.
Some of the stability was just the mass of the ring that
slowed down the frequency response of the motions.

http://www.cr-modelltechnik.de/turbopla.htm

[MarkusN]

Yep. That was it. All-up weight 3.5 kg (roughly 7 lbs). Does a .61 engine with a stnadard propeller develop that much thrust?

[biber]

An airplane is able to use a relatively small amount of thrust from its propeller to sustain flight. All the energy going into the system goes through the inefficient propeller.Efficiency is not about forces its about work and energy.
Propellers are very efficient and there is not much you could do better.
Propellers can reach more than 80% eta, so there are only 20% left for improvements, if you don't believe in finding perpetuum mobile.

If you have an amount of power to generate aero forces, you may be able to increase the force, but it is just like what you do,
if you are driving a car up a hill and the downshifting gear will give you more force at the expense of speed.

biber

[underthefloor]

In the coanda saucer the prop is the conversion device and therefore governed by the efficiency of the small diameter, so the overall efficiency of the system is never going to be better than the small prop.

Well, I think the whole point of the coanda disk is to act as the "conversion device."

[mnowell129]

Well, I think the whole point of the coanda disk is to act as the "conversion device."
That's the whole point. Once you take the loss through the small prop, even if the coanda device is 100% efficient, the total efficiency is just that of the small prop.
Once the little prop converts mechanical energy into a mass of air at a given flow rate, that's the amount of energy/lift available. The coanda device can turn, rotate, change speed, whatever on this mass flow rate, but it will never make any more energy than what left the prop.

[underthefloor]

That's the whole point. Once you take the loss through the small prop, even if the coanda device is 100% efficient, the total efficiency is just that of the small prop.


If the problem was loss of efficiency due to a small prop, airplanes would have the same problem.

[mnowell129]

If the problem was loss of efficiency due to a small prop, airplanes would have the same problem.
No, because airplanes move through a large volume of air, hovering saucers do not.
I'm now done with this conversation with you because:
1) You won't do a controlled experiment to prove your point.
2) You don't understand the logical impossibility of trying to
prove a negative hypothesis. That is, you won't prove that the
coanda device makes more lift than the prop alone and I can't prove
that it doesn't. So you will continue arguing that just because no one
has made it work yet that that doesn't prove that it can't work....

Great, we've now found the aero equivalent of Aliens, Yeti and The Loch Ness monster.....No one can prove they don't exist, yet those that insist they exist cannot provide the singular example to prove that they do.....

fin

[underthefloor]

"No, because airplanes move through a large volume of air, hovering saucers do not."

The fact that airplanes move through large volumes of air isn't all that relevant.

If you took that same motor and propeller and put it on the end of a rotor you could hover a helicopter. If you took that same motor and propeller, it might be possible to generate more lift using a coanda device than the propeller produces. In the case of the hovering heli and the coanda craft, both are not moving through the air.

Im not claiming that coanda devices work or don't work, Im just calling you on your BS. Your assertion that a coanda craft would violate conservation of energy is absolutely wrong.

[mnowell129]

In the case of the hovering heli and the coanda craft, both are not moving through the air.

Insanely I reply:
But the shockingly obvious point you are missing is that the rotor IS moving through the air in a big circle, while the coanda device is not.
I assert that a prop blowing air on a bowl that is not moving, cannot make more lift than the prop itself.
Prove otherwise.
But of course you will not.

[mnowell129]

The fact that airplanes move through large volumes of air isn't all that relevant.


This explains everything about your understanding of this topic.

[underthefloor]

Here is a link to an experiment done in the 20s with thrust augmenters. They were able to increase the thrust of a jet by 20 to 40 percent.

http://naca.central.cranfield.ac.uk/report.php?NID=961

A thrust augmenter increases the thrust of a jet of air. Its been proven. It doesn't violate conservation of energy.

"These results show conclusively that it is possible to increase the thrust of a jet by use of suitably designed augmenters."

So yeh, you can increase the thrust from a propeller using augmenters. No moving parts necessary.

[MarkusN]

Once the little prop converts mechanical energy into a mass of air at a given flow rate, that's the amount of energy/lift available. The coanda device can turn, rotate, change speed, whatever on this mass flow rate, but it will never make any more energy than what left the prop.
Once more: Energy != Lift.

I'm kinda sitting on the fence if increasing lift from a given airstream is possible. But the argument you give above is no proof.

One example where this is done are injectors. A high speed jet is used to accelerate a large mass of fluid. The mixed fluid at the end of the mixing chamber has less speed, but higher mass flow.

Any proof if increasing lift is possible or not needs to use the law of conservation of momentum, not energy.

[Stef]

Yes You Can Increase The Thrust And Volume Of A High Speed Jet But At A Sacrifice (trade Off) Of Velocity The Amount Of Energy In The System Remains The Same Minus Friction Loses.

[mnowell129]

The mixed fluid at the end of the mixing chamber has less speed, but higher mass flow.

But the same energy as the two fluids before mixing. And it doesn't have a higher mass flow rate.
Mass flow rate is mass/time or rho*A*V. With rho constant, increasing
the area and lowering the velocity doesn't change the mass flow rate.
Same as a converging diverging nozzle, the velocity changes but the
mass flow rate doesn't. And we're back to a basic principle, in a closed
system mass cannot be created or destroyed and the energy doesn't increase unless you do work.
Explain how the coanda device does work on the fluid.
To clarify. I'm not saying that the coanda device does not make lift, just that it makes it less efficiently than some other use of the mechanical energy available.

Somebody please explain to me how in fifty years or so of the coanda effect being known about no one has yet made a device that proves to any degree that the coanda device makes lift more efficiently than something else. And please don't point to the channel wing airplane because there is no scientific evidence from that aircraft any more than the moller sky car has produced.

[Brandano]

mnowell, I think that here you are making a small mistake. you are saying that a coanda device won't increase static thrust, while I think it could do so, by trading speed of the airflow for volume. Where you are probably right is that the same motor could obtain more thrust than when used with the same prop and a coanda device if it were to be used with a gearbox and a properly designed rotor, trading again airspeed for volume but doing so in a more efficient way, and using the same amount of energy as in all three examples. "thrust augmenters" DO work, though not nearly as efficiently as NASA hoped they would. I believe that the "20 to 40 percent" that underthefloor quoted was an early overly optimistic estimated figure that was later reduced for practical cases to 10-15 percent.

[MarkusN]

But the same energy as the two fluids before mixing.Nope. Energy is lost in the chaotic movement of mixing which is converted into heat. Momentum is retained.

Much like the difference between elastic and plastic collision. In elastic collision both energy and momentum are retained. In plastic (corresponding to mixing fluid flows) only momentum is retained.


And it doesn't have a higher mass flow rate.Nope again. A very simple argumentation chain disproves that. The driving jet has a certain mass flow rate enter the mixing chamber. This mass flow has to also leave it at the end. But you have the mass flow of the driven mass added. The flow leaving necessarily must be larger.
Re-reading my statement, I should have been more precise: Higher mass flow than the driving jet.


Somebody please explain to me how in fifty years or so of the coanda effect being known about no one has yet made a device that proves to any degree that the coanda device makes lift more efficiently than something else.Nobody claims that. At least I won't. But there remains the question if higher lift can be obtained by blowing an airstream over a cleverly designed surface than by using that airstream as a lifting jet directly, which you deny. Using the unfit law of conservation of energy.

These things are often interesting to follow just for the fun of it, not to design a more efficient craft. At least in modelling they are.

[mnowell129]

Where you are probably right is that the same motor could obtain more thrust than when used with the same prop and a coanda device if it were to be used with a gearbox and a properly designed rotor,
This is my point.

[mnowell129]

Nope again. A very simple argumentation chain disproves that. The driving jet has a certain mass flow rate enter the mixing chamber. This mass flow has to also leave it at the end. But you have the mass flow of the driven mass added. The flow leaving necessarily must be larger.
Re-reading my statement, I should have been more precise: Higher mass flow than the driving jet.

Simple but maybe not accurate. The mass flow rate in and out of the system has to be the same, the system can't create mass. The energy of the exiting mass will be higher than incoming, hence the production of thrust. Suppose you devise a device that is fed 1 bb per second at low velocity, the device ejects the BB at a high velocity in the other direction, the work done on the BB to accelerate it generates thrust on the device. The mass flow rate in and out of the system is (1 BB mass)/second, but the energy of each BB changes as it goes through the system. Reduce the BB's to the size of air particles and the same argument holds true, the props mass flow in and out are the same but the energy of the exiting mass is higher, the acceleration of which causes a opposite reaction which is thrust.

Let me see if I understand the basic argument.
It is that the coanda device can be used to make lift. Thus if you make a device (saucer) where the prop is used to blow air over the device it will make lift. I agree with this statement.
The point I disagree with is does it make more lift than if you just used the prop to make the lift directly.
The theory here is that because the device can make the air curve in an arc that this somehow adds energy to the air so it makes more thrust. I just have not heard a valid argument as to how this adds energy to the system.
It's a simple test, measure thrust with a prop compared to energy input, measure the thrust from the same energy input and see if you get more thrust.
I'll admit I'm wrong If someone shows me a valid scientific test that shows more lift coming from the coanda device than some other way of making lift.

[Brandano]

The theory here is that because the device can make the air curve in an arc that this somehow adds energy to the air so it makes more thrust.Nope, it isn't. The theory is that it adds mass flow, while subtracting impulse. It effectively increases STATIC thrust, at the expense of dynamic thrust.
I just have not heard a valid argument as to how this adds energy to the system.It doesn't. The entire concept doesn't exclude the trade-off. Theoretically it just allows the prop to behave as a bigger, slower one. However, using a bigger and slower prop would probably work better.

[MarkusN]

Again, my inital explanation was not precise enough. Of course the overall mass flow must be in equilibrum.

I wanted to compare the mass flow entering the system with (significant) impulse (i.e. the drive jet) to the mass flow exiting with the same feature (the overall flow). The same point Brandano is making above.

As for the scientific test: I was aiming at that with the Turboplan. I have no idea how much thrust its engine would deliver on its own. I don't remember the F3A planes of the time climbing vertically indefinitely, however.

[mnowell129]

Theoretically it just allows the prop to behave as a bigger, slower one.

Ok so how does it do that? I understand the use of the coanda effect to
enhance attached flow. I understand what slotted flaps do. But this is using
the coanda effect to control another flow. Clearly coanda can be used to influence a flow of air to stay attached, stay laminar, and even cause circulation in the first place and therefore increase the lift of a flying surface. Coanda is used on the tail boom of the NOTAR, but again it is controlling a larger external flow.
In the case of the coanda saucer there is no other flow to affect.
So I'm still waiting for rational argument as to how the flow behind a propeller can be made to follow a curve and create more lift than the prop made in the first place. The whole "entrains outside air" concept is BS, especially when the free flow velocity is 0.
If the coanda device made sense so would blowing the prop blast at a bigger propeller that turned more slowly at larger diameter and thus converted the high speed air into low speed air. This is equally preposterous.

I buy that coanda effect can be used to modify an airflow. What I doubt is that it can be used to create that airflow in the first place.

So it seems the argument is the coanda device can make a little prop behave like a big prop and increase the static thrust.
Again, I'm waiting for a real scientific test that confirms this. It's an easy test. Motor, prop, scale, wattmeter. Then motor, prop, scale, bowl, wattmeter.
And I won't be doing the test since I can't disprove the positive. It's up to someone else to prove the positive.
The odd thing is that if this were really true, somewhere in the history of aerodynamics this would have been quickly checked out, found to be true, and have some application, like maybe coanda cones on the exhausts of Harrier engines. Seems like if this coanda thing does what it is rumored to that would be the perfect application, some kind of collapsable structure that converted the jet exhaust to static thrust....

I'm not trying to stop anyone from building a saucer. I'm just not ready to accept that it is an efficient way to make lift.

"airplanes don't fly, they just quickly move into a new section of air before it falls"

[Brandano]

I have to be careful choosing my words, I guess. I never said that it actually works, only that this is the theory that coanda "crafts" are based on. I expect that the idea is that by enlarging surface the airflow is moving on and keeping the flow more laminar it exacerbates the boundary layer effects, trapping more air than it would if it was just the fast turbulent flow behind a prop. The path the air is forced on also lowers its pressure, so that more air is likely to be trapped and add to the mass flow.

[Texas Buzzard]

The only emperical evidence I have seen appears on Post #2 (a video).

Conjecture and misapplied physics doesn't answer the question. Do the experiment then report.

How is "effeciency" defined? If the motor/prop develops 16 ounces of thrust then isn't it true that the "bowl" in deflecting air more horizontally would have a vector acting downward which would reduce the overall lifting ability of this system?

[Accu157]

Isn't part of the idea behind the coanda effect is that by blowing air over the curved surface beneath the prop, that the surface with air being blown onto it generates lift? Isn't this somewhat similar to having a fan shroud on a ducted fan increasing thrust? I know they're used to reduce losses at the tips of the blades, can those shrouds act as a lifting surface?

Right or wrong, coanda flying saucers sure have a strange way of being controlled. :eek: I've seen one before at a hobby show. It still didn't quite look like a UFO, but it used something like a .15 engine to generate lift, and some form of coanda-looking control system.

I think it's worth looking at the website about the guy who made coanda-thing mentioned in the second post. I think he wants to build a flying saucer flown via the biefield-brown effect and zero point energy cold fusion... er something like that. Sounds like he's having fun, although there are several instances where he is clearly not getting more power out than he's putting in (he claims the impossible... sorta.) Otherwise, some of the goals he has are ok. This one (http://jlnlabs.online.fr/cfr/index.htm) looks like he's claiming that by placing electrodes in water with a salt solution in it, he's getting more energy out than he's putting in. Must be cold fusion. Yeah. My glider climbed without a motor. Must be antigravity.....

I like the title in one of the photographs set up by someone else who did the same experiment: "elucidation of the anomalous generation of hydrogen by plasma electrolysis".... lol. Yeah, so the hydrogen got pulled to the anode. Or is it the salt that gets pulled to the anode and the hydrogen is release? I forgot, need to review my chemistry. That doesn't impress me much.

http://jnaudin.free.fr/

[underthefloor]

This is the company that invented the GFS.

http://www.gfsprojects.co.uk/index.htm

http://www.youtube.com/watch?v=DW0cgBoWGVM