Large scale motion in turbulent boundary layers

Eddies in the outer flow field of turbulent boundary layers are described. The turbulent regions have a small velocity away from the wall, the nonturbulent zones move towards the wall. The wallward motion increases significantly deep in the valleys between the eddies, indicating that this region is important for mixing and entrainment. Zone averages of tangential Reynolds stress reveal that it occurs mostly near the backs of the eddies. Temperature tagging indicates that the backs consist of a shear layer which maintains its identity into the full turbulent region.