Regeneration mechanisms of oblique and streamwise vortices in oblique transition

Oblique transition can be triggered by introducing componentwise optimal perturbations into a plane Couette flow. It is shown that in the middle stage of transition, oblique vortices are generated again through transient spanwise velocity energy growth presence developed streamwise streaks. In following stage, independent kinetic energies cross-streamwise velocities intensified due to nonlinear contribution caused amplified together with pressure transport, and increased cross-stream fluctuations strengthen lift-up effect. As result, formed again, streaks even enhanced prior their final breakdown turbulence.