Modelling of Depth Averaged Velocity and Boundary Shear Stress Distributions in Open Channel Flow

Abstract

Flood disaster has become an import an unfavourable factor to a country's social and economic development. Frequency of future floods (predicted worldwide) in the rivers will be more frequent and will be more serious to the society in the future. Improving the prediction of river flood discharge capacity (for design of hydraulic structure) and reducing the flood and environment risk and currently become an urgent and long-term task in many countries. To estimate flow or the stage discharge relationships of a channel generally indirect method i.e. measurement approach by the Manning equation is used. However, the Manning coefficient largely depends on (A) bed forms, (B) Bed materials and vegetation, (C) Aspect ratio, (D) meandering effect. The Depthaveraged models are frequently applied to open channel flow hydraulic engineering problems because of their efficiency and practical utility. Depth average velocity and boundary shear stress for simple, meandering and compound channels depends on different factors such as Width ratio, Aspect ratio, Sinuosity, Froude’s no. (Fr), Reynolds's no (Re), Longitudinal slope(S), Relative flow depth, Absolute roughness, Roughness ratio (Nr), Percentage of shear force. Depth Averaged Velocity and boundary shear stress modelling are generally achieved through three approaches i.e. (A) Measurement Techniques, (B) Modelling through Analytical or Mathematical and (C). Modelling using Numerical Methods are generally presented in 2-D, 3-D, LES, DNS,of which 2- D are often used for engineering at present. The article describes different approaches for predicting the depth averaged velocity and boundary shear stress of both simple and compound channel flow under different hydraulic and geometric and roughness conditions.