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Merged DDWFTTW in a “Real” Wind
- Thread starter ynot
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None. But are authorities in their own right.
NALSA is neither. Averaging the windspeed is a technical howler, and shows that they do not even have the experience in that field, let alone expertise.
The Met One weather stations are not designed nor calibrated for use in motion. AFAIK, there is no NIST standard for that use.
All prior NALSA records use GPS to determine land speed, and nothing else is employed save for a fixed anemometer to record the general windspeed.
There are countless windsurfing clubs that measure speed using GPS, and have developed software to analyse the data. All data is publicly submitted, and use standardized protocols and data processing. Like this one:
http://www.gps-speedsurfing.com/default.aspx?mnu=forum&forum=6&val=16889&StartRow=10
NALSA, have much less authority, less experience, fewer publications, technical references and discussion of them, than that group alone.
EHocking
Penultimate Amazing
Cite?
Which peer-reviewed journal states this?
B.L. Blackford, American Journal of Physics, Vol 46, No 10, Oct 1978
And my remarks about Drela's "paper" are correct. Challenge them if you want.
Same for Bauer BTW. Different again. All chalk and cheese.
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This paper doesn't say that ddwfttw is not possible in general. It merely considers certain cases of gearing (see A & E in my table) that obviously cannot achieve it.
It says it is not possible, by dint of calculation.
I Ratant
Penultimate Amazing
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I can't comprehend the satisfaction of blanket dismissal instead of explaining any errors.
The prop diagrams are confused, or confusing, because the rotor is operating as both a turbine and a prop. It does not matter how one chooses to argue about which is which or what way.
Propellers accelerate the air using force and energy applied at the prop from an engine. To save the Carteers arguing about what an "engine" is, I will refer them to Drela's man-powered plane.
The engine's power accelerates the air, the reaction to that is the motion of the prop, and called thrust.
Turbines decelerate the air against the blades surface, and the reaction to that is torque at the shaft. That is used to generate power.
The difference is not merely one of profile or direction, but totally different functions. Wind farms do not generate thrust, but the contrary. The air is slower at the exhaust than at the input. Therefore a freewheeling rotor, cannot generate thrust, because it is a turbine. Your "propeller" anemometer is a turbine.
As for the BB, it is a conflicting disaster.
Via the rotor, the force from the wheel accelerates the air (prop), while the tailwind is decelerated against the rotor (turbine). The opposing forces due to the acceleration and deceleration of the air, occur there, at the prop, and not at the "gears"
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Seriously? You showed up and basically insulted everyone for even discussing this, and when some of us tried explaining the mechanism involved, you were completely and utterly dismissive. Now you complain that people are doing it to you?
The start up situation is determined by the direction of the net torque on the prop shaft, which is in turn determined by the combination of wheel size, gearing, and prop pitch. AT's diagram shows how prop pitch alone effects the start up situation, while keeping gearing and wheel size constant. Choose a different gearing, and the pitches would have to change accordingly.
No it doesn't. Blackford's calculations are based on arbitrary assumptions like:
air-rotor turns water-rotor
So he only shows that DDWFTTW is impossible with this configuration. He says nothing about the case:
water-rotor turns air-rotor
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Worse. Transpose the relative values of media density (p)
The opposing forces occur at the prop, where the work is actually done. The gears are not involved in that, because they are only a transmission.
This diagram is less ambiguous than the other ( the two orientations of the other diagram are not directly comparable, leading to ambiguity about the direction of thrust, so room for Carteers to bicker). I am sure all you cart-following "imagineers" can readily mentally spin this image to be in accord with the BB.
This diagram is less ambiguous than the other ( the two orientations of the other diagram are not directly comparable, leading to ambiguity about the direction of thrust, so room for Carteers to bicker). I am sure all you cart-following "imagineers" can readily mentally spin this image to be in accord with the BB.
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Blackford doesn't show this. So, there is NO peer reviewed paper, which shows that DDWFTTW is impossible.
CORed
Penultimate Amazing
Clearly, humber is still pretty confused. The only time the rotor of a ddfttw cart acts as a turbine in any sense is at startup. However, because of relationship of pitch, gearing and wheel size, the drag from the tailwind overcomes the torque the tailwind generates on the rotor. Once the cart is in motion, the rotor is a propeller, pure and simple and generates thrust that accelerates the cart. This is why the cart is a real slug "off the line" and starts a lot better if given a push. However, far from being a disaster, it is what allows the cart to continue accelerating beyond wind speed.
Of course, in humber logic, a successful downwind cart is a failed upwind cart.
What, not in crayon? The math says so.
I Ratant
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Good.
Now do a diagram.
Use the BB configuration.
Wind directions, vehicle speeds, -prop angle-, it can't hurt.
And I can't comprehend your blanket dismissal of my suggestion to read the diagram legend.
Just look at the left-side airfoil from the right-side to see exactly the same what my diagram shows.
Of course the diagram applies to both blades, because (as the legend explains) the vertical diagram axis represents the tangential direction, not the vertical to the ground direction. But in the perspective mentioned above they coincide.
Not Blackford's math. So, there is NO peer reviewed paper, which shows that DDWFTTW is impossible.
I Ratant
Penultimate Amazing
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I Ratant
Penultimate Amazing
- Joined
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A proper diagram should be clear and simple.
Your propeller shows the blade on the other side of a cart.
Why?
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