It's not outputting any more. It's extracting power from a wheel system that is travelling at one speed (frame of reference is the ground) and then applying that power to a propeller system travelling at a different speed (frame of reference is the wind).
This is the concept you continually dismiss, bypass or ignore. It is THE heart of the Blackbird doing what it can - and has - done. By refusing to even consider this concept as a possibility you are condemned to remain ignorant.
QuoteThat university professor that lost the bet (his fault for gambling) said nothing wrong in Derek's video but since it was unable to explain how the treadmill prototype worked it was forced to pay the money not to be seen as not honoring his obligations. He should have asked for help and try to understand why it works then make that information public.Poor, dumb professor.
I do suggest you spend more time thinking about this (valid for all people here).
I spent enough time trying to help and I feel I repeated my self more than I needed to so it will not be helpful for me to help if you do not want to put the brain to work.
Try to learn what power and energy is as that should help.
Do you understand that power you take from the wheel will brake the vehicle ?
Please read again my formula as you forgot a very important part and that is the area that wind pushes against.
0.5 * air density * area * windspeed3
This is the formula anyone designing a wind turbine will use except that is is ideal 100% of available wind power and to this they need to add the turbine efficiency usually around 40% and the generator efficiency that can be over 90%
For a vehicle driving directly down wind ideal case all you need is to subtract vehicle speed from wind speed since wind speed relative to vehicle is what can power the vehicle.
This formula
0.5 * air density * area * (wind speed - vehicle speed)3 is what will apply to any wind only powered vehicle driving directly downwind.
This is also the ideal case so absolutely max that is available to the vehicle meaning that if you do not add an energy storage device to this vehicle or some external energy source like gasoline and an engine then your vehicle can not exceed wind speed.
For direct downwind blackbird is clear to me that energy is stored in pressure differential generated by the propeller and that is what allows it to exceed wind speed even if it may be for just a few minutes depending on the design, how fast it will use that stored energy.
I certainly do - and the fact you want to make a point of this seems to be a desperate move to discredit me.
Do you realise that while that extraction of power will slow the vehicle, that the loss of velocity will result in the wind directly applying more force to the vehicle as it will be travelling below wind speed? This results in an increase in total power applied to the vehicle. Pull 5.5W from the wheels and, as the vehicle slows, the wind adds more power. Even if that additional power is just 2W or 1W or even 1mW, the overall power delivered to the vehicle by the wind has increased.
You have never mentioned this increased power, which indicates your understanding is less than comprehensive and your analysis certainly incomplete.
And we haven't even looked at the harvested power component. Apply that harvested power into driving the propeller and now the backward thrust will be trying to slow the wind, but the wind (having a practically infinite energy store) will just push against this - applying even more power into the system.
The extra power required for the Blackbird to do its thing, comes precisely from the wind as the wind pushes against those forces which come from the elements that are trying to slow the vehicle down down.
At this point, even your intuition must be curious as to where this total system will settle - and what parameters will affect that point.
I would really encourage you to do a proper job of investigating this - rather than do your typical handwaving dismissal. The total power has increased, so you cannot just say the additional power is of no significance without providing real numbers.
power is instantaneous contains no time dimension
Here are the correct equations for wind power available to a vehicle traveling directly down wind
0.5 * air density * area * (wind speed - vehicle speed)^3 yes this is the correct equation. Notice how you have highest power at low vehicle speed and power drops to zero by the time vehicle speed equals wind speed.
The point is not in reading the euqations, the point is understand what they are actually calculating. The first one is the power theortically available from the wind as the kinetic energy in the moving air.
The second equation is giving the energy available at the reduces wind speed, e.g. for a wind-turbine on the moving vehicle. This is not the maximum energy available to the vehicle.
The wind turbine also creates some drag force, comparable to a sail and this drag force also creates power to a moving vehicle. This power contribution is force times vehicle speed. For a sail this is the only way it creates power.
The wind turbine (=porp) on the vehicle could create some extra power directly. For the sail the drag force is proportional to (wind_speed-vehicle_speed)². For the prop the drag force (called thrust when caused by the driven prop) also depends on the speed the prop rotates. depending on the direction and speed this can be less, but also more than just a sail. With the driven prop there can be drag/thrust even with zero wind speed.
But why is this the correct equation?
Please derive this equation step by step from first principles, stating any assumptions made at each step.
Then you will understand where and how this equation can be applied, and what limitations exist in its usage.
One part will be stored as kinetic energy the other part will be stored as both rotational kinetic energy in the rotating propeller and pressure differential by increasing the difference in pressure between upwind side of the propeller and down wind side.
Then this stored pressure differential energy storage is what will allow blackbird to exceed wind speed for some limited amount of time.
There are multiple resources here is one
http://web.mit.edu/wepa/WindPowerFundamentals.A.Kalmikov.2017.pdf
The equation can be applied anywhere starting with wind turbine design, power available to any wind powered vehicle, drag power needed for vehicle design .....
Unfortunately school is mostly for those that can memorize facts and equations an understanding is completely irrelevant.
One part will be stored as kinetic energy the other part will be stored as both rotational kinetic energy in the rotating propeller and pressure differential by increasing the difference in pressure between upwind side of the propeller and down wind side.
Then this stored pressure differential energy storage is what will allow blackbird to exceed wind speed for some limited amount of time.
But the pressure after the propeller is lower than the pressure in front of the propeller: https://www.quora.com/Why-is-the-static-pressure-before-a-fan-higher-than-after-the-fan
I have shown you a video illustrating this. Do you think that video was manipulated or faked in some way? Every engineer knows that video shows the truth. You can do the same experiment yourself. Just use any household fan. You will find the pressure in the moving airstream is lower than the surroundings.
You should stop looking at that Wikipedia article. It does not say what you think it says.
No, I want you to derive it yourself, and give your assumptions in the derivation.
If you cannot do that, you are merely quoting facts and equations from others, which in your own words shows a lack of understanding.Unfortunately school is mostly for those that can memorize facts and equations an understanding is completely irrelevant.
Not sure what you mean by after and front. Here is the graph for pressure difference.
Never claimed that anything was faked. It works exactly as shown from the equations and theory I presented.
Never claimed that anything was faked.
The difference is that sail vehicle (an ideal one) takes all this available power and stores it as kinetic energy thus not able to exceed wind speed.
Blackbird will split this available wind power in to two. One part will be stored as kinetic energy the other part will be stored as both rotational kinetic energy in the rotating propeller and pressure differential by increasing the difference in pressure between upwind side of the propeller and down wind side.
Then this stored pressure differential energy storage is what will allow blackbird to exceed wind speed for some limited amount of time.
Do not be afraid just open the pdf and look at page 4.
So why is there no pressure differential energy stored behind the sail?
Stored rotational kinetic energy can not cause a fixed-geometry propeller to increase rotational speed. It can at best reduce the rate that the propeller rotation will slow down.
In your models and equations, stored pressure differential energy will not cause the vehicle to accelerate to above windspeed, since any pressure differential will diminish to zero at windspeed, and go negative when the vehicle is above windspeed.
Your errors in analysis have been explained many times.
Do not be afraid just open the pdf and look at page 4.
Do you understand that power you take from the wheel will brake the vehicle ?
If you talk about power and taking a power from the wheel then there is no speed change as power is instantaneous contains no time dimension.
as power is instantaneous contains no time dimension.
Do you understand thatpoweryou take from the wheel will brake the vehicle ?
Let's revisit:Do you understand thatpoweryou take from the wheel will brake the vehicle ?I presume you mean energy.
I certainly do - and the fact you want to make a point of this seems to be a desperate move to discredit me.
Do you realise that while that extraction of energy will slow the vehicle, that the loss of velocity will result in the wind directly applying more force to the vehicle as it will be travelling below wind speed? This results in an increase in total power applied to the vehicle. Pull 5.5W from the wheels and, as the vehicle slows, the wind adds more power and, thus, more energy. Even if that additional power is just 2W or 1W or even 1mW, the overall energy delivered to the vehicle by the wind has increased.
The above is perfectly reasonable and reads pretty clearly, even before throwing in the word "energy". There is no conflict in using the terms power or energy. Each describes a particular quantity and those terms can be mixed quite happily. It is for the reader to understand what information each quantity provides. The only difference is time and the context gives enough structure for the appropriate consideration of time.
Below are the correct equations
Below are the correct equations
If you would stop making assertions like this, and instead ask questions like, "Are these the correct equations?" or "What is the correct way to analyze this system?", then you would become far more enlightened.
As it is, you are unable to make any progress in your understanding.