In the game of golf, the pros tell you to keep your eye on the ball. So you remember to do that when the ball is on the tee. After you swing, it doesn't take much remembering. Natural suspense keeps your eye on the ball as it's lofting through the air. And no matter how much English or prayer you may try to put on it then, the ball is headed where you sent it.

Gosh, how it sails. It may slice in a graceful arc to land in the rough or fall short into the lake. Perhaps worst of all, it could beat astronomical odds and make a hole in one, and then you'd have to buy drinks for everybody in the clubhouse.

No matter where the ball goes, however, there's an almost gravity-defying handsomeness about its flight. That's due to those other folks, who have their eye on the ball even before they make it. They look at the various features—all those dimples, for instance—to see just how they help or hinder the ball.

Kevin Shannon, a research scientist at Spalding Sports Worldwide in Chicopee, Mass., said that his company uses computational fluid dynamics software to determine early in the design cycle whether a golf ball will fly. The software, CFdesign from Blue Ridge Numerics of Charlottesville, Va., helps reduce the number of physical prototypes engineers need to test. Instead, they can use CFD to simulate the ball's velocity and speed while it is still being designed.

Shannon said that Spalding initially used the program to simulate a digital ball in flight. The ball had already been designed, though not produced. Today, Spalding uses the technology at an earlier stage of design to determine which new designs would make good balls.

Spalding Sports Worldwide uses CFD analysis to predict airflow around golf balls.

While it might appear to be simple in shape, a golf ball is a very complex model, Shannon said. All 300 to 500 dimples on the ball must be defined as individual features within a computer-aided design model.

According to Shannon, the dimples cause turbulence in the boundary layer, the air nearest the surface of the ball. The turbulence induces some drag, but in the long run it reduces the total drag in flight so the ball will travel farther.

That's why, before golf balls had dimples, players preferred those with nicks, cuts, and dents.

Before the company began using CFD, engineers would design the ball and send the design to the tooling room, where technicians would create a cavity. The balls would then be molded from the cavity and flight tested to evaluate how the new design performed, Shannon said.

"It wasn't until that point that we'd even know whether new geometry had any merit or not," he said.

"The one wild card is that we have a ball that is spinning and that changes things," Shannon said of the CAD model. The CAD program can't predict airflow through the dimples. But the CFD program does.

Spalding used the CFD application to help design two new balls, the Strata and the Top Flight XL3000. It allowed engineers to visualize airflow through the dimples, to quantify how much better the new designs performed compared to the previous designs, and to weed out bad designs earlier in the design cycle.

Bad design information is still useful, Shannon said. "A failure can actually help us to move in the proper direction, so that we can focus our designs based on what we know are good dimple designs," he said.

By putting the new dimple designs through CFD simulations first, before tooling, the company cut several physical prototypes out of the development process, which saves money in development costs and cuts time to market.

"Now we can screen new dimple designs and get a good feeling for whether they have merit or not while they're still on the drawing board," Shannon said. "CFD is the step that we use before we go to the tooling room, which has helped us to cut several prototypes out of the design process."

home | features | weekly news | marketplace | departments | about ME | back issues | ASME | site search

© 2003 by The American Society of Mechanical Engineers