Comparison between Turbulence Structure in an Open Channel and in a Closed-Duct

Abstract

Structure of turbulence is compared to study dynamic effects of free surface in open channel flows and in duct flows. Two types of turbulence are measured with Laser Doppler Anemometer, one is uniform flow and the other is in wake flow. A visualization technique is also utilized to observe the bursting phenomena. The applicability of the κ-e model is checked in cases of open channel flow and duct one. The following are concluded.(1) A conventional symmetric boundary condition is inapplicable at free surface in open channel flow.(2) The wake decays faster in open channel flow than in duct flow and the structure of wall turbulence recoveres.