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Mess with your minds: A wind powered craft going faster than a tail wind speed.

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CatalinaWOW:
The automakers have not much interest in the zero wind speed case.  For their purposes a treadmill does not work.  But the zero relative windspeed case is absolutely the point of most interest for this particular problem.

bdunham7:

--- Quote from: CatalinaWOW on September 04, 2021, 07:35:15 pm ---But the zero relative windspeed case is absolutely the point of most interest for this particular problem.

--- End quote ---

I'm not sure I agree that the case where the vehicle speed matches the wind speed is particularly special in terms of operating the vehicle or laying out the equations that govern its operation.  It may be the point where ones initial intuition is challenged, but that's about it.  The operational mode where the wheels power the propeller has to be started well before this point.

bdunham7:

--- Quote from: Brumby on September 04, 2021, 01:04:30 pm ---When such arguments come from those who cannot understand fundamental principles, their process is bound to be flawed and their conclusions will be of no value to anyone but their delusion.

--- End quote ---

I was trying for the longest time to figure out where the problem in understanding was, but at one earlier point, and then again in reply #445 it became apparent that the contentious one had been exposed to and was aware of the basic principles that I was trying to explain, but has chosen to deny that they are true.  Education can't fix that.  I think people have a tendency to try to rationalize other people's irrationality instead of just seeing it for what it is, which is why it took me so long to recognize what was going on.

jeffjmr:
Tally me on the skeptic side.

The sail analogy doesn’t hold water, pardon the pun.  The sailboat sail is not traveling along the same vector as the wind. The propellor on this contraption is.  At ground speed equivalent to wind velocity, there is no longer any wind force being applied to the propellor airfoil, unlike a tacking boat sail. Envision a ball traveling down an incline. Its speed relative to the surface of the incline is faster than its velocity vector towards the ground, and in the absence of friction, its acceleration across the surface of the incline would exceed the acceleration of gravity. Simple vector analysis. Doesn’t apply to this vehicle if it is aligned with the wind.

Carefully edited video showing the wind string indicating forward airspeed could result under a number of different, TEMPORARY scenarios. I never saw a view from directly in front of the vehicle to confirm perfect alignment with the wind.

Not only do I not believe this vehicle’s speed can exceed the wind speed when aligned downwind, I don’t believe it can equal the wind speed due to frictional losses. Believers will have to explain to me what source of energy can accelerate this vehicle above the wind speed once the speed is equivalent, at which point every molecule of air surrounding and in contact with it has 0 relative velocity, and overcoming frictional losses at the same time!

Set this up with anemometers along the path to confirm the constant wind velocity, evidence of perfect alignment with the wind, a long enough course to eliminate the possible effects of wind gusts, and an unedited, continuous video, and you’ll have my attention. Until then, to me this myth is busted.

Jeff




bdunham7:

--- Quote from: jeffjmr on September 05, 2021, 12:28:41 am ---Tally me on the skeptic side.

--- End quote ---

Oh dear!  How much of the thread have you read?  Have you read reply#20 earlier?

You can be skeptical, that's fine.  But before anyone tries to convince you, are you familiar with Newton's laws of motion and are you willing to analyze and consider basic equations of motion?  If not, there's not much point...

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