Turbulent spots in plane Couette flow

An experimental study of the coexistence of laminar flow and turbulent spots in plane Couette flow is presented. Coherent structures within turbulent spots near the critical Reynolds number of this subcritical transition are visualized and studied. Characteristic spanwise lengths and streamwise lengths of the structures are measured. In addition, a characteristic fluctuation time is also measured. These lengths are interpreted as the typical width and typical length of streamwise vortex structures observed to be pervasive in these spots. The characteristic fluctuation time measured the combination of the lifetime and the convective motion of these vortices. The turbulence generating mechanism at the laminar-flow-turbulent-flow interface is discussed.