The Effect of Curvature on the Transition from Laminar to Turbulent Boundary Layer

In practically every paper on the performance of the modern high-speed airplane, a statement can be found to the effect that, since great strides have been made in "cleaning up" airplanes aerodynamically, the points which once seemed unimportant have recently become the focus of the designer's attention. This statement is exemplified by the interest shown in the skin-friction drag. It has long been known that for a certain range of Reynolds Numbers the laminar skin-friction coefficient is much smaller than the turbulent skin-friction coefficient for any Reynolds Numbers obtainable in practice. It has also been discovered that the transition from laminar to turbulent boundary layer on the top surface of a wing occurs at a point much farther back on the wing than would be predicted from transition measurements made on a flat plate. The primary cause of this discrepancy was thought to be due to the effect on the boundary layer of the very high curvature of the upper surface of the wing. It was to investigate this point that the present series of tests was instituted.