Directorly Downwind Faster than the Wind

[sterlinga]

This one will blow you away.

Is it possible to build a device in which the forward motion turns a wheel that turns a propeller which provides enough wind propulsion to accelerate the device forward faster than the air around it? You would think not, but some investigators appear to have accomplished just that.

http://peswiki.com/index.php/Directory:Directly_Downwind_Faster_than_the_Wind

Plans included.

http://peswiki.com/index.php/Directory:Directly_Downwind_Faster_than_the_Wind#Parts_List

Anyone game to build one quickly and validate?

Sterling

[TechStuf]

Interesting....


Now, how about travelling 64% of current windspeed.


Directly against such wind.


http://www.sciencedaily.com/releases/2008/08/080827104702.htm


I'd bet I can count on one hand the number of years ago that many "lettered men" would have scoffed at such a preposterous proposition.



Regards,



TS

[sterlinga]

I talked with Spork33 today, after posting the above.  He's the person featured in several of the DDFTTW videos.

He is convinced that existing laws of aerodynamics can explain this phenomena, and he is in process of composing a scientific paper for publication in a refereed journal that will detail the mechanics involved.

Bear in mind that you will not be able to just plop this on a flat surface such as a gym floor, give it a good push, and it take off accelerating. The device on the treadmill is analogous to a cart going along with a tail wind of the same speed, and the mechanism makes it go faster than the tail wind.
He said he has been assembling about 20 of these to ship out to a few people (primarily skeptics) from various forums who have asked to replicate the effect. He said that in doing several at once, the parts run around $40.00 USD. He asks another $5.00 for shipping. So at this juncture he's only doing it on a limited basis for scientific advancement. At that price, he's not willing to make very many.

Until the thing is mass produced, it will be fairly expensive. We (PES Network, Inc.) are in discussion with him about entering into an agreement to build and ship kits with adequate mark-up to make it worth our while, e.g. $80 retail. If you are interested (customer side or business side), please send an email to DDWFTTW.kit@pureenergysystems.com .

Because the gadget won't accelerate across a flat surface but will only move forward on a treadmill, the number of people wanting one will probably be fairly low, and the practical aspects perhaps lower yet.

It certainly is a scientific curiosity. Perhaps the principles underlying it may eventually spur some significant aerodynamic advancements in efficiency.

[Mr.Entropy]

It's counter-intuitive, but physics is OK with this device.  This possibility has been discussed at length on Steorn here:

http://www.steorn.com/forum/comments.php?DiscussionID=60059&page=5&Focus=2265999

My contribution:

Given access to two streams with parallel velocities (relative to you) Va and Vb, apply net force Fa to the first and Fb to the second.

your acceleration is determined by the net reaction force -(Fa+Fb):

No matter what those relative velocities are, as long as they're different you can acheive any net acceleration force F without expending energy by setting:

Fa = F*Vb/(Va-Vb)
Fb = F*Va/(Vb-Va)

Calculate power expenditure using P=F.v:

P = Fa*Va + Fb*Vb
= F*Va*Vb/(Va-Vb) + F*Va*Vb/(Vb-Va)
= F*Va*Vb/(Va-Vb) - F*Va*Vb/(Va-Vb)
= 0

Check net reaction force

-(Fa + Fb)
= - ( F*Vb/(Va-Vb) + F*Va/(Vb-Va) )
= - ( F*(Vb-Va)/(Va-Vb) )
= F

[Goat]

@ All

Does this theory mean that we could apply it to a windmill in reverse to get more energy out of the wind ?

Regards,
Paul