The characteristics of coherent structures in the near-wall region of turburent open channel flow changing with Reynolds number are investigated using flow visualization. The flow visualization were done in the streamwise view using fluorescent dye illuminated by a sheet of Argon laser light.
Some new aspects of the characteristics are inffered from this experiment. The ratio of the inner length to water depth in turbulent open channel flow is governed by Reynolds number. The greatest number of streamwise vortices are formed in the buffer layer. Futher non dimensional vertical and spanwise scale of streamwise vortices are constant changing Reynolds number from 2000 to 7000.