Turbulent spots in plane Poiseuille flow–flow visualization

Abstract

The structure and spreading of turbulent spots in plane Poiseuille flow were studied through flow visualization, in the Reynolds number range 1100 to 2200 (based on centerline velocity and channel half-height). The spot spreading half-angle varied from 6° for the lowest Re to 12° for the highest Re. The propagation velocity of the rear laminar–turbulent interface was slightly above 50% of the centerline velocity. Spotsplitting, as reported in earlier studies, seems to occur only at low Re.