Analytical solution of non-uniform flow in compound channel

Kamalini Devi,Jnana R Khuntia,Bhabani S Das,Kishanjit K Khatua,A Paquier,N Rivière

doi:10.1051/e3sconf/20184006041

Kamalini Devi, Jnana R Khuntia + Show 4 more

Open Access

https://doi.org/10.1051/e3sconf/20184006041

Copy DOI

Abstract

The present work investigates the analysis of depth-averaged velocity and boundary shear stress distribution in compound channels with non-uniform flow condition. A quasi two-dimensional model is proposed to assess the flow variables by accounting the physical processes that are specific to non-uniform flow. For analyzing the flow behavior, experimental data sets concerning compound channels with narrowing and enlarging floodplains of previous investigators are considered. The model accounts the influence of momentum transfer on the flow variables through additional shear stresses that are developed in non-uniform flow. Three types of effective stresses produced by molecular viscosity, turbulent and dispersion on the vertical planes are discussed. An analytical solution to the model is presented. Terms associated with the effective stresses are investigated relating them to the geometric and hydraulic parameters. The significance of lateral variation of energy slope is further investigated. For both homogenous and heterogeneous non-prismatic channels, the approach is examined to predict the flow variables with reasonable accuracy.

Highlights

Studies on the momentum exchange in compound river channels are focused for many decades especially in case where the overall channel width is constant along the length. These studies are commonly handled by simplification of the Navier-Strokes equation, to determine the transverse distribution of velocity and boundary shear-stress for steady uniform flow
The enhanced versions of these methods account for bed friction, lateral turbulent shear stress and secondary current term
The flow variables have been numerically described by various researchers for this case

Summary

Introduction

Studies on the momentum exchange in compound river channels are focused for many decades especially in case where the overall channel width is constant along the length These studies are commonly handled by simplification of the Navier-Strokes equation, to determine the transverse distribution of velocity and boundary shear-stress for steady uniform flow. Analytical studies on gradually varied flow are limited For these channels, Bousmar and Zech [1] split up the secondary current term into two parts ; (1) dispersion term in uniform flow resulting from helical secondary currents which is similar to Γ in the Shiono and Knight Method [2]; (2) transverse convection term resulting due to the mass transfer because of non-prismaticity of the channel. An analytical solution is obtained for the depth-integrated turbulent form of Navier-Stokes equation for non-uniform flow to predict the depth averaged velocity and bed shear stress. To illustrate the implementation of proposed solution, laboratory data sets of compound channels of both converging and diverging floodplains are considered

Methods

Discussion

Conclusion