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Mess with your minds: A wind powered craft going faster than a tail wind speed.
gnuarm:
--- Quote from: fourfathom on December 28, 2021, 08:40:21 pm ---
--- Quote from: gnuarm on December 28, 2021, 08:19:33 pm ---So the full equation for the power applied to the vehicle through the wheels is
0.5 * air density * area * (wind speed - vehicle speed)² * vehicle speed
--- End quote ---
Are you sure about that? When wind speed = vehicle speed, that equation still reduces to zero.
--- End quote ---
Yes, that is correct. When the wind speed and the vehicle speed are the same, there is no wind force on the vehicle and so no force required to maintain the vehicle speed... other than friction which we are not factoring in here. This is just about the wind forces.
electrodacus:
--- Quote from: gnuarm on December 28, 2021, 08:48:59 pm ---I don't care about the wind power. This equation was being tossed about when there seemed to be a discrepancy of whether the power to move a vehicle falls to zero when the vehicle approaches a zero velocity. To determine that, the force is required which is
0.5 * air density * area * (wind speed - vehicle speed)²
This is the force provided by the wind which must then be applied by the wheels to move the vehicle at a speed in the face of the wind. To find the power that must be applied to the vehicle you multiply by the relative speed of the vehicle and the point applying the force, the ground, or "vehicle speed". The equation for the applied power then becomes
0.5 * air density * area * (wind speed - vehicle speed)² * (vehicle speed)
There's no point in shifting the conversation to rivers or moats or spacecraft. We are talking about a ground vehicle in the wind. Your equation is for power in the wind and the wind alone and has nothing to do with the power required to move the vehicle.
Until you understand your mistake here, you have no possibility of understanding the blackbird. You really need to listen to those who are trying to help you understand. This is not a battle, this is your friends who want to see you succeed in learning the correct way to understand this issue.
--- End quote ---
The equation for force is correct and includes wind speed - vehicle speed the equation for power will also need to include both.
Just imagine air as a solid hitting the vehicle. Can you see why there power available and not just force will include the speed of that solid ?
This is just wrong equation 0.5 * air density * area * (wind speed - vehicle speed)² * (vehicle speed) the correct one is this for all applications
0.5 * air density * area * (wind speed - vehicle speed)² * (wind speed - vehicle speed)
Kleinstein:
electrodacus starts to repeat of old nonsense over an over again. Chance are he not at all interested in learning something. Given his inablity to see the contradictions his claims cause, I don't think it makes much sense to argue any more. Chances are all other have got the point by now.
gnuarm:
--- Quote from: electrodacus on December 28, 2021, 08:50:26 pm ---I have no intention for this to continue in fact my goal is to get this done as soon as possible.
--- End quote ---
Lol! Your first post was Reply #45 and your last was 1280!!! If you didn't intend to keep this going so long you sure seem impotent to end it.
--- Quote ---I'm sure not the only person understanding this as many product designs depend on using the correct equation.
--- End quote ---
Yes, they do, just not the way you think they do.
--- Quote ---I work in the field where understanding power and energy is super important (I designed my own wind turbine) and my business is in the renewable energy storage thus I investigated all energy storage sources including but not limited to eletrochemical energy storage, kinetic energy storage and thermal energy storage.
--- End quote ---
I pity anyone buying your products. Really!
--- Quote ---There will always be people that do not understand some parts of physics and I will not get bothered by this particular problem if it was not such a wide spread misinformation involving science communicators and university professors.
--- End quote ---
The real issue is that both upwind and downwind motion is possible being powered by the wind. You seem to want to complicate the issue by dragging in imaginary storage of energy and refusing to discuss details that would show you wrong. Even after we point to the spots in the conversation where you stop discussing an idea that would prove you wrong, you continue to refuse to discuss those issues.
I'm voting for number 3. He does now understand that he is wrong (it would be so nearly impossible for him to not see this) and is continually back peddling so he doesn't have to admit it.
The funny thing is the only thing worse than admitting you are wrong, is refusing to admit it in the face of incontrovertible proof. So he applies the wrong equation to the right situation (or is it the other way around?), changes the discussion to extraneous topics and poor analogies and refuses to continue a thread of discussion when it is clear it will prove him wrong. This has to be knowing evasion of the truth. Even a troll eventually gets tired of the game.
IanB:
--- Quote from: fourfathom on December 28, 2021, 08:40:21 pm ---Are you sure about that? When wind speed = vehicle speed, that equation still reduces to zero.
--- End quote ---
It is supposed to reduce to zero. When the vehicle is moving at the same speed as the wind, the power transfer from the wind to the vehicle is zero.
See here:
https://www.eevblog.com/forum/chat/mess-with-your-minds-a-wind-powered-craft-going-faster-than-a-tail-wind-speed/msg3888830/#msg3888830
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