How about this:
Aerodynamic advantages of bumpy leading edges
After two decades of experimentation, including wind-tunnel testing, professor Frank E. Fish has come to the conclusion that the bumps confer significant aerodynamic advantages… the flippers with bumpy leading edges generate as much as 32 percent less drag and as much as 8 percent more lift than similarly sized flippers with a conventional smooth leading edge…
Scientific American magazine, August 2004.