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

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gnuarm:

--- Quote from: electrodacus on December 28, 2021, 01:15:51 am ---
--- Quote from: gnuarm on December 28, 2021, 01:07:19 am ---
The first video doesn't seem to show much in the way of speed variation.  The second video shows the gear driving the track slipping from time to time and I'm not sure, but I think the fan is being turned on and off so it doesn't blow so hard.  If it blows too hard the gear slips and the vehicle goes nowhere.

Either way, the storage has nothing to do with nothing.  You just provided two examples of vehicles moving INTO the wind being powered by the wind.  The first one even goes up a 30 or 40 degree ramp!

When are you going to respond to my prior post about the power to hold a vehicle stationary?  You've already said the power was zero if the bike rider simply puts his weight on the pedal into a 20 km/s wind.  So doesn't the rest follow, the equations are as I've shown them?


Quote from: electrodacus on Today at 07:33:23 pm
    A rider with sufficient weight standing on the pedal will still be a form of brake. It is a gravitational based one but still a brake.



Let's just deal with one detail at a time.  So do you acknowledge that the correct equation for the power at the wheels to move the vehicle into the wind must contain a factor which is just the velocity of the vehicle relative to the ground the wheel is pushing against?

The force from the wind is

Fd = 1/2 · Cd · A · p · (vw + vo)^2

The power required at the vehicle wheels to maintain a speed into the wind is

Pv = 1/2 · Cd · A · p · (vw + vo)^2 · vo

Correct?

--- End quote ---

I think is fairly clear to see the stop start movement in both videos while second video is better quality and easier to see. You just try to find some other non existent reasons but the reason it moves that way is due to energy storage charge and discharge.
Like I mentioned even presenting clear evidence you will try to find some other reasons to exclude the energy storage witch is essential.
--- End quote ---

The first video very clearly shows the device moving continuously with no stopping.  However, that is irrelevant.  The device moves into the wind.  Thank you for proving my case.  You are a mensch.  :clap:


--- Quote ---Evacuation for force is correct for power it is not and correct one is below. 
Pv = 1/2 · Cd · A · p · (vw + vo)^2 · (vo+vw)

--- End quote ---

That equation may be correct for something regarding power in the wind, but it's not the power applied to the vehicle to move into the wind.  That is the force exerted by the wheels which must match the force from the wind, 1/2 · Cd · A · p · (vw + vo)^2.  This force is multiplied by the velocity of this applied force which is vo giving 1/2 · Cd · A · p · (vw + vo)^2 · vo for the power to propel the vehicle.

[mic drop]

gnuarm:

--- Quote from: electrodacus on December 28, 2021, 01:24:24 am ---
--- Quote from: gnuarm on December 28, 2021, 01:16:17 am ---
The stopping is irrelevant.  It is moving INTO the wind.  You were trying to argue that when moving downwind it was on average moving slower than the wind because of some speed variation that no one else thought was relevant.  Moving into the wind the only requirement is that the speed must be greater than zero. 

The first video clearly shows the vehicle moving with a positive velocity at all times.  So clearly any energy storage is incidental.  The second video clearly shows the gear slipping on the belt rather than energy storage.  Even so, why does that matter?  Both vehicles move INTO the wind.  Energy storage is not relevant.  They do what we are talking about - moving into the wind while powered by the wind.

If you want to use a river example, how about we use a sailboat on the water sailing into the wind?  This happens all the time... literally!

--- End quote ---

The stopping is relevant as it confirms my energy storage theory.  The video shows a upwind version not sure why you include the downwind in discussion as that is competently different.
For upwind as shown in the video there is a small capacity energy storage that charges and discharges even a few times a second and that is what allows the vehicle to move against the wind direction for unlimited amount of time.
For the down wind version energy storage is the pressure differential much, much larger energy storage capacity and so the vehicle will move above wind speed for a few minutes before staring to slow down below wind speed.
Without energy storage neither upwind at any speed or down wind at higher than wind speed will be possible.

--- End quote ---

Ok, tons of energy storage is happening.  Nuclear bombs of energy is being stored and released.  Doesn't matter all the energy is coming from the wind, so the wind is propelling the vehicle upwind, just like the wind propels the vehicle downwind faster than the wind in that case. 

All your energy storage BS is just that, BS and adds nothing to the discussion. 

[another mic drop]

electrodacus:

--- Quote from: gnuarm on December 28, 2021, 01:29:15 am ---
The stopping is relevant as it confirms my energy storage theory.  The video shows a upwind version not sure why you include the downwind in discussion as that is competently different.
For upwind as shown in the video there is a small capacity energy storage that charges and discharges even a few times a second and that is what allows the vehicle to move against the wind direction for unlimited amount of time.
For the down wind version energy storage is the pressure differential much, much larger energy storage capacity and so the vehicle will move above wind speed for a few minutes before staring to slow down below wind speed.
Without energy storage neither upwind at any speed or down wind at higher than wind speed will be possible.

--- End quote ---

Well it is very relevant as the direct downwind vehicle will not travel indefinitely at 2x or 3x the wind speed but only for a limited amount of time proportional with the amount of stored energy.
Also to store that energy the vehicle will accelerate much slower when below wind speed compared to a sail vehicle that will not store anything other than kinetic energy. So Blackbird direct down wind version spends more time below wind speed to charge the energy storage (pressure differential) then uses that stored energy to accelerate above wind speed and stay a bit above that speed before returning to below wind speed.



--- Quote from: gnuarm on December 28, 2021, 01:29:15 am ---The energy storage explanation will not violate the conservation of energy.

Ok, tons of energy storage is happening.  Nuclear bombs of energy is being stored and released.  Doesn't matter all the energy is coming from the wind, so the wind is propelling the vehicle upwind, just like the wind propels the vehicle downwind faster than the wind in that case. 

All your energy storage BS is just that, BS and adds nothing to the discussion. 

[another mic drop]

--- End quote ---

I hope you keep your microphone on the floor and I'm getting tired to explain the same thing multiple times to someone that will not understand power, energy and conservation of energy.

fourfathom:

--- Quote from: electrodacus on December 28, 2021, 01:37:58 am ---Also to store that energy the vehicle will accelerate much slower when below wind speed compared to a sail vehicle that will not store anything other than kinetic energy.
--- End quote ---

I've asked you this before, but why does a sail not store energy when below windspeed, but a propeller does?

electrodacus:

--- Quote from: fourfathom on December 28, 2021, 01:46:49 am ---
--- Quote from: electrodacus on December 28, 2021, 01:37:58 am ---Also to store that energy the vehicle will accelerate much slower when below wind speed compared to a sail vehicle that will not store anything other than kinetic energy.
--- End quote ---

I've asked you this before, but why does a sail not store energy when below windspeed, but a propeller does?

--- End quote ---

A sail has no mechanism to store energy. It can not increase the pressure differential like a fan can.
So if the brake is applied there is be a presume differential between the front and the back of the sail proportional with the wind speed but as vehicle starts to move this pressure drops to zero by the time vehicle gets to wind speed.
Is sort of similar with a vehicle pushing another and having a spring between them. If the back vehicle starts to push while the front vehicle has the brakes on then spring will compress storing energy but then as the vehicle releases the brakes it accelerates faster because of that super long compressed spring but as the vehicle speeds are equalized the spring is fully relaxed.
On the blackbird you also have that starting pressure differential proportional with wind speed but since part of the energy is taken and put back in to this pressure differential by the propeller the presume differential continues to stay high (higher than on a sail that is at the same speed as sail could not push back to increase the pressure).
All this only works because air is compressible it will just not work if air was replaced with water witch is a non compressible fluid.

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