Abstract
Turbulent boundary layers with main stream having negative or positive velocity shear were formed along a concave solid wall in a wind tunnel. Effects of the shear on the separation of the turbulent boundary layers were investigated in detail. A new direction-sensitive hot-wire anemometer system was developed and used exclusively in the measurement of the velocity in the region with flow reversal. We could obtain an instantaneous velocity with positive or negative sign. The backflow factor which is defined as the fraction of time of flow reversal is a useful quantity in describing the separation region. The plot of the backflow factor clearly indicated that the negative shear-greater velocity near the wall-delays the separation, whereas the positive shear results in an early separation. One of the reasons for this difference might be the less large-scale components in the velocity fluctuations in the boundary layer with negative shear.
