Dynamics of the structures of near wall turbulence

Abstract

Numerical experiments on modified turbulent channels are used to differentiate between possible turbulence generation mechanisms in wall bounded flows. It is shown that a regeneration cycle exists which is local to the near-wall region and does not depend on the outer flow. It involves the formation of velocity streaks from the advection of the mean profile by streamwise vortices, and the generation of the vortices from the instability of the streaks. Interrupting any of those processes leads to laminarisation of the wall. The production of secondary vorticity at the wall is not important in turbulence generation.