Re: wheel cover turbineOn Dec 22, 2:02 am, Buteo lineatus <Buteo.linea...@gmail,com > wrote:
> On Dec 21, 4:01=EF=BF=BDpm, "gdewi...@gmail,com " <gdewi...@gmail,com > wrot=
e:
>
> > Thanks for the references. I confess I don't know much about the
> > topic.
>
> I think you should study up on boundary layer, Reynolds numbers,
> laminar flow, turbulent flow, Coanda effect, and Tesla boundary layer
> pumps before considering any technological solutions if you're trying
> to set some kind of record with a bicycle.
>
You are of course right but I'm just being curious. Who knows what we
can come up with.
> > To me it seems like a simple flexible extension at the front of the
> > rear wheel cover (like in my illustration) would suffer a downwards
> > force. As this would tend to bend the extension forwards it should
> > create some trust.
>
> Yes, it could create some small amount of thrust, but you have to
> realize that the dynamic pressure of air =3D density ratio X mass of air
> X velocity in ft/sec^2 X cross-sectional area pf the stream
>
> The mass of air is so low and the velocity of the air pumped by the
> tire is very low,
> so the dynamic pressure will be small.
>
> > The boundary layer flow is already squashed into
> > the ground, I don't think it can get much worse application as that.
>
> No, the boundary layer is viscous and stays attached to the rotating
> tire as long as flow in laminar. The larger stream of air outside the
> boundary layer would be moving slower than the air stuck in the
> boundary layer.
>
I didn't word that correctly. The layer closest to the tire would go
almost as fast as the tire. The first one is glued onto the tire,
every next layer goes a bit slower.
I was suggesting to gradually compress the slowest part so that it
goes faster as the medium flow. In stead of having a solid frame
around the wheel it would then be sealed in (some what) moving air.
> > By gradually making the circle smaller the air accelerates around the
> > rim. Like a ballerina pulling her arms in.
>
> You're thinking of angular momentum, and I doubt if the polar moment
> of inertia of a mass of air amounts to anything. You can google up
> "flywheel" at Wikipedia to study that subject.
>
Only the fastest moving layer should remain on the tire. The slower
layers create drag on the ground and cross the air flowing around the
bike.(underneath)
So it would be thrust in exchange for drag.
If it's really worth it we should investigate how to create additional
drag with the wheel.
So far I found this patent from Mr Barefoot, not entirely sure how it
works but the toy makes lift from spin and the patent makes
interesting citations from sailing and flying machines.
http :// www .google,com /patents?vid=3DUSPAT4051622
> > Would that make the boundary layer drag go faster as the tire?
>
> > If so, would it create any note-worthy trust?
>
> I doubt it. The fastest dustbin-faired downhill bicycle I ever saw
> only went about 130 mph. With 32-inch diameter wheels, the RPM at 130
> is only 1365 RPM.
>
> But, if you study Tesla boundary layer pumps you can get some idea of
> how fast the disks have turn to move an appreciable amount of air.
I started thinking about this when I saw the wind coming from the rear
wheel of a bicycle riding in front of me.
The owner had covered the back seat in aluminum foil (as a joke) but
the foil was blowing upwards from the tire. He wasn't going that fast
and there was at least 15 cm of space between the wheel and the
spontaneously self assembled measurement apparatus. :-)
As that was just a slow moving bike I became curious how much wind
motor cycles blow into the ground. The tire isn't quite flat like a
Tesla turbine.
Still that doesn't mean there is note worthy action to be exploited.
I'm just curious :-)
http :// gabydewilde.googlepages,com /wheel-cover-turbine
gabydewilde - wheel cover turbine