Ejection mechanisms in the sublayer of a turbulent channel

The structure of the vorticity field in the viscous wall layer of a turbulent channel is studied by examining the results of a fully resolved direct numerical simulation. It is shown that this region is dominated by intense three‐dimensional shear layers in which the dominant vorticity component is spanwise. The advection and reproduction processes of these structures are examined and shown to be consistent with the classical generation mechanism for two‐dimensional Tollmien–Schlichting waves. This process is fundamentally different from the usually accepted mechanism involving hairpin vortices.