Fluvial sediment transport at a large bed shear stress
Thesis DisciplineCivil Engineering
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
The mechanics of a layer, many particle diameters thick, of a particle fluid system where the particles are large and exist at high concentrations is examined. Two distinct matters are examined, the first being the development of equations describing the overall characteristics of the system if the "local" equations governing the system at a point are known, and the second being the development of these local equations for large particles. It is shown that, if the local equations describing the dispersive stress - shear stress relationship and the stress - rate of strain relationship are single valued functions of the concentration, then the concentration profile in the bed of an open channel can be obtained by integrating a first order differential equation and the velocity profile obtained by carrying out a further integration. A method of obtaining the local equations is developed using previous results from a theory of a gas of rigid elastic spheres. Using these results and an equation derived from the calculated energy dissipation, local equations are developed. Results obtained theoretically are compared with previous experimental results and also with the results obtained using an open channel with a bed of gravel particles. A significant discrepancy between the results predicted by the theory developed and the results found by experiment was observed at high concentrations.