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Golfball Dimples+engine=thinking too much

General engine tech -- Drag Racing to Circle Track

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Golfball Dimples+engine=thinking too much

Post by Smokumxxx » Sat Apr 06, 2013 1:25 am

I was just messing around with some engine Sim software and a thought came to mind. I know the Golfball dimples increase air flow, what about using that Tech on the intake curves Alowing the velocity to not slow down? Comments guys??? :idea:

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Re: Golfball Dimples+engine=thinking too much

Post by ProPower engines » Sat Apr 06, 2013 2:14 am

Dimples where used back in the day before cylinder head technology had improved to the point that they hurt
performance.
My guess is that it was also done on intakes. Post and intake porters have got better pasrts to work with in the last 15years
and that said its the main reason its not really done any more,
Its not to say its not worth trying but depending on the intake it may hurt flow rather then help it.

Are you using some 80's style parts.
What intake are you working with?
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Re: Golfball Dimples+engine=thinking too much

Post by JoePorting » Sat Apr 06, 2013 2:55 am

If anybody on here actually plays golf, they'd know that golf ball dimples actual grab the air. If you cut across a golf ball in one direction, the ball will spin off to the right (slice). If you cut across the ball in the other direction, the ball will spin off to the left (hook). If you hit a one wood just right, you'll give a top spin to the ball which will cause it to rise as it progressives forward. Therefore, the golf dimples grab the air and force the ball in whatever direction it is spinning. Based on that, I'd assume if you put dimples in a port, the air would slow down, not speed up. Maybe what the dimples or a course surface is actually doing in a port is causing the air to slow down so that it can turn easier. ??? I find the subject interesting, but I think people are making wrong conclusions about what is actually happening.
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Re: Golfball Dimples+engine=thinking too much

Post by racear2865 » Sat Apr 06, 2013 9:49 am

Golf ball technology is a study in itself. In the early years, golf balls were made smooth and during early playing, many players noticed that scuffed up golf balls traveled further than new smooth balls. So every one started scuffing up their golf balls to get distance. this is where dimples came into existence--too get more distance. Golf balls are a subject you may want to Google to learn as it is a study of flow around an object. There are two types of flow around an object--laminar flow and turbulent flow. Golf ball has turbulent flow. Upon launch, a golf ball has slightly more drag BUT it has more adhesion and as a result it has less separation. The dimples turbulate the BOUNDARY layer. I bet you have heard of the boundary layer in heads and intakes and yes that was why you saw people put dimples in heads. Joe, there is a reason for your science. The way you shape the dimples and how many dimples determines how to change the characteristic movement of the ball. Have you ever wondered why no one has ever played with dimple technology on heads to the point that we get the the TYPE of flow that we want. Man I couldnt help myself on telling you about golf balls. I aint worth a crap at the game but I surely love doing something else that I aint good at eder. I guess I aint good at building motors either.. Ok back to heads. Google golf ball technology and it may start you to thinking, again. on cylinder heads. You would mostly definitely need a wet flow bench to make it easier but I feel it is worhty of thought.
reed

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Re: Golfball Dimples+engine=thinking too much

Post by vincenelson » Sat Apr 06, 2013 10:43 am

I remember AFR playing around with dimples for a while in the mid 80's .....but that was before all the good heads started being manifactured.

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Re: Golfball Dimples+engine=thinking too much

Post by bigjoe1 » Sat Apr 06, 2013 10:59 am

Some of my best heads still have the dimples in the chamber, even in 2013. I worked with Ken Sperling ( AFR ) way back when he showed me what to do. I saw a 15 or 20 HP gain on my 750 HP SB Chevy way back in the early 1990 time period. It does not cost anything, if you know what to do, it is free.


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Re: Golfball Dimples+engine=thinking too much

Post by BrazilianZ28Camaro » Sat Apr 06, 2013 11:06 am

bigjoe1 wrote:Some of my best heads still have the dimples in the chamber, even in 2013. I worked with Ken Sperling ( AFR ) way back when he showed me what to do. I saw a 15 or 20 HP gain on my 750 HP SB Chevy way back in the early 1990 time period. It does not cost anything, if you know what to do, it is free.


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Thats amazing Bigjoe!

You simply did the dimples with a center punch on all the chamber surface?
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Re: Golfball Dimples+engine=thinking too much

Post by Kevin Johnson » Sat Apr 06, 2013 11:10 am

Study the lotus leaf.

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Re: Golfball Dimples+engine=thinking too much

Post by ALKYAL » Sat Apr 06, 2013 11:19 am

I had a set of AFR ported BBC alum heads in the late 80 s. They had the "HURRICANE" chamber option. the engine/alky, ran very well and showed a very good burn pattern upon dis-assy. I can remember the spark plug side of the chamber being layed-out with scribe lines upon recipt of the heads. I did measure and note the pattern. The actual marks were made with a prick punch type tool and were SHARP at the top of the divit. I made NO effort to smooth the tops, as I figured this increased the tubulance. I ran the same amount of advance as always, Didnt have equpt. then to see if less timing was better. Al
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Re: Golfball Dimples+engine=thinking too much

Post by eikoor » Sat Apr 06, 2013 11:26 am

If what they show here is true then it looks like something that would help the short turn and possibly the entire port.
http://www.youtube.com/watch?v=LvVuuaqCC7A

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Re: Golfball Dimples+engine=thinking too much

Post by BrazilianZ28Camaro » Sat Apr 06, 2013 11:57 am

eikoor wrote:If what they show here is true then it looks like something that would help the short turn and possibly the entire port.
http://www.youtube.com/watch?v=LvVuuaqCC7A

But the short turn should have the flow atached to it right?
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https://www.youtube.com/watch?v=99p13UK ... ture=share

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Re: Golfball Dimples+engine=thinking too much

Post by BrazilianZ28Camaro » Sat Apr 06, 2013 11:59 am

I'd love to see that same golf ball simulation with 300ft/s of air velocity, because I do believe the air behavior is greatelly dependant of air speed. :-k
'71 Z28 street strip car
Pump gas All motor SBC 427
3308 lbs-29x10.5 Hoosiers
NEW BEST ET
1.40 60' / 4.05 330' / 6.32@111.25mph

https://www.youtube.com/watch?v=99p13UK ... ture=share

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Re: Golfball Dimples+engine=thinking too much

Post by SchmidtMotorWorks » Sat Apr 06, 2013 12:17 pm

Way back in 1998 I did some work for a golf ball manufacturing company in San Diego. They wanted to be able to make the molds to produce dimple shapes within 0.0002". They had 2 full-time aerodynamics engineers on staff designing dimples.
Dimples do reduce drag by filling the space behind the ball.
http://www.schmidtmotorworks.com Prototypes, Tooling, Molds.

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Re: Golfball Dimples+engine=thinking too much

Post by Daniel Jones » Sat Apr 06, 2013 12:50 pm

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

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Re: Golfball Dimples+engine=thinking too much

Post by Erland Cox » Sat Apr 06, 2013 1:15 pm

Very well written Dan. I like to see much more like that .

Erland

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