Flow Analysis of Compound Channels With Wide Flood Plains
Prabir

Abstract

This Ph.D. research analyses the flow in straight and meandering compound channels having wide floodplains of large width ratio of value of nearly 12 and main channel aspect ratio of more than 5, which is very significant in the field of river hydraulics. Experiments were conducted in the Fluid Mechanics and Hydraulics laboratory of National Institute of Technology, Rourkela, India by casting smooth and rigid, straight and meandering compound channels inside a tilting flume. The research investigates the distribution of longitudinal velocity; depth averaged velocity for inbank and overbank flow cases in both straight and meandering compound channels. The measurement of the boundary shear stress for those flow conditions was done by Preston tube technique.As a complementary study to the experimental research undertaken in this work, two numerical hydrodynamic tools viz. Conveyance Estimation System (CES) developed by HR Wallingford,UK and CCHE2D developed by NCCHE, University of Mississippi,US are applied to simulate the overbank flow cases for both straight and meandering compound channels, for large scale EPSRC-FCF experiments and for a natural river. All the important flow parameters are also extracted numerically from the simulation results to study them vis a vis their observed values.From the study of isovels for straight and meandering compound channels, velocity distribution coefficients are measured and new models are suggested for energy coefficient and momentum coefficient values in straight compound channels and meandering compound channels by validating the developed models with present data and data sets from previous research projects. Integrating the distribution of boundary shear stress over different zones of compound section of straight channel and analyzing them with several data sets of other researchers, new models for subsection shear force are suggested in case of straight compound channels. Using these models, the stage–discharge relations in case of straight compound channels having different width ratios are then developed. These developed models are validated with new experimental data as well as data sets of large scale experimental facility of FCF (Series A),UK; small scale data sets from flume experiments of other past researchers and with some field data of real river flood cases. The flow distribution in straight compound channel is also modeled and validated with data sets from different past studies