Shear Turbulence: Onset and Structure

Figure 1: Reynolds’ 1883 experiment, still operating at the University of Manchester, UK. Water flows down a long pipe and ink is introduced at the pipe centerline. On the right are the original drawings showing the dye filament in laminar flow (a), and the rapid mixing of the dye and water when the Reynolds number is larger than about 2000 in (b). (c) shows details of vortical structures in turbulent flow, visualized with a spark.