Rough cars would go faster
James Wanless
Ed Green
>cf. the golfball
AFAIK the golf ball is rough to translate spinning into lift.
I don't think this decreases surface friction, just the opposite.
Gregory L. Hansen
Some racers of sailboots have tried dimpled hulls, and they seem to work.
--
"'No user-serviceable parts inside.' I'll be the judge of that!"
Ian Stirling
>In article <20010626092632...@ng-ca1.aol.com>,
>Ed Green <null...@aol.com> wrote:
>>From: "James Wanless" ja...@grok.ltd.uk
>>
>>>cf. the golfball
>>
>>AFAIK the golf ball is rough to translate spinning into lift.
>>
>>I don't think this decreases surface friction, just the opposite.
>Some racers of sailboots have tried dimpled hulls, and they seem to work.
Where do the masts go?
--
http://inquisitor.i.am/ | mailto:inqui...@i.am | Ian Stirling.
---------------------------+-------------------------+--------------------------
Windows 2000, software for next millenia. <latin pun alert> - Ian Stirling.
Ed Green
>Gregory L. Hansen <glha...@steel.ucs.indiana.edu> wrote:
>>In article <20010626092632...@ng-ca1.aol.com>,
>>Ed Green <null...@aol.com> wrote:
>>>From: "James Wanless" ja...@grok.ltd.uk
>>>
>>>>cf. the golfball
>>>
>>>AFAIK the golf ball is rough to translate spinning into lift.
>>>
>>>I don't think this decreases surface friction, just the opposite.
>
>>Some racers of sailboots have tried dimpled hulls, and they seem to work.
>
>Where do the masts go?
The same place mast would go otherwise?
I'm interested it the sailboats. I presume the dimples are on
the underwater hull, and are intended to reduce friction at the
boundary layer?
Does a rough surface layer increase drag or create a turbulent
layer which somehow reduces drag?
Johannes Swartling
news:20010627020811...@ng-fz1.aol.com...
Generally a turbulent boundary layer increases drag. It needs more energy to
sustain the increase in shearing in the viscous fluid that comes with the
turbulence. For sailboats, only the area close to the bow will experience
laminar flow. The boundary layer around most of the hull will be turbulent,
and you want to reduce this to a minimum. About the dimpled hulls, afaik it
has not been proved that dimples reduce drag. According to theory they
should not.
Golf balls are a different matter. The dimples increase the skin friction,
but at the same time delay the separation of the boundary layer, which
decreases the pressure drag (the drag induced by the low pressure area
behind the ball). You can say that the dimples trade a small increase in
skin friction for a large decrease in pressure drag. The same does not apply
for sailboats, because the skin friction component of the drag is much
larger than the pressure drag component.
Johannes
Gregory L. Hansen
Ed Green <null...@aol.com> wrote:
>From: Ian Stirling Inqui...@I.am
>
>>Gregory L. Hansen <glha...@steel.ucs.indiana.edu> wrote:
>>>In article <20010626092632...@ng-ca1.aol.com>,
>>>Ed Green <null...@aol.com> wrote:
>>>>From: "James Wanless" ja...@grok.ltd.uk
>>>>
>>>>>cf. the golfball
>>>>
>>>>AFAIK the golf ball is rough to translate spinning into lift.
>>>>
>>>>I don't think this decreases surface friction, just the opposite.
>>
>>>Some racers of sailboots have tried dimpled hulls, and they seem to work.
>>
>>Where do the masts go?
>
>The same place mast would go otherwise?
>
>I'm interested it the sailboats. I presume the dimples are on
>the underwater hull, and are intended to reduce friction at the
>boundary layer?
Yup.
>Does a rough surface layer increase drag or create a turbulent
>layer which somehow reduces drag?
I saw a blurb about it on TV years ago, but never took the time to
look into it. If it's on the web, I can't seem to find the magic set of
search words that will bring the subject up on Google.
Jan Panteltje
Green) wrote in <20010627020811...@ng-fz1.aol.com>:
Wow I wanted to keep out of this due to a lack of practical experience with
this..
But a few weeks ago I did see an interesting program on some German TV channel.
In this that made a plastic surface with what looked like little; bubbles and
glued it on aircraft wings.
That gave them some 6 % less fuel consumptions./
So, anyways, it works in air too.
I you want a practical 'in house' example, look at the video heads in your
VHS.
In the middle there are some grooves.
Without these the tape would stick to it, and a lot of frictions.
With these, some sort of air cushion seems to form, and there is (almost) no
friction.
In that TV program, they also had little flaps on the wing that, if the plane
stalled, came up, and prevented the air form flowing backwards (in opposite
direction, so from the rear of the wing over the top to the front) thus
preventing stalling, and giving control at extremely low speeds.
They got this (some professor) from studying bird wings during landing..
Seemed so simple , just think of it:-)
Also they were experimenting with dolphin and penguin shaped forms for
better aerodynamics.
Well, so flat surfaces (to get back to the subject), well, these 'rough'
patters seem to have their applications.
Regards
Jan
G=EMC^2 Glazier
friction that is the "Rub" Ice on ice is still the most
frictionless stuff. Computers could control the space
between the cars. The only problem with this is air friction is still
there.Well the only way to solve air friction is to have a vacuum up
front. Best regards to all herb PS I forgot to add the cars need a 65
mph push
Ian Stirling
>From: Ian Stirling Inqui...@I.am
>>Gregory L. Hansen <glha...@steel.ucs.indiana.edu> wrote:
>>>In article <20010626092632...@ng-ca1.aol.com>,
>>>Ed Green <null...@aol.com> wrote:
>>>>From: "James Wanless" ja...@grok.ltd.uk
>>>>
>>>>>cf. the golfball
>>>>
>>>>AFAIK the golf ball is rough to translate spinning into lift.
>>>>
>>>>I don't think this decreases surface friction, just the opposite.
>>
>>>Some racers of sailboots have tried dimpled hulls, and they seem to work.
>>
>>Where do the masts go?
>The same place mast would go otherwise?
Wouldn't they get in the way of the wearers legs?
--
http://inquisitor.i.am/ | mailto:inqui...@i.am | Ian Stirling.
---------------------------+-------------------------+--------------------------
If God hadn't intended us to eat animals,
He wouldn't have made them out of MEAT! - John Cleese
Ed Green
>Generally a turbulent boundary layer increases drag. It needs more energy to
>sustain the increase in shearing in the viscous fluid that comes with the
>turbulence. For sailboats, only the area close to the bow will experience
>laminar flow. The boundary layer around most of the hull will be turbulent,
>and you want to reduce this to a minimum. About the dimpled hulls, afaik it
>has not been proved that dimples reduce drag. According to theory they
>should not.
>
>Golf balls are a different matter. The dimples increase the skin friction,
>but at the same time delay the separation of the boundary layer, which
>decreases the pressure drag (the drag induced by the low pressure area
>behind the ball). You can say that the dimples trade a small increase in
>skin friction for a large decrease in pressure drag. The same does not apply
>for sailboats, because the skin friction component of the drag is much
>larger than the pressure drag component.
Ok. Now where does that leave my conjecture that golf balls
are dimpled in order to help convert spin to lift?
Ed Green
>Wow I wanted to keep out of this due to a lack of practical experience with
>this..
>But a few weeks ago I did see an interesting program on some German TV
>channel.
>In this that made a plastic surface with what looked like little; bubbles
>and
>glued it on aircraft wings.
>That gave them some 6 % less fuel consumptions./
>So, anyways, it works in air too.
>I you want a practical 'in house' example, look at the video heads in your
>VHS.
>In the middle there are some grooves.
>Without these the tape would stick to it, and a lot of frictions.
The VCR example at least is looking at the friction of
tape/head vs. tape/air/head, so this really doesn't count.
Uncle Al
Spin to lift is the Magnus effect, as a left-bent gun barrel
shooting to the right. A rough surface would have more bite into
the air and increase the Magnus effect, as with a pitcher using
baseball seams' orientation to control his curve. A
professionally thrown baseball that has a pinkish cast is moving
very differently from one appearing white to the batter.
http://farside.ph.utexas.edu/teaching/329/lectures/node79.html
--
Uncle Al
http://www.mazepath.com/uncleal/
http://www.ultra.net.au/~wisby/uncleal/
(Toxic URLs! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!
Michael Groszek
Ed Green
>Date: 6/27/2001 9:17 AM Eastern Daylight Time
>Message-id: <9hcmch$871$1...@jetsam.uits.indiana.edu>
"dimpled hull" brought up enough links to discussions to show:
(1) there is a widespread idea that dimples 'n turbulence 'n
boundary layers 'n things have something or other to do with
lift 'n drag 'n vicosity 'n stuff.
(2) there is as much confusion and folk knowledge surrounding
this as many topics in aerodynamics and fluid mechanics; which
is to say, considerable.
Ed Green
>Date: 6/28/2001 4:35 AM Eastern Daylight Time
>Message-id: <3B3AEC48...@dingoblue.net.au>
>
>Damn trolls
Intesting sentiment.
Is that active voice, "Damn those trolls", or
interjective, "It's those damn trolls again"?
Damn the trolls, full net ahead!
Ed Green
Herb, I have it.
Ram jet on roof evacuates volume in front of car, lowers
friction, also provides thrust. Duct some exhaust to form
air cushion; almost as good as ice. Braking is problem.
We must accept minor hop from 30k to 300k fatalities/year.
They didn't stop progress because of steam boat explosions,
did they?
Anyway, we can market after-market conversion kits.
Arkane
-silence-
Ed Green
>Look, its a bird, noo, its a plane... Noo! its a bird! ....-explosion-
>
>
>-silence-
Shh. That was an evil propaganda film promulgated by
the internal combustion cartel. It was faked.
G=EMC^2 Glazier
forward. Best all this be happening inside a tunnel. That billion dollar
a mile expressway going into Boston,and Logan airport will cause more
problems than icy roads. You still have to get into the Ted William's
tunnel to go under the harbor to get to the airport.That is the rub. You
can create a lot of friction when cars cram in from 8 lanes to 2
Cars should go into above ground pipes to cross over water. They are
cheaper and faster to build than bridges or tunnel. There is a small
problem in holding the pipe up over a long distance,but that can be
worked out. Best regards herb
spock
> this as many topics in aerodynamics and fluid mechanics; which
> is to say, considerable.
The much confusion about topics in aerodynamics and fluid mechanics is
due mostly to one thing, aeronautic text. People read it as the gospel
yet it is filled with narrow minded, self serving ideology. The
misconception that a spinning ball generates lift may be born from an
inaccurate definition of lift and drag that is typical of aeronautic
text. It may be accurate in the artificial world of aeronautic formula
based text to define lift and drag in relation to the flight path but
not in the real world. Aerodynamic force requires a solid object and a
relative fluid flow. Relative flow does not require a flight path or
the movement of a solid object or the movement of air.
The major use of lift in aeronautics is to resist gravity yet drag is
defined as a resistance force. Drag has been used exclusively for
acceleration by aircraft to circumnavigate the earth yet drag is
defined as a resistance force.
I think that dimples on a non-spinning golf ball do reduce some types
of drag. A turbulent boundary layer can better follow the curvature of
the ball's profile. It travels farther around the ball before
separating, which creates a much smaller wake, and less dynamic drag.
The Magnus effect is defined as the force perpendicular to the forward
motion of a spinning object moving through a fluid or gas, lift is
not. Lift is the movement or tendency to move of a solid object
perpendicular to the relative fluid flow that caused it. If the
relative flow of a solid object were caused solely by its forward
motion through still air lift would be coincidentally perpendicular
to the forward motion.
Most all text give credit for the curve of a spinning golf ball
through the air to the fact that it is spinning. When it comes to
determining this aerodynamic force they ignore totally the fact that
it is spinning. For this to be lift it would have to be determined by
the relative flow created by the balls linear motion through the air.
If the ball curved as it moved through the air solely as a result of
the relative flow caused by its linear movement through air (no
spinning) it would most certainly be lift.
The spin put on the ball has a dramatic effect on its relative flow
caused by its linear movement. It not only causes a large speed
differential in the relative flow on the top and bottom of the ball it
can cause the relative flow to change directions. That's pretty
impressive, especially for something totally ignored when determining
what aerodynamic force caused it. A spinning golf ball generates drag,
a golf ball moving through air generates drag but a ball spinning and
moving through air generates lift?
If you drive a nail through a golf ball and chuck it up in a drill and
pull the trigger the ball will generate an aerodynamic drag force that
opposes the direction of its spin. This drag is all friction drag. Of
course the dimples enhance this effect. Now push the spinning ball
into a surface like a table top. The uneven friction drag on the ball
causes the ball to generate a linear movement. If you were to pinch
the ball between your thumb and index finger in such a way as to cause
equal amounts of drag by each finger no linear force is generated.
This is because the direction of the drag on one side of the ball is
opposite the drag on the other.
I know I know a golf ball hit with a spin does not curve because it's
rubbing a table top. It curves because it rubs the oncoming air a lot
harder than it rubs the ongoing air. The high pressure air in front of
the spinning ball is a characteristic of the dynamic drag caused by
its linear movement through the air. If the ball is hit with enough of
a back spin that causes the surface speed to be greater than the
forward speed the drag on the top of the ball is in the same direction
as its forward flight while the drag on the bottom is much greater it
the opposite direction. I think this asymmetric drag around the ball
can certainly cause a little curve on the ball.