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Mess with your minds: A wind powered craft going faster than a tail wind speed.

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Labrat101:
@ electrodacus

Your Forum is also full of stupid answers .. Now you have plagued us with your stupidity of Not seeing what is true life Working .
 If it works don't brake it . Your Maths is no better than a 1st grader . Just picking up numbers @ random will never solve this .
 Nor will you ever learn . and worst still your not willing to learn .
As hard as it is for you to except you are making a terrible mistake .
      Maybe it would have been a wise questions to ask what are our Degree's   :popcorn:

electrodacus:

--- Quote from: lordium on December 29, 2021, 08:53:18 am ---Is it possible to get an summary from start to finish about why it is impossible?
Examples and illustrations along to way would be helpful so that I can follow all the steps.
I'm really struggling to follow the thought process here. Guess I'm not smart enough. So please put it as plainly as possible.

--- End quote ---

I have made a video but is maybe a bit long and boring

In any case I will try to make a summary.
The easiest part will be to show that directly down wind faster than wind is not possible without some sort of energy storage device or an external energy source.
That can be proved with the correct equation for wind power available to any wind powered vehicle

Pw = 0.5 * air density * area * (wind speed - vehicle speed)3

It is irrelevant how vehicle is build as long as wind power is the only source then the above is the correct formula for an ideal system (so absolutely best case scenario).
The air density can be considered a constant so not very relevant and then there are just two other therms the area of the vehicle that in the particular case of blackbird will increase with speed up to a max of swept area of the propeller but while that increase in area helps make more power available to vehicle it will only be valid as long as vehicle speed is smaller than wind speed since as it can be seen in the equation if vehicle speed equals wind speed the wind power will be zero.

This formula is all that is needed in order to demonstrate that any wind powered only vehicle will need an energy storage device in order to exceed wind speed directly down wind.
It seems that many people do not work with power and prefer to work with force and speed separately and this is how a wrong equation ended everywhere.
The equation for force is correct
Fw = 0.5 * air density * area * (wind speed - vehicle speed)2

But then when they want to calculate wind power they just multiply by vehicle speed and leave the wind speed out of the equation.  The most likely reason they do that is because someone made this mistake first and they just copy paste the same wrong equation everywhere without thinking to much or testing to see if it is true.

They just think that if vehicle speed is zero the wind power available to that vehicle is zero and they think that since they imagine zero speed as a vehicle with brakes engaged.  That seems as a super silly mistake to make is like saying that a sail boat has zero wind power available when boat speed is zero because the boat is anchored to the ground.

Let me know if you agree with the above and then I can continue with how the Blackbird can actually exceed wind speed for a limited amount of time using energy storage in pressure differential created by the propeller with part of the wind power.

fourfathom:

--- Quote from: electrodacus on December 29, 2021, 06:31:48 pm ---That can be proved with the correct equation for wind power available to any wind powered vehicle

Pw = 0.5 * air density * area * (wind speed - vehicle speed)3

It is irrelevant how vehicle is build as long as wind power is the only source then the above is the correct formula for an ideal system (so absolutely best case scenario).
--- End quote ---

So do the wheels in contact with the ground make no difference?  Your equation might be appropriate for a hot-air balloon.

electrodacus:

--- Quote from: fourfathom on December 29, 2021, 06:53:15 pm ---
--- Quote from: electrodacus on December 29, 2021, 06:31:48 pm ---That can be proved with the correct equation for wind power available to any wind powered vehicle

Pw = 0.5 * air density * area * (wind speed - vehicle speed)3

It is irrelevant how vehicle is build as long as wind power is the only source then the above is the correct formula for an ideal system (so absolutely best case scenario).
--- End quote ---

So do the wheels in contact with the ground make no difference?  Your equation might be appropriate for a hot-air balloon.

--- End quote ---

They are ideal wheels so yes they make no difference as there is no friction thus best case scenario.
If you use real wheels with friction then vehicle acceleration rate will be lower and max speed for a direct down wind vehicle will be lower than wind speed.

Kleinstein:

--- Quote from: electrodacus on December 29, 2021, 06:31:48 pm ---
The easiest part will be to show that directly down wind faster than wind is not possible without some sort of energy storage device or an external energy source.

Let me know if you agree with the above and then I can continue with how the Blackbird can actually exceed wind speed for a limited amount of time using energy storage in pressure differential created by the propeller with part of the wind power.

--- End quote ---
The calculation this way is absolutely not easy, as there is no accepted formula for the maximum power available to a vehicle. So the difficulty is  in deriving (not just propose a solution and claim it must but ture as an act of god). As there are multiple possible ways to harness the wind power this is a really difficult task. To make it a proof it needs a really good explaination that most people would agree with.

Just presenting an expression that most people think is wrong is far from supporting the claim. It is more like showing poor understanding of logic and science in general.

The V_w * F_w form was never claimed to be the available wind power, but the power needed by the vehicle. Just like for another force to push against the power is force times speed (by definition and not by mistake). Thinking the power would stay constant, essentially independent of the speed is just a rediculous idea, that causes obvious contradictions.  One such contraticion would be that the power when going in the same direction as the wind would be the same as the maximum avialable power and thus all wind genrator would be 100% efficient. I don't think that sounds plausible.

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