4 ms·

I know next to nothing as well, but I think that perfectly laminar flow would be worst case. However if the inside of the tube had divots like a golf ball, the

I know next to nothing as well, but I think that perfectly laminar flow would be worst case. However if the inside of the tube had divots like a golf ball, the slower-moving turbulent vortices would push the faster-moving laminar stream away from the walls, so that the boundary layer doesn't impact the velocity of the central air column nearly as much. Again: "I think..." I'd be happy if someone who knows more would chime in to tell me why I'm wrong. :-)

30thElement 13y ago
Turbulent flow would increase the overall drag in this situation. You're essentially taking energy from the free-flowing middle of the pipe and using it to drag more air along the wall. The reason why turbulence helps a golf ball is because it decreases flow separation http://en.wikipedia.org/wiki/Flow_separation http://en.wikipedia.org/wiki/Flow_separation. Separated flow makes a ridiculous amount of drag, and it's worth the extra skin drag to keep the flow attached.