Coherent structures in the outer layer of turbulent channel flow

Abstract

Coherent structures in the outer layer of turbulent channel flow are investigated using a visualization technique that utilizes fluorescent dye excited by a sheet of laser light (2 watt argon laser).
The results indicate that large scale ejection in the outer layer is formed by which some streamwise vortices in the near-wall region collect and develop away from the wall, and induces the boil near the water surface. Further studies suggest that the large scale transverse vortex exists in the outer laver. It is not clear of the corelation between the transverse vortex and the streamwise vortices in the near-wall region.