Science Questions

Is the use of bumps on turbine blades similar to putting dimples on golfballs?

Is the use of bumps on turbine blades similar to the dimples on golf balls? Is it a similar function that’s going on? Silverwing Benoir, SecondLife

We posed this question to Professor Frank Fish from Westchester University...

It has similarities, but there are distinct differences.  What a golf ball does by having the dimples on it is to turbulise the air over the surface of the golf ball.  So normally air will move in nice, even layers over a surface, and that’s what we call laminar flow.  The trouble with laminar flow is it’s not very stable.  You can't maintain it at very high speeds or with very large entities.  And so, by having the dimples that turbulises the flow over the golf ball, which means that the flow will continue over more of the surface, and as a result, there’s less resistance, and the ball travels further when it’s hit.  With the tubercles, or these bumps along the leading edge, what they do is they do create a different flow regime, but not necessarily turbulising the flow.  What they do is they produce large swirling masses of flow, what are called vortices.  And these vortices interact over parts of the wing to actually help to speed up the flow over say, the bump itself and keep that flow attached over the entire surface of the wing, so that you don't stall out.

February 2010