How to Turn Laminar Flow into Eddies

In this talk, we present a mechanism by which a laminar flow containing a weak pair of streamwise vortices generates new cross-stream vortices. This process works by transporting and concentrating wall-bounded vorticity from the laminar background flow into thin sheets. These sheets subsequently undergo a Kelvin-Helmholtz instability to create vortex filaments. Moreover, we conjecture that these vortices can induce the creation of more vortices, initiating a self-sustaining transition to turbulence. The underlying mechanism and critical conditions for this process are identified through a combination of experimental, numerical, and theoretical analyses.