Why don't wings have dimples?

"Capt. Geoffrey Thorpe" The Sea Hawk at wow way d0t com wrote in message
...

wrote in message
ups.com...

Capt. Geoffrey Thorpe wrote:

...
So maybe you could use dimples on fairings, fuselage or struts,
especially
if the struts are circular tubing, eh?

--

FF

Could be. Somewhere or another I saw some wind tunnel data on golf balls
that nicely showed how the flow remained attached further around the back
side (no spin was involved - just a reduction in the wake). But you would
have to find out what the range of Reynolds number this works for...

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.


I've seen a video of that, but don't recall where. However, I believe that
you have it backward--the flow detaches earlier (from the non-spinning golf
ball) and reduces the drag.

I am not quite sure how that might relate to wings and propellers; but I
suspect that they (wings and props) are two radically different, and
possibly opposite, phenomena.

Peter

"Peter Dohm" wrote in message
...

I've seen a video of that, but don't recall where. However, I believe
that
you have it backward--the flow detaches earlier (from the non-spinning
golf
ball) and reduces the drag.

I am not quite sure how that might relate to wings and propellers; but I
suspect that they (wings and props) are two radically different, and
possibly opposite, phenomena.

Peter

Ok, now you've done it. You are going to make me look this up...

http://www.fi.edu/wright/again/wings...r/golf-01.html
description and a drawing...

http://www.aerospaceweb.org/question...cs/q0215.shtml
with a little math and some graphs

http://turb.seas.ucla.edu/~jkim/sciam/0197moinbox3.html
plots drag as a function of Reynolds number for a golf ball and a smooth
sphere - a good starting pont if you want to dimple your nosegear strut to
reduce drag - just figure you your own Reynolds number...

That's enough. Didn't find the picture I was looking for. But I see
references to both the reduction in wake and Magnus effect that converts the
spin into lift. Apparently both contribute to the increase in range. (and
the drawings I've seen show the boundry layer staying attached longer as I
thought.)

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

"Capt. Geoffrey Thorpe" The Sea Hawk at wow way d0t com wrote in message
...
"Peter Dohm" wrote in message
...

I've seen a video of that, but don't recall where. However, I believe
that
you have it backward--the flow detaches earlier (from the non-spinning
golf
ball) and reduces the drag.

I am not quite sure how that might relate to wings and propellers; but I
suspect that they (wings and props) are two radically different, and
possibly opposite, phenomena.

Peter

Ok, now you've done it. You are going to make me look this up...


http://www.fi.edu/wright/again/wings...r/golf-01.html
description and a drawing...

http://www.aerospaceweb.org/question...cs/q0215.shtml
with a little math and some graphs

http://turb.seas.ucla.edu/~jkim/sciam/0197moinbox3.html
plots drag as a function of Reynolds number for a golf ball and a smooth
sphere - a good starting pont if you want to dimple your nosegear strut to
reduce drag - just figure you your own Reynolds number...

That's enough. Didn't find the picture I was looking for. But I see
references to both the reduction in wake and Magnus effect that converts
the
spin into lift. Apparently both contribute to the increase in range. (and
the drawings I've seen show the boundry layer staying attached longer as I
thought.)

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.


It looks like I misremembered as well, since all of them show the flow
remaining attached further around the dimpled ball. However, the
explanation of top spin under "How a Golf Ball Produces Lift" in the first
link does introduce a problem, since the result of Magnus Effect seems
(intuitively) reversed from the separation issue. The author's description
of the direction of lift is consistent with the description under "Hook and
Slice" which I know (regrettably) to be absolutely true.

So all of the articles agree on a couple of points, and appear to have
obtained the same photo for publication. However the Magnus Effect, while
well known to be true to every golfer (usually in a detrimental way) appears
to be backward in some sense.

For the moment, this appears to have moved from my Solved Problems List to
my Unsolved Problems List.

Peter

Peter Dohm wrote:

"Capt. Geoffrey Thorpe" The Sea Hawk at wow way d0t com wrote in message
...

"Peter Dohm" wrote in message
. ..

I've seen a video of that, but don't recall where. However, I believe
that
you have it backward--the flow detaches earlier (from the non-spinning
golf
ball) and reduces the drag.

I am not quite sure how that might relate to wings and propellers; but I
suspect that they (wings and props) are two radically different, and
possibly opposite, phenomena.

Peter

Ok, now you've done it. You are going to make me look this up...



http://www.fi.edu/wright/again/wings...r/golf-01.html

description and a drawing...

http://www.aerospaceweb.org/question...cs/q0215.shtml
with a little math and some graphs

http://turb.seas.ucla.edu/~jkim/sciam/0197moinbox3.html
plots drag as a function of Reynolds number for a golf ball and a smooth
sphere - a good starting pont if you want to dimple your nosegear strut to
reduce drag - just figure you your own Reynolds number...

That's enough. Didn't find the picture I was looking for. But I see
references to both the reduction in wake and Magnus effect that converts

the

spin into lift. Apparently both contribute to the increase in range. (and
the drawings I've seen show the boundry layer staying attached longer as I
thought.)

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.



It looks like I misremembered as well, since all of them show the flow
remaining attached further around the dimpled ball. However, the
explanation of top spin under "How a Golf Ball Produces Lift" in the first
link does introduce a problem, since the result of Magnus Effect seems
(intuitively) reversed from the separation issue. The author's description
of the direction of lift is consistent with the description under "Hook and
Slice" which I know (regrettably) to be absolutely true.

So all of the articles agree on a couple of points, and appear to have
obtained the same photo for publication. However the Magnus Effect, while
well known to be true to every golfer (usually in a detrimental way) appears
to be backward in some sense.

For the moment, this appears to have moved from my Solved Problems List to
my Unsolved Problems List.

Peter



Will forward your Unsolved Problem to Mary Shafer (NASA).

Maybe the Lift Demons have a clue?

"Peter Dohm" wrote in message
news

"Capt. Geoffrey Thorpe" The Sea Hawk at wow way d0t com wrote in message
...
http://www.fi.edu/wright/again/wings...r/golf-01.html
description and a drawing...

...
So all of the articles agree on a couple of points, and appear to have
obtained the same photo for publication. However the Magnus Effect, while
well known to be true to every golfer (usually in a detrimental way)
appears
to be backward in some sense.

For the moment, this appears to have moved from my Solved Problems List to
my Unsolved Problems List.

Peter

Dunno, looked OK to me. If the ball is flying across your screen from right
to left think of an airfoil moving from right to left, low pressure on top,
circulation has to be clockwise in this view to accelrate the flow across
the top and decelerate it around the bottom -

"1877, British scientist P.G. Tait learned that a ball, driven with a spin
about a horizontal axis with the top of the ball coming toward the golfer
produces a lifting force. This type of spin is know as a backspin."

That would be clockwise in a view where the ball is moving from right to
left...

Note: Have you ever seen a drawing or wind tunnel picture where the object
was traveling from left to right or the air was moving from right to left?
How did we become so consistant?

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

"Capt. Geoffrey Thorpe" The Sea Hawk at wow way d0t com wrote in message
news:HvednScQQ67J5A3ZnZ2dnUVZ_oGdnZ2d@wideopenwest .com...


"Peter Dohm" wrote in message
news

"Capt. Geoffrey Thorpe" The Sea Hawk at wow way d0t com wrote in
message
...
http://www.fi.edu/wright/again/wings...r/golf-01.html
description and a drawing...

...
So all of the articles agree on a couple of points, and appear to have
obtained the same photo for publication. However the Magnus Effect,
while
well known to be true to every golfer (usually in a detrimental way)
appears
to be backward in some sense.

For the moment, this appears to have moved from my Solved Problems List
to
my Unsolved Problems List.

Peter

Dunno, looked OK to me. If the ball is flying across your screen from
right to left think of an airfoil moving from right to left, low pressure
on top, circulation has to be clockwise in this view to accelrate the flow
across the top and decelerate it around the bottom -

"1877, British scientist P.G. Tait learned that a ball, driven with a spin
about a horizontal axis with the top of the ball coming toward the golfer
produces a lifting force. This type of spin is know as a backspin."

That would be clockwise in a view where the ball is moving from right to
left...

Note: Have you ever seen a drawing or wind tunnel picture where the object
was traveling from left to right or the air was moving from right to left?
How did we become so consistant?



oops, didn't read far enough:

"The dimples also help in the generation of lift. By keeping the flow
attached, the dimples help promote an asymmetry of the flow in the wake.
This asymmetry can be seen in Figure 5. In this figure, the smoke shows the
flow pattern about a spinning golf ball. The flow is moving from left to
right and the ball is spinning in the counter-clockwise direction. The wake
is being deflected downwards. This downward deflection of the wake implies
that a lifting force is being applied to the golf ball."

This is inconsistant with my thinking and inconsistant with the top of the
ball moving towards the golfer as described earlier on the page...

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

Capt. Geoffrey Thorpe wrote:


oops, didn't read far enough:

"The dimples also help in the generation of lift. By keeping the flow
attached, the dimples help promote an asymmetry of the flow in the wake.
This asymmetry can be seen in Figure 5. In this figure, the smoke shows the
flow pattern about a spinning golf ball. The flow is moving from left to
right and the ball is spinning in the counter-clockwise direction. The wake
is being deflected downwards. This downward deflection of the wake implies
that a lifting force is being applied to the golf ball."

This is inconsistant with my thinking and inconsistant with the top of the
ball moving towards the golfer as described earlier on the page...

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.



Somebody (NASA/University?) built a "tube wing" thing once.

The wing was a large dia tube mounted - well - like a wing.

The tube rotated - "leading edge" up to create a circulation effect.
(as the aircraft moved forward - no hovering allowed this area)

It worked, but drag was a real drag...


Just a suspicion that the lift vector of a golf ball changes in flight.

Any flight path deviation due to rotational lift vectors would be strongest
early in the flight, but decrease as velocity decays below Re(crit)(combined
forward motion plus rotational effects) and the path becomes more ballistic.

Also didja catch the "Happy Non-Hooker" ball?


Richard

cavelamb wrote:

...

Somebody (NASA/University?) built a "tube wing" thing once.

The wing was a large dia tube mounted - well - like a wing.

The tube rotated - "leading edge" up to create a circulation effect.
(as the aircraft moved forward - no hovering allowed this area)

It worked, but drag was a real drag...

Obviously they needed dimples on it...



A few years back I saw a TV show about a sailboat using he same
effect. It had big rotating column on the bow. I think the rotation
rate was adjusted to the windspeed and direction to keep the
thrust aligned astern.

--

FF

"Capt. Geoffrey Thorpe" The Sea Hawk at wow way d0t com wrote in message
news:LbydnT9K86ux5w3ZnZ2dnUVZ_tOdnZ2d@wideopenwest .com...
"Capt. Geoffrey Thorpe" The Sea Hawk at wow way d0t com wrote in message
news:HvednScQQ67J5A3ZnZ2dnUVZ_oGdnZ2d@wideopenwest .com...


"Peter Dohm" wrote in message
news

"Capt. Geoffrey Thorpe" The Sea Hawk at wow way d0t com wrote in
message
...

http://www.fi.edu/wright/again/wings...r/golf-01.html
description and a drawing...

...
So all of the articles agree on a couple of points, and appear to have
obtained the same photo for publication. However the Magnus Effect,
while
well known to be true to every golfer (usually in a detrimental way)
appears
to be backward in some sense.

For the moment, this appears to have moved from my Solved Problems List
to
my Unsolved Problems List.

Peter

Dunno, looked OK to me. If the ball is flying across your screen from
right to left think of an airfoil moving from right to left, low
pressure
on top, circulation has to be clockwise in this view to accelrate the
flow
across the top and decelerate it around the bottom -

"1877, British scientist P.G. Tait learned that a ball, driven with a
spin
about a horizontal axis with the top of the ball coming toward the
golfer
produces a lifting force. This type of spin is know as a backspin."

That would be clockwise in a view where the ball is moving from right to
left...

Note: Have you ever seen a drawing or wind tunnel picture where the
object
was traveling from left to right or the air was moving from right to
left?
How did we become so consistant?



oops, didn't read far enough:

"The dimples also help in the generation of lift. By keeping the flow
attached, the dimples help promote an asymmetry of the flow in the wake.
This asymmetry can be seen in Figure 5. In this figure, the smoke shows
the
flow pattern about a spinning golf ball. The flow is moving from left to
right and the ball is spinning in the counter-clockwise direction. The
wake
is being deflected downwards. This downward deflection of the wake implies
that a lifting force is being applied to the golf ball."

This is inconsistant with my thinking and inconsistant with the top of the
ball moving towards the golfer as described earlier on the page...

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.


I thought that I would be able to find a web site with the wind tunnel video
that I'm sure I've seen of this; however, for this evening at least, I must
admit that I have indeed struck out.

This is a subject that I would really like to understand; although I would
settle for a couple of good practical rules of thumb. If I happen to find
anything, I'll be sure to post it--or a link as appropriate.

Peter

Hopefully these links will help you somehow.

http://www.lessonexchange.net/Mech_E...rodynamics.pdf

http://library.thinkquest.org/10556/.../topics/22.htm

http://www.geocities.com/k_achutarao/MAGNUS/magnus.html

http://www.interactiveinstruments.co...CH%20PAPER.htm

http://mercury.pr.erau.edu/~hayasd87.../2004-06-23-W/

JP

"Peter Dohm" wrote in
t...

I thought that I would be able to find a web site with the wind tunnel
video
that I'm sure I've seen of this; however, for this evening at least, I
must
admit that I have indeed struck out.

This is a subject that I would really like to understand; although I would
settle for a couple of good practical rules of thumb. If I happen to find
anything, I'll be sure to post it--or a link as appropriate.

Peter