Golfball Dimples+engine=thinking too much

[SchmidtMotorWorks]

If you want to do something fun with golfing, attach a hammer head to the longest driver shaft you can find.
The claw heads look the funniest.
They are harder to attach than it might at 1st seem.
Be sure to wear padded gloves and that no one is too close by.

If you get a good connection, it is amazing.
But sometimes you can get a shock up the shaft or a very wild ball.

[eikoor]

I was reading about port texturing in the advanced section and it looks like this could be along the same lines as golf ball texturing.
http://hotrodenginetech.com/pipemax-cre ... d-porting/
Port Texturing viewtopic.php?f=15&t=34837

[tt 383]

Just to throw in something I remember.... Trying to imitate a certain type of sharks skin. something about its texture made it more slippery than other sharks. Cant remember what shark, maybe someone else heard this?

[flyingwedge]

Alas, The dreaded bottom feeder of all sharks, "Lawyer Shark".

[jacksoni]

That Mythbusters video was amazing. 11% improvement! Makes you wonder what else it would work on. Would be interesting to experiment on a Semi-Truck. The whole trailer area could be dimpled. 11% improvement in gas milage would be worth it. Wonder if it could be applied to water. Maybe boat hules could be dimpled. Maybe airplanes..... Can go on and on. 11% port improvement would take a 310 CFM port to 344. Hopefully that Mythbusters story will modivate someone to try it on a car with dimpled sheet metal.

And Hey! Instead of talking to your insurance company after your car or plane was totaled by that hail storm, you can say thank goodness, think of the airspeed and mileage improvements.!

[Olefud]

A lot of people confuse turbulent flow with pressure separation. They are two
separate phenomenon. You can have attached flow or separated flow. Separated
flow generally has much more drag. You can also have a laminar or turbulent
boundary layer. A laminar boundary layer generally has less drag but can be
only maintained over slender bodies, like airfoil sections (and then only
sometimes) which unless some sort of active means of boundary layer control
(e.g. suction) is employed. For low drag on a shape that will not sustain
a laminar boundary layer, you want to eliminate separation. As it turns out,
inducing turbulence is a great way to do this. The profile drag of an object
can be spilt into two components:

Cd = Cdf + Cdp

where

Cd = profile drag coefficient
Cdp = pressure drag coefficient due to flow separation
Cdf = skin friction drag coefficient due to surface roughness
in the presence of laminar/turbulent flow

The drag which comprises the Cdf component is caused by shear stress induced
when air molecules collide with the surface of a body. A smooth surface will
have a low Cdf. Also, the Cdf is lower for laminar flow and higher for
turbulent flow. Cdp, on the other hand, is caused by the fore-and-aft pressure
differential created by flow separation. Usually, Cdp is lower for turbulent
flow and higher for laminar flow. In many cases, inducing turbulence will
dramatically decrease the pressure drag component, decreasing the overall drag.
Airplanes use this trick all the time.

Back in the 19th century, when scientists were just beginning to study the
field of aerodynamics, an interesting observation was made with respect to
the drag of a cylinder. Since a cylinder is symmetric front-to-back (and
top-to-bottom), their early theories predicted it should have no drag (or
lift). If you plot the (theoretical) pressure distribution along the
surface of the cylinder (remembering that pressure acts perpendicular to a
surface) and decompose it into horizontal (drag) and vertical (lift)
components, you'll find that the pressure on the front face of the cylinder
(from -90 to +90 degrees) and the pressure on the rear face ( from +90 to
+270 degrees) are equal in magnitude but opposite in direction, exactly
cancelling each other out. Therefore, there should be no drag or lift.

However, if you actually measure the pressure distribution, you'll find
there are considerably lower pressures on the rear face, resulting in
considerable drag. This difference between predicted and observed drag
over a cylinder was particularly bothersome to early aerodynamicists who
termed the phenomenon d'Alembert's paradox. The problem was due to the
fact that the original analysis did not include the effects of skin
friction at the surface of the cylinder. When air flow comes in contact
with a surface, the flow adheres to the surface, altering its dynamics.
Conceptually, aerodynamicists split airflow up into two separate regions,
a region close to the surface where skin friction is important (termed the
boundary layer), and the area outside the boundary layer which is treated
as frictionless. The boundary layer can be further characterized as
either laminar or turbulent. Under laminar conditions, the flow moves
smoothly and follows the general contours of the body. Under turbulent
conditions, the flow becomes chaotic and random.

It turns out that a cylinder is a very high drag shape. At the speeds
we're talking about, a cylinder has a drag coefficient of between 0.4 and
1.17. An efficient shape like a symmetric airfoil (that is aligned
with the airflow, i.e. is at 0 degrees angle of attack) may have a Cd of
0.005 to 0.01. Think about what this means. An airfoil that is 40 to 80
inches tall may have approximately the same drag as a 1 inch diameter
cylinder.

Luckily, there are easy ways of reducing a cylinder's drag. Another thing
the early aerodynamicists noticed was that as you increased the speed of
the air flowing over a cylinder, eventually there was a drastic decrease in
drag. The reason lies in different effects laminar and turbulent boundary
layers have on flow separation. For reasons I won't get into here, laminar
boundary layers separate (detach from the body) much more easily than
turbulent ones. In the case of the cylinder, when the flow is laminar,
the boundary layer separates earlier, resulting in flow that is totally
separated from the rear face and a large wake. As the air flow speed is
increased, the transition from laminar to turbulent takes place on the front
face. The turbulent boundary layer stays attached longer so the separation
point moves rearward, resulting in a smaller wake and lower drag. In the
case of the cylinder, Cd can drop from 0.4 to less than 0.1.

You don't have to rely on high speeds to cause the bondary layer to "trip"
from laminar to turbulent. Small disturbances in the flow path can do the
same thing. A golf ball is a classic example. The dimples on a golf ball
are designed to promote turbulence and thus reduce drag on the ball in
flight. Trip strips are employed on wings for the same reason. If you look
closely, you'll notice that some Indy and F1 helmets have a boundary layer
trip strip to reduce buffeting. It seems odd but promoting turbulence can
reduce buffeting by producing a smaller wake.

Another consequence of skin friction on a cylinder is that you can generate
substantial lift with a spinning cylinder. By spinning a cylinder you can
speed up the flow over the top and slow down flow under the bottom, resulting
in a lift producing pressure differential. In aerodynamics, this is known as
the Magnus effect.

The speed at which a laminar boundary layer becomes turbulent is determined by
the Reynolds number, which is defined as:

Re_x = (Rho * V * X)/Mu

where:

Re_x = Reynolds number at location x (a dimensionless quantity)
Rho = freestream air density
V = freestream flow velocity
x = distance from the leading edge
Mu = freestream viscosity, a physical property of the gas (or liquid)
involved, varies with temperature, at standard conditions mu is
approximately 3.7373x10E-07 slug/(ft*sec) for air.

The location along the body at which the flow transitions from laminar to
turbulent determines the critical Reynolds number. Below this number, the
flow is laminar, above it's turbulent. Since the Reynolds number varies
linearly with the location along the body and with velocity, the faster you
go, the farther forward the transition point moves. At cruising speed on a
typical jet airliner, only a small region near the leading edge may be
laminar. Slow speed gliders with very slender (but still with rounded, blunt,
leading edges) may maintain laminar flow over most of the wing surface but
this is not the case for most practical aircraft. Note that glider wings
are typically designed with very short chord lengths (x distances) to help
promote laminar flow. A laminar boundary layer is desirable when there is no
pressure separation but when there is, a turbulent boundary layer can yield
less drag. Technically speaking, separated flow is not turbulent, even though
it is random and chaotic (and very draggy). Be aware that the laminar and
turbulent concepts apply only to the boundary layer, which may be a few inches
(or less) thick. Beyond the boundary layer, flow is treated as frictionless
(inviscid).

A couple of guys at work (then McDonnell Aircraft, now Boeing), tufted a 1987
Mustang LX from the center of the roof to the taillights. They were trying to
use vortex generators to increase the flow attachment on the rear glass. Vortex
generators are devices which are put in the flow field to intentionally induce
turbulent flow. They are often used on aircraft to re-attach and direct flow
(especially over control surfaces). Their vortex generators were based on
aircraft designs and they used a hang glider airspeed indicator on a pole to
measure the boundary layer thickness across the roof. They made the vortex
generators two inches tall to be conservative (the boundary layer was
approximately one inch thick and a rule of thumb is to make the generators 1.5
time the boundary layer thickness). They didn't see an improvement in coast
down times, but the tufts did appear a little better behaved with the vortex
generators. They believe the turn at the back of the roof may be too sharp to
permit attached flow. They also noted that much of the clean wing flow
appeared to be coming from around the sides of the car.

Dan Jones

This is an excellent discussion. But it relates to a special case, i.e. the slipstream over a car or plane. The simplifying assumptions are appropriate for such use. However, port flow is a different animal.

For instance, the boundary layer is really all that can be influenced when dealing with the slipstream.
The surrounding atmosphere is essentially a constant. In a port the enclosed flow away from the boundary layer is of prime concern and can be laminar or turbulent. In clean flow regions a thick boundary layer somewhat reduces the effective flow cross section. But in areas where the flow tends to detach from the port wall a thicker boundary layer can maintain flow attachment. More viscose gas (hot) and wall texture thicken and better attach the boundary layer.

Various simplifying assumptions such as air being incompressible and inviscid work well in low speed –up to .3Mach- and outside the boundary layer approximations. However, in a port compressibility and wall friction are important factors.

[JoePorting]

That Mythbusters video was amazing. 11% improvement! Makes you wonder what else it would work on. Would be interesting to experiment on a Semi-Truck. The whole trailer area could be dimpled. 11% improvement in gas milage would be worth it. Wonder if it could be applied to water. Maybe boat hules could be dimpled. Maybe airplanes..... Can go on and on. 11% port improvement would take a 310 CFM port to 344. Hopefully that Mythbusters story will modivate someone to try it on a car with dimpled sheet metal.

And Hey! Instead of talking to your insurance company after your car or plane was totaled by that hail storm, you can say thank goodness, think of the airspeed and mileage improvements.!

I was thinking pretty much the same thing. Maybe we should take our ball pin hammer's out and beat the crap out of our vehicle's. All in the name of better mpg.

[fdicrasto]

I remember Jere Stahl talking about running a vinyl roof on a drag race car to help aerodynamics. If you look at the early vinyl roof material used on,say a 69 camaro, almost resembled dimples on a golf ball. Just a comment derived from decades ago history. Phil D.

[JoePorting]

This starts a whole new subject. How big and how deep should these dimples be on a vehicle. The advantage of these dimples appear to be more on the sides of an object then anything else.

[eikoor]

This starts a whole new subject. How big and how deep should these dimples be on a vehicle.

On mythbuster they did them to scale of what they would be if the golf ball was the size of a car.
From page two https://www.youtube.com/watch?v=eR5SlwNf4K0

[JoePorting]

This starts a whole new subject. How big and how deep should these dimples be on a vehicle.

On mythbuster they did them to scale of what they would be if the golf ball was the size of a car.
From page two https://www.youtube.com/watch?v=eR5SlwNf4K0

They should have tested various sizes to find the optimal size.

[srq]

Just saw this HiTech (Tork-link?) intake manifold on EBay. After some more reading I found Jim McFarland had a hand on the design. The dimples on the floor on the plenum is one thing, but very interesting to note is the dimples in the runners too. Anyone have any experience with this manifold or comments. Not trying to hijack the thread but this is the only manifold or induction system I've seen where the dimples where originally cast in.

HiTech Runner.jpg

HiTech Manifold (2).jpg

HiTech Manifold (1).jpg

[just primer]

If you want to do something fun with golfing, attach a hammer head to the longest driver shaft you can find.
The claw heads look the funniest.
They are harder to attach than it might at 1st seem.
Be sure to wear padded gloves and that no one is too close by.

If you get a good connection, it is amazing.
But sometimes you can get a shock up the shaft or a very wild ball.

This is the single best piece of wisdom I have ever read on a tech board.

[JoePorting]

If you want to do something fun with golfing, attach a hammer head to the longest driver shaft you can find.
The claw heads look the funniest.
They are harder to attach than it might at 1st seem.
Be sure to wear padded gloves and that no one is too close by.

If you get a good connection, it is amazing.
But sometimes you can get a shock up the shaft or a very wild ball.

This is the single best piece of wisdom I have ever read on a tech board.

So what happens??? Does the ball go really far, or does the ball just explode??? I'd be afraid the hammer head would detach in mid swing and kill me or anyone around.

[SchmidtMotorWorks]

If you want to do something fun with golfing, attach a hammer head to the longest driver shaft you can find.
The claw heads look the funniest.
They are harder to attach than it might at 1st seem.
Be sure to wear padded gloves and that no one is too close by.

If you get a good connection, it is amazing.
But sometimes you can get a shock up the shaft or a very wild ball.

This is the single best piece of wisdom I have ever read on a tech board.

So what happens??? Does the ball go really far, or does the ball just explode??? I'd be afraid the hammer head would detach in mid swing and kill me or anyone around.

It goes about 30% farther than the best I ever did with a conventional club.
The suprising thing is how high you can hit them with no angle on the face of the head.
Sometimes the ball doesn't spin like it does from a regular club so it will fly in a cork screw or other wierd trajectory.
I have made about 5 of them over the years and it is really difficult to keep the hammer head on the shaft. Steel Devcon or the slow curing JB weld work the best.
If you keep an eye on it, you can tell when it is going to let go.
Every time I bring one to a driving range someone wants to buy it from me. The rusty claw hammer ones get the most laughs.
It's a lot of fun, and trying it gives you some new understanding about how a regular golf club works.