Thanks Krass
I have played that video several times but still I am confused.
Faster than the wind into the wind!
(130 posts) (12 voices)-
fireflies
MemberKrass said:
For example:
http://orbit.dtu.dk/fedora/objects/orbit:55484/datastreams/file_3748519/contentThat's a great reference Krass
Posted Sunday 2 Dec 2012 @ 12:33:13 pm from IP # -
Jeffbloggs
MemberHey Krass
Welcome to the forum. You sure know how to enter with style
Thanks for all the links, good stuff. You'll probably get further proving it to this bunch with a load of references rather than some "home made" explanations...
But that's just the cognitive culture that reigns here. lolOn your static friction comment: I don't doubt for a moment that it is possible to accelerate from a stand still (my propeller experiment shows that) but I don't think it will work with the DDW gearing as shown in the videos to overcome the inertia of the vehicle and the turbine. For me it doesn't detract from the functionality of the device, for others it might.
Good info so far keep it up!
-
S2S buddy
Do you think that it can go faster into the wind than the speed of the wind?
And: Do you think at least that it is possible that it can accelerate up to (nearly) the speed of the wind into the wind, like a sail boat?As I tried to explain in my previous post, and even with my previous energy balance analogy addressed to you, it is important to do you assumptions based on the right perspectives. In this case consider the 3 different reference points I mentioned, and how they differ from the simplified assumption of apparent wind and the "sailing" aspect of the vehicle. Balance the different points and it will make it easier to see. It did for me at least.
Posted Sunday 2 Dec 2012 @ 12:51:00 pm from IP # -
fireflies
MemberFrom Krass' reference
http://en.wikipedia.org/wiki/Sailing_faster_than_the_wind#Sailing_dead_downwind_faster_than_the_wind"To put it in a sentence: the cart accelerates direct down-wind to near wind speed with its rotor acting as a wind-driven turbine driving the wheels, and then further accelerates to 2.8 times wind-speed with its road-driven wheels driving the same rotor acting as a propeller."
Which is different to what I initially thought was being described. Hence the propeller acts as power source for the wheels at lower speeds and means of propulsion at higher speeds.
Curiouser and curiouser...
Posted Sunday 2 Dec 2012 @ 12:59:32 pm from IP # -
Jeffbloggs
MemberFireflies
Funny I said that in the beginning...
The wheels propel the vehicle over the speed of the wind BUT from the energy captured by rotor from the speed of the wind over the ground. It's all angles, fulcrums and levers!Posted Sunday 2 Dec 2012 @ 1:21:56 pm from IP # -
Krass
Memberfireflies said:
From Krass' reference
http://en.wikipedia.org/wiki/Sailing_faster_than_the_wind#Sailing_dead_downwind_faster_than_the_wind"To put it in a sentence: the cart accelerates direct down-wind to near wind speed with its rotor acting as a wind-driven turbine driving the wheels, and then further accelerates to 2.8 times wind-speed with its road-driven wheels driving the same rotor acting as a propeller."
It is possible to use the rotor as a turbine below windspeed, to improve intial acceleration. But this is not what the Blackbird does in the downwind runs. Look at the blades in the beginning of the run, they turn opposite to how a turbine would turn. The rotor is always a propeller turned by the wheels here.
Posted Sunday 2 Dec 2012 @ 1:25:21 pm from IP # -
Jeffbloggs
Member -
Krass
MemberJeffbloggs said:
Note that curiously the wheels drive the turbine not the other way around!This is correct for the downwind case, but "turbine" is the wrong word here. If it is turned by the shaft against the aerodynamic torque, then it is a "propeller". Or you call it "rotor" which is general and applies to both cases.
Posted Sunday 2 Dec 2012 @ 2:13:12 pm from IP # -
Jeffbloggs
MemberKrass
I concede turbine is the wrong word. Propeller or rotor would have been better. The sentence doesn't really change it's meaning though.Posted Sunday 2 Dec 2012 @ 2:23:04 pm from IP # -
Krass
Membersun2steam said:
I do not doubt that a vehicle with a propeller can go against the wind.
...
What I do not understand and what seems highly unlikely to me is moving with the wind at the speed faster than the wind...Mechanically the two cases are symmetric. Just the roles of air and surface are swapped. See these analogies that show both cases:
sun2steam said:
Where should the energy come from?From reducing the velocity difference between air and surface. In both cases.
Posted Sunday 2 Dec 2012 @ 2:25:24 pm from IP # -
Krass
MemberJeffbloggs said:
I don't doubt for a moment that it is possible to accelerate from a stand still (my propeller experiment shows that) but I don't think it will work with the DDW gearing as shown in the videos to overcome the inertia of the vehicle and the turbine.The downwind self-start is shown in several videos. The upwind self-start works as well according to the builders:
This was a low-speed test to simply determine whether the cart would self-start and go upwind at all. It worked well in the light and flukey winds.
From: http://fasterthanthewind.wordpress.com/2012/05/15/first-upwind-test/
Posted Sunday 2 Dec 2012 @ 2:36:28 pm from IP # -
Jeffbloggs
MemberKrass
Without wanting to be pedantic, what I said was only in direct relationship to the upwind videos. I haven't seen a video of the DDW starting upwind yet. Do you know of one? If it would have different ratios to select from there wouldn't be a problem for sure, but with such a high gearing it just "looks" to be difficult. I don't know if the pitch range is sufficient, but I could be wrong.Jeffbloggs said:
As Russell pointed out in the upwind video the actual start is not shown. I think they gave it a nudge to get the turbine spinning/vehicle moving as both are fixed together through the gearbox. I don't think it will work without a nudge.BTW are you affiliated with any of this? If you don't mind me asking what is your background? Always interested in getting to know a co-contributor!
Regards
JBPosted Sunday 2 Dec 2012 @ 3:20:26 pm from IP # -
Krass
MemberJeffbloggs said:
I haven't seen a video of the DDW starting upwind yet.At 7:40 in this video:
http://www.metacafe.com/watch/8679238/blackbird_going_directly_upwind_faster_than_the_wind/Jeffbloggs said:
BTW are you affiliated with any of this?No, just find it interesting.
Posted Sunday 2 Dec 2012 @ 3:42:44 pm from IP # -
Jeffbloggs
MemberKrass Awesome! Thanks for that, looks good! I'm sometimes to lazy to look at other sites apart from youtube. I agree that it's interesting. Always good to broaden those horizons!
Posted Sunday 2 Dec 2012 @ 3:58:03 pm from IP # -
JB,
Your experiment with the propellor gave me a few thoughts as did the video below posted by Krass. It is clear that 'something' is going on and I have now watched other videos of other craft. I like your explanation but there seems (to me anyway) to be other forces also at work.
Sometimes it is easy to overlook the obvious. It is easy to make objects move towards the wind and I forgot that we have previously corresponded about this as per HC's 1938 patent I Emailed...you simply direct a stream of air over a curved surface and the object will move forwards and even upwards if the air stream is directed from above.
I think that the vehicle in the video below has blades that are recognised as a curved surface to air flow and vorticity does the rest. This is different to the Blackbird. Yes? No?
Krass said:
The wind vane on the chase vehicle has been a distraction as it indicates that the vehicle is travelling directly into the wind but this is only because the vane is reacting to the vehicle's speed but wind direction constantly varies; to have a vane hold steady would mean no air movement.
The Blackbird also has an aerodynamic foil in addition to the turbine/propellor. Unfortunately, there are no close up images and so it is impossible to see if there are any control flow enhancements. For example, it is easy to generate micro vortices at a foil's leading edge and direct them across the boundary layer to enhance lift. The practice of generating boundary layer vortices by using serrated leading edges has been common use in F1 for a number of years and every performance enhancement would surely be looked at by the Blackbird's builders. Micro leading edge vortices directed across the blade’s boundary layers would allow the greater angle of attack.
Vorticity is everywhere and its presence cannot be discounted as a force to help push the craft into the wind. There has to be an interaction between the turbine/prop and the foil and as already noted, the wind that the vehicle is heading into will not be constantly directly ahead. The turbine/prop will also be causing other air/wind to be drawn in from the sides and above and so this will also be reacting with the foil, the same as with a sail boat side on to the wind. A small Cesna for example creates a downwash of 5 tons of air every second and while this vehicle won't come near that rate, the forces will be present and the data would be interesting to read.
(I think!)
Posted Sunday 2 Dec 2012 @ 4:37:38 pm from IP # -
Jeffbloggs
MemberDiver
There are two different mechanisms in play for upwind/downwind. In the upwind one the rotor acts as a turbine and drives the wheels like with my screw experiment. Only in the downwind scenario do the wheels drive the rotor as a propeller. In both cases the power is from the relative wind speed to the anchor or "true wind speed"(ref point 1 in my experiment) I agree that the wind vane interferes a little with the logic, that's why I tried to split it in three ref. points to explain it. Check out the little three wheel model videos on the table that Krass posted, they help visualise the mechanics involved.However on the subject of vortices etc, I wouldn't be surprised if there is some interactions, the video you posted does have quite a different design (ie it's foil-less for starters and the source of wind is unknown) and as per our previous discussions with the X-Zylo, there are still unexplained phenomena when it comes to the dynamics involved. TonyT's insert about the electrostatic potential between the earth and the outer atmosphere actually plays a role there. Just don't tell S2S otherwise he won't sleep at night!
Na just kidding! All good S2S buddy. How small the vortices are is what we are talking about here. Back to some "field theory" for us then!
Posted Sunday 2 Dec 2012 @ 5:12:52 pm from IP # -
It's doing my head in! I can understand the fulcrum concept now but while it is something that really interests me, I am unfamiliar with this field. Fascinating stuff!
The vid is one that Krass posted earlier.
I always mentally convert air flow back to water to visualise the action/reaction but it hasn't worked in this instance.
Posted Sunday 2 Dec 2012 @ 5:49:49 pm from IP # -
Jeffbloggs
MemberDiver sleep over it... bed is where I'm heading now! Us "knight owls" won't get a medal from our wives in the morning otherwise! G'night!
Posted Sunday 2 Dec 2012 @ 6:06:42 pm from IP # -
Krass
MemberDiver said:
I think that the vehicle in the video below has blades that are recognised as a curved surface to air flow and vorticity does the rest. This is different to the Blackbird. Yes? No?The small UTS model in the wind tunnel is exactly the same as the Turbine-Blackbird used to go directly upwind. There are also small models of the Propeller-Blackbird that goes directly downwind faster than wind.
Diver said:
The Blackbird also has an aerodynamic foil in addition to the turbine/propellor.You mean the vertical pylons? They have fairings to reduce drag, but are irrelevant for propulsion. The prototype had just very non-aerodynamic boards, and it still worked great.
Diver said:
...vortices...Way to complicated thinking. Forget the complex fluid dynamics stuff for a moment. Try to understand the basic mechanical principle of gearing:
Posted Sunday 2 Dec 2012 @ 6:53:41 pm from IP # -
Thanks JB & Krass,
I had thought that the Blackbird's 'pylon' was a foil (several references in my earlier posts) and that this gave it its initial forward momentum; the first vid I watched was downwind. When it started off up wind, this then had to come back to the variant nature of wind direction and interaction with the high AoA blades interacting with the "foil" even though I couldn't work out how the air flow required by the "foil" was generated and directed. That's where vorticity came in! You would have no idea how intently I have been looking at the blade's profile, AoA and the "foil" etc.
I was absolutely sure that the small model's forward momentum was due in part at least to Coanda Effect and vorticity given that it didn't have a "foil" like Blackbird, meaning that it was a variant and as such dependent on a different influence that would still apply in part to the Blackbird.
Explaining prototype results with maths has always been my weakness and having it in front of me was no better. If I can get the time next year, I will probably make a 1:20 model; probably a water craft but I already see problems with the centre of gravity in that concept.
JB,
re your blower test, did you know that you can hold the blower (I think) at 45 degrees and keep a table tennis ball elevated? I know that it works with a hair dryer anyway.EDIT: If I do a water craft, it will have to be SWATH.
Posted Sunday 2 Dec 2012 @ 10:43:24 pm from IP # -
fireflies
MemberJB my mistake I thought you were talking the downwind example when you said the rotor acts a turbine. Anyway, I think Krass has covered that territory already - he's hit the ground running eh? Anyhoo, must get to work. Enough fun so far.
Posted Sunday 2 Dec 2012 @ 11:22:26 pm from IP # -
TonyT
MemberAt
http://www.ata.org.au/forums/topic/5720/page/3#post-34723Diver said:
" ... did you know that you can hold the blower (I think) at 45 degrees and keep a table tennis ball elevated? I know that it works with a hair dryer anyway."
When I still had hair, if I dried it using an electric hair-dryer I could feel the effect of the electrostatic charge that repelled the individual negatively-charged hairs.
Air-flow over any object imparts a large negative charge to that object.
An electric charge that is stationary or that moves within an electric field experiences a force.
The typical size of the electric field in the atmosphere is large at about 100 volts per vertical metre:
the electric potential at my nose is plus 200 volts compared with my toes.Q1. How many coulombs of negative charge would be imparted to the rotor as it spins at (? revs per minute) in the air ?
Q2. In the direction of the axis of the rotor, what is the size of the electrostatic-induced-force that is experienced by the spinning rotor ?
I think that this force is significant in size.
Posted Monday 3 Dec 2012 @ 12:58:50 am from IP # -
fireflies
MemberTonyT - There are of course so many forces acting on the rotor and component materials in the examples shown above, magnetic fields, Van der Waals forces, cosmic rays, gravity, wind resistance. The scale of the forces required to cause the forward motion however can be explained with aerodynamics.
As with JBs short experiment with the rotor on a spindle - air moving over a curved surface imparts lift, and what was suprising to me was that lift/ and rotational moment exceeds the retropulsive force on the object.
To me the clue to why there is any debate at all here, and elsewhere, as to whether a 'faster than wind directly down wind' or 'directly into the wind' vehicle is possible, is that we are forgetting that the lifting forces created at the edge of the curved rotar are due to tangential movement of the rotor through the air (EDIT: not actually 'directly downwind' after all) - hence the lift - just as it would be with any sailing craft with a sail moving across the wind.
Posted Monday 3 Dec 2012 @ 2:09:54 am from IP # -
TonyT
Memberff
Yes there are many forces and most of them are very small and can be neglected.
An hypothesis of Pollack's is that the huge weight of water ("elephants") in the clouds is held in the sky by the electrostatic repulsion between the negatively-charged cloud and the negatively-charged earth plus the electrostatic attraction between the negative cloud and the positively-charged ionosphere.
The size of the earth's electrostatic field is significant and Pollack suggests that it may provide the energy for a small bird to fly half way around the earth without landing and eating / re-fueling.
It may explain how an aeroplane can fly upside-down and why the wing of a B2 bomber carries a significant negative electrostatic charge.
Earth's electrostatic field may also apply a significant force to a sailing boat or to this device.
I am frustrated that my rusty memory will not re-call the correct equations (coulombs, electric fields, Maxwell ???? ) with which to calculate (1) the size of the electric charge or (2) the size of the electrostatic force.
I agree that the principles that are operating with this rotor-driven device are the same principles that apply to a sail-powered device / boat.
Posted Monday 3 Dec 2012 @ 2:34:02 am from IP # -
fireflies
MemberTonyT
It's not my field so I couldnt comment in any informed way but I think there may be some basis for his theory of "clouds ... held in the sky by the electrostatic repulsion between the negatively-charged cloud and the negatively-charged earth plus the electrostatic attraction between the negative cloud and the positively-charged ionosphere."WRT
"a small bird (ability) to fly half way around the earth without landing and eating / re-fueling."
is probably better understood by rising columns of air/thermals providing some updraft as well as prevailing wind patterns assisting their flight direction.The aileron and elevator are what allows upside down flight, planes certainly arent as efficient or aerodynamic in upside down flight. The B52 electrostatic charge would have similarities to your described head full of hair/hairdryer scenario.
These are different mechanisms for different situations. A Unified Theory of Airborne Objects will not come from a Pollackian line of thought I'm afraid.
Posted Monday 3 Dec 2012 @ 4:44:36 am from IP # -
Jeffbloggs
MemberS2S
Would you care to respond to my post at the top of this page directed at you in regards to the subject of this thread? I would like to understand exactly which components of this device that you think do not work, are unscientific or go against the laws of physics.-
Fireflies
Good one. You speak the truth. You can't "see" what you don't believe in.-
TonyT/Fireflies
Every interaction of matter in the visible universe is a field interaction.
We are all "swimming" in one field or another (or all). The propagation of such fields and their exact mechanics are yet to be fully understood. Hence the LHC "experiment" etc.Wiki on fields: http://en.wikipedia.org/wiki/Field_(physics)
"In physics, a field is a physical quantity that has a value for each point in spacetime.[1] A field can be classified as a scalar field, a vector field, a spinor field, or a tensor field according to whether the value of the field at each point is a scalar, a vector, a spinor (e.g., a Dirac electron) or, more generally, a tensor, respectively. For example, the Newtonian gravitational field is a vector field: specifying its value at a point in spacetime requires three numbers, the components of the gravitational field vector at that point. Moreover, within each category (scalar, vector, tensor), a field can be either a classical field or a quantum field, depending on whether it is characterized by numbers or quantum operators respectively.
A field may be thought of as extending throughout the whole of space. In practice, the strength of every known field has been found to diminish with distance to the point of being undetectable. For instance, in Newton's theory of gravity, the gravitational field strength is inversely proportional to the square of the distance from the gravitating object. Therefore the Earth's gravitational field quickly becomes undetectable (on cosmic scales).
Defining the field as "numbers in space" shouldn't detract from the idea that it has physical reality. “It occupies space. It contains energy. Its presence eliminates a true vacuum.”[2] The field creates a "condition in space"[3] such that when we put a particle in it, the particle "feels" a force."and
"The fact that the electromagnetic field can possess momentum and energy makes it very real... a particle makes a field, and a field acts on another particle, and the field has such familiar properties as energy content and momentum, just as particles can have."
Read up on Maxwell (especially his original unmodified work), Faraday (avoid Hertz, he goes completely 2D
) and of course good old Tesla (he called it aether which stems from medieval science also known as the fifth element). It's sometimes humbling to see what history can teach us and how the "religions" of the day only gestated what was stabilising in order to control, rather than "de-culturalising" and progressive development. No wonder it took us so long to learn how to fly, even though birds have been doing it for eons. But to get back on subject a little more: The effects of flying an aircraft upside down is not only dependant on it's control surfaces for changes in angle of attack. The airfoil profile is typically "flatter" on the bottom and curved on top as well, this camber is said to be responsible for lift. Airfoils, especially complex ones, are typically tested and not calculated. Current fluid dynamic calculations are quite "2D" in that complex vortices are best left to experimentation in wind tunnel testing. Most aircraft fly on a collection of about 40 or so airfoils "tested" in WW2. By testing them we can be confident in the safety of sitting in the latest A380 at 30,000feet, luckily for us calculations were only secondary to their development.
Also the COG changes considerably with inverted flight. 
Much discussion has already been done here on this forum on the mechanics involved in the flying of a X-Zylo, which is essentially just a piece of spinning round foil. If one considers that the opposites of the airfoil camber should counteract eachothers lift, and that the aerodynamic performance is "nearly" unreal for a hand thrown device, one has to wonder how exactly the X-Zylo achieves this feat. (It too suffers the same fate of being conveniently ignored)
That reminds me of a joke:
One Atlantic sunset, two old ladies are flying to England in a 747 when all of a sudden there is a loud bang. Shortly after the pilot announces "Ladies and Gentleman we have just experienced an engine failure, there's nothing to worry about, but our landing will be delayed by half an hour". The two ladies look at eachother, mutter "typical BA" under their breath and carry on knitting.Shortly after there is another bang. Once again the pilot announces "Ladies and Gentleman we have just experienced another engine failure, there's nothing to worry about, but our landing will be delayed by at least an hour and a half because we have to reduce our cruising altitude". The two ladies exchange looks and the one with the feathered cap says, "Well dear, we have a three hour layover before our bus trip home, so we'll still make it on time". They both nod, order a cup of tea from the stewardess and carry on knitting.
A half an hour later there's a third bang and once again the pilot announces, "Ladies and Gentleman we have just experienced another engine failure, currently there's nothing to worry about and we will still continue our flight to England, but our landing will be delayed by at least another two hours or more. I will keep you regularly updated on our progress".
The two old ladies look at each other with deep burrows of concern forming on their weathered foreheads. The lady in the cap says, "Jeez, I hope the other one doesn't fail otherwise we will be up here all night!!".
Sadly this story is very typical of cultural cognition of every period of humanity, including ours today. The "passengers" of this planet are all so concerned with achieving their own goals and reaching their own destinations, that they neglect the reality of what is keeping them suspended in thin air. Their unwavering faith in those "in control" places them in sweet ignorant bliss, and whilst they sip tea oblivious to their predicament, the flight engineers "in control" of the cockpit of progress are franticly trying to keep the craft afloat. Who is that person that wishes to remind them of the truth and by doing so wreak havoc and despair in the passenger compartment we call life?
Benjamin Franklin said:
“Those who surrender freedom for security will not have, nor do they deserve, either one.”
and:
“If everyone is thinking alike, then no one is thinking.”Posted Monday 3 Dec 2012 @ 7:33:54 am from IP #
