ORIGINAL: Louis9624
Dimples work on a golf ball because the shape of the ball is not aerodynamicaly efficient. The dimples cause the air to break free of the back side of the ball. this is good because the ball (if it were smooth) is asking the air to follow the surface of the ball all the way around to the back. This pulls back on the ball more than if the air were to break free. A tear drop is an aerodynamically efficient shape. Think of what the air looks like if it were to break free of the back side of a ball. The air breaks free of the ball and gradually closes in to itself some distance behind the ball. This patern looks just like a teardrop.
Hi Louis9624,
Actually, the situation is the opposite of your description. Without dimples, the flow at the surface of the ball tends to be laminar, which allows it to separate, or break free, earlier. This causes high drag, because the area on the back of the ball (behind the line where the flow breaks free) is subjected to low pressure. Dimples cause the flow to be turbulent, which delays the separation, thus reducing the amount of area on the back that is subjects to low pressure.
Low pressure on the back of a moving body increases the drag. Engineers who design airfoils sometimes refer to the rearward portion of the top of the airfoil as the "pressure recovery" region, because on a well-designed airfoil, the pressure will be "recovering", or increasing. The minimum pressue tends to occur near the thickest part of the wing, and failure of the pressure to recover toward the trailing edge results in increased drag.
banktoturn