Thesis (M.Eng.) - Asian Institute of Technology, 1993

A Thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering.

This work presents numerical methods for computation of two dimensional supercritical and subcritical flow in open channel transitions. The system of equations describing unsteady rapidly varied flow in open channel are developed to analyze the flow in channel transitions. The Boussinesq theory are applied to account for non-hydrostatic pressure distribution. The twodimensional unsteady flow equations are obtained by depth averaging the three-dimensional flow equations. A simple algebraic transformation is used to transform the transition geometry into a rectangular computational domain. Two explicit shock capturing finite difference schemes -second order Maccormack and third order Worming-Kutler-Lomex (WKL) are investigated. The models developed in this study numerically solved the unsteady flow equations in the transform coordinate system. The numerical models are verified by comparing the computed result with the experimental data for different channel transitions having supercritical flow or hydraulic jump. Good agreement between computed and experimental result is observed in almost all the cases analyzed. The third order model gives comparatively better result however the additional Boussinesq term does not improve the result significantly. Sensitivity analysis is also done for some parameters. The Manning's n influences the computed water depth specially in the downstream of channel. Dissipation coefficient (K) has very little effect on the solution. A finer grid size gives better result however beyond certain extent further reduction of grid size does not improve the result significantly. The models can be used confidently to simulate the basic features of different practical problem similar to that investigated in this study.