General > General Technical Chat
Mess with your minds: A wind powered craft going faster than a tail wind speed.
IanB:
--- Quote from: electrodacus on December 19, 2021, 06:21:37 pm ---Do not be afraid just open the pdf and look at page 4.
--- End quote ---
Do you think the teachers do not know how to do the exercise?
But apparently, you cannot do it. You are just quoting facts and equations, which by your own words shows you do not understand.
electrodacus:
--- Quote from: fourfathom on December 19, 2021, 06:26:41 pm ---
So why is there no pressure differential energy stored behind the sail?
--- End quote ---
There is but that pressure drops to zero by the time sail vehicle gets to wind speed so it is not useful to exceed wind speed
With propeller that already existing pressure differential created by wind is increased by the propeller that pushes air in the opposite direction while vehicle is below wind speed. It can no longer increase that pressure while it is above wind speed so at some point that pressure differential drops to nothing and then is when blackbird will start to slow down.
--- Quote from: fourfathom on December 19, 2021, 06:26:41 pm ---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.
--- End quote ---
Yes that is true the rotational kinetic energy can not do that but the pressure differential can. And yes that stored rotational energy will help sow down the deceleration after the pressure differential stored energy is used up.
My models (see in my video) perfectly describe how wind speed is exceeded using stored pressure differential energy.
IanB:
--- Quote from: electrodacus on December 19, 2021, 06:21:37 pm ---Do not be afraid just open the pdf and look at page 4.
--- End quote ---
Yes, and pages 3 and 4 of that pdf contain proof that your equation is wrong, which is why I am asking you to derive it for yourself, so you can understand why you have the wrong equation.
Brumby:
--- Quote from: electrodacus on December 19, 2021, 05:45:16 am ---Do you understand that power you take from the wheel will brake the vehicle ?
--- End quote ---
--- Quote from: electrodacus on December 19, 2021, 05:53:12 pm ---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.
--- End quote ---
Which is it? You can't have it both ways.
Brumby:
--- Quote ---as power is instantaneous contains no time dimension.
--- End quote ---
Now that's just funny ... in a sad, sad way.
You're tripping over yourself.
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