In the flow over the upper surface of a wing, a discrepancy between the predicted and actual point of transition from laminar to turbulent boundary layer had been found. This effect may be due to the comparatively small radius of curvature of the upper surface of the wing. The present tests were undertaken to investigate this effect.
As no available channel was suitable for this work, a new channel with two working sections was built. One working section had a wall with a twenty inch radius of curvature and the other section had a flat wall.
Three types of measurements were made: a. Traverses were made with a total head tube to determine the character of the boundary layer at various Reynolds numbers. b. The turbulence distribution in the boundary layer was investigated by means of a hot wire and a vacuum tube amplifier. c. A similar investigation of the mean velocity distribution in the boundary layer was made by means of a hot wire anemometer.
It was found that by using an abbreviated form of the turbulence level traverses, critical Reynolds Numbers of the transitions could be established. These critical Reynolds are plotted as a function of x/r (x being the distance of the transition from the leading edge of the plate; r being radius of curvature of the plate) for both the convex and concave side of the plate.