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| Mess with your minds: A wind powered craft going faster than a tail wind speed. |
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| Kleinstein:
--- Quote from: electrodacus on December 27, 2021, 04:55:42 am ---Also if you double the speed drag power increases 8x not 2x or even 4x --- End quote --- It is darg force, not power. --- Quote from: electrodacus on December 27, 2021, 04:23:04 am --- --- Quote from: bdunham7 on December 27, 2021, 04:20:18 am --- No, they got it exactly right here and we've all been telling you the exact same thing.... --- End quote --- OK then why that second formula that should represent the same thing provide a different value ? --- End quote --- The problem is not with the 2nd formular, but with the 1st. If to claculations don't agree one (at least one) has to be wrong (or using different approximations). If you get one of the formulas from text books and many sources chances are that that's the good one and the other is the bad one. For the second formular there is a simle derivation: The drag force is proportional to relative wind speed squared and the mechanical power is force times relative speed (in this case bicycle relative to ground). |
| gnuarm:
--- Quote from: electrodacus on December 26, 2021, 11:53:41 pm --- --- Quote from: gnuarm on December 26, 2021, 11:21:22 pm ---Except my car has no battery and neither does the blackbird. Also, the blackbird has both a wheel and a propeller while my car ONLY has a wheel. --- End quote --- It was my assumption that you own a Tesla due to referral program mentioned in your signature. --- End quote --- I'm talking about my imaginary car for this example. --- Quote ---Why do you think a propeller that is less efficient than a wheel can help ? The propeller itself has no advantages over wheels other than it is to travel trough air and it can store energy as pressure differential. --- End quote --- The issue is the blackbird has wheels that pick up power from the motion and provide it to the propeller. This additional energy turns the propeller so it pushes against the wind so the car can run faster than the wind. There is no need to invoke imaginary storage. --- Quote from: gnuarm on December 26, 2021, 11:21:22 pm ---Ok, now you are going into pointless details because this is not how the blackbird works. --- End quote --- That is exactly how blackbird or any wind powered vehicle works. This is your fallacy. Until you can get past this, you will never understand why the blackbird works. --- Quote from: gnuarm on December 26, 2021, 11:21:22 pm ---Nothing, literally NOTHING you have talked about here has to do with the blackbird, so just stop the insanity! It is clear that you will never understand anything anyone tells you that doesn't agree with your idea because you reject it out of hand without understanding it. I keep coming to the conclusion that you can't be taught anything, but I get suckered in when I see a point that is so crystal clear to anyone else that it must be possible to show it to you. However, as others have pointed out, instead of understanding what they tell you, you simply duck the issue and start talking about something different. So no more replying to your nonsense. --- End quote --- The fact that you do not understand how blackbird works will not make all that I mentioned very relevant. That is about what I think about you but I'm still hopeful. [/quote] The blackbird is actually quite simple to understand. It is when you start imagining energy storage being a part of the matter that you go astray. I know nothing I'm posting will have any impact on your understanding. I don't know where this comes from. Every time someone gives you a clear explanation you seem compelled to invent something new that explains how it doesn't work, in spite of the fact that there are videos showing the blackbird working both downwind and upwind. The only limitation seems to be the length of the track they run on. So your storage idea is bogus. If there was a track that circled the earth they probably could circumnavigate the globe easily... without storing any energy. |
| gnuarm:
--- Quote from: electrodacus on December 27, 2021, 12:04:05 am --- --- Quote from: bdunham7 on December 26, 2021, 11:46:46 pm ---No, you really don't and that's where you are failing hard. You do not understand or correctly apply the basic tenets of junior high-school level physics, namely: 1. The principles of Archimedes 2. Newton's laws of motion 3. The principle of conservation of energy--the one you keep bringing up but clearly have no clue as to how to apply it. --- End quote --- OK answer this. Max wind power available to a direct down wind powered vehicle is when vehicle just starts moving so low speed (Fact 1). equation for ideal 100% power available to any direct down wind powered vehicle is 0.5 * air density * area * (wind speed - vehicle speed)^3 (Fact 2) What powers the vehicle when vehicle speed is above wind speed ? --- End quote --- This has been explained to you many times. The propeller pushes against the wind, so the car gets energy from the combined speed of the wind and the exhaust of the propeller. This forward motion is from the combined forces of the wind and the propeller. The wheels pick up energy from this combined motion and uses it to turn the prop. Since the prop only has to supply part of the combined energy, the resistance of the wheels is less than the total of the wind and the prop. --- Quote ---Clearly not wind power (at least not directly but stored wind power). I'm starting to get very tiered by this level of stupidity. I asked for the equation showing the available wind power for Blackbird and nobody presented one that will match the observed results in both blackbird and treadmill model. --- End quote --- The observed results being that the blackbird travels faster than the wind or upwind? Yes, I get tired of the insanity as well. |
| gnuarm:
--- Quote from: electrodacus on December 27, 2021, 12:32:54 am --- --- Quote from: IanB on December 27, 2021, 12:18:45 am --- --- Quote from: electrodacus on December 27, 2021, 12:04:05 am ---equation for ideal 100% power available to any direct down wind powered vehicle is 0.5 * air density * area * (wind speed - vehicle speed)^3 (Fact 2) --- End quote --- Except: a) You cannot derive this equation from first principles when asked to do so, b) You have not pointed to any authoritative source that gives this equation (online or textbook). Therefore you cannot take this as fact, and if you rely on it all your arguments are flawed. --- End quote --- It is a fact. Please provide an equation that you think is correct. This equation is used everywhere from wind turbine design to vehicle drag so it is one of the most used equations and you can find it literally everywhere. Your problem seems to be not understanding power and working with forces only not understanding what speed will correspond to get the correct result. --- End quote --- If you claim this equation is universal, why don't you provide a link showing this? If you can't provide a link, it must not be very universal. |
| gnuarm:
--- Quote from: bdunham7 on December 27, 2021, 04:28:49 am --- --- Quote from: electrodacus on December 27, 2021, 04:23:04 am ---OK then why that second formula that should represent the same thing provide a different value ? --- End quote --- Because it doesn't represent the same thing. You are 'intuiting' (assuming wrongly) what the result should be and then assuming the formula is wrong when it doesn't match your preconceived notion. The result of the formula, which is correct, is that it takes more power to go 20km/h in still air than it does to go 10km/h against a 10km/h headwind. --- End quote --- I don't want to go through the entire history of this. Why would that be true? Are they taking into account the other losses like tire drag? The air drag would only be a matter of bike vs. air, no? |
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