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Newton's third law problem.
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electrodacus:

--- Quote from: AndyBeez on November 24, 2022, 12:38:49 pm ---Harsh dude 8)

Maybe these wikis will help OP:

https://en.m.wikipedia.org/wiki/Fluid_dynamics

https://en.m.wikipedia.org/wiki/Radiation_pressure

https://en.m.wikipedia.org/wiki/Yarkovsky_effect

--- End quote ---

Quote from your first link:
"Fluids are composed of molecules that collide with one another and solid objects."
PlainName:

--- Quote from: electrodacus on November 24, 2022, 04:01:26 pm ---
--- Quote from: PlainName on November 24, 2022, 11:00:41 am ---
--- Quote ---The only way the vehicle is powered by wind is by air particles colliding and providing their kinetic energy to vehicle.
--- End quote ---

Wrong. You'll never get how it works whilst you persist on thinking this.

--- End quote ---

Please enlighten me.
How do air particle transfer energy to vehicle if not through collision ?

And as you claim to know how it works please also provide the equation describing the amount of wind power available to vehicle.

--- End quote ---

In the previous threads I tried stepping you though it very simply (and it was tough keeping you ontrack and not racing ahead down distraction rabbit holes), but once you saw where it was going you disappeared. Why would this time be any different?

Nevertheless, your problem is starting with the wind power first and then trying to apply that to obvious stuff. Forget where the power comes from for the moment and look at how it's actually working, then figure how to power it.

First, you have a propeller which is pushing the vehicle along. We know that works because jets take off - if the prop is turning then it is pushing the vehicle even if ever so slightly. It's pushing against the prevalent wind, and you even agreed earlier in this thread that this kind of thing is additive. If the prop can push a 5m/s and the wind is 10m/s then the vehicle will go at 15m/s.

That's uncontestable physics and fact, but feel free to disagree if you dare.

So, what we're stuck for is the power that drives the prop. We know it is coming from the wheels (that is, the wheels drive the prop and not vice versa), and the wheels get it from the vehicle being pushed by the wind. But... the vehicle is going faster than the wind so what does the wind push on? It is the backwash from the propeller - remember the 5m/s plus whatever the prevalent wind is, which is this case is maybe -2m/s, so a small forward movement for a larger backwards jet.

Hang on, isn't this free energy or something? No, because of drag, which will require more power to overcome, and loss of power as more is extracted. Just think about it for a moment: the wind is pushing the vehicle (yes, due to air bouncing off it) at almost wind speed and there is no drag. All that's required is for the prop to turn however, slowly, and produce a minute amount of thrust which will increase the vehicle speed a tiny amount and it's game on, but go a bit faster and you need more power to overcome the drag and similar losses. But if you have drag you are going faster than the wind. Can the wheels extra that tiny amount of power without slowing the vehicle? That's where leverage, size of prop and angle of blades come in.

Equations? Dunno. I'm not clever enough to work one out that you would reject or ignore anyway, and I doubt there is one on t'web to copy like you do. But I can point to video of the actual vehicle and many models working continuously and without any energy storage facilities.

Edit: forgot to point out that the wind power increases as the vehicle slows. There is far more power available than is consumed to push the vehicle forward - it's just that there is nothing to suck it up normally so the vehicle accelerates. At wind speed, there is 0 power pushing the car forward, but all the power of the wind is still available if you can work out how to access it. That's where the wheels are getting apparently free power from.
Nominal Animal:

--- Quote from: electrodacus on November 24, 2022, 04:01:26 pm ---How do air particle transfer energy to vehicle if not through collision ?

--- End quote ---
Modeling the macro-scale properties of compressible fluids as colliding solid particles is just not tenable.  I know, because my proper field is molecular dynamics simulations.

In particular, a molecule does not have a well-determined surface at all; there is just a "shroud" of delocalized outermost electrons, and we assign an arbitrary electron density as the "surface".

Molecule interactions can be split into four categories: Pauli exclusion principle, electrostatic interactions between permanent charges (ions and multipoles), induction/polarization ("Debye force"), and London dispersion.  "Collision" does not even begin to describe all these.  At the molecular scale, even defining "a collision" is difficult, as there is no strict distance at which interactions start or stop: they interact, exchanging energy.  Not just "kinetic" energy –– as in the movement of the center of mass of the molecule ––, but also energy related to internal excitation states (often part of the "thermal" energy of that molecule).

When we are dealing with air, the key physics field to consider is aerodynamics.  In particular, most useful effects are related to changes in pressure, not "collisions".  However, the case where the vehicle is in connection to ground, differs a lot from aeroplanes, because the key velocity is not airspeed, i.e vehicle velocity with respect to surrounding air, but groundspeed, because the vehicle uses the contact with ground for acceleration.


--- Quote from: electrodacus on November 24, 2022, 04:01:26 pm ---And as you claim to know how it works please also provide the equation describing the amount of wind power available to vehicle.
--- End quote ---
It depends on the vehicle.  For a ground vehicle, what matters is that it depends not on the vehicle airspeed (speed of vehicle relative to the surrounding air), but on the velocity and pressure of air with respect to ground.  This is because the vehicle spends its energy in an effort to accelerate with respect to ground, not with respect to wind; to compensate for the drag and friction (i.e., losses) the vehicle experiences.

Yes, aeroplanes and ground vehicles differ significantly in this.

An easy to understand vehicle that can extract energy from air when their relative speeds are the same, is a cart with a vertical axis airfoil wind turbine.  The airfoils do not "catch" wind, they act like aeroplane wings, generating torque from the pressure differential on different sides of the blade.  During any motion of the vehicle, the VAAWT is rotating.  When the vehicle travels downwind at the same speed as the wind, the blades of the VAAWT can still extract energy from the wind in all phases except when the blade is in its extremum position with respect to the travel direction.  It is obvious, since the blade is moving wirth respect to air surrounding it.  Because of the pressure differential principle, the direction of the wind is easily compensated by changing the blade orientation/attack angle.  The only limiting factor is how efficient you can make your vehicle, how small you can make the losses in its mechanisms.
electrodacus:
Thanks for taking the time to replay.
I also need to mention for others that below discussion is about direct downwind since this thread was about the upwind mainly.


--- Quote from: PlainName on November 24, 2022, 04:40:08 pm ---
In the previous threads I tried stepping you though it very simply (and it was tough keeping you ontrack and not racing ahead down distraction rabbit holes), but once you saw where it was going you disappeared. Why would this time be any different?

Nevertheless, your problem is starting with the wind power first and then trying to apply that to obvious stuff. Forget where the power comes from for the moment and look at how it's actually working, then figure how to power it.

--- End quote ---

I think that is the logical place to start from figuring out the amount of wind power available then decide what you can do with that.
If you forget about that you will think that you can do anything.




--- Quote from: PlainName on November 24, 2022, 04:40:08 pm ---First, you have a propeller which is pushing the vehicle along. We know that works because jets take off - if the prop is turning then it is pushing the vehicle even if ever so slightly. It's pushing against the prevalent wind, and you even agreed earlier in this thread that this kind of thing is additive. If the prop can push a 5m/s and the wind is 10m/s then the vehicle will go at 15m/s.

That's uncontestable physics and fact, but feel free to disagree if you dare.

--- End quote ---

If by pushing you mean accelerating then you need to apply power to the propeller.
So if the starting point is that vehicle is at 15m/s driving in the same direction as wind witch is at just 10m/s and there is zero friction so ideal case the vehicle will be able to maintain that speed but will be unable to accelerate if there is no stored energy other than the vehicle kinetic energy.
   



--- Quote from: PlainName on November 24, 2022, 04:40:08 pm ---So, what we're stuck for is the power that drives the prop. We know it is coming from the wheels (that is, the wheels drive the prop and not vice versa), and the wheels get it from the vehicle being pushed by the wind. But... the vehicle is going faster than the wind so what does the wind push on? It is the backwash from the propeller - remember the 5m/s plus whatever the prevalent wind is, which is this case is maybe -2m/s, so a small forward movement for a larger backwards jet.

--- End quote ---

Getting 100W as an example from the wheels means you are decelerating the vehicle by that exact amount and so if you provide that to an 100% efficient propeller you will get back 100W worth of acceleration thus you end up with nothing.
In a real vehicle doing such a thing will result in deceleration as for 100W taken at the wheel you will be able at most to say provide 80W worth of thrust thus you are decelerating at a 20W rate (slowing down).
 


--- Quote from: PlainName on November 24, 2022, 04:40:08 pm ---Hang on, isn't this free energy or something? No, because of drag, which will require more power to overcome, and loss of power as more is extracted. Just think about it for a moment: the wind is pushing the vehicle (yes, due to air bouncing off it) at almost wind speed and there is no drag. All that's required is for the prop to turn however, slowly, and produce a minute amount of thrust which will increase the vehicle speed a tiny amount and it's game on, but go a bit faster and you need more power to overcome the drag and similar losses. But if you have drag you are going faster than the wind. Can the wheels extra that tiny amount of power without slowing the vehicle? That's where leverage, size of prop and angle of blades come in.

--- End quote ---

Too much nonsense to be able to provide a constructive replay.


--- Quote from: PlainName on November 24, 2022, 04:40:08 pm ---Equations? Dunno. I'm not clever enough to work one out that you would reject or ignore anyway, and I doubt there is one on t'web to copy like you do. But I can point to video of the actual vehicle and many models working continuously and without any energy storage facilities.

Edit: forgot to point out that the wind power increases as the vehicle slows. There is far more power available than is consumed to push the vehicle forward - it's just that there is nothing to suck it up normally so the vehicle accelerates. At wind speed, there is 0 power pushing the car forward, but all the power of the wind is still available if you can work out how to access it. That's where the wheels are getting apparently free power from.

--- End quote ---

There is no problem copying an equation from either the web or your mind if it is the right one for the subject.
There is no video showing a direct downwind vehicle driving continuously. As far as I know large scale model is just one the Blackbird  and all the treadmill models have a very limited space before they fall out on the other side.
But what you can do is take a video from the side on one of the treadmill models and you will see the rate of acceleration decreasing meaning it at some point get to zero and start decelerating.

"Free power"  :) There is no such thing.
Nominal Animal:
Direct upwind is trivial to demonstrate: just put an efficient horizontal turbine on a cart, and use a very low gearing to the wheels (i.e. turbine turns many tens of times per one rotation of the wheels).  Make it a VAWT and the cart will move regardless of the wind direction.

This matches my Lego trike I demonstrated earlier, and whose exact behaviour I described mathematically (in terms of velocities or displacements, and gear ratio); instead of wind, it used a spool of thread, or a Lego chain/track.

If one were to build a model where the ground wheel is actually a pulley with a wire looped around it and fixed to ground at both ends, it shows that no slip is required at all for it to function as described.  Indeed, if the wire is looped many times around the pulley, and fixed to the pulley at the midpoint, then no slip is even possible if one uses e.g. thin steel cable.
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