Visualization of Large-scale Coherent Structure in an Turbulent Open Channel Flow

Abstract

Large-scale coherent structure in an turbulent channel flow are visualized by three methods. One is plan view methods used of fluorescent dye tracer excited by ultraviolet lamps. And the others are plan and streamwise sectional view methods that utilize fluorescent dye excited by a sheet of laser light. By synthesizing each results of their visualization methods, a few features of large- scale coherent structure are cleared. Large-scale coherent structure are formed by concentrating of wall streamwise vortices. And large- scale coherent structure have branch vortical structures at both sides.