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Electroboom: How Right IS Veritasium?! Don't Electrons Push Each Other??
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electrodacus:

--- Quote from: Naej on July 10, 2022, 12:42:49 am ---I'm not.
Mass flow is close to the density*area*relative wind speed.
(Not equal because when you have a relative wind speed equal to 0, you can still get some mass flow on your propeller)

The wheel. Perhaps the guy is some gears connected to the wheel.
And the ball stops moving relative to the ground, it loses its kinetic energy.

--- End quote ---

So you changed now to relative wind speed but you need to do the same on the other part of the equation.

You specifically mentioned "guy in the vehicle slaps the ball at 10m/s"
If vehicle is at wind speed all balls will look stationary so hitting the ball at 10m/s means the guy will have needed energy.
There is the vehicle kinetic energy that the guy could have used but that means reduction in vehicle kinetic energy which also means reduction in speed.

Wind power is only available to vehicle when vehicle speed is lower than wind speed while both vehicle and air particles travel in the same direction.

I guess the confusion comes from the fact that you think that using power taken at the wheels (breaks the vehicle) can result in more power output at the propeller (propulsion power) witch is obviously not allowed by energy conservation law.


You have potential energy that will be based on wind speed relative to vehicle and that can be converted into kinetic energy.

No direct downwind vehicle powered by wind can exceed wind speed as the max kinetic energy of that wind only powered vehicle can be ideal case equal with potential wind energy.
In non ideal case you have friction so max speed will be significantly lower than wind speed for a direct downwind vehicle but if you add an energy storage device then you can get to almost any speed as vehicle kinetic energy can get as high as the energy storage capacity of the device minus the friction losses.


a) Will you agree that I can build a sail vehicle (no propeller) where I add a super capacitor or similar energy storage device that I charge while vehicle is below wind speed and the exceed wind speed for some limited amount of time with that vehicle using the stored energy?

b) Will you agree that pressure differential created by the propeller is an energy storage device that can easily contain way more energy than needed to accelerate the blackbird to that record 13m/s ?

But if you still insist your equation is correct and different than the one I provided
Pw = 0.5 * air density * area * (wind speed - vehicle speed)3

Then just write it in the simplest form and we will put that to the test (see what prediction it makes in a few different cases and see if that matches reality).
To my understanding and your latest modifications this is what you say all speeds relative to ground.
Pw = 0.5 * air density * area * (wind speed)2 * (wind speed - vehicle speed)
gnuarm:
I should have known.  You are LITERALLY incapable of understanding anything anyone tells you.

The design of the sails that move backward on the car, means the wind vs. sail relative speed is maintained as the rest of the car speed increases.  So the available energy never changes by your equation. 
gnuarm:
Let's try this one more time. 

Car has upright sails mounted on a track, like a treadmill.  The track runs backwards when the car moves forward, as the track is geared to the wheels. 

When the sails reach the rear of the car and would otherwise go under the car with the track, they fold up so as to no longer interact with the wind.  When the sails reach the front of the car, they rise upward with the track and unfurl. 

The rest of the car is adequately aerodynamic so that any wind resistance is minute compared to the forces on the sails.

As the car moves forward, the sails move backward at the same speed, relative to the car, so the sails while unfurled, are motionless with respect to the ground.  Now the vehicle speed in YOUR equation is the speed of the sails, not the car.  This speed is always zero.

It should be apparent, that the speed of the car is irrelevant to this thought experiment.  The speed that does matter, is the speed of the sails, which is always zero.  Relative to the wind, the sail speed is always the wind speed alone, never changing, so the full power of the wind is always available. 

The maximum speed of the car will only depend on the losses in this imaginary sail mechanism and any real wind resistance of the car along with rolling resistance.  The wind will continue to push against the sails transferring the full power of the wind (calculated by any formula you want to think up) accelerating the car until the losses in the car equal that wind power.
electrodacus:

--- Quote from: gnuarm on July 10, 2022, 02:25:17 am ---I should have known.  You are LITERALLY incapable of understanding anything anyone tells you.

The design of the sails that move backward on the car, means the wind vs. sail relative speed is maintained as the rest of the car speed increases.  So the available energy never changes by your equation.

--- End quote ---

Are you talking about a vehicle driving perpendicular to wind direction ? As that is a very different case that direct downwind.
If you are talking about a direct downwind vehicle no matter the design it can not exceed wind speed without energy storage. And obviously since stored energy is used it will only exceed wind speed for a limited amount of time and it will need to drop well below wind speed in order to recharge and repeat the cycle.

The one incapable of understanding may be you.
Do you notice that you provide no equations to support your claim?

All is needed is an equation describing the amount of wind power available to vehicle since the one I provided shows no wind power available when vehicle speed is at and above wind speed for a direct down wind vehicle.
I did not invent that equation it is used by many people in multiple scenarios.
It is simple high school level physics and just classical mechanics.  Not being able to understand this simpler case of energy conservation will basically make it impossible to understand the problem discussed in this main thread that also has to do with energy conservation and energy storage.
For you (and apparently many others) tho air seems to be as invisible and magic as the electrons.

But as I mentioned before the ones that know the least are the most confident. It is not that different from people that LITERALLY and confidently think feries and other similar creatures are real or think earth is flat despite all the evidence to the contrary.
electrodacus:

--- Quote from: gnuarm on July 10, 2022, 02:52:22 am ---Let's try this one more time. 

Car has upright sails mounted on a track, like a treadmill.  The track runs backwards when the car moves forward, as the track is geared to the wheels. 

When the sails reach the rear of the car and would otherwise go under the car with the track, they fold up so as to no longer interact with the wind.  When the sails reach the front of the car, they rise upward with the track and unfurl. 

The rest of the car is adequately aerodynamic so that any wind resistance is minute compared to the forces on the sails.

As the car moves forward, the sails move backward at the same speed, relative to the car, so the sails while unfurled, are motionless with respect to the ground.  Now the vehicle speed in YOUR equation is the speed of the sails, not the car.  This speed is always zero.

It should be apparent, that the speed of the car is irrelevant to this thought experiment.  The speed that does matter, is the speed of the sails, which is always zero.  Relative to the wind, the sail speed is always the wind speed alone, never changing, so the full power of the wind is always available. 

The maximum speed of the car will only depend on the losses in this imaginary sail mechanism and any real wind resistance of the car along with rolling resistance.  The wind will continue to push against the sails transferring the full power of the wind (calculated by any formula you want to think up) accelerating the car until the losses in the car equal that wind power.

--- End quote ---

I think you will need to make a drawing as your explanation of how the vehicle is constructed and works makes little sense.
It sort of seems like you are talking about a direct upwind rather than a direct down wind vehicle.  Is that right ?
A vehicle driving directly upwind has always access to wind energy unlike a vehicle driving directly downwind when it exceeds wind speed and no wind power is available to accelerate the vehicle.

As for the direct upwind vehicle that you seem to describe it will also not work without energy storage (a much smaller capacity charged and discharged multiple times per second but still necessary else it will not work).
What prevents a direct upwind vehicle to work without energy storage is the Newton's third law the one about equal and opposite reaction.
Fortunately energy storage is always present in basically any real system especially when we are talking about a super small storage capacity like a rubber belt or even a loose chain or gears.
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