  To produce a vortex, a torque must be applied to the fluid. In viscous
fluids, the torques that produce turbulent vortices result from the loss of
symmetry of the stress tensor, once the viscous friction exceeds the shear
stress resistance of the fluid. In wall-bounded flows, in particular, the
turbulent vortices form in a thin layer of fluid adjacent to the wall,
practically coinciding with the so-called viscous sublayer, where the viscous
friction reaches the largest values. The present paper determines a vortex
structure for this sublayer, consistent with the well-known linearity of the
diagram of the mean streamwise velocity of this region. The analysis enables us
to calculate the diameter, angular velocity, and interaxis of the vortices in
the viscous sublayer in steady-state conditions. The lifting force that makes
the vortices migrate from the wall towards the mainstream flow is determined,
and the crucial role played by gyroscopic precession in the reorientation of
the vortex axis is discussed.
