Spinning cylinder as a wing

[matrix0f8h]

I am considering building an rc model that uses a spinning cylinder instead of a wing. I am using the Kutta-Joukowski Lift Theorem(?http://hyperphysics.phy-astr.gsu.edu/hbase/fluids/kutta.html ) to calculate the lift created:

Lift per unit length = L = rGV
-where:
-r is the air density: 1.225 kg/(m^3)
-G is the vortex strength (see below)
-V is the velocity of flow: 15 mph = 6.71 m/s

Vortex Strength = G = 2(pi)w(r^2)
-where:
-w is the angular velocity of the cylinder: @5000 rpm with a r=0.15m: 78.57 m/s
-r is the radius: 0.15m

So:

G=2(22/7)(78.57 m/s)(0.15 m)^2 = 11.11 m^3/s

and then

L = 1.225 kg/(m^3) * 11.11 m^3/s * 6.71 m/s
= 91.32 (kg*m)/(s^2) = 91.32 Newtons per unit length

So if the wing were 0.33 m in length, then the lift produced would be: 0.33m * 91.32 = 30.14 N

I am pretty sure I messed up somewhere up there and possibly completely misunderstanding the theorem. Because this comes out to be 6.776 pounds of lift. Any ideas

[Karl B²]

Seems like the L/D would be pretty high. What sort of surface, rough, smooth, dimpled?

Someone once made a successful small RC model using a winglike plate rotating around the long axis, in much the same manner as a sheet of balsa fluttering/rotating down in a steep glide.

[matrix0f8h]

I imagine I will try all three. Although intuitively it seems that dimpled would be a good choice since that is what golf balls use.

[BMatthews]

Spin it fast enough and it'll VTO. But I don't think it would work for forward flight at much airspeed. I see it as a helicopter thing.

Or perhaps as an alternate to an autogyro.

[Stregone]

I doubt it. It appears to me that it needs to be already moving through the air before it will create any lift.

[matrix0f8h]

Right. It needs to have air flowing over the spinning cylinder in order for it to create lift. (note that lift increases as the size of the cylinder, or the speed of the cylinder through the air, or the angular velocity of the cylinder increases)


This is the page that gave me the idea:
http://www.howstuffworks.com/airplane4.htm

[Majortomski]

since it didn't take into account the surface texture I notice no ref to reynols numbers either. I know there are several attemps to use the benefit in full scale A/C but the mechanical complexity of keeping the cylinder straight and spinning offset any useable payload

YMMV
MrT

Personally I stick to helium to offset that weight;)

[Sparky Paul]

Originally posted by Thomas Solinski
since it didn't take into account the surface texture I notice no ref to reynols numbers either. I know there are several attemps to use the benefit in full scale A/C but the mechanical complexity of keeping the cylinder straight and spinning offset any useable payload

YMMV
MrT

Personally I stick to helium to offset that weight;)
.
Bending! Yes.. light enough to spin, stiff enough to not bend.. probably not possible with a flyable full-scale structure.

[Bob Chiang]

Here's a link you'll be interested in:

http://www.fanwing.com/

[Stregone]

Whoah...that thing is really slow... Very interesting.

[Sparky Paul]

I'm impressed... but bottom-lining..
noise is energy that's not going into propulsion or lift.
Too many moving parts.
Too many special parts.
Much more "stuff" than the equivalent fixed wing.
It would be a hard sell.

[Sail 'n Soar]

Originally posted by matrix0f8h

Vortex Strength = G = 2(pi)w(r^2)
-where:
-w is the angular velocity of the cylinder: @5000 rpm with a r=0.15m: 78.57 m/s
-r is the radius: 0.15m

So:

G=2(22/7)(78.57 m/s)(0.15 m)^2 = 11.11 m^3/s

Any ideas

You can use the Kutta-Joukowski Lift Theorem to predict the lift of all subsonic airfoils. However, I don't believe you can use the angular velocity of the spinning cylinder to calculate the vortex strength of the surrounding air. Standing still, you will have a very thin boundary layer near the cylinder, with the angular velocity dropping off MUCH faster than the 1/r^2 for a fortex. What the spinning cylinder does for a moving cylinder is keep the flow attached longer on the aft moving side of the cylinder, and cause a flow separation sooner on the forward moving surface, e.g., throwing curves in base balls and lofting golf balls. The shift in the wake relates to the vortex strength you should use for your lift calculation. Also, the wake moves, but is is still a fat, draggy wake compared to an airfoil, so the L/D would be low.

[vintage1]

I read about this a long time ago. Its the same principle as backspin on a ball to loft it. I think that it is at its best at low flying speeds - same sort of profile as an autogyro. Not sure if you could glide it tho with the wings spinning.

I would thgink styrofoam cylinders with carbon fibre shafts would be a place to start.

Some ship or other used it once to gain wind assistance - sort of sialing ship with a motor to just spind the rotors.

No idead where to find details tho.

[downeym]

another thing to consider is that the spinning cylinder would be a nice gyroscope, which means that your control system would probably be pretty squirrelly. Imagine... you give right rudder, which induces left roll.... or something to that effect....

[Sparky Paul]

When you look at the wing section, it reminds me of an extremely cusped airfoil developed in Oz.
A test I'd make would be to cover the rotating cylinder completely, as if it were an airfoil, and see how that flew without the cylinder rotating.. if it could.

[BMatthews]

Originally posted by Sparky Paul
I'm impressed... but bottom-lining..
noise is energy that's not going into propulsion or lift.
Too many moving parts.
Too many special parts.
Much more "stuff" than the equivalent fixed wing.
It would be a hard sell.

I don't know..... Compared to a helicopter this doesn't look bad. Sure the rotor is spinning but it's just a basic one peice fabrication. Mind you a bird strike on the full size may be.... er..... "interesting"?

The big question I have is what happens if the engine fails. In other words how does it descend with no power. Can't have the skies raining people in strange fan'ish machines now can we?

It's obviously very STOL'ish and while the speed isn't any great deal I could see it being useful for inner to outer city bussing. Especially if the claims of low fuel consumption hold up in real life with real payloads.

And it sort of looks like if they rotate the fixed portion of the trailing fairing that the plane could achieve either very STOL or true VTOL and transition into normal forward flight with not much problem. In fact judging by the way it climbs after takeoff they could probably get a better cruise by rotating the rear section further up.

Yes, very interesting.

[Sail 'n Soar]

If you were wanting to model something, you might consider something based on toy kites with wind driven "S" shaped wings that rotate about a central axis. The concave side toward the wind creates more drag than the convex, which causes the wing to rotate and sets up the vortex. (BTW, these take a lot more wind to fly than is required for a conventional kite.) This is a simpler implementation of the roatating wing plane illustrated in the http://www.fanwing.com/ site and this or the simpler S wing you can make fly.

But remphasizing my earlier post, the rotational speed of the motor driven cylinder, dimpled or not, does not represent the vortex strength of the surrounding air mass. Baseballs curve noticeably because the V is large, not because the separation induced wake shift, and associated G, is large. Your plane might fly, but could it take off?

[Stregone]

I vote for contacting the fanwing guy for info and making one of those :)

[Bigfoot]

Commandant Cousteau, the French underwater explorer, used the Turbovoile (turbo sail) on his oceanic laboratory ship 'Alcyone'.

[vintage1]

Ok, while waiting for the model airplane factory (TM) to warm up, I thought I'd try and scratch those grey cells to exorcise the dim memory of that rotor ship...and came up with the keyword FLETTNER

And lo and behold, here is wind tunnel and nasty tensor calculus from 1925 tests.

You need to check this out

http://naca.larc.nasa.gov/reports/1925/naca-tn-228/

Do a google search on 'Flettner' and loads of stuff comes up.

It WILL work with sensible lift to drag ratios, but it needs to spin damned fast.

Issues to do with spanwise flow also need to be looked at.

I actually think that a pair of lighweight foam and CF cylinders spinning backards fast enough, with another prop on the front, and some tail feathers out the back, would actually fly!


You could even test build one as a glider. I'd assume that CG about 1/3 of cylinder diameter from the front might work.

Lord knows how you would do roll axis control - I'd probably give it 'dihedral' and use the rudder :) Or maybe use elevon mixing on teh elevator.

[vintage1]

More gen on the flettner rotor ship
Jonathan, Lancaster UK

* The rotating-sail ship was developed by Anton Flettner, a German engineer at the University of Gottingen in 1922. He had been carrying out experiments to determine how much greater the force exerted by wind on a revolving disc is in comparison with a stationary surface of the same area. This effect is used, for example, by bowlers at cricket to swing the ball. The ships had two rotors, each turned by a small engine at its base. When the rotor surface speed was four times the wind speed, the force exerted on it was 15 times greater than that of a sail the same size. On transatlantic voyages rotor ships reached speeds of up to 17 knots, though this was of course dependant on the available wind. They were small vessels, around 600 tonnes, and the rotors looked like enormous funnels - 20 metres high and 3 metres in diameter. Unfortunately the incessant and unavoidable vibration from the rotors lead to mechanical damage and poor reliability. Enthusiasts at the time predicted that all the world's shipping would soon be using rotor power, but less than 20 years later they had all been broken up for scrap.

Paul Dixon, Didcot UK

* Jacques Cousteau commissioned a ship with a similar rotor drive in 1985. It was called the Alcyone and was used as an expedition vessel next to the Calypso. Although the rotating sails served mainly as an auxiliary drive, they reduced the average fuel consumption by more than 30%. I remember seeing it in several TV films Cousteau made in that period. I have no idea what became of it since.

Luc Pandelaers, Antwerp Belgium

* The Cousteau Society's Alcyone is such a vessel. Last I heard, the Alcyone was still in fine working order. I was lucky enough to spend a very pleasant evening on her deck with her crew and some friends, while they were docked in Montreal. The Cousteau people had been filming a documentary on the whales in the St Lawrence River, and they still use the Alcyone for such expeditions. The ship is an eye-catcher- there is nothing afloat that looks anything like her. Absolutely beautiful!

Christopher Blanar, St Andrews Canada

* The Flettner 'Rotor Ships' certainly seemed to meet with a favourable response at the time. There is a good report on the performance of the ship in a NACA web archive article on the Magnus effect. A larger ship, the 92m 'Barbara' was constructed by the German naval authorities and successfully operated out of Hamburg for six years carrying up to 3000 tonnes of cargo. The Cousteau ships Alcyone and Calypso II use a slightly different type of 'Turbosail' (TM). These use air blown through a slot in the cylinder and take advantage of the Coanda effect.

Chris, Edinburgh UK

[Karl B²]

Originally posted by vintage1
Lord knows how you would do roll axis control - I'd probably give it 'dihedral' and use the rudder :) Or maybe use elevon mixing on teh elevator.
How about differential rotor speed?
;)

[vintage1]

well thoise rotors will be spinning fast. I'd say it would take a LONG time to bank and even LONGER to pull it straight.

No thanks!

[Karl B²]

Not to mention torque considerations. A spoileron above each cylinder might work, though it would be flying at all times, adding more drag.

Curiosity factor high, practicality low, though who knows what unexpected side benefits might come to light in pushing this forward?

Karl

[AuHunter]

Take a look at the recent issue of Flying Models there is a small rotating wing control liner plan in it. Ive been eyeballing it to try a small RC version.

[Biggles604]

From what I have read, a rotating wing might make a novel addition to a fixed wing in place of standard flaps.
Given the aspect of a rotating wing (1:1) the drag would be hideous!
Steve

[Neil Stainton]

Originally posted by matrix0f8h
Vortex Strength = G = 2(pi)w(r^2)
-where:
-w is the angular velocity of the cylinder: @5000 rpm with a r=0.15m: 78.57 m/s
-r is the radius: 0.15m

So:

G=2(22/7)(78.57 m/s)(0.15 m)^2 = 11.11 m^3/s


Some thoughts:

1. w = angular velocity usually = radians/sec = 2 pi revs/sec. Dimension is 1/T (inverse time)

2. In http://www.grc.nasa.gov/WWW/K-12/airplane/cyl.html

NASA says that
G=2 * pi * length *velocity at surface of cylinder
They give the units as Sq ft/sec (dimension = L^2/T). In your calc you gave the dimension as L^3/T.

Also from NACA
velocity at surface of cylinder = 2 * pi * radius * spin (revs/sec)

So I think:
G = 4 * pi^2 * length * radius * spin
which has a dimention of L^2/T

It is a very interesting project. I have thought of making a model like this. Hope this helps and you are successful.

Neil.

[lymon]

... squirrel-ly...