Plane analog of spontaneous swirling

A plane analog of the problem of spontaneous swirling–the occurrence of a free transverse flow due to disturbance of the initial plane-parallel flow–is considered. It is shown that in flows with circular streamlines between coaxial cylinders, loss of stability can result in the occurrence of axial flow that is axisymmetric on the average (averaging over the axial coordinate and the azimuthal angle) because of the countergradient transfer of the axial momentum component by Reynolds stresses.