[QUOTE]Техник пишет:
Однако тема энергии осталась нераскрытой, тут я согласен.[/QUOTE]Ну вот, наконец то - "истина где-то рядом". Наконец дошло, что это не просто машина, а "того кого надо машина" :D
И совсем не простая и не тривиальная.
Наткнулся тут вот на коммент в сети по этой чудо-машине с претензией, что они могут посчитать баланс энергии этого устройства.
Некоторые моменты там привлекли моё внимание. Я потом отдельно на каждом тезисе остановлюсь.
Но первое на что хочу обратить внимание, что они там даже предельную скорость этого девайса вычислили.
[quote][i]Hello gentlemen!
I came across your video the other day regarding the operation of the original mechanical device Blackbird vehicle.
"A Physics Prof Bet Me $10,000 I'm Wrong" https://youtu.be/yCsgoLc_fzI?t=277
I also found an article by Mark Drela - "Dead-Downwind Faster Than The Wind" - regarding the explanation of how this original device works.
As indicated, in the annotation to the video it is said that at first glance the work of this device does not seem obvious and allegedly violates the laws of physics.
I would like to point out that I consider the phrase "violates the laws of physics" incorrect, and I consider even the formulation of the question in such wording is incorrect. Since, if it seems to us that some device violates the laws of physics, it is not a problem of the device or physics, but a problem of our understanding of this question. Which, in fact, was proved by subsequent events.
I can assume that those materials attracted our attention because of their noticeable correlation with our work.
I believe that the correlation between our turbine and this car, is that they both have two energy elements linked by positive feedback. Both our turbine and the Blackbird vehicle use a chain transmission that provides feedback between these elements with redistribution of energy between them.
At certain parameters (speed, pressure) this feedback becomes positive or negative. Thanks to this, these elements, balancing the energy between them, bring the system to an optimal energy state, which is not obvious to everyone and seems paradoxical.
Somebody may even interpret this into a seemingly endless acceleration of the vehicle, leading to absurd conclusions. Moreover, the same mistake, as it seems to me, is made by some scientists who have dealt with this issue. In particular, in the explanations there is a reference to the US Physics Olympiad Semi-Final Exam in 2013 (p. 10). It also says that "with sufficiently low energy loss, any speed is possible". This contradicts the obvious logical conclusions - if the speed of the vehicle can grow unlimitedly, then the speed of the air behind the propeller must also grow unlimitedly, which means that to accelerate this air it will be necessary to expend unlimited energy, and there is nowhere to get it.
However, judging by our calculations, in such systems with positive feedback and the possibility of energy redistribution between the parts of the system, there is a critical state due to the extremum of the energy balance. The diagrams in my articles show these extrema under several input parameters.
At the same time, in transient processes (in particular, at start-up) self-excitation and acceleration of the system occurs, but this process does not continue endlessly, as it may seem to uninformed readers. It goes to the so-called "saturation", i.e. to the extremum on the energy diagram.
If the forces acting on each element of the device and allowing this device to move have been considered sufficiently, the energy balance is much worse.
Some people frankly declare that they have reached a dead end (and there are many scientists among them), and some evade this question, veiling the answer with intricate phrases.
We also do not pretend to have a complete answer to this question, especially as our calculations are made for a hydraulic device, and the principles of fluid dynamics and aerodynamics still have some differences.
But we operate only with basic concepts - Bernoulli's equation and the principle of continuity of flow (the conservation of mass).
The solution of energy balance, as it seems to us, is quite simple (without taking into account adiabatic cooling/heating of air, turbulence, etc). As the air velocity increases at the fan outlet, the local air pressure drops according to Bernoulli's law. The dependence of kinetic energy on velocity is quadratic, while the dependence of potential energy (pressure) is linear.
Thus, the difference between the total energy of air before and after the propeller (kinetic energy of air movement plus potential energy of pressure) will almost NEVER be equal to zero.
Up to certain parameters - up to the critical state - it is positive, afterwards it is negative. Part of this energy is spent on overcoming resistance to motion (friction), and part of it is dissipated in the downward trace behind the propeller.
It is a pity that the experiment did not include introducing a smoke trail behind the propeller. It would have been interesting to see how the air behind the propeller behaves.
All these conclusions are valid if there is an active device in the flow that can take energy from the flow or add it to the flow (propeller, turbine, pump, etc.).
In the absence of an active device in the flow, the flow will immediately go to the supercritical state, with the equality of energies at the inlet and outlet and the predominance of kinetic energy.
The same mode is possible in the presence of an active device in the flow, if it works in idle mode, not taking energy and just accelerating the flow to the conjugate supercritical state.
[b]Thus, based on the abovesaid and our preliminary calculations considering the energy balance, the critical state for "Blackbird" is reached when the air speed behind the propeller is approximately 43-45 m/s.
It is this speed that is assumed to be the theoretical speed limit for this device.[/b]
I do not exclude that I have not found all materials on the subject and a similar explanation given in my articles may have already been given by someone else. So if you are familiar with such materials, I would be very grateful to you if you could give me a link to them.
[/i][/quote]
