Ejection mechanisms in the sublayer of a turbulent channel

摘要

A possible model for the inception of vorticity ejections in the viscous sublayer of a turbulent rectangular channel is presented. It was shown that this part of the flow is dominated by protruding strong shear layers of z-vorticity, and it was proposed as a mechanism for their maintenance and reproduction which is essentially equivalent to that responsible for the instability of 2-D Tollmien-Schlichting waves. The efforts to isolate computationally a single structure for its study have failed up to now, since it appears that single structures decay in the absence of external forcing, but a convenient computation model was identified in the form of a long and narrow periodic computational box containing at each moment only a few structures. Further work in the identification of better reduced systems is in progress.