Numerical Analysis of Three-Dimensional Turbulent Structure in Compound Open Channel Flows Using Algebraic Reynolds Stress Model.

Abstract

An investigation of turbulent structure accompanying secondary flow of the second kind in a compound open channel flow is very important in basic hydraulics and river engineering. In this study, a numerical analysis has been performed on fully developed turbulent flow in a compound open channel that is formed by the main channel and flood plain. In calculation, an algebraic stress model was adopted in order to predict Reynolds stresses precisely. Calculated results were compared with the available experimental data. It is pointed out from the experiment that the maximum velocity appears not at the surface, but rather just below it, and the secondary flow, which proceeds toward the free surface from the junction between the main channel and the flood plain, is observed. Moreover, the secondary currents in the main channel proceed downward from the free surface to the bottom wall. As a result of this characteristic phenomenon, the wall shear stress along the bottom wall of the main channel shows the maximum value at the location where the secondary flow arrived at the bottom wall. The present method can predict these characteristic features without great discrepancy. Furthermore, five of the six Reynolds stress components were compared with that of experiment.