laminar to turbulent

[tspeer]

Just some useless information about laminar flow wings. During WWII the designers where all going for laminar flow for the performance increase in their designs, which was achieved. But what they didn't know at the time until it became evident due to losses in combat, a laminar flow wing had a major drawback, hence the highlight part in Petros quote. If a laminar flow wing took damage from bullets or flak, it would tranistion from laminar to turbulent and the pilot would have trouble flying the plane. Which i guess was a good tatic if the enemy they where trying to shoot down wouldn't stay still for them, they would spray for the outer part of the wing, the targets pilot would lose the ability to dodge and become an easier target to finish off.

Actually, I doubt WWII aircraft obtained much laminar flow at all due to matt camouflage paint applied to the surface, skin joints, and rivets. It's really been the advent of composite light aircraft and sailplane structures that have made it routine to achive large amounts of laminar flow.

Even without laminar flow the NACA 6-series sections have been a success, however. Because skin friction is proportional to velocity squared, the rooftop pressure distribution of the laminar flow sections worked well to lower turbulent profile drag. And the linear pressure recovery pressure distribution of the NACA 6-series airfoils resulted in measured growth of trailing edge separation with angle of attack and a gradual stall. (At low Reynolds numbers, the NACA 6-series airfoils are prone to leading edge stall due to laminar separation triggered by the leading edge suction peak, but this wasn't such a problem at fighter Reynolds numbers.)