Numerical Analysis of Velocity and Boundary Shear Stress Distribution in a Meandering Channel

Abstract

Rivers are one of the most important sources of water, which are constantly changing. It is vital to recognize and perceive components which influence the conduct and the morphology of the waterway or channel, for example, the type of the Meander River, conduit geometry, the state of the channel bed and the profile of the channel. In particular, these factors are valuable for meandering channel which has unsteady flow patterns. The geometry selected for this study is that of a meandering channel. In this research work the parameters, water depth and incoming discharge of the main channel were gradually varied. This aggregate subject speaks to the variety of speed profile along the width and profundity of the channel has been systematically broken down at curve peak along a wander way of a crooked channel of 60° crossover edge. Riverway considered is starting with one curve pinnacle then onto the next twist zenith, which changes its course at the crossover. Bend apex is the position of maximum curvature and crossover represents the section at which the sinuous channel changes its sign. Flow structure in meandering channel is more complex than straight channels due to the 3-Dimentional nature of the flow. The constant variation of channel geometry along the water course associated with secondary currents makes the depth averaged velocity computation difficult. The present experimental meandering channel is wide (aspect ratio = b/h > 5) and with a sinuosity of 2.04. Then the numerical method is applied to calculate water surface elevation in a meandering channel configuration, the output of calculations show good agreement with the experimental data. As statistical hydraulic models can significantly reduce costs associated with the experimental models, an effort has been made through the present investigation to establish the different flow characteristics of a meandering channel such as longitudinal velocity distribution, depth averaged velocity distribution. As a complementary study of the experimental research undertaken in this work, three numerical hydrodynamic tools viz.three-dimensional CFD model (ANSYS – FLUENT), two dimensional numerical model National Center of Computational Hydrodynamic and Engineering of 2D (CCHE2D) developed by NCCHE, University of Mississippi, US and a quasi1D model Conveyance Estimation System (CES) developed by HR Wallingford,UK are applied to simulate the flow in meandering channels .This study aims to validate CFD simulations of free surface flow by using Volume of Fluid (VOF) method by comparing the data observed in the hydraulics laboratory of the National Institute of Technology, Rourkela. The volume of fluid (VOF) method was used to allow the free-surface to bend freely with the underlying turbulence. In this study Smagorinsky model is used to carry out for both three dimensional and two dimensional flow simulation.The LES results are shown to accurately predict the flow features, specifically the distribution of secondary circulations for in-bank channels at varying depth and width ratios in meandering sections.