Numerical Study on Fully-Developed Turbulent Flow in Vegetated and Non-Vegetated Zones in a Cross-Section of Open Channel

Abstract

Part of cross section of streams is often vegetated, and faster flow over non-vegetated zone and retarded flow in vegetated zone neighbor with each other. In such situations, horizontal mixing of momentum dominates though the flow is three-dimensional. In this paper, numerical 3D calculation of such flows is attempted based on an algebraic stress model. One of the characteristics of the, present calculation is that the form drag is taken into account in the vegetation zone. The calculated results explain the flow structure surveyed by flume measurements, and particularly depth-averaged properties can be well described. The model-parameter which contributes the amplitude of cellular motion near the boundary of two regions is favorably neglected, which may imply that the cellular motion no longer dominates in the flow with vegetated zone.