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

--- Quote from: electrodacus on December 26, 2021, 06:52:41 pm ---It will behave the same way if you push the cart with your hand.  If cart needs to be powered by the two treadmill then it will not behave anywhere close to this it will just move backwards.
--- End quote ---
If you say the cart will behave differently than the diagram when powered by the treadmill, then you need to explain what part of the geometric model will behave differently in the physical model. What will be different in the real world?


--- Quote ---There is a lot of confusion as you seen those toy cars that move against the paper moving direction but that will also not work that way without energy storage and stick slip
--- End quote ---
It's a geometric diagram. Where is the energy storage and stick slip in a drawing on the screen? It cannot have any of those things.
electrodacus:

--- Quote from: IanB on December 26, 2021, 06:55:18 pm ---
This is true for a simple sail-driven vehicle, but is not necessarily true for a vehicle with a more complex mechanism like a propeller.

--- End quote ---

The reason propeller makes any diffrence has to do with air being compressible and the ability of the propeller to create a pressure differential when used in air.


--- Quote from: IanB on December 26, 2021, 06:55:18 pm ---Relative to the vehicle, but not necessarily relative to the pitch angle of the propeller.

--- End quote ---

The propeller pitch angle is the same as the gear ratio on a gearbox. That means output power will be lower than input power same as with any gear box thus it offers no advantage.



--- Quote from: IanB on December 26, 2021, 06:55:18 pm ---This is an assertion without proof. Nor is it something you can prove, since once you use words like "there is no way", you are required to prove that no possibility exists out of all the infinite ways it might be done. You cannot feasibly analyze an infinity of designs and eliminate all of them.

--- End quote ---

It is already proven look at the data. Use my exhumations and get the exact results as seen in all tests done use yours and get some crazy results that where never observed in practice.
And yes I can say "there is no way" because I can understand conservation of energy.
gnuarm:

--- Quote from: electrodacus on December 26, 2021, 05:51:20 pm ---
--- Quote from: Domagoj T on December 26, 2021, 08:29:28 am ---
The energy which is extracted from slowing down the wind.

--- End quote ---

Yes that is a perfectly fine explanation for when vehicle is below wind speed. But how you do that when you are above wind speed and apparent wind speed changes direction?
--- End quote ---

In the blackbird type craft the propeller blows the car forward in the same direction as the wind.  In that case the propeller blows against the wind slowing it.  Even when the car is traveling down wind faster than the wind, the exhaust from the prop leaves the prop faster than the wind recedes and so is slower (relative to the ground) than the wind. 

The gearing between the prop and the wheels provides the power to turn the prop.  The wind is pushing against the prop wash and the combination of forces between the prop and the wheels provides the energy, i.e. the power to make this work.  The fact that the wheels move with the full velocity of the vehicle while the wind speed is a part and the prop wash is the other part means the wheels get power from the force of the wind and the prop, but only have to power the prop.  Net power input is from the wind. 
electrodacus:

--- Quote from: gnuarm on December 26, 2021, 07:20:26 pm ---
--- Quote from: electrodacus on December 26, 2021, 05:51:20 pm ---
--- Quote from: Domagoj T on December 26, 2021, 08:29:28 am ---
The energy which is extracted from slowing down the wind.

--- End quote ---

Yes that is a perfectly fine explanation for when vehicle is below wind speed. But how you do that when you are above wind speed and apparent wind speed changes direction?
--- End quote ---

In the blackbird type craft the propeller blows the car forward in the same direction as the wind.  In that case the propeller blows against the wind slowing it.  Even when the car is traveling down wind faster than the wind, the exhaust from the prop leaves the prop faster than the wind recedes and so is slower (relative to the ground) than the wind. 

The gearing between the prop and the wheels provides the power to turn the prop.  The wind is pushing against the prop wash and the combination of forces between the prop and the wheels provides the energy, i.e. the power to make this work.  The fact that the wheels move with the full velocity of the vehicle while the wind speed is a part and the prop wash is the other part means the wheels get power from the force of the wind and the prop, but only have to power the prop.  Net power input is from the wind.

--- End quote ---

Just noticed your signature so I will assume you may be owning an EV.
Imagine your EV has an empty battery (completely empty) and you have a strong wind from the back of the vehicle and you are on a perfectly flat road.
Now the wind will push your vehicle and your vehicle max speed while pushed by the wind can not exceed wind speed. (I hope you will agree with that).
But now you can use your regenerative brake to start charging battery while your vehicle wind speed will be way lower than wind speed since now there is a lot of resistance as you take wind energy and store it in to the battery and at some point you decide you got enough maybe 1% SOC and even with that you can exceed wind speed for a few minutes.
That is exactly how blackbird works other than propulsion is delivered by a propeller fan (instead of the more efficient wheel) and the energy is not stored in a lithium battery but in the air as pressure differential so as you charge you also start using some of the energy.

And to make it even more clear say your Tesla has a flat rear end with a total surface area of 2m^2 (not aerodynamic at all so CoD of 1).
We will also make the assumption that vehicle drive train is perfectly efficient no friction or even rolling resistance.
Also let say wind speed is a constant 25m/s = 90km/h = 55.9mph

Then direct down wind Tesla will have this amount of wind power available  0.5 * 1.2kg/m^3 * 2m^2 * (25m/s-vehicle speed)^3
If vehicle speed is zero (friction brakes ON then there is of course no wind power available to charge the battery).
Then as soon as you remove the friction brakes wind power will be available.

Say vehicle barely moves at 2m/s then if you want to maintain this low speed all you need to do is charge the battery at this rate
0.5 * 1.2 * 2 * (25-2)^3 = 14.6kW  (it may be just half of this in a real vehicle as there is a wind gradient due to interaction with road and vehicle has quite a bit of friction loss).

If you where to drive at 10m/s while you where charging then less wind power will be available  0.5* 1.2 * 2 * (25-10)^3 = 4.05kW

And at 20m/s vehicle speed it is only 0.5* 1.2 *2 * (25-20)^3 = 150W

You can see where this is going.
There is no wind power available to a direct down wind vehicle even if it is ideal case no friction loss and if there is no energy storage device then it is not possible to exceed wind speed.
gnuarm:

--- Quote from: electrodacus on December 26, 2021, 09:07:30 pm ---
--- Quote from: gnuarm on December 26, 2021, 07:20:26 pm ---
--- Quote from: electrodacus on December 26, 2021, 05:51:20 pm ---
--- Quote from: Domagoj T on December 26, 2021, 08:29:28 am ---
The energy which is extracted from slowing down the wind.

--- End quote ---

Yes that is a perfectly fine explanation for when vehicle is below wind speed. But how you do that when you are above wind speed and apparent wind speed changes direction?
--- End quote ---

In the blackbird type craft the propeller blows the car forward in the same direction as the wind.  In that case the propeller blows against the wind slowing it.  Even when the car is traveling down wind faster than the wind, the exhaust from the prop leaves the prop faster than the wind recedes and so is slower (relative to the ground) than the wind. 

The gearing between the prop and the wheels provides the power to turn the prop.  The wind is pushing against the prop wash and the combination of forces between the prop and the wheels provides the energy, i.e. the power to make this work.  The fact that the wheels move with the full velocity of the vehicle while the wind speed is a part and the prop wash is the other part means the wheels get power from the force of the wind and the prop, but only have to power the prop.  Net power input is from the wind.

--- End quote ---

Just noticed your signature so I will assume you may be owning an EV.
Imagine your EV has an empty battery (completely empty) and you have a strong wind from the back of the vehicle and you are on a perfectly flat road.
Now the wind will push your vehicle and your vehicle max speed while pushed by the wind can not exceed wind speed. (I hope you will agree with that).
But now you can use your regenerative brake to start charging battery while your vehicle wind speed will be way lower than wind speed since now there is a lot of resistance as you take wind energy and store it in to the battery and at some point you decide you got enough maybe 1% SOC and even with that you can exceed wind speed for a few minutes.
That is exactly how blackbird works other than propulsion is delivered by a propeller fan (instead of the more efficient wheel) and the energy is not stored in a lithium battery but in the air as pressure differential so as you charge you also start using some of the energy.
--- End quote ---

Except my car has no battery and neither does the blackbird.  Also, the blackbird has both a wheel and a propeller while my car ONLY has a wheel. 



--- Quote ---And to make it even more clear say your Tesla has a flat rear end with a total surface area of 2m^2 (not aerodynamic at all so CoD of 1).
--- End quote ---

Ok, now you are going into pointless details because this is not how the blackbird works.



--- Quote ---We will also make the assumption that vehicle drive train is perfectly efficient no friction or even rolling resistance.
Also let say wind speed is a constant 25m/s = 90km/h = 55.9mph
--- End quote ---

More pointless details...



--- Quote ---Then direct down wind Tesla will have this amount of wind power available  0.5 * 1.2kg/m^3 * 2m^2 * (25m/s-vehicle speed)^3
If vehicle speed is zero (friction brakes ON then there is of course no wind power available to charge the battery).
Then as soon as you remove the friction brakes wind power will be available.

Say vehicle barely moves at 2m/s then if you want to maintain this low speed all you need to do is charge the battery at this rate
0.5 * 1.2 * 2 * (25-2)^3 = 14.6kW  (it may be just half of this in a real vehicle as there is a wind gradient due to interaction with road and vehicle has quite a bit of friction loss).

If you where to drive at 10m/s while you where charging then less wind power will be available  0.5* 1.2 * 2 * (25-10)^3 = 4.05kW

And at 20m/s vehicle speed it is only 0.5* 1.2 *2 * (25-20)^3 = 150W

You can see where this is going.
There is no wind power available to a direct down wind vehicle even if it is ideal case no friction loss and if there is no energy storage device then it is not possible to exceed wind speed.

--- End quote ---

Nothing, literally NOTHING you have talked about here has to do with the blackbird, so just stop the insanity! 

It is clear that you will never understand anything anyone tells you that doesn't agree with your idea because you reject it out of hand without understanding it. 

I keep coming to the conclusion that you can't be taught anything, but I get suckered in when I see a point that is so crystal clear to anyone else that it must be possible to show it to you.  However, as others have pointed out, instead of understanding what they tell you, you simply duck the issue and start talking about something different. 

So no more replying to your nonsense. 
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