If you’re like the majority of teens, you probably don’t think all that much about golf. With Tiger Wood’s rise in popularity, there has certainly been a surge in the number of young golfers, but Canada isn’t exactly at risk of having its future athletes turn in their skates and sticks for golf shoes and a pitching wedge.
While you might not go a round of 18 holes regularly, you probably have picked up a golf ball at the local mini-golf course or while you were accompanying your dad to the driving range to hit a “bucket of balls”.
And when you did, did you ever wonder why on earth golf balls are designed with dimples? Still don’t have the answer? Take it in stride; golfers needed nearly four hundred years to figure that one out.
The short answer is that balls with dimples travel further in the air.
Did you know? The first golf balls dating back to the 16th century, had a smooth surface and were difficult to hit even 100 yards.
Golfers noticed that older balls with a few knicks on the surface would travel further. In response, manufacturers began modifying the surface of the golf ball by adding bumps and then dimples finally in 1905.
The optimal shape, number, and pattern of the dimples are still under debate. The longest shot (or drive) to date with a dimpled ball is 515 yards. By now, you’re still probably asking yourself why it’s the dimples that result in longer drives...
After striking a golf ball, the distance it travels depends on the force applied to it by the air it travels through. One part of this force, drag, can be minimized by adding dimples to the balls.
Air flow over a sphere results in laminar flow however air flow over a sphere with dimples results in turbulent flow. This might sound counterintuitive at first since the dimples would add a small amount of turbulent airflow around the ball. However a critical component to the drag force is not only how air flows at the front and sides of the ball, but at the back.
When a smoothly-surfaced sphere travels through the air, it creates a high pressure area at the front side. The air flows smoothly over the front side but due to friction, separates easily from the ball about halfway across it. Because of this separation of the airflow directly behind the ball, a large turbulent low pressure area, called a wake is created (see above diag. A larger wake results in a larger drag force and a slower ball.
So how does one drive a ball over 500 yards? Well, you’d try to delay the airflow separation from the ball in order to reduce the size of the wake and consequently drag force.
Did You Know? The chances of making two holes-in-one in a round of golf are one in 67 million.
The presence of dimples on a golf ball affects the airflow in such a way that it actually sticks to the ball a little longer and separates later. This slightly turbulent airflow around the dimpled ball is a small trade-off for the greatly reduced wake at the back side of the ball. A smaller wake leads to reduced drag and a faster moving ball.
Dimples also increase lift, keeping the ball in the air longer. And so the question shifts from why do golf balls have dimples to why don’t other aerodynamic shapes like wings use dimples as well! And all this time you thought the dimples were there just to make the golf balls look pretty…
Common myths about the ball dispelled
Aerodynamics of the ball 101 and why wings don't have dimples
Movie: A car with minimal drag in a wind tunnel. Click here
Movie of study on fluid flow around various objects. Pay particular attention to the last two objects, the flat plate vs. the wing.
Make your own wind tunnel. Click Here
Mike is a tennis instructor in Toronto and starting law school at McGill. He also volunteers with the SciHigh program at Mt. Sinai Hospital, which brings cool science experiments to students in Grades 2-12. Interested in seeing glow-in-the-dark mice or carrying out a CSI DNA fingerprinting experiment? Check out SciHigh if you’re in the greater Toronto area!